TECHNICAL MANUAL AVIATION UNIT MAINTENANCE …chinook-helicopter.com/Publications/.../TM_1-1500-204-23-4.pdf · tm1-1500-204-23-4 technical manual aviation unit maintenance (avum)

TM1-1500-204-23-4

TECHNICAL MANUAL

AVIATION UNIT MAINTENANCE (AVUM)

AND

AVIATION INTERMEDIATE MAINTENANCE (AVIM)

MANUAL

for

GENERAL AIRCRAFT MAINTENANCE

(ELECTRICAL AND INSTRUMENT MAINTENANCE

PROCEDURES AND PRACTICES)

VOLUME 4

*This manual together with TM 1-1500-204-23-l through TM1-1500-204-23-3 and TM l-l 500-204-23-5through TM 1-1500-204-23-10, dated 31 July 1992, supersedes TM 55-1500-204-25/1, dated 6 April 1970,including all changes.

DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.

HEADQUARTERS, DEPARTMENT OF THE ARMY

31 JULY 1992

TM 1-1500-204-23-4

PRECAUTIONARY DATA

Personnel performing instructions involving operations, procedures, and practices which are includedor implied in this technical manual shall observe the following instructions. Disregard of thesewarnings and precautionary information can cause serious injury, death, or an aborted mission.

WARNING, CAUTIONS, and NOTES are means of attracting attention to essential or criticalinformation in a manual. Definitions are outlined as follows.

WARNING: An operating or maintenance procedure, practice, condition, statement, etc. , which ifnot strictly observed, could result in injury to or death of personnel.

CAUTION: An operating or maintenance procedure, practice, condition, statement, etc. , which if notstrictly observed, could result in damage to, or destruction of, equipment or loss of missioneffectiveness or long term health hazards to personnel.

NOTE: An essential operating or maintenance procedure, condition, or statement, which must behighlighted.

WARNING

ELECTRICAL TESTS

Electrical power up to 500 volts is used in testing the equipment. Exercise extreme caution during these tests.

ELECTRICAL EQUIPMENT

All switches and electrical equipment shall be of the enclosed explosion-proof type. All metal apparatus shall begrounded to avoid the danger of igniting test fluid fumes or creating electrical shock.

USING SOLVENTS/PAINTS

Standard precautions such as fire prevention and adequate ventilation shall be exercised when using solvents orapplying primer and coating.

Wear gloves or gauntlets when handling solvents as solvents may cause skin disorders.

Cements and solvents used to repair liferafts are flammable and shall be treated as such. Never smoke or permit anytype of open flame near when using cements or solvents.

Dichloromethane (methylene chloride) vapor is heavier than air; adequate ventilation shall be provided for workingpersonnel. Dichloromethane (methyene chloride) is toxic when vapors are inhaled over an extended period of time.

Acrylic monomer and polymer base adhesive, MIL-A-8576, contains a volatile liquid which may prove toxic when vaporsare inhaled over extended periods. Use only with adequate ventilation.

Observe fire precautions when using aliphatic naphtha, Federal Specification TT-N-95.

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TM 1-1500-204-23-4

HANDLING PLASTICS

Wear gloves to protect hands when handling hot plastic. Boiling water shall not be used for heating acrylate baseplastics.

Provide adequate ventilation when working with Furane Plastics, Epocast H-991-A, Furane hardener 941, or equivalents,as these materials are toxic.

LUBRICATING OIL

Lubricating oil, MIL-L-7808 or MIL-L-23699, contains an additive which is poisonous and absorbed readily through theskin. Do not allow oil to remain on skin any longer than necessary.

FUEL

When servicing aircraft or support equipment, clean up spilled fuel with cotton mops or cotton rags. Wash off any fuel onhands, body, or clothing.

HANDLING ACID

Wear protective clothing when mixing acid with water. Always pour acid into water, never water into acid.

HANDLING PYROTECHNIC FLARES

Handle pyrotechnic flares with the same care as high explosives.

MAGNESIUM ALLOY FIRE

Do not use water or any standard liquid or foam-type fire extinguishers on a magnesium alloy fire, as they may cause anexplosion. Use dry sand or talcum powder, Federal Specification U-T-30.

REMOVING CORROSION

Take precautions to prevent possible dust explosions when removing corrosion from steel alloys. Use goggles or faceshield when removing paint or corrosion with a wire brush or by the grinding method.

OXYGEN SYSTEM

Do not allow petroleum base products to come in contact with oxygen system components, as an explosion or fire mayresult.

Do not use masking tape to seal openings in oxygen regulators. Masking tape constitutes a safety hazard when used oneither serviceable or repairable oxygen equipment.

Do not use drycleaning solvent, Federal Specification P-D-680, near oxygen storage or transfer systems; the combinationof these two will form a highly explosive mixture.

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TM 1-1500-204-23-4

GROUND SUPPORT EQUIPMENT

Do not attempt to lift any load when the hydraulic axle jack is tilted.

To prevent accidental falls, appropriate maintenance platforms/safety stands illustrated in appropriate workstandmanuals or any other approved locally procured/manufactured safety stands/restraint equipment will be used whenworking (above 10 feet) on aircraft in a nontactical environment.

Install safety lock when an adjustable-height maintenance platform is in use.

Ensure the air hose used with compressed air is safe for the pressure being handled.

Release air pressure in air compressor tank before performing maintenance on air compressors.

Disconnect power before changing belts on electrically-driven compressors.

Disconnect electrical power before opening or disassembling any part of electrical equipment.

RADIOGRAPHIC EQUIPMENT

Exercise extreme caution when performing radiographic inspections to prevent personnel from coming in contact withradiation. Radiation from X-ray units and radioisotope sources is extremely destructive to living tissue.

FIRE EXTINGUISHERS

Monobromotrifluoromethane (CF3Br) is highly volatile, but not easily detected by odor. Although nontoxic, CF3Br shallbe considered in the same class as other freons and carbon dioxide, i. e., capable of causing danger to personnelprimarily by reduction of oxygen available for proper breathing. The liquid may cause frostbite or low temperature burnsif allowed to come in contact with the skin.

Bromochloromethane (CB) is a narcotic agent of moderate intensity, but of prolonged duration. It is considered less toxicthan carbon tetrachloride, methylbromide, or the usual products of combustion. Normal precautions should be takenwhile using bromochloromethane, including the use supplied breathing air in enclosed spaces.

HYDRAULIC FLUID

To avoid contamination, do not use previously opened cans of hydraulic fluid. Cans of hydraulic fluid cannot beresealed. Immediately transfer unused hydraulic fluid to an approved airtight, pressure venting, stainless steel storage

COMPRESSED AIR

Compressed air shall not be used for cleaning purposes except if reduced to less than 30 psi and then only with effectivechip-guarding and personal protective equipment.

TURBINE ENGINE OIL

To avoid contamination, do not use previously opened cans of engine oil. A new sealed can of fluid must be opened andused. When opening can, clean top and use a clean sharp, unplated instrument to prevent contamination.

Change 5 c

reservoir, an approved hydraulic servicing unit or a hydraulic test stand containing the same hydraulic fluid. When opening can, clean top and use a clean, sharp, unplated instrument to prevent contamination. Can openers attached tothe aircraft must be cleaned before using.

TM 1-1500-204-23-4

MERCURY

Mercury is extremely hazardous by inhalation or skin absorption. Be thoroughly trained and knowledgeable about yourHazard Communication program for Mercury prior to use. Refer to TM-385-4, Safety Precautions for Maintenance ofElectrical/Electronic Equipment, for safety precautions to use when handling mercury and for methods that are used toclean up mercury spillage.

PROPER USE OF PLATED TOOLS

Use only chrome-plated steel or unplated steel tools for disassembly or reassembly procedures described in this manual.Use of cadmium-plated or zinc-plated tools is not permitted since these platings are prone to chipping and flaking.Should these chips or flakes become imbedded in aircraft parts galvanic corrosion will result. Should these chips orflakes enter fuel wetted or oil wetted components they may eventually clog the filter or produce intergranular attack ofnickel or titanium base alloys at elevated temperature. All tools regardless of type plating should be serviceable and freeof chipping.

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TM 1-1500-204-23-4

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CHANGE HEADQUARTERS

NO. 5DEPARTMENT OF THE ARMY

WASHINGTON, DC., 8 June 2004


AND

AVIATION INTERMEDIATE MAINTENANCE (AVIM) MANUAL

for




VOLUME 4


TM 1-1500-204-23-4, dated 31 July 1992, is changed as follows:

1. Remove and insert pages as indicated below. New or changed text material is indicated by a vertical barin the margin. An illustration change is indicated by a miniature pointing hand.

Remove pages

A/(B blank)3-9 and 3-104-15 and 4-164-23 and 4-24

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2. Retain this sheet in front of manual for reference purposes.

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TM 1-1500-204-23-4 C5

0412403 DISTRIBUTION: To be distributed in accordance with Initial Distribution Number (IDN) 313302, requirements for TM 1-1500-204-23-4.

By Order of the Secretary of the Army:

PETER J. SCHOOMAKER General, United States Army

Chief of Staff Official:

JOEL B. HUDSON Administrative Assistant to the

Secretary of the Army

TM 1-1500-204-23-4

C4

CHANGE HEADQUARTERS

NO. 4DEPARTMENT OF THE ARMY

WASHINGTON, DC 30 July 1999


AND


for




VOLUME 4



1. Remove and insert pages as indicated below. New or changed text material is indicated by a vertical barin the margin. An illustration change is indicated by a miniature pointing hand.

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i / (ii blank)4-21 and 4-22Index 3 thru Index 6Cover

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TM1-1500-204-23-4C4


Official:

ERIC K. SHINSEKIGenera/, United States Army

Chief of Staff

Administrative Assistant to theSecretary of the Army

9916617

DISTRIBUTION:

To be distributed in accordance with Initial Distribution Number (IDN) 313302, requirements forTM1-1500-204-23-4.

TM 1-1500-204-234C3

CHANGE HEADQUARTERSDEPARTMENT OF THE ARMY

NO. 3 WASHINGTON, D.C., 30 April 1996

AVIATION UNIT MAINTENANCE (AVUM)AND

AVIATION INTERMEDIATE MAINTENANCE (AVIM) MANUALFOR

GENERAL AIRCRAFT MAINTENANCE(ELECTRICAL AND INSTRUMENT MAINTENANCE


DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited


1. Remove and insert pages as indicated below. New or changed text material is indicated by a vertical bar in themargin. An illustration change is indicated by a miniature pointing hand.

Remove pages Insert pagesi/(ii blank) i/(ii blank)2-1 and 2-2 2-1 and 2-23-3 through 3-6 3-3 through 3-63-9 and 3-10 3-9 and 3-103-13 through 3-18 3-13 through 3-184-3 and 4-4 4-3 and 4-44-7 and 4-8 4-7 and 4-84-15 through 4-18 4-15 through 4-184-21 through 4-24 4-21 through 4-24A-1/(A-2 blank) A-1/(A-2 blank)Index 1 through Index 9/(Index 10 blank) Index 1 through Index 9/(lndex 10 blank)



DENNIS J. REIMERGeneral United States Army

Chief of Staff

Acting Administrative Assistant to theSecretary of the Army

01628

To be distributed in accordance with DA Form 12-31-E, block no. 3302, requirements for TM 1-1500-204

TM 1-1500-204-23-4C 2

URGENT


NO. 2 WASHINGTON, D.C., 29 JULY 1993




(ELECTRICAL AND INSTRUMENT MAINTENANCE PROCEDURES AND PRACTICES)

VOLUME 4


TM 1-1500-204-23-4, 31 July 1992, is changed as follows:


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GORDON R. SULLIVANGeneral, United States Army

Official: Chief of Staff

MILTON H. HAMILTONAdministrative Assistant to the

Secretary of the Army04900

DISTRIBUTION:To be distributed in accordance with DA Form 12-31-E, block no. 3302, requirements for TM 1-1500-204-23-4.

TM 1-1500-204-23-4C-1


NO. 1 WASHINGTON, D.C., 28 MAY 1993




(ELECTRICAL AND INSTRUMENT MAINTENANCE PROCEDURES AND PRACTICES)

VOLUME 4


TM 1-1500-204-23-4, 31 July 1992, is changed as follows:


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i/(ii blank) i/(ii blank)4-19 and 4-20 4-19 and 4-20




Official: Chief of Staff



DISTRIBUTION:To be distributed in accordance with DA Form 12-31-E, block no. 3226, requirements for TM 1-1500-204-23-4.

TM 55-1500-204-23-4

LIST OF EFFECTIVE PAGES

Insert latest changed pages; dispose of superseded pages in accordance with regulations. NOTE: On a changed page, the portion of the text affected by the latest change is indicated by a vertical line, or other change symbol, in the outer margin of the page. Changes to illustrations are indicated by miniature pointing hands. Changes to wiring diagrams are indicated by shaded areas. Dates of issue for original and changed pages are: Original …….. 0 …….. 31 July 1992 Change …….. 3 …….. 30 April 1996 Change …….. 1 …….. 28 May 1993 Change …….. 4 …….. 30 July 1999 Change …….. 2 …….. 29 July 1993 Change …….. 5 …….. 8 June 2004 Total number of pages in this publication is 492 consisting of the following: Page *Change No. No. Cover...............................................4 a through b......................................0 c .....................................................5 d ......................................................0 A .....................................................4 B blank ............................................0 i .......................................................4 ii blank ............................................0 1-1 ……...........................................0 1-2 blank .........................................0 2-1 and 2-2......................................3 2-3 through 2-9................................0 2-10 blank .......................................0 3-1 and 3-2......................................0 3-3...................................................3 3-4 and 3-5......................................0 3-6...................................................3 3-7 and 3-8......................................0 3-9...................................................5 3-10.................................................3 3-11 through 3-13............................0 3-14.................................................3 3-15.................................................0 3-16 through 3-18............................3 3-19 and 3-20..................................0 4-1 and 4-2......................................0 4-3 and 4-4......................................3

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TECHNICAL MANUAL

TM 1-1500-204-23-4

TM 1-1500-204-23-4

HEADQUARTERSDEPARTMENT OF THE ARMY

WASHINGTON, D.C., 31 July 1992

TECHNICAL MANUAL



forGENERAL AIRCRAFT MAINTENANCE

(ELECTRICAL AND INSTRUMENT MAINTENANCEPROCEDURES AND PRACTICES)

REPORTING ERRORS AND RECOMMENDING IMPROVEMENTS

You can help improve this manual. If you find any mistakes or if you know of a way to improve theprocedures, please let us know. Mail your letter or DA Form 2028 (Recommended Changes to Publicationsand Blank Forms) or DA Form 2028-2 located in the back of this manual directly to: Commander, US ArmyAviation and Missile Command, ATTN: AMSAM-MMC-LS-LP, Redstone Arsenal, AL 35898-5230. Youmay also submit your recommended changes by E-Mail directly to [email protected] or by fax (256)842-6546/DSN 788-6546. A reply will be furnished directly to you. Instruction for sending an electronic2028 may be found at the back of this manual immediately preceding the hard copy 2028.

Distribution Statement A. Approved for public release; distribution is unlimited.

TABLE OF CONTENTS

PageCHAPTER 1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1CHAPTER 2 ELECTRIC SHOP OPERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1CHAPTER 3 ELECTRICAL MAINTENANCE PRACTICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1CHAPTER 4 INSTRUMENT SHOP PRACTICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1APPENDIX A REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GLOSSARY 1INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . INDEX 1

*This manual together with TM 1-1500-204-23-1 through TM 1-1500-204-23-3 and TM 1-1500-204-23-5 throughTM 1-1500-204-23-10, dated 31 July 1992, supersedes TM 55-1500-204-25/1, dated 6 April 1970, including allchanges.

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TM 1-1500-204-23-4

CHAPTER 1

INTRODUCTION

1-1. Purpose. This volume provides generalinformation pertaining to the electrical and instrumentmaintenance procedures and practices. Specificmaintenance practices are found in the individualaircraft maintenance manuals. This volume is ofmaximum benefit to the mechanic who desiresinformation about electric shop operations, electricalmaintenance practices, and instrument shop operations.This volume furnishes the mechanic a source ofinformation about how to perform various mechanicalfunctions which are used on all aircraft. This volume isnot a requisitioning authority, and applicable repair partsand special tools list should be consulted to obtain the

unit of issue and National Stock Number of the itemsrequired for maintenance.

1-2. Scope. General information to guide aircraftmaintenance personnel is covered within this volume;however, no attempt has been made to include specialparts or equipment which are applicable only toindividual or special aircraft.

1-3. Consumable Materials. Refer to TM 1-1500204-23-6 for consumable materials in this volume.

1-1/(1-2 blank)

TM 1-1500-204-23-4CHAPTER 2

ELECTRIC SHOP OPERATIONS

2-1. General Shop Rules. The practices andprocedures described in this chapter pertain to the repairfunctions of aviation activities and are applicable to alllevels of maintenance. Because of the many types ofArmy aircraft, each shop within the manufacturing andrepair section must, of necessity, have personnel trainedin general practices and procedures to the extent thatdifferent type and model aircraft do not upset a smoothrunning shop.

a. Responsibility. All supervisory personnel in themanufacturing section are responsible for a continuingand effective shop safety program. To implement andmaintain this program, shop supervisors will utilizebulletin boards, signs, and any other effective method.Shop personnel will cooperate in the shop safetyprogram by making helpful recommendations, andcontinually exercising care and caution in the operationof all shop equipment. All shop personnel will strive toimprove the safety program and be especially alert toobserve and correct unsafe shop practices. Allaccidents, no matter how minor, shall be reported to theshop supervisor, and all published instructions regardingsafety shall be strictly adhered to. Also, safetyengineers and safety officers will ensure that propersafety procedures are adhered to in accordance with AR385-10, Army Safety Program; AR 385-30, Safety ColorCode Markings and Signs; AR 385-32, ProtectiveClothing and Equipment; TB 385-4, Safety Precautionsfor Maintenance of Electrical/Electronic Equipment; TheOccupational Safety and Health Act of 1971, OSHA1910. 251; all applicable fire codes, NFPA 410; andother accepted civilian and military safety practices.

b. Shop Housekeeping. Housekeeping is theyardstick by which the shops in the manufacturingsection are judged. A dean, well-arranged shop is asafe shop and reflects credit on all personnel concernedwith its operation. The following shop practices shall beobserved:

(1) Oil pans or drip pans shall be used whereleaking oil, grease, and similar materials may causehazardous accumulations on equipment or floors. Allspills shall be cleaned up immediately. Approvedsweeping compound may be used to remove thesematerials from the floor.

CAUTION

Floors shall not be cleaned withvolatile or flammable liquids. Aflammable film may remain andcause a fire hazard.

(2) Floors shall be maintained smooth andclean, free of all obstructions and slippery substances.Holes and irregularities in floors shall be repaired tomaintain a level surface free from tripping hazards.

(3) All unnecessary materials on walls shallbe removed and projections shall be kept to a minimum.

(4) Aisles shall be dearly defined and keptfree of hazardous obstructions. Where possible, aislesshall be suitably marked by painting.

(5) All machines, work benches, aisles, etc. ,shall be adequately illuminated.

c. Equipment Safety Unsafe equipment shall bereported immediately. The following equipment safetypractices shall be observed:

(1) Machines shall be located to provideoperators with sufficient space to handle materials andperform job operations without interference.

(2) Substantial low resistance conductorsshall be used to ground all stationary and portablemachines, equipment, or other devices where staticcharges may be generated, or which require electricalcircuits of a hazardous nature.

(3) Shop machinery shall be operated only byqualified personnel observing safe practices.

(4) Safety devices, such as guards,interlocks, automatic releases, and stops, shall alwaysbe kept in operating condition.

(5) Ensure that all unauthorized personnelare clear of area before opening valves or energizingelectrical circuits for starting machinery.

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(6) Suitable mechanical guards, such asenclosures or barricades, shall be permanently installedon all machinery not already equipped with such toeliminate danger of injury from moving parts.

(7) Machinery shall not be adjusted, repaired,oiled, or cleaned while machine is in operation or poweris on.

(8) Personnel operating machinery shall wearprotective clothing as prescribed. A protective faceshield or goggles shall be worn when operating a grinderregardless of whether grinder is equipped with attachedshields.

(9) Jewelry shall not be worn whileperforming any maintenance.

d. Fire Safety. A constant vigilance must bemaintained to seek out fire hazards. Fire hazards areconstantly present in the shop where sparks, friction, orcareless handling can cause an explosion that maydestroy equipment or buildings, and injure or killpersonnel. Refer to AR 385-10, The Army SafetyProgram and The Occupational Safety and Health Act of1971.

(1) NO SMOKING signs shall be placed inareas where smoking could create a fire hazard.

(2) Personnel shall be trained in the use,knowledge, and location of shop fire fighting equipment.

(3) Each shop shall be equipped with fireextinguishers suited for type fire most likely to occur.

(4) Use correct fire extinguisher for class offire as follows:

• Class A fire (wood, paper, trash, etc). Use water orbromotrifluoromethane fire extinguisher.

• Class B fire (oil, paint, fuel, grease, etc). Use

bromotrifluoromethane or carbon dioxide fireextinguisher, or dry chemical extinguisher with classB rating.

• Class C fire (electrical equipment). Use

bromotrifluoromethane or carbon dioxide fireextinguisher, or dry chemical extinguisher with classC rating.

• Class D fire (combustible metals) magnesium,titanium, zirconium, sodium, lithium, andpotassium). Use dry powder type fire extinguisher.

(5) Oily waste, rags, and similar combustiblematerials shall be discarded in self-closing metalcontainers which shall be emptied daily.

(6) Use only approved cleaning solvents.

(7) Flammable materials shall not be storedin the shop.

e. Maintenance of Shop Equipment. Maintenanceof shop equipment consists of cleaning, preventivemaintenance, and replacement of defective parts.Preventive maintenance includes before-operation,during-operation, after-operation, services performed byoperator, and scheduled services to be performed atdesignated intervals. Consult the operation and serviceinstructions manual for specific maintenanceinstructions on particular types of equipment.2-2. Basic Principles and Theory for Direct Current.Direct Current (dc) flows constantly in only one directionwith a constant polarity. It changes magnitude onlywhen the circuit is opened or dosed, as shown in the dcwave form in figure 2-1.2-3. Basic Principles and Theory for AlternatingCurrent. Alternating current (ac) flows periodically firstin one direction and then in the opposite direction, asshown in figure 2-2. The time necessary for the currentto go from 0 to a maximum positive, to 0, to maximumnegative, and return again to 0 is the time for one cycle.That portion of the cycle during which the current flowsin one direction only is called an alternation. Frequencyis the number of I cycles occurring per second, and analternating current may be any frequency.2-4. Wiring Diagram Symbols, Charts, andSchematics. See figures 2-3 and 2-4 for wiringdiagram symbols and schematics.2-5. Basic Circuits. The basic electrical circuits ofseries, parallel, and compound are explained in thefollowing paragraphs.

a. Series. The series circuit, as shown in figure 2-5, is the most basic type of electrical circuit. It providesa complete path for current to flow from the negative to

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Figure 2-1. Direct Current Wave Form

Figure 2-2. Alternating Current Cycle

the positive terminal of the battery. It provides only onepossible path for current to flow. Current flow passesthrough circuit components, battery, and resistor, oneafter the other, or in series.

b. Parallel. A circuit in which two or more electricalresistances, or loads, are connected across the samevoltage source, as shown in figure 2-6, is a parallel circuit.The parallel circuit differs from the series circuit in thatmore than one path is provided for current flow. Theminimum requirements for a parallel circuit are thefollowing:

• A power source. • Conductors. • A resistance or load for each current path. • Two or more paths for current flow.

c. Compound. A compound circuit is a combinationof series and parallel circuits. A series-parallel circuitconsists of groups of parallel resistors. An example of aseries-parallel circuit is shown in figure 2-7. Therequirements for a series-parallel circuit are as follows:

• Power source (battery). • Conductors (wires). • Load (resistances). • More than one path for current flow. • A control (switch). • Safety device (fuse).

2-6. Measuring Equipment. Various lights, testers, andmeters used to measure electrical values are explained inthe following paragraphs.

a. Test Lights. Test lights consist of ordinary lowvoltage incandescent lamps, neon lamps or headsets, anda pair of leads for connecting the indicator to the circuit tobe tested. These testers are simple pieces of testequipment used to. check the continuity of fuses and linecircuits. These testers do not give accurate qualitativemeasurements such as can be obtained with a meter.However, their simplicity is of considerable advantagewhen open and closed circuit tests are made. The neonand lamp testers also can be used to distinguish betweenac and dc supplies and to test capacitors. In some testersa switching arrangement allows a source of voltage to beinserted in series with the test lamp, so that circuits withno voltage applied to them can be checked.

b. Continuity Tester. A continuity tester uses theconstant-current circuitry of a multimeter formeasurements of resistance. It can be used to check foropens, shorts, or grounds, as shown in figure 2-8.

c. D'Arsonval Meter. The D'Arsonval meter, asshown in figure 2-9, is a dc galvanometer consisting of anarrow rectangular coil suspended between the poles of apermanent magnet. The D'Arsonval meter movement isa current measuring device which is used in ammeters,voltmeters, and ohmmeters. The D'Arsonval meter isbeing phased out by digital measuring equipment.

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Figure 2-3. Wiring Diagram Symbols (Sheet 1 of 2)

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Figure 2-3. Wiring Diagram Symbols (Sheet 2 of 2)

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Figure 2-4. Typical Electrical System Schematic

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Figure 2-5. Series Circuit

Figure 2-7. Compound Circuit

d. Ammeter. An ammeter measures either dc or accurrent. To measure current, the circuit under test isbroken, and an ammeter is inserted into the break. Itsscale is usually graduated in kiloamperes, amperes,milliamperes, or microamperes.

e. Voltmeter. A voltmeter is a current measuringinstrument designed to indicate voltage by measuring thecurrent flow through a resistance of known value. Itsscale is usually graduated in volts. D'Arsonval voltmetersare being phased out by digital voltmeters.

f. Ohmmeter. An ohmmeter measures electricalresistance and is used to check circuit continuity. Itsscale is usually graduated in ohms, megaohms, or both.

g. Multimeter. A multimeter is an instrumentincorporating two or more meter circuits and a metermovement in a single case. A typical multimeter containsvoltmeter, ammeter, and ohmmeter circuits using a singlemeter movement. The function switch,. as shown infigure 2-10, must be placed in the proper position for thetype of measurement to be made. The range switch mustbe set to the range desired.

h. Electrodynamometer. The electrodynamometeror wattmeter generally is used to measure power takenfrom the line for operation of any piece of electricalequipment.

i. Rectifier Meter. Low-frequency ac measurementsare made with a rectifier meter. The rectifier meter ismore sensitive and more accurate than the moving vaneD'Arsonval-type meters. The function of a rectifier meteris to change ac to a form of dc. The ac is rectified, andthe pulsating dc is measured by the meter.

j. Wattmeter. The wattmeter (electrodynamometer)is used to measure power in an electrical circuit. Its scaleis usually graduated in watts. The wattmeter consists oftwo stationary coils and one moving coil. The stationarycoils have many turns of small wire with high resistance.The movable coil has a few turns of large wire with lowresistance and is pivoted in jewelled bearings. The meterneedle is attached to one end of the movable-coil shaft,and the damping arrangement, similar to that of themoving-vane meter, is attached to the other end. Springsare provided to control the needle swing.

k. Frequency Meters. Frequency or wavelength,however, may be determined also by frequencymeasuring devices known as wavemeters or beatfrequency meters. These meters indicate thefundamental or harmonic frequencies of oscillators orharmonic generators on a calibrated dial. The wavemeteris calibrated in terms of wavelength, and contains avariable tuned circuit whose resonant frequency isdetermined by the unknown frequency. The beat, orheterodyne frequency, meter uses an oscillator togenerate signals of known frequencies and-comparesthese with the unknown frequency.

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TM 1-1500-204-23-4

Figure 2-9. D'Arsonval Meter

2-8

TM 1-1500-204-23-4

Figure 2-10. Multimeter

CAUTIONIf following procedures are notcomplied with, meters may bedamaged.

l. Meter Safety Precautions. Before using anymeter, carefully read and observe all of the instructionscovering its use in the instruction book furnished with it.When using any instrument, the front panel, particularlythe area around the jacks and terminals, should beclean and dry. This prevents surface leakage whichacts as a shunt and may cause an appreciable error inreadings on the more sensitive ranges of the instrument.

(1) Ammeter precautions. Since an ammeterhas a low resistance, it is important to be especiallycareful in using it. If mistakenly put across a voltagesource, the meter can be damaged. Never connect anammeter or milliammeter across a battery or resistor.Always break the circuit and connect the meter in series,one meter lead going to each point of the circuit break.

(a) Range. Always start at the highestmeter range when measuring an unknown quantity, thendrop down to a lower range if necessary. This practiceprotects the meter from damage which may result if anattempt is made to read a high value in a low range.

(b) Polarity. Observe polarity. Testleads are usually color-coded black for negative and redfor positive. Place them in their proper pin jacks.

(2) Voltmeter precautions. Connectvoltmeters in parallel or across the circuit componentbeing measured.

(a) Range. Always start at the highestmeter range when measuring an unknown quantity, thendrop down to a lower range if necessary. This practiceprotects the meter from damage which may result if anattempt is made to read a high value in a low range.

(b) Polarity. Observe polarity. Testleads usually are color-coded black for negative and redfor positive. Place them in their proper pin jacks.

(3) Ohmmeter precautions. Before makingresistance measurements, be sure that no voltage existsin the circuit under test. Discharge all capacitors. Thepresence of any voltage through the external resistance,in addition to the voltage of the battery in the ohmmetercircuit, can damage the meter.

2-9/(2-10 blank)

TM 1-1500-204-23-4

CHAPTER 3

ELECTRICAL MAINTENANCE PRACTICES

3-1. Installation Inspection of Wires and Cables.Installation inspection of wires, cables, and theircomponents is explained in the following paragraphs.Refer to TM 55-1500-323-24 for wire maintenancepractices.

a. Inspection Requirements. Wires and cablesshall be inspected for adequacy of support, protection,and general condition throughout. The desirable andundesirable features in aircraft wiring are outlined belowand indicated as conditions that should or should notexist. Inspect aircraft wiring as follows:

(1) Ensure wires and cables are supported bycushion clamps, grommets, or other approved devices,at intervals of not more than 24 inches, except whencontained in troughs, ducts, or conduits. The supportingdevices must be of a suitable size and type, and thewires and cables must be held securely in place withoutdamage to the insulation.

(2) Provide adequate stand-off support wherewires are routed over any structural member in such amanner that chafing is likely to occur. Ensure that theuse of proper insulating material, is wrapped over wireor cable to protect against chafing, is not being used inapplications where stand-off supports could be installed.

(3) Ensure phenolic blocks, plastic liners, orrubber grommets are installed in holes in bulkheads,floors, or structural members through which wiring mustpass and it is impossible to install off-angle clamps tomaintain wiring in a fixed position away from edges ofholes. In such cases, additional protection, in the formof plastic tubing or insulating tape is optional.

(4) Ensure wires and cables in junctionboxes, panels, and bundles are properly supported andlaced to provide proper grouping and routing.

WARNINGMake sure any retaining screw orbolt protruding throughbulkheads, panels, etc. , does notinterfere with flight controlsfluid/fuel lines or any othercomponent.

(5) Ensure clamps and retaining screws areproperly mounted and secured so that any movement ofwires and cables is restricted to the span between pointsof support. Movement of wires and cables should notbe transmitted to soldered or mechanical connectionssuch as terminal posts or connectors.

(6) Check that wires and cables aresupported and bound so that interference with otherwires, cables and equipment does not exist.

(7) Check that wires and cables areadequately supported to prevent excessive movementin areas of high vibration.

(8) Ensure insulating tubing and tape issecured in place by tying or with clamps.

(9) Ensure continuous lacing is not used,except in panels and junction boxes where this practiceis optional. Lacing installed in this manner outsidejunction boxes shall be removed and replaced withindividual loops.

(10) Ensure that tapes (such as friction tape)which will dry out in service, produce chemical reactionswith wire or cable insulation, or absorb moisture, are notused.

(11) Ensure minimum use of insulating tubingis made when used to protect wire and cable fromabrasion, chafing, exposure to fluids, and otherconditions which could affect cable insulation. Use ofinsulating tubing for support of wires and cablesprohibited.

(12) Do not use moisture-absorbent materialas fill for clamps or adapters.

(13) Check that wires and cables are not tiedor fastened together in conduit or insulating tubing.

(14) Check that cable supports do not restrictthe wires or cables in such a manner as to interfere withoperation of equipment shock mounts.

3-1

TM 1-1500-204-23-4

(15) Ensure tape or cord are not used forprimary support.

(16) Ensure drain holes are present in driploops or lowest portion of tubing placed over wiring.

(17) Check that wires and cables are routed insuch a manner that chafing will not occur.

(18) Ensure wires and cables are positioned insuch a manner that they are not likely to be used ashandholds, or as support for personal belongings andequipment.

(19) Check that wires and cables are routed sothat they are not exposed to damage by personnelmoving in the aircraft.

(20) Check that wires and cables are locatedso as not to be susceptible to damage by the storage orshifting of cargo.

(21) Check that wires and cables are routed sothat there is no possibility of damage from batteryleakage or any other fluids.

(22) Ensure wires and cables are adequatelyprotected in wheel wells or other areas where they maybe exposed to damage from impact of rocks, ice, mud,etc. If re-routing of wires or cables is not practical, it ispermissible to install metal shielding or insulating tubing.This should be held to an essential minimum.

(23) Ensure wires and cables routed within 6inches of any flammable liquid or fuel line are closelyand rigidly supported, and are not attached to fuel lines.Ensure wires and cables are routed above fluid/fuellines.

(24) Ensure a trap or drip loop is provided toprevent fluids or condensed moisture from running intowires and cables dressed downward to a connector,terminal block, panel, or junction box.

(25) Ensure wires and cables, installed inlocations where fluids may be trapped, are routed ashigh as possible, and protected with insulating tubingwhen this is not possible.

(26) Check that wires and cables are keptseparate from high temperature equipment, such asresistors, tailpipes, heating ducts, and deicers.

(27) Ensure the minimum radius of bend forwire or cable is 10 times the outside diameter of the wireor cable, except that at the terminal strips where thewire is suitably supported, the radius may be 3 times thediameter of the wire or cable. Where it is impractical toinstall wiring or cable within the radius requirements, thebend shall be enclosed in insulating tubing.

(28) Ensure coaxial cables are not bent at aradius of less then 6 times the outside diameter of thecable.

(29) Check that wires and cables attached toassemblies where relative movement occurs (such as athinges and rotating pieces, particularly control sticks,control wheels, columns and flight control surfaces) areinstalled or protected in such manner as to preventdeterioration of the wires and cables caused by therelative movement of the assembly parts.

(30) Ensure wires and cables are provided withenough slack to meet the following requirements:

• Permit ease of maintenance.• Allow replacement of terminals at least two times,

except for sizes AN-2 and AL-4 and larger whereonly one replacement should be made.

• Prevent mechanical strain on the wires, cables,junctions and supports.

• Permit free movement of shock-and-vibrationmounted equipment.

• Allow shifting of equipment as necessary to performalignment, servicing, tuning, removal of dust covers,and changing of tubes, while installed in aircraft.

(31) Check that unused wires are individuallydead-ended, tied into a bundle, and secured to apermanent structure. Each wire is to have strands cuteven with insulation and a pre-insulated closed endconnector, or a 1-inch piece of insulating tubing placedover wire with its end folded back and tied.

(32) Check that shielding is in place andproperly fastened.

3-2

TM 1-1500-204-234

b. Replacement Criteria. Wiring shall be replacedwhen found to have any of the following defects:

• It becomes unmanageable due to splice or number ofsplices.

• The primary insulation has been broken. • The outer insulation is weather-cracked. • It is known to have been exposed to battery acid or

the insulation is beginning to deteriorate due tosuspected exposure to battery acid.

• It shows evidence of overheating. • The insulation has been saturated with engine oil,

landing gear lubricant, hydraulic fluid, or solvent. • It shows evidence of having been crushed or severely

kinked.

CAUTIONCleaning agents or preservativesshall not be used to minimize theeffects of corrosion on ordeterioration of wire shields.Further damage may occur.

• The metallic shield on shielded wire is frayed orcorroded.

• The insulation sleeves placed over wire splices or

terminal lugs show evidence of breaks, cracks, dirt, ormoisture.

c. Wire Sizes. Wire is manufactured in sizesaccording to a standard known as the American WireGauge (AWG). Wire size may be determined by using awire gauge as shown in figure 3-1. This type of gauge willmeasure wires ranging in size from number 0 to number36. The wire to be measured is inserted in the smallestslot that will just accommodate the bare wire. The gaugenumber corresponding to that slot indicates the wire size.The slot has parallel sides and should not be confusedwith the semicircular opening at the end of the slot. Theopening simply permits the free movement of the wire allthe way through the slot.

Figure 3-1. Wire Gauge

NOTEGauge numbers are useful incomparing the diameter of wires,but not all types of wire or cablecan be accurately measured with agauge. Large wires are usuallystranded to increase their flexibility.In such cases, the total area can bedetermined by multiplying the areaof one strand (usually computed incircular mils when diameter orgauge number is known) by thenumber of strands in the wire orcable.

d. Wire Identification. To make maintenance easier,each interconnecting wire and cable installed in aircraft ismarked with a combination of letters and numbers whichidentify the wire, the circuit it belongs to, its gauge size,and other information necessary to relate the wire to awiring diagram. This marking is called the cableidentification code. Details of the code are given in MIL-W-5088. Wire received from the manufacturer is printedwith the manufacturer's code designation is a light greencolor at intervals of one to five feet, the MS number anddash number of the wire, and a one-, two-, or three-digitnumber indicating the color of the basic wire insulationand the color of the stripes (if present). The color code isas follows:Black 0 Blue 6Brown 1 Violet 7Red 2 Gray 8Orange 3 White 9Yellow 4 (includes alsoGreen 5 uncolored insulations)

Change 3 3-3

TM 1-1500-204-23-4e. Wire Stripping. Insulation must be be stripped

from connecting ends to expose the bare conductorbefore wire can be assembled to connectors, terminals,or splices. The following general precautions arerecommended when stripping any type of wire:

• When using any type of wire stripper, hold the wireso that it is perpendicular to cutting blades.

• Adjust automatic stripping tools carefully; follow the

manufacturer's instructions to avoid nicking, cutting,or otherwise damaging strands. This is especiallyimportant for aluminum wires and for copper wiressmaller than No. 10. Examine stripped wires fordamage. Cut off and restrip (if length is sufficient),or reject and replace any wires having more thanthe allowable number of nicked or broken strandslisted in the manufacturer's instructions.

• Make sure insulation is clean-cut with no frayed or

ragged edges. Trim if necessary. • Make sure all insulation is removed from stripped

area. Some types of wires are supplied with atransparent layer of insulation between theconductor and the primary insulation. If this ispresent, remove it.

• When using hand-plier strippers to remove lengths

of insulation longer than 3/4 in. , it is easier toaccomplish in two or more operations.

• Re-twist copper strands by hand or with pliers, if

necessary, to restore natural lay and tightness ofstrands.

(1) Aluminum wire. Aluminum wire must bestripped with extreme care, since individual strands willbreak very easily after being nicked.

(2) Copper wire. Copper wire can be strippedin a number of ways, depending on the size andinsulation. Table 3-1 lists some types of stripping toolsrecommended for various wire sizes and types ofinsulation.

f. Marking of Wires with Marking Machine.Marking machines, as shown in figures 3-2 and 3-3, areused to stamp the identification code. For stamping alarge number of long wires, use an automatic-wiremarking machine. In machines of this type as shown infigure 3-2, wire sizes No. 26 through No. 14 are fedthrough and stamped automatically. Wires larger thanNo. 14 are fed through by hand, but stampedautomatically. For short wires, on repair or maintenancework, a hand operated wire marking machine is moreconvenient and economical as shown in figure 3-3. Inthis type of machine, the desired amount of wire is fedthrough by hand, and stamped by operating the handlefor each marking. Wire guide holders in sizes to fitwires, and slot holders to hold appropriate size type, arefurnished to fit the machines. Type is supplied in threesizes to mark wire No. 26 through No. 0000, as shownin table 3-2. Marking foil is available in black or white(and other colors if needed for special applications).

NOTEStore foils at approximately 70°Fand 60 percent relative humidity.

g. Terminals and Terminal Blocks. When installingterminals and terminal blocks, inspect using thefollowing procedures:

(1) Check that insulating tubing is placedover terminals (except pre-insulated types) to provideelectrical protection and mechanical support, and issecured to prevent slippage of the tubing from theterminal.

Table 3-1. Copper Wire StrippersStripper Wire size Insulations

Hot-blade No. 26 - No. 4 All except asbestosRotary, Electric No. 26 - No. 4 AllBench No. 20 - No. 6 AllHand Pliers No. 26 - No. 8 AllKnife No. 2 - No. 0000 All

3-4

TM 1-1500-204-23-4

Figure 3-2. Automatic Wire Marking Machines

3-5

TM 1-1500-204-23-4

Figure 3-3. Hand Wire Marking Machine

Table 3-2. Recommended Sizes of Marking TypeHeight of letters

Wire size (Inches)No. 26 and No. 22 1/16No. 20 thru No. 14 5/64No. 12 thru No. 0000 and 7/64Coaxial Cable

(2) Ensure terminal blocks are securelymounted.

(3) Ensure terminal connections to terminalblock studs, and nuts on unused studs, are tight.

(4) Ensure evidence of overheating andcorrosion is not present on connections to terminal blockstuds.

(5) Ensure the number of terminal connectionsto a terminal block stud does not exceed four.

(6) Inspect for physical damage to studs, studthreads, and terminal blocks. Replace cracked terminalstrips and those studs with stripped threads.

h. Fuses and Fuse Holders. When installing fusesand fuse holders, inspect using the following procedures:

(1) Inspect for security of connections to fuseholders.

(2) Inspect for the presence of corrosion andevidence of overheating on fuses and fuse holders.Replace corroded fuses and clean fuse holders. Ifevidence of overheating is found, check for correct ratingof fuse.

(3) Inspect for security of mounting of fuseholder.

(4) Inspect for replenishment of spare fusesused in flight. Replace with fuses of appropriate currentrating only.

(5) Inspect for exposed fuses susceptible toshorting. Install cover of non-conducting material ifrequired.

i. Splices. When installing crimp type connectors,inspect splices using the following procedures:

(1) Check for the presence of snug-fittingtransparent insulating tubing extending at least 1/2 inchover each end and tied in place with waxed cord unlessthe connector is of the pre-insulated type. Use oftransparent tape is approved, but only as a temporarymeans, to be replaced as soon as possible.

(2) Check for the spacing of splices atstaggered intervals to prevent excessive enlargement ofthe bundle. Groups of non-staggered splices need not bereplaced; however, it may be necessary to use extradamps to support the added localized weight.

NOTE• Splices may be used within 12

inches of a termination devicewhen attached to the pigtailspare lead of a pottedtermination device, or to splicemultiple wires to a single wire,or to adjust the wire sizes sothat they are compatible withthe contact crimp barrel sizes.

• The application of splices shallbe design control and beauthorized by the applicabletechnical manual or ATCOMengineering.

Change 3 3-6

TM 1-1500-204-23-4

j. Conduits. When installing conduits, inspectusing the following procedures:

(1) Ensure the conduit is installed so thatstrain and flexing of ferrules is relieved.

(2) Ensure the conduit is not collapsed orflattened from excessive bending.

(3) Ensure that conduits are installed so thatfluids or condensed moisture will not be trapped.Suitable drain holes shall be provided at the low points,except for magneto ground-cable conduit and metallicflexible conduit.

(4) Ensure that bonding clamps are installedin such a manner that damage to the conduit cannotresult.

k. Bonds. A bond is any fixed union existingbetween two metallic objects that results in electricalconductivity between them. Such union results fromeither physical contact between conductive surfaces ofthe objects or from the addition of a firm electricalconnection between them. Inspect for the followingdesirable features:

NOTEIntermittent electrical contactbetween conducting surfaces,which may become part of aground plane or a current path,shall be prevented either bybonding, or by insulation, ifbonding is not necessary.

• Metallic conduits shall be bondedto the aircraft structure at eachterminating and break point. Thebonding path may be through theequipment at which the conduitterminates.

• Bond connections shall be secureand free from corrosion.

• Bonding jumpers shall be installedin such a manner as not tointerfere in any way with theoperation of movable componentsof the aircraft.

• Self-tapping screws shall not beused for bonding purposes. Onlystandard threaded screws or boltsof appropriate size shall be used.

• Exposed conducting frames or parts ofelectrical or electronic equipment shallhave a low resistance bond of less than0.1 ohm to structure. If the equipmentdesign includes a ground terminal or pinwhich is internally connected to suchexposed parts, a ground wireconnection to such a terminal will satisfythis requirement.

• Bonding jumpers shall be kept as shortand direct as possible, and whenpracticable, shall not exceed 3 inches inlength.

• Bonds shall be attached directly to thebasic aircraft structure rather thanthrough other bonded parts insofar aspractical.

• Bonds shall be installed to ensure thatthe structures of military aircraft areelectrically stable and free from thehazards of lightning, static discharge,electrical shock, etc., and to provide forthe suppression of radio interferenceresulting from these hazards.

l. Junctions. Ensure that only approved devices,such as solderless type terminals, terminal blocks,connectors, disconnect splices, permanent splices,and feed-through bushings are used for cablejunctions. Inspect for the provisions outlined below:

• Electrical junctions shall be protectedfrom short circuits resulting frommovement of personnel, cargo, shellcases, clips, and other loose or storedmaterials. Protection shall be providedby covering, installing them in junctionboxes, or by locating them in such amanner that additional protection is notrequired.

• Exposed junctions and busses shall beprotected with insulating materials.Junctions and busses located withinenclosed areas containing onlyelectrical and electronic equipment arenot considered exposed.

• Electrical junctions shall bemechanically and electrically secure.They shall not be subject to mechanicalstrain or used as a support for insulatingmaterials, except for insulation onterminals.

m. Toggle Switches. Inspect toggle switches usingthe following procedures:

3-7

TM 1-1500-204-23-4

NOTEIn the event the followinginspections reveal that theswitches are unserviceable,replace defective switches withswitches of the same type andcurrent rating.

(1) Conduct a visual examination forphysical damage, and check to see that switches aresecurely attached to the mounting panel.

(2) Check for loose or deformed electricalconnections or evidence of corrosion of the terminals,terminal lugs or screws.

(3) Check for manual operation by actuatingtoggle lever several times. This also serves to removeany superficial contamination or foreign deposits on theinternal electrical contacts. Return toggle lever toproper position.

(4) Test for electrical continuity asmeasured across the external terminals by means of anohmmeter. Electrical resistance across any set ofclosed contacts should not exceed 1 ohm. Intermittentor excessive resistance normally indicates that theinternal contacts are corroded. In the event a fewadditional actuations of the switch does not clear up thiscondition, replace the switch with like item. Continuitytests of installed switches require that the switch beelectrically isolated from other circuitry to precludemeasurement of low resistance parallel systems. Thiscan usually be accomplished by opening the circuitbreaker or fuse on the line side of the switches.

(5) Check switches that are frequentlyexposed to direct water spray, rain or heavy dustconcentration. These switches require timely checks formanual operation, corrosion and continuity.

n. Circuit Breakers. Inspect circuit breakers usingthe following procedures:

NOTEReplace breakers with breakers ofthe same type and current ratingunless otherwise specified,providing the followinginspections reveal that thebreaker is unserviceable.

(1) Determine that the breaker case andmounting means are secure to the mounting panel andthere is no evidence of physical damage.

(2) Inspect for loose electrical termination orevidence of corrosion of the terminals, terminal lugs orscrews.

(3) Ensure positive manual operation byactuating push-pull button or toggle several times. Thisoperation also serves to remove any superficialcontaminants or foreign deposits present on the surface,of the internal electrical contacts. Return actuator toproper position.

(4) Check for evidence that breaker hadbeen subjected to burning or overheating in the areaadjacent to the manual actuator. The burned area isusually caused by electrical arcing as a result of acombination of the presence of excessive moisture andpoor dielectric characteristics of the breaker.

CAUTIONDo not connect ohmmeter to a livecircuit.

(5) Test for electrical continuity, asmeasured across the external breaker terminals. Use areliable ohmmeter capable of indicating an appropriatedc resistance value for the purpose of determining thatthe maximum overall electrical resistance does notexceed 1 ohm. Intermittent or excessive resistancereadings normally indicate that the internal breakercontacts are corroded. In the event a few additionalactuations of the breaker do not clear up this condition,the breaker should be replaced. Continuity tests ofinstalled breakers require that the breaker be electricallyisolated from other circuitry to preclude measurement oflow resistance parallel systems. This can usually beaccomplished by opening the switch or switches on theload side of the breaker. Circuit breakers in live circuitscan be checked by performing a voltage check.

(6) Test and physically inspect associatedwiring for short circuit condition to the aircraft structure.Tripped circuit breakers indicate that an abnormalelectrical overload occurred and require immediateinvestigation to determine the cause for the fault.Repetitive tripping in the same circuit will require anengineering investigation if the operating equipment orelectrical load otherwise functions properly and thebreaker replacement does not correct the fault.

(7) Check circuit breakers that arefrequently exposed to direct water spray, rain, snow orheavy dust concentrations. These breakers requiretimely checks for manual operation, corrosion,continuity, evidence of burning or electrical arcing.

3-8

TM 1-1500-204-23-4

o. Kapton Wiring. Kapton wire MIL-W-81381 isgeneral purpose wire for use in high voltageapplications. The insulation is tape of polyimide orpolyimide-fluorocarbon films. The conductors are silveror nickel plated copper, or a high-strength copper alloy.At present Kapton wiring is being phased out on newaircraft and is restricted to ballistically hardened areas.The preferred wire is MIL-W-22759 which can bemixed in the same wire bundle as Kapton wire. Refer toTM 55-1500-323-24 for inspection, stripping, andinstallation of connectors on Kapton wiring. Kaptoninsulated wire should be inspected whenevermaintenance is performed. Slight flaking of top coat isacceptable, however this is considered as a first stage ofdeterioration. When flaking is observed, closeinspection shall be performed at regular intervals todetermine if further deterioration occurs. Excessiveflaking or other damage (cuts, chaffing, etc) to insulationrequires that the wire be replaced.

3-2. Troubleshooting. Troubleshoot electrical circuitsand components when malfunctions cannot be readilylocated. Use procedures outlined below.

Omit operational check in caseswhere it is evident that an operationalcheck could result in damage to theaircraft.

a. Operational Check. Perform an operational

primarily for high potential voltage testing on aircraftelectrical cabling can be extremely hazardous in thoseareas where fuels, explosive vapors, or fumes arepresent in the aircraft. The term high potential voltagetesting as used herein is described as that condition ofapplying a voltage of sufficient magnitude andapproaching maximum insulation breakdown limits asspecified to determine leakage resistance between wireinsulation, conductors, conductor pairs, or groups ofconductors individually insulated within an insulatedcable jacket. High potential voltage or insulationbreakdown testing of aircraft electrical wiring andcabling will be conducted as a last resort after allprevious methods of detecting faulty cabling have beenaccomplished. These methods will consist of continuity,visual inspection, common voltmeter and ohmmeterchecks, and other methods not involving high potentialvoltage tests. The following procedures will apply wheretests, employing high potential testers, are made tocheck aircraft electrical cabling and wiring involvingthose areas where fuels, fumes, or explosive vaporsmay possibly be present:

(1) It will be the responsibility of allpersonnel using high potential voltage test apparatus totrace the physical location of the circuit being tested anddetermine if explosive vapors, fuels or fumes, arepresent in any areas of this circuit.

(2) When explosive vapors, fuels, or fumesare determined to be present and adequate ventilationor air circulation is not provided, the following twoparagraphs will apply:

(a) If fumes or vapors can beremoved by isolating fuel from the areas involved bymeans of shutoff or bypass valves, only that portion ofthe fuel system which is isolated must be drained andpurged.

Change 5 3-9

CAUTION

check of the system involved to determine when it isfunctioning in accordance with the applicable aircraftmaintenance manual. When a malfunction exists,perform the following procedures:

(1) Obtain a wiring diagram of systeminvolved. Be sure wiring diagram is current andapplicable to particular model aircraft.

(2) Review operating principles andperformance requirements of the system.

(3) Recall similar situations and checkEquipment Improvement Recommendation (EIR) file.

(4) Examine aircraft maintenance forms tosee what maintenance has been performed on systemor general area of system or components.

(5) Decide on all possible component andwiring malfunctions which could cause system toperform as it does. A typical electrical systemschematic is shown in figure 2-4.

(6) Of all possible faults or troubles found instep (5), decide which troubles are most probable causeof malfunctions and proceed to test circuits orcomponents with test equipment.

NOTE

The applicable aircraft maintenancemanual contains troubleshootingelectrical circuits and components.

(7) Upon location of defective component orwiring, accomplish repairs or replacements as necessary.

b. Precautions. Use of test equipment designed

TM 1-1500-204-23-4

(b) If adequate isolation cannot be accom-plished, the entire fuel system will be drained and purged.

3-3. Installation of Electrical Connectors andCommon Plugs. Plugs and receptacles are providedthroughout the aircraft to provide a means of connectingindividual components to the electrical system and tofacilitate their removal and installation. Electricalconnectors also are provided at some firewalls,bulkheads, and decks to provide wire routing throughthe aircraft structure and to facilitate removal andreplacement of wiring harness segments. Thoseconnectors installed in areas of high vibration or in areasnot accessible for periodic inspection are secured withwire or otherwise mechanically locked to preventopening of the connector due to vibration.

a. Types of Connectors. Connectors areidentified by AN or MS numbers and are divided intoclasses with the manufacturer's variations in each class.The manufacturer's variations are differences inappearance and in the method of meeting aspecification. Some commonly used connectors areshown in figure 3-4. There are five basic classes of ANor MS connectors used in most aircraft. Each class ofconnector has slightly different constructioncharacteristics. Classes A, B, C, and D are made ofaluminum, and class K is made of steel.

• Class A - Solid, one-piece back shell, general-purpose connector.

• Class B - Connector back shell separatesinto two parts lengthwise. Used primarilywhere it is important that the soldered con-nectors be readily accessible. The backshell is held together by a threaded ring orby screws.

• Class C - A pressurized connector withinserts that are not removable. Similar to aclass A connector in appearance, but theinside sealing arrangement is sometimesdifferent. It is used on walls of bulkheads ofpressurized equipment.

• Class D - Moisture - and vibration-resistantconnector which has a sealing grommet inthe back shell. Wires are threaded throughtight-fitting holes in the grommet, thussealing against moisture.

• Class K - A fireproof connector used in areaswhere it is vital that the electric current isnot interrupted, even though the connectormay be exposed to continuous open flame.Wires are crimped to the pin or socketcontacts and the shells are made of steel.This class of connector is normally longerthan other classes of connectors.

(1) MS connectors. MS connectors asshown in figure 3-4 are electric connectors with solder orremovable crimp contacts (both front and rear release).These connectors are for use in electronic, electricpower, and control circuits.

(2) Special-purpose connectors. In additionto the MS connectors, special purpose types arecommonly found in military aircraft. These aredescribed in the following paragraphs.

(a) Moisture-proof connectors(Cannon KE series). These connectors are similar tothe MS-K series, with the additions of a moisture-resisting seal. They will mate with MS-K plugs orreceptacles, but retain the moisture sealing feature onlywhen mated with corresponding KE series plugs orreceptacles.

(b) Subminiature connectors (CannonUS Series). These connectors, as shown in figure 3-5,are wire connecting types only; they have no mountingflanges, but can be mounted with nut and lockwasher.They are used on instruments, switches, relays,transformers, amplifiers, etc.

(c) Rectangular shell connectors(Bendix SR; Cannon DPD). These connectors, asshown in figure 3-6, are flanged for panel or equipmentmounting. They consist of an aluminum alloy shell, rigidor resilient insert, and pin or socket contact. They areusually potted to protect connections against moisture atthe back of the connector. The mating faces are notmoisture sealed.

3-10 Change 3

TM 1-1500-204-23-4

Figure 3-4. MS Connectors

3-11

TM 1-1500-204-23-4

RECEPTACLE WITH PIN INSERTFigure 3-5. Subminiature Connectors Figure 3-6. Rectangular Shell Connectors

(d) Potting connectors. Theseconnectors, as shown in figure 3-7, are used only wherepotting is required. They are similar to other standardtypes except that they have a shorter body shell andinclude a potting boot. MS potting connectors areavailable in the following types:

• MS3103-a receptacle with flange formounting to a firewall or bulkhead.

• MS25183-a straight plug used at the end ofa wire or wire bundle.

• MS25183A-similarto MS25183, with theaddition of a grounding screw.

b. Inspection of Connectors. Ensure reliability ofconnectors by seeing that the following conditions aremet or that repairs are effected as required:

(1) Inspect connectors for security, evidenceof overheating, and exteriors for corrosion and cracks.

(2) Replace overheated connectors. Wiresleading to connectors must also be inspected fordeterioration due to overheating.

(3) Replace corroded connectors. Ifcorrosion is a recurring problem, install a pottedconnector.

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TM 1-41500-204-23-4

Figure 3-7. Potting Connectors

(4) Check fuses in associated circuitry forcorrect current rating.

(5) Ensure installation of MS3057 cabledamp adapters on all MS connectors except those thatare moisture-proof.

(6) Ensure that vinyl tape is wrapped aroundwires in MS3057 cable damp adapters so that tighteningof the cable damp adapter cap provides sufficient gripon the wires to keep tension from being applied to theconnector pins.

(7) Ensure that unused plugs andreceptacles are covered with moisture-proof paper, tiedwith waxed cord, and appropriately tagged to indicatethe circuit or accessory with which associated. The unitswill then be secured with damps to the aircraft structureor to other wiring that is properly anchored.

(8) Ensure that the coupling nut of ANconnectors is lockwired as required by the applicableaircraft maintenance handbook.

(9) Ensure that moisture-absorbent typematerial is not used as fill for MS3057 damps oradapters.

(10) Ensure that there is no evidence ofdeterioration of potting compound in potted connectors.

(11) Replace cracked dielectric inserts.c. Installation of Connectors on Wires. The

following paragraphs describe how solders and otherfastening means are matched to the wire type and to theinstallation as follows.

(1) Soldering. Soldering is used for tin-coated copper wire, coaxial, cable, and silver-coatedcopper wire.

(a) Tin-lead solder. Soft solder-60/40tin-lead (Federal Specification QQ-S-571, compositionSn 60) is used for fin-coated copper wire and for coaxialcable.

(b) Lead-silver solder. Soft solder-lead-silver (Federal Specification QQ-S-571,composition Ag 2.5 or Ag 5.5) is used for silver-coatedcopper wire.

NOTESolder cup contacts are silver orgold plated to provide low contactresistance. Silver plated contactshave pretinned solder cups. Goldplated contacts are not pretinnedbecause the gold preventsoxidation and is therefore alwayseasy to solder.

(2) Crimping. Crimp connections are usedfor nickel-dad copper wire, and tin, silver, or nickelcoated copper wire.3-4. Electrical System Components. Variouselectrical system components used in Army aircraft areexplained in the applicable maintenance manual.

a. Storage Battery. The battery provides enginestarting power, back-up emergency power, and gundrive power during firing of the turret weapons. Thebattery installation usually includes vent tubes, eyeboltsfor attaching tiedown rods, and a battery cable.

(1) Inspection. Inspect for corrosion,overheating, and overcharging. Every 120 days orevery 100 flight hours, remove the battery and return todirect

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TM 1-1500-204-23-4

support on direct exchange basis. TM 11-6140-203-23provides instructions for the proper maintenance ofaircraft nickel-cadmium batteries.

NOTEIf the battery being replacedexhibited any signs ofoverheating or overcharging (e.g., fumes or vapor coming fromthe vent tubing, free electrolyte ispresent inside the case, etc.)adjustment of the voltageregulator should bechecked/adjusted in accordancewith applicable maintenancemanual.

(2) Cleaning. Clean battery in accordancewith TM 11-6140-203-23. Clean battery compartment inaccordance with TM 1-1500-344-23.

b. Relays. Army aircraft use generator field,reverse current, bus control, non-essential bus, andelectronic/solid state relays. Relays are used for remotecontrol of circuits carrying heavy currents. Two relaytypes are shown in figure 3-8.

(1) Inspection. Inspect contact points forcorrosion.

(2) Replacement criteria. Replace whencontact points are corroded beyond depth of pin plating.

c. Inverters. Inverters, as shown in figure 3-9, aresometimes used to convert aircraft dc power to acpower. The ac power is mainly used for instruments,radios, radar, lighting, weapons, and other accessories.

(1) Types. There are two basic types ofinverters: the rotary and the static. Either type can besingle phase or multiphase.

(2) Inspection. Use the applicable aircraftmaintenance manual for inspection of inverters.General inspection procedures are as follows:

(a) Inspect case for cracks ordamage.

(b) Inspect electrical connectors forbroke pins or cracked connector inserts.

(c) Check for bonding and securitymounting.

(d) Check for faulty operation.(3) Adjustment. Usually, no adjustments

can be made. (Refer to TM 11-6130-385-34).

Figure 3-8. Typical Relays

Change 3 3-14

TM 1-1500-204-23-4

Figure 3-9. Inverter

(4) Replacement criteria. Inverterreplacement criteria are as follows:

• Replace rotary inverters whenany unusual bearing or gearnoises are detected duringoperation.

• Replace rotary inverters whencommutator bars are rough,scored, pitted, loose, high, orworn to the depth of insulatingmica between bars.

• Replace rotary inverter brushesthat are cracked, broken,chipped, unevenly worn, orworn beyond maximum wearingdepth slot.

• Replace static inverters whenelectrical connectors havebroken pins or crackedconnector inserts.

• Replace static inverters thathave cracked cases.

• Replace static inverters that failto operate properly.NOTE

Remove components from aircraftwhen replacing brushes.

d. Starters. Army aircraft are started by a devicecalled a starter. The starter develops large amounts ofmechanical energy, causing the engine to rotate.

(1) Types. The following paragraphs namevarious starters used with turbine engines. Turbineengine starters. Turbine engines use air-turbine(pneumatic) or electric starters. The air-turbine starter isbecoming the most common type.

(2) Inspection. General inspectionprocedures for starters removed from the aircraft andstarters installed on the aircraft are described in thefollowing paragraphs.

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(a) Starters removed from aircraft. Inspectthe starter as follows:

1 Inspect starter for dents andcracks.

2 Inspect starter for stripped ordamaged threads.

3 Inspect drive shaft spline forexcessive wear.

4 Inspect for smooth rotation andaxial/radial play of bearings.

5 Inspect electric starters for thefollowing:

• Starter brushes for freedom ofmovement in brush holders.

• Brush leads for deteriorationand chaffing.

• Brushes for wear.• Commutator for evidence of

arcing and presence of metalparticles.

6 Inspect air-turbine starters forthe following:

• Metal particles on drain plug.• Nozzle vanes that are broken.• Oil level.• Extemal oil leakage.7 Inspect hydraulic starters tor the

following:• Hydraulic fluid leakage.• Proper operation of

accumulator.NOTE

Consult applicable maintenancemanual for specific allowablelimits for starter brushes.

(b) Starters installed on aircraft.Inspect the starter as follows:

1 Open engine cowling asrequired.

2 Inspect all parts for obvioussigns of wear, cracks, distortion, corrosion, and otherdamage.

3 Inspect commutator for arcingand wear, using a mirror and bright light.

4 Inspect brush retainers forbreaks and unseated condition, using a mirror and brightlight.

5 Inspect brush heads forcondition, using a mirror and bright light.

6 Inspect mounting location andtorque.

7 Inspect for fluid leakage.8 Close cowling.

(3) Replacement criteria. Starterreplacement criteria are as follows:

• Replace when any unusualbearing or gear noises aredetected during operation.

• Replace when commutator barsare rough, scored, pitted, loose,high, or worn to the depth ofinsulating mica between bars.

• Replace brushes that arecracked, broken, chipped,unevenly worn, or worn beyondmaximum wearing depth slot.

• Replace when magneticparticles on drain plug arecoarser than fuzzy, such aschips, slivers, etc.

• Replace when there are intemalstarter malfunctions.

• Replace when seal assembliesare leaking.

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TM 1-1500-204-23-4

NOTE• Remove components from

aircraft when replacingbrushes.

• If brushes are worn to orbeyond allowable limits, brushleads are deteriorated,commutator shows evidenceof excessive arcing, or if metalparticles are present, replacethe starter.

Figure 3-11. Microswitche. Switches. Switches control the current flow in

most aircraft electrical circuits. A switch is used to start,stop, or change direction of current flow.

(1) Types. Toggle (see figure 3-10), push-button, micro switches (see figure 3-11), rotary-selector(see figure 3-12), and relay switches are used in Armyaircraft. Toggle switches are used more than any othertype of switch.

(2) Inspection. General inspectionprocedures for switches are as follows:

(a) Inspect terminals for distortion,malformed threads, and corrosion.

(b) Operate switch and observe forproper actuation.

(c) Inspect switch and mountinghardware for malformed threads and damage.

(3) Replacement criteria. Replace switcheswhen moving parts are binding, scraping, or have deadspots as evidenced by erratic operation of theirrespective components. Replace switches that do notpass a continuity check.

NOTEReplace toggle switches whendust boots are deteriorated.

f. Built-In Test Equipment. Built-in test equipmentis used to test various systems while installed upon theaircraft. When button or switch is activated a lightcomes on to indicate system continuity or properoperation. Built-in test equipment is commonly used incommunication systems, fire warning systems, andweapon systems.

g. Electronic Control Units. Electronic controlunits provide regulated power and contains thenecessary information to control weapon systems andother electronic equipment on Army aircraft.

(1) Types. Various types are used toregulate APU, weapon systems, and other installedequipment.

(2) Inspection. General inspectionprocedures for electronic control units are as follows:

(a) Inspect case for cracks or dents.(b) Inspect for secure mounting.(c) Inspect electrical connectors for

broken pins, cracked inserts, or corrosion in accordancewith TM 1-1500-343-23.

(3) Replacement criteria. Electronic controlunits shall be replaced if case is damaged or unit isfound to be defective. Perform functional check inaccordance with the applicable technical manual.

Change 3 3-17

TM 1-1500-204-23-4

Figure 3-12. Rotary-Selector Switch

h. Motors. Motors transform electrical energyinto mechanical energy. Many aircraft devices, from thestarter to the automatic pilot, depend on motors formechanical energy.

(1) Types. Series, shunt, and compoundmotors are the three basic types of dc motors. Inductionand synchronous motors are the two general types of acmotors.

(2) Inspection. General inspectionprocedures for motors are as follows:

(a) Check the operation of the unitdriven by the motor in accordance with the instructionscovering the specific installation.

(b) Check all wiring, connections,terminals, fuses, and switches for general condition andsecurity.

(c) Check brushes for condition,length, and spring tension. Minimum brush lengths,correct spring tension, and procedures for replacingbrushes are given in the applicable maintenancemanual.

(d) Inspect commutator for cleanness,pitting, scoring, roughness, corrosion or burning.

(e) Check for high mica (if the copperwears down below the mica, the mica will insulate thebrushes from the commutator).

WARNINGDrycleaning solvent is flammableand solvent vapors are toxic. UseP-D-680, Type II Solvent in a well-ventilated area. Keep away fromopen flames. Avoid prolongedsolvent contact with skin.

(f) Clean dirty commutators with acloth moistened with the recommended cleaningsolvent.

CAUTIONWhen polishing, never use emerypaper since it contains metallicparticles which may cause shorts.Damage to equipment may occur.When using compressed airreduce pressure to 30 psi orlower.

(g) Polish rough or corrodedcommutators with fine sandpaper (000 or finer) and blowout with compressed air.

(h) Inspect all exposed wiring forevidence of overheating.

(i) Adjust and lubricate the gearbox, orunit which the motor drives, in accordance with theapplicable maintenance manual covering the unit.

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TM 1-1500-204-23-4

NOTELubricate only if called for by themanufacturer's instructionscovering the motor. Most motorsused in aircraft require nolubrication between overhauls.

(3) Replacement criteria. Motor replacement criteria areas follows:• Replace if the insulation on leads or windings is

burned, cracked, or brittle.• Replace when any unusual bearing or gear noises

are detected during operation.• Replace when commutator bars are rough, scored,

pitted, loose, high, or worn to the depth of insulatingmica between bars.

NOTERemove motor from aircraft whenreplacing brushes.

• Replace brushes that are cracked, broken, chipped,unevenly worn, or worn beyond maximum wearingdepth slot.

i. Thermocouples. Thermocouples are usedthroughout the aircraft to detect and measuretemperature changes. A thermocouple, as shown infigure 3-13, is the junction of two dissimilar metals whichgenerate a small electric current according to the rate oftemperature rise. Thermocouples are commonly usedin fire warning systems and temperature indicatinginstruments on Army aircraft.

18

j. Ignition Systems. Ignition systems on Armyaircraft are used for engine starting and operation.Turbine engine ignition systems are usually operatedonly for a brief period during the starting cycle, duringtakeoff and landing, and during flight in bad weather(i.e., icing conditions). Turbine engines use capacitor orelectronic ignition systems.

(1) Troubleshooting. Use applicable aircraftmaintenance manuals to troubleshoot aircraft ignitionsystems. Table 3-3 is an example of a typicaltroubleshooting chart for an Army aircraft ignitionsystem.

(2) Replacement criteria. Refer toapplicable aircraft maintenance manual for replacementcriteria.

k. Lighting Systems. Army aircraft lightingsystems include cockpit lights, instrument panel andconsole lights, caution and warning light systems,position lights, anti-collision light, searchlight, andtransmission oil level lights. Instrument panel andcockpit lighting is provided to enhance night vision ofthe flight crew.

(1) Inspection. Inspect lights for corrodedlamp socket terminals, shorted or broken wires, crackedlens, or burned out lamp bulbs.

(2) Troubleshooting. Use applicable aircraftmaintenance manuals to troubleshoot aircraft lightingsystems. Table 3-4 is an example of a typicaltroubleshooting chart for an Army aircraft lightingsystem.

(3) Replacement criteria. Light assemblymay be repaired by replacing damaged or defectivecomponent parts. If light case is damaged beyondrepair, complete unit must be replaced. Replacemissing or burned out fuses, lamps, and discolored lens.

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TM 1-1500-204-23-4

Table 3-3. Typical Ignition System Troubleshooting Chart

Condition Isolation procedure Corrective action

1. Igniter fails to operate a. Determine that starter If starter switch contactswhen starter switch is switch contacts are not cor- are corroded or burned,depressed. roded or burned. replace switch.

b. Determine that key lock If key lock ignition switchignition switch is functional. is not functioning proper-

ly, replace switch.

c. Determine that fuel switch is If fuel switch is notfunctional. functioning properly,

replace switch.

d. Ensure igniter is functioning Replace igniter as re-properly. quired.

Table 3-4. Typical Lighting System Troubleshooting Chart

Condition Isolation procedure Corrective action

1. Switch fails to operate a. Determine that lighting If lighting switch/rheostatlights. switch/rheostat is function- is functioning properly,

ing properly. replace light.

2. One light dim or out a. Check that light is properly If lighting is not properlyintermittently. grounded. grounded, remove light

and clean ground.

b. Check for corrosion in light Clean light socketsocket. terminals or replace light

if required.

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TM 1-1500-204-23-4

CHAPTER 4INSTRUMENT SHOP

4-1. General Shop Rules. The maintenanceinstructions and procedures contained in this chapter aregeneral in nature and apply to instruments installed inDepartment of the Army aircraft. Specific maintenanceinstructions that are peculiar to particular instrumentsare contained in applicable aircraft maintenancemanuals and instrument overhaul manuals and will beused, when specified, in conjunction with instructionscontained in this chapter. The practices and proceduresdescribed in this chapter pertain to the manufacturingand repair functions of aviation activities and areapplicable to all levels of maintenance. Because of themany types of Army aircraft, each shop within themanufacturing and repair section must, of necessity,have personnel trained in general practices andprocedures to the extent that different type and modelaircraft do not upset a smooth running shop.

a. Responsibility. All supervisory personnel areresponsible for a continuing and effective shop safetyprogram. To implement and maintain this program,shop supervisors will utilize bulletin boards, signs, andany other effective method. Shop personnel willcooperate in the shop safety program by making helpfulrecommendations, and continually exercising care andcaution in the operation of all shop equipment. All shoppersonnel will strive to improve the safety program andbe especially alert to observe and correct hazardousconditions and unsafe shop practices. All accidents, nomatter how minor, shall be reported to the shopsupervisor, and all published instructions regardingsafety shall be strictly adhered to. Also, safetyengineers and safety officers will ensure that propersafety procedures are adhered to in accordance with AR385-10, Army Safety Program; AR-385-30, Safety-ColorCode Markings and Signs; The Occupational Safety andHealth Act of 1971, OSHA 1910.251; all applicable firecodes, NFPA 410; and other accepted civilian andmilitary safety practices.

b. Shop Housekeeping. Housekeeping is theyardstick by which the shops are judged. A clean, well-arranged shop is a safe shop and reflects credit on allpersonnel concerned with its operation. The followingshop practices shall be observed:

(1) Oil pans or drip pans shall be usedwhere leaking oil, grease, and similar materials maycause hazardous accumulations on equipment or floors.All spills shall be cleaned up immediately. Approved

sweeping compound may be used to remove thesematerials from the floor.

CAUTIONFloors shall not be cleaned withvolatile or flammable liquids. Aflammable film may remain andcause a fire hazard.

(2) Floors shall be maintained smooth andclean, free of all obstructions and slippery substances.Holes and irregularities in floors shall be repaired tomaintain a level surface free from tripping hazards.

(3) All unnecessary materials on walls shallbe removed and projections shall be kept to a minimum.

(4) Aisles shall be clearly defined and keptfree of hazardous obstructions. Where possible, aislesshall be suitably marked by painting.

(5) All machines, work benches, aisles, etc.,shall be adequately illuminated.

c. Equipment Safety. Unsafe equipment shall bereported immediately. The following equipment safetypractices shall be observed:

(1) Machines shall be located to provideoperators with sufficient space to handle materials andperform job operations without interference.

(2) Bolt down all machinery that can moveor walk due to vibration (drill press, bench grinder, etc.).

(3) Substantial low resistance conductorsshall be used to ground all stationary and portablemachines, equipment, or other devices in which staticcharges may be generated, or which require electricalcircuits of a hazardous nature.

(4) Shop machinery shall be operated onlyby qualified personnel observing safe practices.

(5) Safety devices, such as guards,interlocks, automatic releases, and stops, shall alwaysbe kept in operating condition.

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TM 1-1500-204-23-4

(6) Ensure that all unauthorized personnelare clear of area before opening valves or energizingelectrical circuits for starting machinery.

(7) Suitable mechanical guards, such asenclosures or barricades, shall be permanently installedon all machinery not already equipped with such toeliminate danger of injury from moving parts.

(8) Machinery shall not be adjusted,repaired, oiled, or cleaned while machine is in operationor power is on.

(9) Personnel operating machinery shallwear protective clothing as prescribed. A protectiveface shield or goggles shall be worn when operating agrinder regardless of whether grinder is equipped withattached shields.

(10) Jewelry shall not be worn whileperforming any maintenance.

(11) All electrical binding posts shall beinsulated, covered, and clearly marked with voltage andcurrent values.

(12) Do not lay soldering irons down excepton a holder. Always unplug soldering irons beforeleaving work stations. Soldering irons shall not be lefton for extended periods.

(13) Shop humidity should not be higherthan 50 percent, and temperature should be maintainedat approximately 77 °F (25 °C).

(14) Shop must be kept as clean and dust-free as possible.

d. Fire Safety. A constant vigilance must bemaintained to seek out fire hazards. Fire hazards areconstantly present in the shop where sparks, friction, orcareless handling can cause an explosion that maydestroy equipment or buildings, and injure or killpersonnel. The following fire safety practices shall beobserved:

(1) NO SMOKING signs shall be placed inareas where smoking could create a fire hazard.

(2) Personnel shall be trained in the use,knowledge, and location of shop fire fighting equipment.

(3) Each shop shall be equipped with fireextinguishers suited for type fire most likely to occur.

(4) Use correct fire extinguisher for class offire as follows:

• Class A fire (wood, paper, trash,etc). Use water orbromotrifluoromethane fireextinguisher.

• Class B fire (oil, paint, fuel,grease, etc.).bromotrifluoromethane or carbondioxide fire extinguisher, or drychemical extinguisher with ClassB rating.

• Class C fire (electricalequipment). Usebromotrifluoromethane or carbondioxide fire extinguisher, or drychemical extinguisher with ClassC rating.

• Class D fire (combustible metals)magnesium, titanium, zirconium,sodium, lithium, and potassium.Use dry powder-type fireextinguisher.

(5) Oily waste, rags, and similar combustiblematerials shall be discarded in self-closing metalcontainers which shall be emptied daily.

(6) Flammable materials shall not be storedin the shop.

(7) Use only approved cleaning solvents.

4-2. Maintenance of Shop Equipment. Maintenanceof instrument shop equipment is covered in the followingparagraphs. The instructions and procedures aregeneral in nature. Specific maintenance instructionsthat apply to particular pieces of equipment arecontained in applicable operation and serviceinstructions manuals.

a. Manometers. A manometer, as shown infigure 4-1, measures pressures, and is used for testingand calibrating differential and absolute pressureinstruments such as altimeter, airspeed indicators, rate-of-climb indicators, and suction gauges. Exercise carewhen reading a manometer, because curvature of theliquid level varies for mercury and water, as shown infigure 4-2.

(1) Inspection. Inspect manometers fordamage using the following procedures:

(a) Inspect glass cover for breaks andchips.

(b) Inspect glass tube for scratchesand dirt.

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TM 1-1500-204-23-4

Figure 4-2. Manometer Reading Level

WARNINGA scratched tube may shatterunder relatively low internalpressure.

(2) Cleaning. When visually determined asnecessary, periodically clean manometer using theinformation provided in the following paragraphs.

(a) Mercury cleaning. Use thefollowing procedures tor mercury cleaning:

WARNINGBe extremely careful whenhandling mercury. A very smallamount of mercury may producehazardous vapors. For methodsthat are used to dean up mercuryspillage, see paragraph 4-2a (6).

1 Clean mercury by washing in asolution of nitric acid, Federal Specification O-N-350 (10percent acid and 90 percent distilled water), or a solutionof sulfuric acid, Federal Specification O-S-09 (80percent acid and 20 percent distilled water).

2 Using apparatus shown in figure4-3, pour mercury through funnel and filter paper andallow to pass through acid solution.

3 After mercury collects at bottomof glass tube, open pinch cock and let dean mercurypass into beaker. Control pinch cock carefully toprevent acid solution from entering beaker.

4 Next, pass clean mercurythrough distilled water. Place beaker of dean mercuryon a sheet of asbestos and heat until dry over an openflame not to exceed 230°F (110°C).

(b) Manometer tube cleaning. Usethe following procedures for manometer tube cleaning:

CAUTIONWhen manipulating swab insidethe glass tubing, take care not toscratch the tube bore. Ascratched glass tube may shatterunder relatively low pressure.

1 Clean manometer tubes using aswab attached to a medium stiff piano wire. First swabout

Figure 4-1. Manometer

Change 3 4-3

TM 1-1500-204-23-4

Figure 4-3. Mercury Cleaning Apparatus

tube with solution of strong soap and ammonia, FederalSpecification O-A-445.

2 Next swab tube with a solutionof nitric acid, (25 percent acid and 75 percent distilledwater).

3 Rinse cleaned tube with distilledwater and dry with ethyl alcohol, Federal SpecificationO-E-760, Type II.

(3) Reservoir servicing. Fill reservoir whenrequired using the following procedures:

CAUTIONThe fill mark is located on a plate,or plates, near the bottom of themanometer scale. Either a waterfill or a mercury fill plate or bothmay be used. The presence ofeither or both plates indicates thematerials of construction used forparts that come in contact withthe indicating fluid and indicateswhat fluids may safely be used inthe manometer. Improper fluidmay cause damage to manometer.

(a) Remove fill plug from well andensure drain plug is tight.

(b) Pour indicating fluid into the wellto bring level up to the fill mark designated by the fillplate of the liquid being used.

NOTEKeep manometer reservoirs filledto specified level (mercury orwater). When water is used, add asmall amount of aniline dye, MIL-A-10450 (usually red), to facilitatequick and accurate readings.

(4) Operating procedures. With suitableconnections made and the manometer adjusted, applypressure (or vacuum) to the manometer and theinstrument being tested. Gradually apply the pressurecovering the entire instrument range and recordcomparative readings. Refer to TM 55-6685-201-12.

(5) Safety practices. All of the cleaningagents except water are toxic and should be used withcare.

WARNINGAll except water and carbontetrachloride are highlyflammable. Use in well-ventilatedarea, avoid inhalation of fumesand skin contact. When mixingacid and water together, alwayspour the acid into the water.Never pour water into acid. Avoidskin contact with the acid andwith the mixture. Avoid skincontact with the alcohol used fora rinse. Do not drink the alcohol:acute illness and death mayresult.

(6) Mercury spill procedures. Do thefollowing whenever mercury is spilled:

(a) Deactivate equipment, give thealarm, and activate exhaust systems which exhaustroom air to the outside.

(b) Deactivate air-conditioningsystems. Close vents and doors that would allowmercury fumes and vapors to enter other work areas.

(c) Leave the area and take action toassure that personnel are kept out of the contaminatedarea.

Change 3 4-4

TM 1-1500-204-23-4

(d) Contact safety specialist andmedical personnel to determine the extent ofcontamination and corrective procedures to follow. Amercury vapor detector will be used to monitor the air inareas where mercury contamination is suspected.Operations will not be resumed until the concentration ofmercury vapor drops below 0.05 milligram per cubicmeter.

(e) Recover visible droplets ofmercury with a mercury vacuum cleaner, mercuryscoop, or a suction device equipped with a water trap.The contaminated areas should then be coated with amercury suppressant, such as one percent calciumpolysulphide, flours of sulfur, or equivalent; thencarefully sweep and pick up contaminated suppressantmaterials, and wet-mop the area. The decontaminantsdo not remove mercury but coat the droplets and thusreduce volatilization of the mercury. Monitoring of thearea with a mercury vapor detector should be performedto determine the thoroughness of the decontaminationprocedures.

(f) Air-conditioning systems ofSheffield Modulabs will be deactivated untilcontaminated areas have been decontaminated. Areawill be monitored with a mercury vapor detector todetermine thoroughness of decontamination.

(7) Maintenance. To ensure that themanometer is ready for operation at all times, it must beinspected systematically before, during, and afteroperation. Defects should be discovered and correctedbefore they result in serious damage or failure. Defectsor unsatisfactory operating characteristics beyond thescope of the operator to correct must be reported at theearliest opportunity to organizational maintenance.Responsibility for performance of preventivemaintenance services rests not only with the operator,but with the entire chain of command from section chiefto commanding officer.

b. Vacuum Chambers. Vacuum chambermaintenance procedures are covered in the followingparagraphs.

(1) Inspection. Inspect door seal for defectsor damage. When seal is damaged to the extent that itwill not seal properly, it shall be replaced. A thin coatglycerol, Federal Specification O-G-491, may provide atemporary seal when defects are slight.

WARNINGDrycleaning solvent is flammableand solvent vapors are toxic. UseP-D-680, Type 11 Solvent in awell-ventilated area. Keep awayfrom open flames. Avoidprolonged solvent contact withskin.

(2) Cleaning. Periodically clean vacuumchamber with a cloth dampened in drycleaning solvent,Federal Specification P-D-680, and wipe dry with aclean cloth.

c. Turntable Instrument Tester. The turntableinstrument tester, as shown in figure 4-4, is used fortesting gyroscopic instruments that are not required toindicate aircraft attitude.

(1) Inspection. Periodic inspection of theunit is required after every 200 hours of operation. Theonly inspection required is for chipped, broken, orcracked gears and components.

Figure 4-4. Turntable Instrument Tester

4-5

TM 1-1500-204-23-4


(2) Cleaning. Clean turntable assemblyperiodically with cloth dampened in drycleaning solvent,Federal Specification P-D-680, Type II, and wipe drywith a clean cloth.

(3) Operating procedures. Refer to TM 55-4920-377-1 3&P for tester operating procedures.

(4) Safety practices. The following generalsafety practices shall be observed:

• Do not use any other electricalpower except 115 vac at 60 Hz.Other frequencies will alter theoperation of the turntable.

• Do not over tighten gear clutchwhen making adjustments.

(5) Maintenance. The followingmaintenance procedures are for turntable instrumenttesters:

(a) Using 1 drop of lubricating oil,MIL-L-8383, periodically lubricate sleeve bearings.

(b) Lubricate worm and worm wheelgear teeth with grease, MIL-G-23827.

(c) Lubricate gear shaft collar withgrease, MIL-G-23827.

d. Scorsby Base. The Scorsby base, as shown infigure 4-5, is used as a primary test apparatus for testinggyroscopic instruments.

(1) Inspection. Inspect the Scorsby baseusing the following procedures:

(a) Inspect fan belt once a month forwear and looseness. Replace fan belt if worn or loose.

(b) Inspect motor for smoothoperation. Replace motors that do not operatesmoothly.


Figure 4-5. Scorsby Base

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TM 1-1500-204-23-4

(2) Cleaning. Clean all exposed surfaceswith a cloth moistened in drycleaning solvent, FederalSpecification P-D-680, Type II, and wipe dry with a dryclean cloth.

(3) Operating procedures. Refer to TM 55-4920-229-12 for proper operating procedures.

(4) Maintenance. Maintenance of theScorsby base is as follows:

NOTEThe oil in gear reducer shouldflow slightly when petcock isopened.

(a) When oil does not flow, add oil,Federal Specification VV-L-1071, until proper level isreached.

(b) Lubricate two ball joints whichsupport head of Scorsby base with grease, MIL-G-23827.

e. Pitot Static System Tester. The tester is aportable, self contained vacuum and pressure testerwhose purpose is the testing of aircraft altimeters, rateof climb indicators, and fuel pressure gauges.

(1) Inspection. Inspect for defects,damaged leads, broken connections, and evidence ofleakage.

WARNINGDrycleaning solvent is flammableand solvent vapors are toxic. UseP-D-680, Type 11 Solvent in awell-ventilated area. Keep awayfrom open flames. Avoidprolonged solvent contact withskin.

(2) Cleaning. Clean with a cloth moistenedin drycleaning solvent, Federal Specification P-D-680,Type II, and wipe dry with a clean cloth.

(3) Operating procedures. Refer to TM 55-4920-231-14 for proper operating procedures.

(4) Safety practices. Secure all connectionsto prevent leakage or loosening due to vibration.Remove sleeve from pitot tube and secure allconnections to prevent leakage or loosening due tovibration.

(5) Maintenance. To ensure that theequipment is ready for operation at all times it must beinspected systematically so that defects may bediscovered and corrected before they can result inserious damage or failure. Defects discovered duringoperation of unit will be noted for future correction to be

made as soon as operation has ceased, or operation willbe stopped if defect will cause damage to equipment,should operation be continued. After operation, serviceswill be performed at intervals based on normal operationof equipment, reducing interval to compensate forabnormal conditions. Defects or unsatisfactoryoperation beyond the scope of the operator to correctmust be reported at earliest opportunity. Maintenanceprocedures are covered in applicable maintenancemanuals.

f. Jetcal System Tester. A jetcal tester, as shownin figure 4-6, is a portable instrument made ofaluminum, stainless steel, and plastic. The majorcomponents of the analyzer are the thermocouple, rpm,Exhaust Gas Temperature (EGT) indicator, resistance,and insulation check circuits, and the potentiometer,temperature regulators, meters, switches, and all thenecessary cables, probes, and adapters for performingall tests. The jetcal tester is used to analyze turbineengines.

(1) Purpose and uses. The jetcal testermay be used to:

• Functionally check the aircraftEGT system for error withoutrunning the engine ordisconnecting the wiring.

• Check individual thermocouplesbefore placement in a parallelharness.

• Check each engine thermocouplein a parallel harness forcontinuity.

• Check the thermocouples andparallel harness for accuracy.

• Check the resistance of the EGTcircuit.

• Check the insulation of the EGTcircuit for shorts to ground, or forshorts between leads.

• Check EGT indicators (either in orout of the aircraft) for error.

• Determine engine rpm with anaccuracy of (± 0.1) percent duringengine runup. Added to this is thechecking and troubleshooting ofthe aircraft tachometer system.

Change 3 4-7

TM 1-1500-204-23-4

Figure 4-6. Jetcal Tester• Establish the proper relationship

between the EGT and engine rpmon engine runup during tabbing(micing) procedures by the rpmcheck (takcal) and potentiometerin the jetcal analyzer. (Tabbingprocedures are those proceduresfollowed when adjusting fixedexhaust nozzle exit areas.)

• Check aircraft fire detector,overheat detector, and wing anti-icing systems by using tempcalprobes.WARNING

Drycleaning solvent is flammableand solvent vapors are toxic. UseP-D-680, Type II Solvent in a well-ventilated area. Keep away fromopen flames. Avoid prolongedsolvent contact with skin.

(2) Cleaning. Clean jetcal tester with a clothmoistened in drycleaning solvent, Federal SpecificationP-D-680, Type II, and wipe dry with a dean cloth.

(3) Operating procedures. Refer to step-by-step procedures on the instruction plate of the jetcaltester.

(4) Safety practices. Observe the followingsafety practices while operating the jetcal analyzer:

• Never use a volt-ohmmeter tocheck the potentiometer forcontinuity. If a volt-ohmmeter isused, damage to thegalvanometer and standardbattery cell will result.

• Check the thermocouple harnessbefore engine runup. This mustbe done because the circuit mustbe correct before thethermocouples can be used fortrue EGT pick up.

• For safety, ground the jetcalanalyzer when using an ac powersupply. Any electrical equipmentoperated on ac power andutilizing wire-wound coils such asthe probes with the jetcalanalyzer, has an induced voltageon the case that can bedischarged if the equipment is notgrounded. This condition is notapparent during dry weather, buton damp days the operator canbe shocked slightly. Therefore,for protection of the operator, thejetcal analyzer should begrounded using the pigtail lead inthe power inlet cable.

4-8

TM 1-1500-204-23-4

• Use heater probes designed foruse on the engine thermocouplesto be tested. Temperaturegradients are very critical in thedesign of heater probes. Eachtype of aircraft thermocouple hasits own specially designed probe.Never attempt to modify heaterprobes to test other types ofthermocouples.

• Do not leave heater probesassemblies in the tailpipe duringengine runup.

• Never allow the heater probes togo over 1,652°F (900°C).Exceeding these temperatureswill result in damage to the jetcalanalyzer and heater probeassemblies.

(5) Maintenance. Apply a few drops of oil tohinges, then wipe off excess oil with clean cloth. Withwheels removed, apply a light coating of grease towheel mount axles.4-3. Instruments and Instrument SystemMaintenance. General maintenance procedures forinstruments and instrument systems are covered in thefollowing paragraphs. General precautions are asfollows:

• Instruments are delicate devicesand will always be handled verycarefully.

• Always replace instruments withanother of like kind and type, or asuitable substitute as listed inapplicable repair partsappendixes and special tool lists.

• Configuration of aircraft (locationand positioning of instruments orcomponents) will not be alteredunless authorized by AVSCOM.

• Never exceed pressures or valuesspecified in publications dealingwith test procedures for thatparticular instrument.

• Thread compound will be used onall threaded coupling connectors(except electrical) of theinstrument system. Threadcompound shall be applied so thatentrance into gauge is prohibited(i.e., apply a light coating to twothreads of male end, starting at

second thread). Pliers andadjustable wrenches will not beused on coupling connectors.

a. Inspection of Instrument Systems. Instrumentsystems will be inspected and functionally checked inthe aircraft. However, indicators or transmitters may beremoved from the aircraft and bench checked wheneverfacilities permit.

b. Inspection Requirements. Use the followingparagraphs to inspect instruments.

(1) Range markings. Instruments must berange-marked in accordance with applicable operatormanual and TM 55-1500-345-23.

(2) Mounting. Shock-mounted instrumentpanels will be free to move in all directions with aminimum clearance of 1/4 inch between panel and itssupporting structures. When panel does not havespecified clearance, inspect rubber shock mounts forlooseness, cracks, or deterioration. Loose mountingswill be tightened, and cracked or deteriorated mountingswill be replaced.

(3) Connecting lines. Wiring or flexibletubing behind instrument panel will be sufficiently longto permit easy connection to indicators (a minimum of 4inches in front of panel). All electrical wiring will beanchored to prevent swinging or sagging, but must notinterfere with free movement of shock-mountedinstrument panel.

NOTEExamine all instrumentconnection threadings and all lineconnection threadings to be surethey are the same thread. Do notforce under any circumstances.

(4) Operation of instruments. Instrumentsmust operate satisfactorily as required by applicableoperator manuals. Instruments that do not operatesatisfactorily will be replaced.

(5) Physical defects. Instruments withphysical defects or damage must be replaced.

(6) Corrosion. Replace instrument ifcorrosion damage is present.

(7) Color coding. The Army uses two typesof identification systems to color code the plumbinglines and electrical conduits of aircraft. The twosystems used are the printed-symbolized tape system,the preferred

4-9

TM 1-1500-204-23-4

method, and the solid color band, the alternate method.Identification tapes will be applied to plumbing lines andelectrical conduits of all Army aircraft.

(a) Printed-symbolized tape system. Thislatest and preferred system utilizes printed colored tape(1 inch wide) with geometrical symbols. The mainfunction of the line is printed on the tape.

(b) Solid color band system. This alternatesystem consists of the use of one, two, or three bands of1/2-inch wide solid colored tape wrapped on variouslines for identification. .

c. Pitot Static System. The pitot static system, asshown in figure 4-7, consists of pitot-static tubes or pitottubes with static pressure ports or vents and their relatedheaters, if any, and includes lines, tubing, water drainsand traps, and selector valves. Pressure actuatedindicators such as the altimeter, airspeed, and rate-of-climb indicators, and control units such as air datatransducers, and automatic pilots may be connected tothe system.

(1) Principles of operation. Ram pressureenters the pressure line through an opening at theforward end of pitot tube and passes through thepressure line to the airspeed indicator. Static pressureis passed through the static pressure line to the verticalvelocity indicator, altimeter, and airspeed indicator staticpressure connections.

(2) Inspection of System. Inspect airpassages in the systems for water, paint, dirt or otherforeign matter. Remove obstructions in accordance withapplicable maintenance manual.

(a) Required equipment. A pitot staticsystem tester, as shown in figures 4-8 and 4-9, isneeded to complete pitot static system tests.

(b) Pitot line leak test procedures.Pitot line leak test connections are shown in figure 4-8.Do tests using the procedures that follow:

1 Seal pitot tube drain holes airtight with pressure sensitive tape, Federal SpecificationA-A-883.

CAUTIONDo not apply suction to pitot linesor pressure to static lines.Damage to bellows, indicators,and computer equipment mayoccur.

(3) System Leak Testing. Pitot-static leaktests should be made with all instruments connected toassure that no leaks occur at instrument connections.Such tests should be made whenever a connection hasbeen loosened or an instrument replaced. Pitot systemsshould be tested in accordance with the aircraftmanufacturer's instructions. If the manufacturer has notissued instructions for testing pitot systems, thefollowing may be used:

Figure 4-7. Pitot Static System

4-10

TM 1-1500-204-23-4

Figure 4-9. Static Leak Test Connections

Figure 4-8. Pitot Leak Test Connections

4-11

TM 1-1500-204-23-4

2 Slowly apply pressure to pitotline until the airspeed indicator reads normal cruisingspeed. Use appropriate power supply in accordancewith pilot-static system being tested. Pinch off pressuresupply at flexible tube.

3 Tap indicator to remove frictioneffects. When indicator pointer drops more than 10miles an hour (8.7 knots) in 1 minute, a leak is indicated.Repair faulty connections or cracks in pitot lines asnecessary.

4 Remove test apparatus frompitot tube.

5 Remove tape from the pitottube drain holes.

(c) Static line leak test procedures.Static line leak test connections are shown in figure 4-9.Do tests using the procedures that follow:

1 Set altimeter pointers to fieldelevation.

2 Tape unused static ports.CAUTION

When applying suction to thestatic line, the airspeed indicatorand computer equipment may bedamaged.

3 Slowly apply suction to staticline until airspeed indicator reaches full scale. Closevacuum source and tap altimeter at same time until rateof climb stabilizes at zero. After stabilization, thealtimeter should not drop more than 100 ft. in the nextminute.

4 Slowly remove suction fromstatic lines until altimeter reads field elevation.

5 Remove test apparatus fromstatic port.

6 Remove tape from static ports.d. Pitot Static System Heater. Pitot static tubes,

as shown in figure 4-10, are provided with heaters toprevent icing during flight. Principles of operation andtesting procedures are described in the followingparagraphs.

(1) Principles of operation. During ice-forming conditions, pilot heat is selected by a switch inthe cockpit. Heating elements heat the pitot head toprovide pitot anti-icing.

(2) Testing. Test pitot static system heaterusing the following paragraphs.

(a) Required equipment. No specialrequired equipment is needed.

(b) Pitot static heater test procedures.Test using the procedures that follow:

WARNINGExercise caution when touchingpitot tube with fingers as seriousburns may result.

1 Turn aircraft battery switch ON.2 Turn pilot heater switch ON and

check for heat rise by touching pitot head lightly withfingers.

3 When elements do not heatwithin 2 minutes, and wiring is correct, pitot head mustbe replaced.

e. Airspeed Indicators. Principles of operator andtesting procedures are described in the followingparagraphs.

(1) Principles of operation. The airspeedindicator, as shown in figure 4-11, shows the speed ofthe aircraft relative to the air mass through which it isflying. Each instrument is a pressure-sensitive unitactuated by the differential between impact and static airpressures. The impact (pitot) pressure is transmittedfrom the pitot head to the inside of the pressure-sensitive diaphragm in the instrument case, while staticpressure is applied to the interior of the case.

Figure 4-10. Pitot Tube

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TM 1-1500-204-23-4

Figure 4-11. Airspeed Indicator

Movements of the capsule caused by the resultingpressure difference are converted by mechanicallinkage to pointer movement over the calibrated dial.The airspeed indicator face is graduated in knots.

(2) Testing. The following paragraphsdescribe test procedures and replacement criteria forairspeed indicators while installed on aircraft.

(a) Required equipment. To test theairspeed indicator, use the following requiredequipment:

• Pitot static system tester (Thetester must show evidence ofcurrent calibration)

• Adapters and fittings• Plugs and caps(b) Airspeed indicator test

procedures. Test using the procedures that follow:1 Disconnect pitot static lines on

airspeed indicator.2 Plug lines to prevent

contamination.3 Connect airspeed indicator to

pitot static system tester.

4 Compare the reading of theinstalled indicator against the reading on the tester atthe test points shown in table 4-1.

NOTE• Tests do not need to go

higher than the rated speed ofthe aircraft.

• Gently tap indicator beforereading.

5 Perform pitot line leak testparagraph 4-3c(2)(b).

6 Perform static line leak testparagraph 4-3c(2)(c).

7 Disconnect pitot static systemtester.

8 Connect pitot static lines toairspeed indicator.

(c) Replacement criteria.Replacement criteria are as follows:

• Replace airspeed indicator if itfails to meet the tolerances intable 4-1.

NOTEThe airspeed indicator does notalways have graduations for eachknot; therefore, interprettolerances 3, 4, and 6 to retainrather than to replace indicator.

• Airspeed indicators which do notpass the performancerequirements shall be turned infor overhaul.

f. Vertical Speed Indicators. Principles ofoperation and testing procedures are described in thefollowing paragraphs.

(1) Principles of operation. The verticalvelocity indicator, as shown in figure 4-12, located onthe flight instrument panel, indicates the rate of ascentor descent in feet per minute. The pointer movesclockwise when indicating ascent and counterclockwisewhen indicating descent. The vertical velocity indicatorincorporates two air-enclosing chambers: a pressure-sensitive diaphragm vented directly to the static line,and the air-tight case of the instrument vented to thestatic line through a thin-walled porcelain capillary tube.

4-13

TM 1-1500-204-23-4

Table 4-1. Airspeed Indicator Test Tolerances

MS28045 MS28021 MS28046Airspeed test 10 to 150 20 to 250 40 to 400 points

(knots) (knots) (knots) ( = knots)

40 3 5 460 3 3 380 3 3 3

100 3 4 3120 3 4 3140 3 5 4160 5 4180 5 4200 5 5220 5 5240 5 5260 5280 5300 5320 6340 6360 6380 6400 6

Changes in pressure resulting from changes in altitudeare transmitted quickly to the inside of the diaphragmand slowly through the capillary tube to the inside of thecase. This results in a pressure differential causing thediaphragm to expand or contract according to the rate ofchange of altitude. The motion of the diaphragm istransmitted to the pointer. When the aircraft assumes afixed altitude, the pressure in the diaphragm and caserapidly equalize and the pointer returns to 0. Anadjusting screw, located in the lower left corner, isprovided for adjusting the zero indication.

(2) Testing. The following paragraphsdescribe test procedures and replacement criteria forvertical speed indicators while installed on aircraft.

(a) Required equipment. To test thevertical speed indicator, use the following requiredequipment:

• Pitot static system tester• Adapters and fittings• Plugs and caps

(b) Vertical speed indicator testprocedures. Functionally test using a pitot and statictester.

(c) Vertical speed indicatoradjustment. With all aircraft systems inoperative, setvertical velocity indicator pointer to 0 (nine o' clockposition) by means of adjusting screw at lower left ofinstrument face.

(d) Replacement criteria. Replaceindicators with dents or cracks in glass, stripped fittings,or illegible markings.

g. Altimeters. Principles of operation and testingprocedures for three pointer and counter drum pointeraltimeters are described in the following paragraphs.

(1) Principles of operation. Altimeters, asshown in figure 4-13, have pressure-responsiveelements (aneroids) which expand or contract with thepressure change of different altitudes. The expansion orcontraction of the aneroid with pressure changesactuates the linkage which is connected to the indicatinghands that show altitude. A bi-metal yoke isincorporated around the aneroid to compensate fortemperature effects on the metals of the aneroidmechanism.

4-14

TM 1-1500-204-23-4

Figure 4-13. Altimeter

(2) Testing while altimeter is installed onaircraft. General test procedures are described in thefollowing paragraphs.

(a) Leak test. Using the pitot-staticsystem tester, test for leakage in accordance withparagraphs 4-3c (2) (b) and 4-3c (2) (c).

(b) Altimeter setting test. Altimeteraccuracy can be checked by setting the altimeter at thecorrect barometric setting and noting field elevation by

contacting control tower. Altimeter should read fieldelevation when correct barometric setting is used. See

(3) Testing altimeter when removed fromaircraft. Test procedures and replacement criteria for

Figure 4-12. Vertical Speed Indicator

Change 5 4-15

Table 4-2 for acceptance/rejection criteria with aircraftpower on.

TM 1-1500-204-23-4

three pointer and counter drum pointer altimeters aredescribed in the following paragraphs.

(a) Three pointer altimeters. Performthe following tests in the instrument shop. Tests shall beperformed at approximately 77 (±9)°F or 25 (±5)°Cusing a Hass Type A-1, or equivalent mercurialbarometer. Unless otherwise specified, each test forperformance may be conducted with the instrumentsubjected to vibration to remove friction effects, andwith the barometric pressure scale of the altimeter set to29.92 inches of mercury (Hg).

1 Scale error test. With thebarometric pressure at 31.02 inches of mercury, thealtimeter shall be subjected successively to pressurescorresponding to the altitudes specified in table 4-2 upto the maximum altitude. The reduction in pressureshall be made at a rate not in excess of 20,000 feet perminute to within approximately 300 feet of the test point.The test point shall be approached at a rate compatiblewith the test equipment. The altimeter shall be kept atthe pressure corresponding to each test point for at least1 minute, but not more than 10 minutes, before areading is taken. The error at all test points must notexceed the tolerances specified in table 4-2.

2 Hysteresis test. The hysteresistest shall begin not more than 15 minutes after the initialexposure of the altimeter to the pressure correspondingto the upper limit of the scale error test prescribed inparagraph 1; and while the altimeter is at this pressure,the hysteresis test shall commence. Pressure shall beincreased at a rate simulating descent in altitude at therate of 5,000 to 20,000 feet per minute until within 3,000feet of the first test point (16,000 feet). The test pointshall then be approached at a rate of approximately3,000 feet per minute. The altimeter shall be kept atthis pressure for at least 5 minutes, but not more than15 minutes, before the test reading is taken. After thereading has been taken, the pressure shall be increasedfurther, in the same manner as before, until the pressurecorresponding to the second test point (12,000 feet) isreached. The altimeter shall be kept at this pressure forat least 1 minute, but not more than 10 minutes, beforethe test reading is taken. After the reading has beentaken, the pressure shall be increased further, in thesame manner as before, until atmospheric pressure isreached. The reading of the altimeter at either of thetwo test points shall not differ by more than thetolerance specified in table 4-3 from the reading of thealtimeter for the corresponding altitude recorded duringthe scale error test prescribed in paragraph 1.

3 After-effect test. Not more than5 minutes after completion of the hysteresis testprescribed in paragraph 2, the altimeter reading(corrected for any change in atmospheric pressure) shallnot differ from the original atmospheric pressure readingby more than the tolerance specified in table 4-3.

4 Friction test. The altimeter shallbe subjected to a steady rate of decrease of pressureapproximating 750 feet per minute. At each altitudelisted in table 4-4, the change in reading of the pointersbefore and after vibration shall not exceed thecorresponding tolerance listed in table 4-4.

5 Case leak test. The leakage ofthe altimeter case, when the pressure within itcorresponds to an altitude of 18,000 feet, shall notchange the altimeter reading by more than the toleranceshown in table 4-3 during an interval of one minute.

6 Barometric scale error test. Atconstant atmospheric pressure, the barometric pressurescale shall be set at each of the pressures (falling withinits range of adjustment) that are listed in table 4-2, andshall cause the pointer to indicate the equivalent altitudedifference shown in table 4-5 within a tolerance of 25feet.

(b) Counter drum pointer altimeters.Perform the following tests in the instrument shop.Tests shall be performed under the following conditionsusing a Hass Type A-1, or equivalent mercurialbarometer or manometer:

• Room temperature 77 (±9)°F or25 (±5)°C.

•

of mercury (Hg).

• Lighting power 5.0 (±0.1) volts ac

Barometric pressure 29.92 inches

or dc or 4.0 watts maximum.

• Vibrator power 28 (±1.0) volts dcor 90.0 milliamps.

1 Scale error test. Connectbarometer and vacuum pump to altimeter. Connectelectric lines to altimeter. The scale error check (ordiaphragm error check) is conducted as follows. For aperiod of at least 6 hours prior to testing, altimeter shallbe held at atmospheric pressure. The barometric dialshall be set at 29.92 inches of mercury (Hg) and remainthere throughout the test. The direction of approach in setting

4-16 Change 3

TM 1-1500-204-23-4

Table 4-2. Scale Error (Three Pointer)

Equivalent atmosphericpressure (mercury)

Altitude Tolerancetest (± feet)

pressure at(feet) (mm) (inches) ± 25°C

0 760.00 29.921 30500 746.37 29.385 35

1,000 732.93 28.856 351,500 719.70 28.335 402,000 706.65 27.821 402,500 693.80 27.315 453,000 681.14 26.817 454,000 656.38 25.842 505,000 632.36 24.896 556,000 609.05 23.978 608,000 564.51 22.224 70

10,000 522.65 20.577 8012,000 483.34 19.029 9014,000 446.46 17.577 10015,000 428.90 16.886 10516,000 411.90 16.216 11018,000 379.53 14.942 12020,000 349.25 13.750 13022,000 320.96 12.636 14025,000 282.03 11.103 15530,000 225.69 8.885 180

Table 4-3. Test Tolerances (Three Pointer)

ToleranceTest (feet)

Case leak test ............................................ ±100Hysteresis test:

First test point (16,000) 75Second test point (12,000) 75

After-effect test ..............................................30

Table 4-4. Friction Test Tolerances(Three Pointer)

Altitude Tolerance(feet) (feet)1,000........................................... ±702,000........................................... 703,000........................................... 705,000........................................... 70

10,000........................................... 8015,000........................................... 9020,000........................................... 10025,000........................................... 12030,000........................................... 140

Change 3 4-17

TM 1-1500-204-23-4

the barometric dial is immaterial. The vibrator must beenergized throughout this test. Beginning with thebarometric pressure at 31.018 inches of mercury thealtimeter shall be subjected to successively decreasingthen increasing pressures corresponding to altitudesspecified in table 4-6. The reduction m pressure shallbe made at a rate not in excess of 10,000 feet perminute to within approximately 300 feet of the test point.The test point shall be approached at a rate compatiblewith

Table 4-5. Pressure Altitude Difference(Three Pointer)

Pressure Altitude(inches of difference

mercury (Hg)) (feet)28.10 .......................................... -172728.50 .......................................... -134029.00 .......................................... -86329.50 .......................................... -39229.92 .......................................... 030.50 .......................................... +53130.90 .......................................... +89330.99 .......................................... +974

Table 4-6. Scale Error (Counter Drum Pointer)Altitude Equivalent pressure Tolerance

(feet) Inches of mercury-Hg) ±(feet)-1000 31.018 ±30

0 29.921 ±30500 29.385 ±35

1000 28.856 ±352000 27.821 ±403000 26.817 ±455000 24.896 ±508000 22.224 ±60

10000 20.577 ±6512000 19.029 ±7015000 16.886 ±8018000 14.942 ±9020000 13.750 ±9525000 11.103 ±10530000 8.885 ±11535000 7.041 ±12538000 6.097 ±14040000 5.538 ±14045000 4.355 +18550000 3.425 ±500

the test equipment. The altimeter shall be kept at thepressure corresponding each test point for at least oneminute, but not more than five minutes before a readingis taken. The error at all test points must not exceed thetolerance specified in table 4-6.

2 Hysteresis test. The hysteresistest shall begin not more than 15 minutes after initialexposure of the altimeter to the pressure correspondingto the upper limit of the scale error test prescribed inparagraph 1. While the altimeter is at this pressure, thehysteresis test shall commence with vibrator operative.Pressure shall be increased at a rate simulating adescent in altitude at the rate of 5,000 to 20,000 feet perminute until within 3,000 feet of the first test point, table4-7. The test point shall then be approached at a rate ofapproximately) 3,000 feet per minute. The altimetershall be kept at this pressure for at least 1 minute, butnot more than 15 minutes, before the test reading istaken. After the reading has been taken, the pressureshall be increased further, in the same manner asbefore, until the pressure corresponding to the secondtest point table 4-7, is reached. The altimeter shall bekept at this pressure for at least 1 minute, but not morethat 10 minutes, before the test reading is taken. Whenthe reading has been taken, the pressure shall beincreased further, in the same manner as before, untilthird test point table 4-7 is reached. The reading of thealtimeter at either of the three test points shall not differby more than the tolerance specified in table 4-7 fromthe reading of the altimeter for the correspondingaltitude recorded during the scale error test prescribed inparagraph 1.

3 After-effect test. With vibratoroperative and not more than five minutes aftercompletion of the hysteresis test prescribed inparagraph 2 the altimeter reading (corrected for anychange in atmospheric pressure) shall not differ fromthe original atmospheric pressure reading by more thanthe tolerance specified in table 4-7.

Table 4-7. Test Tolerances (Counter Drum Pointer)Tolerance

Test (feet)Case LeakTest ...................................... 100Hysteresis Test:First Test Point (25,000)........................ 60Second Test Point (20,000)................... 60Third Test Point (0) ............................... 30After-Effect Test.................................... 30

Change 3 4-18

TM 1-1500-204-23-4

4 Friction stop and jump test. Thealtimeter shall be tested for friction in both ascendingand descending directions at the test points specified intable 4-8. With the internal vibrator energized, thepressure to the static port of the altimeter shall beapplied at the rates indicated for the test points in table4-8. The change in the indicating position of the pointer,due to apparent stopping and jumping as the counter isturning or at any other place around the dial, shall berecorded as friction and shall not exceed the tolerancesspecified in table 4-8, column C. This test shall berepeated with all electrical power off. The stop andjump friction for the test as specified shall not exceedthe tolerances in specified table 4-8, column D.

5 Static friction test. At thecompletion of the friction stop and jump test paragraph4, and with all electrical power off, the altimeter shall besubjected to a constant rate of decreasing pressure notexceeding 3,000 feet per minute until the pressure iswithin 100 feet of the tolerance listed in table 4-9 foreach test point. At this time, the rate of pressurechange shall be gradually decreased until the desiredtest point is obtained. The pressure shall then be heldconstant while two readings of the altimeter are taken,the first without the integral vibrator operating and thesecond with the vibrator operating. The differencebetween the two readings shall be recorded as staticfriction and shall not exceed the tolerances listed intable 4-9.

6 Case leak test. The leakage ofthe altimeter case, when the pressure within itcorresponds to an altitude of 30,000 feet, shall notchange the altimeter reading by more than the toleranceshown in table 4-7 during an interval of one minute.

7 Barometric scale error test. Atconstant atmospheric pressure, the barometric pressurescale shall be set at each of the pressures (falling withinits range of adjustment) that are listed in table 4-10 andshall cause the pointer to indicate the equivalent altitudedifference shown in table 4-10 within a tolerance of 25feet.

8 Internal lighting test. Red andwhite internal lighting shall be functionally tested inaccordance with applicable maintenance manual.

(c) Replacement criteria. Aftercompletion of tests, a tamper seal shall cover thebaroset locking screw. An inspection sticker with date ofcompleted bench test shall be placed on the outside ofthe case. Compute reinspection date from date on theinspection sticker.

h. Direct Reading Pressure Indicators. Principlesof operation, types, and testing of direct readingpressure indicators are described in followingparagraphs.

(1) Principles of operation and typesindicators. Direct reading pressure indicators areconnected directly to pressure source by tubing orflexible hose. Typical of the direct reading pressureindicators are the fuel pressure, oil pressure, hydraulicpressure, manifold pressure, and vacuum pressure.

(2) Testing. The following paragraphsdescribe tests and replacement criteria for direct readingpressure indicators.

(a) Pressure pointer oscillation test.When pressure indicator pointers oscillate excessively(more

Table 4-8. Friction Stop and Jump Error (Counter Drum Pointer)

Column A Column B Column C Column Dtest point rate of ascent tolerance tolerancealtitude or descent vibrator vibrator

(feet) (feet per minute) operative (feet) inoperative (feet)

0 500 25 3001,000 500 25 1203,000 500 25 1205,000 500 25 120

10,000 500 25 35020,000 3,000 25 35030,000 3,000 25 35035,000 3,000 50 60040,000 3,000 50 600

Change 1 4-19

TM 1-1500-204-23-4

than one-half of the minimum scale division), examinelines and connections for security and anchorage.When lines are secure and anchored properly andpointer still oscillates, replace indicator.

(b) Zero check test. At zeroindication, errors must not exceed tolerances specifiedin table 4-11. When tolerances listed in table 4-11 areexceeded, indicator shall be replaced.

i. Remote Reading Pressure Indicators.Principles of operation, types, and testing of remotereading pressure indicators are described in thefollowing paragraphs.

(1) Principles of operation and types.Remote reading pressure indicators are connectedindirectly to the pressure source by electricaltransmitters and wiring. The transmitters are connecteddirectly to the pressure source by tubing or hose. As thepressure increases or decreases, the mechanism in thetransmitter is displaced. When the mechanism isdisplaced, a signal is sent to the indicator through theelectrical wiring which causes the mechanism in theindicator to turn to a corresponding position as that ofthe transmitter, thus giving an indication of the pressurebeing measured. This type system is called self-synchronous (autosyn), and may be adapted topractically all pressure measuring needs. The autosynsystem of transmitting pressure readings may beincorporated for use with oil pressure, fuel pressure,multi-purpose, hydraulic pressure, and manifoldpressure indicators.

Table 4-9. Static Friction Error (Counter DrumPointer) (Vibrator Inoperative)

Test pointaltitude Tolerance

(feet) (feet)

500 .......................................... 701,500 .......................................... 702,500 .......................................... 703,500 .......................................... 707,500 .......................................... 80

12,500 .......................................... 9017,500 .......................................... 11022,500 .......................................... 12032,500 .......................................... 18035,500 .......................................... 30042,500 .......................................... 300

(2) Testing. The following paragraphsdescribe tests and replacement criteria for remotereading pressure indicators.

(a) Continuity check test. Test wiringfor proper continuity as specified in applicable wiringdiagram.

(b) Master transmitter test. Testindicators and transmitters with a synchro test set.When either indicator or transmitter is faulty, it will bereplaced.

(c) Zero check test. With ac power on(26V, 400Hz), error at zero indication must not exceedtolerances specified in table 4-12. When errors exceedtolerances listed in table 4-12 and wiring and transmitterare in correct working order, the indicator will bereplaced.

j. Tachometer Systems. Principles of operation,types, and testing of tachometer systems are describedin the following paragraphs.

(1) Principles of operation and types.Tachometer systems are independent instrumentsystems which furnish their own operating power. Atachometer system consists of an indicator, a generator,and connecting wiring. Synchronous rotor three-wire,synchronous rotor two-wire, dual synchronous rotorthree-wire, and dual synchronous rotor two-wiretachometer systems are the most common types.

(2) Testing. The following paragraphsdescribe tests and replacement criteria for tachometersystems.

Table 4-10. Pressure Altitude Difference (CounterDrum Pointer)

Pressure Altitude(inches of difference

mercury (Hg)) (feet)

28.10................................................. -172728.50................................................. -134029.00................................................. -86329.50................................................. -39229.92................................................. 030.50 ................................................. +53130.90................................................. +89331.00................................................. +983

4-20

TM 1-1500-204-23-4

Table 4-11. Indicator Tolerances (Direct)

Range Types Function Tolerance

NOTEIf aircraft has just completed a flight of one hour or longer at altitudes of 10,000 feet or over, allow twohours for stabilization before testing altimeters.

0 to 25 and MS28061 and Fuel (±0.5) psi0 to 35 psi MS28064

C-32 and C-330 to 50 psi O-1 and O-2 Multi-Purpose (± 1.0) psi0 to 200 psi B-23 Oil (25.5) psi0 to 2000 psi All Hydraulic (±50) psi0 to 4000 psi E-6 and ME-1 Hydraulic (±75) psi0 to 5000 psi All Hydraulic (±100) psiAll Altimeters Altitude (±0-05) inch Hg

All Barometric barometric scalePressure

Range

0 to 50 psi

Table 4-12. Indicator Tolerances (Remote)

Types Function

MS28010-1 Indicator, Multi-PurposeMS28005-1 Transmitter

Tolerance

(k2.0) psi

0 to 100 psi MS28010-2 Indicator,MS28005-2,MH-2 Transmitter

Oil (k3.5) psi

0 to 200 psi MS28010-3 Indicator,MS28005-3 Transmitter

Oil (25.5) psi

0 to 300 psi

0 to 600 psi

MD-1 Indicator,MH-1 TransmitterC-34, MS28010-7indicator E-7MS280057Transmitter

Oil (k9.0) psi

Fuel (k2.0) psi

0 to 4000 psi MS28010-5 IndicatorMS28005-8

Hydraulic (±100) psi

Change 4 4-21

TM 1-1500-204-23-4

Figure 4-14. Synchronous Rotor TachometerWiring Diagram

(Ungrounded Three-Wire System).

Figure 4-15. Synchronous Rotor TachometerWiring Diagram

(Grounded Two-Wire System).

Figure 4-16. Dual Synchronous Rotor TachometerWiring Diagram

(Ungrounded Three-Wire System).

(a) Continuity check test. Test wiring forproper continuity as specified in applicable wiring dia-grams shown in figures 4-14 through 4-17.

(b) Master system test. Using a field porta-ble tachometer tester, Type M-5, or equivalent, test gen-erator and indicator for proper operation. Replace gener-ator or indicator when test proves either to beunserviceable.

(c) Zero check test. With power off, en-gines not running, indicator needles should not revert tolowest reading.

k. Electrical Resistance Temperature IndicatorsPrinciples of operation and testing of electrical resistancetemperature indicators are described in the followingparagraphs.

(1) Principles of operation. The electrical re-sistance temperature indicator consists of an indicator, abulb (located where temperature is to be measured), andconnecting leads.

4-22 Change 3

TM 1-1500-204-23-4

Figure 4-17. Dual Synchronous RotorTachometer Wiring Diagram

(Grounded Two-Wire System)

(2) Testing. The following paragraphsdescribe tests and replacement criteria for electricalresistance temperature indicators.

(a) Continuity check test. Test wiringfor proper continuity as specified in applicable wiringdiagrams.

(b) Master thermometer test. Masterthermometer test. Using an electric thermometer tester,test indicator for proper operation.

(c) Bulb test. Using a precisionohmmeter or a Wheatstone bridge, test bulbs for properresistance values.

(d) Replacement criteria. Replaceindicators or bulbs when proven faulty. Repairs of damagedwiring shall be per Section VII of TM 55-1500-323-25.

I. Thermocouple Temperature Indicators.Principles of operation and testing of thermocoupletemperature indicators are described in the followingparagraphs.

(1) Principles of operation. The thermocoupletemperature indicator consists of an indicator, bulb, andconnecting leads.

(2) Testing. The following paragraphsdescribe tests and replacement criteria for thermocoupletemperature indicators.

(a) Resistance test. Disconnect leadsfrom indicator and test for proper lead resistance with aprecision ohmmeter or a Wheatstone bridge.Resistance value must be as specified on back side ofindicator. Repair or replace leads when resistance isother than specified.

(b) Master thermometer test. With on-leaddisconnected, indicator must read within 18°F (10°C)of surrounding temperature when tested againsta master mercury thermometer. Indicator may beadjusted to read tolerance with zero adjustment screw.When indicator cannot be adjusted, it must be replaced.

m. Outside Air Temperature Gauges. Principles ofoperation and testing of outside air temperature gauges,as shown figure 4-18, are described in the followingparagraphs.

(1) Principles of operation. Outside airtemperature gauges show outside air temperature. Thesystem usually consists of an indicator, bulb, and circuitbreaker.

(2) Testing. The following paragraphsdescribe the test procedures and replacement criteria foroutside air temperature gauges.

(a)Master thermometer test. Test outsideair temperature gauges using the following procedures:

Figure 4-18 Outside Air Temperature Gauge

4-23

TM 1-1500-204-23-4

1 Remove gauge to be shop tested.

2 Obtain mercury centigrade thermo-meter NSN 6685-00-851-4577, or NSN 5905-01-085-1580.

3 Fill container with fresh water andallow water to stabilize at room temperature. (Allow tosit overnight, if possible.

4 Remove sun shields and suspendgauge in such a way that the stems are vertical and areimmersed two to two and a half inches into the water.Simultaneously, suspend the mercury thermometer inthe water to an equal depth.

5 Record the mercury thermometerand gauge temperature after five minutes. Allow anadditional five minutes to pass and record temperaturesagain. Repeat until temperatures stabilize.

6 Fill a container with ice cubes orcrushed ice and water.

7 Place the gauge with stems verticalinto the ice-water approximately two to two and a halfinches. Simultaneously, immerse the mercurythermometer to the same depth.

8 Record the mercury thermometerand gauge temperature after five minutes. Allow anadditional five minutes to pass and record temperaturesagain. Repeat until temperatures stabilize.

(b) Replacement criteria. Gauges mustagree with the mercury thermometer within two degreesat both test points. Failure to meet either test pointwithin two degrees is cause for rejection.

(3) Temperature Conversion. To convertFahrenheit to centigrade or centigrade to Fahrenheit,use table 4-13 or the following conversion formulas.

C = (5/9) x (F-32) F = [(9/5) x C] + 32

Example: change 86 °F Example: change 40°Cto Centigrade to Fahrenheit

C = (5/9) x (F-32) F = [(9/5 x C] + 32C = .5556 x (86-32) F = (1. 8 x 40) + 32C = .5556 x (54) F = 72 + 32C = 30 F = 104°

n. Alternate thermal resistor and multimeter test

o. Magnetic Compass. The magnetic compass, asshown in figure 4-19, consists of liquid-filled bowlcontaining a pivoted float element to which one or morebar magnets, called needles, are fastened. The liquiddampens the oscillations of the float and decreases thefriction of the pivot. A diaphragm and a vent provide forexpansion and contraction of the liquid as altitude andtemperature change. Principles of operation, compasserrors, compass compensation, and replacement criteriaare described by the following paragraphs.

4-24 Change 5

method. Test outside air temperature gauges usingusing the following alternate method.

(2) Obtain a general purpose temperatureadapter for digital multimeter (resister, thermal)NSN 5905-01-085-1580 and digital multimeter NSN

1(1) Remove gauge to be tested.

(3) Fill a container with fresh water and allow to stabilize at room temperature.

(4) Connect thermal resister to the digitalmultimeter by observing the polarity and insertingthermal resister connector pins positive (+) and negative

respectively. Place multimeter selector switch in the

will automatically select the centigrade option.

in such a way that the stem is vertical and immersed intwo to two and a half inches into the water. Simultaneously,suspend the probe of the thermal resister in the water anequal depth.

(6) Record the temperature indicated on themultimeter and gauge after five minutes. Allow an additional five minutes to pass and record temperaturesagain. Repeat until temperatures stabilize.

(7) Fill a container with ice cubes or crushedice and water.

(8) Repeat step six (6).

6625-01-256-6000.

(-) into the OHMS and common plugs of the multimeter

millivolt alternate current (MV AC) position. Multimeter

(5) Remove sun shield and suspend gauge

0

TM 1-1500-204-23-4

Table 4-13. Fahrenheit-Centigrade Conversion Chart°C °F °C °F °C °F °C °F °C °F

-50 -58 -20 -4.0 10 50.0 40 104.0 70 158.0-48 -54.4 -18 -0.4 12 53.6 42 107.6 72 161.6-46 -50.8 -16 3.2 14 57.2 44 111.2 74 165.2-44 -47.2 -14 6.8 16 60.8 46 114.8 76 168.8-42 -43.6 -12 10.4 18 64.4 48 118.4 78 172.4-40 -40.0 -10 14.0 20 68.0 50 122.0 80 176.0-38 -36.4 -8 17.6 22 71.6 52 125.6 82 179.6-36 -32.8 -6 21.2 24 75.2 54 129.2 84 183.2-34 -29.2 -4 24.8 26 78.8 56 132.8 86 186.8-32 -25.6 -2 28.4 28 82.4 58 136.4 88 190.4-30 -22.0 0 32.0 30 86.0 60 140.0 90 194.0-28 -18.4 2 35.6 32 89.6 62 143.6 92 197.6-26 -14.8 4 39.2 34 93.2 64 147.2 94 201.2-24 -11.2 6 42.8 36 96.8 66 150.8 96 204.8-22 -7.6 8 46.4 38 100.4 68 154.4 98 208.4

100 212.0

Change 5 4-24.1/(4-24.2 blank)

TM 1-1500-204-23-4

(1) Principles of operation. A magneticcompass operates on the principle of magneticattraction. The magnets, which are free to pivot in ahorizontal plane, will assume a position with the north-seeking ends pointing toward the earth's north magneticpole. The magnetic heading is read by reading acompass card attached to the float.

(2) Compass errors. Magnetic variation andmagnetic deviation are explained in the followingparagraphs.

(a) Magnetic variation. Magneticvariation is the angular difference in degrees betweenthe geographic north pole and the magnetic north pole.This variation is caused by the magnetic field, which isconstantly changing. Since variation differs accordingto geographic location, its effect on the compass cannotbe removed by any type of compensation. Variation iscalled west variation when the earth's magnetic fielddraws the compass needle to the left of the geographicnorth pole and east variation when the needle is drawnto the right of the geographic north pole.

(b) Magnetic deviation. Magneticdeviation is the magnetic disturbances within the aircraftthat deflect the compass needle from alignment withmagnetic north. Compasses must be checked andperiodically compensated by adjustment. Deviationsremaining after adjustment are recorded on a compasscorrection card, as shown in figure 4-20, mounted nearthe compass.

(3) Compass compensation. Compasscompensation frequency requirements, pre-compensation instructions, compass rose method ofcompensating, and the B-16 master sighting compassmethod of compensating are explained in the followingparagraphs.

(a) Compensation frequencyrequirements. Compass will be checked for accuracy,compensated when necessary, and readings recordedon DD Form 1613 (Pilot Compass Correction Card) atthe following times:

• At least once during each 12 month period

Figure 4-19. Magnetic Compass

4-25

TM 1-1500-204-23-4

Figure 4-20. Compass Correction Card

• After each engine change

NOTE

Check applicable aircraft specialinspection to determine if thecompass check and/or calibration isrequired after engine change.

• After any modification/change to the existingelectrical system of major structural change

• At any time compass is suspected ofbeing in error

• Whenever the flux valve has loosenedin its mounting, has been removedduring troubleshooting, or has beenreplaced with a new unit

• At anytime the applicable aircrafttechnical manual specifies

(b) Pre-compensation instructions.Accomplish the following procedures beforecompensating:

1 Ensure that aircraft is at least 100yards from any steel structure, underground cables,metal pipes, reinforced concrete or other aircraft.

2 Ensure that all items in aircraftcontaining ferrous materials are located in the positionsthey will occupy during flight.

3 Remove all magnetic articles fromone's person. Use a nonmagnetic screwdriver.

4 Using a small permanent magnet,cause compass card to deflect through a small angle.Note whether the card rotates freely on its pivot, andthat its path of rotation is in a horizontal plane. To avoiderroneous readings, read compass only directly in frontof the lubber line.

5 Prior to compensation of magneticcompass, have aircraft headed successively towardmagnetic North, East, South, and West with enginesrunning and all systems operating. Compass readingsmust read within 20 of deviation noted on DD Form1613 (Pilot Compass Correction Card). When reading iswithin specified tolerance, compass does not needcompensating. Transcribe readings from old DD Form1613 to new DD Form 1613; date and sign form. Ifmagnetic compass is not within tolerance, proceed withnext paragraph.

6 Remove one of the retaining screwsand loosen the other from the compensator assemblycover plate, and rotate the plate to allow access to thecompensator adjustment screws. Ensure that errorcompensator adjustment screws are set to neutral priorto realignment of compass transmitter.

7 Run the engines and turn on powerto all electrical equipment which may have magnetic

4-26

TM 1-1500-204-23-4

Figure 4-21. Compass Rose

influence on compass so that flight conditions aresimulated as nearly as possible.

(c) Compass rose method ofcompensating. A compass rose is often used to obtainthe magnetic headings when an aircraft compass isbeing compensated. This method of swinging thecompass is desirable, provided that care is exercised inaligning the

aircraft with various headings. All equipment used inthe vicinity of the compass rose must be nonmagneticmaterials. Use the following procedures to compensatecompass.

1 Place aircraft on compass rose, asshown in figure 4-21, and head toward magnetic north.Record compass reading in column 2, line 1 of DD Form1613 (Pilot Compass Correction Card) as shown infigure 4-22. Assume that the compass reading is 8degrees.

2 Turn aircraft to the east magneticheading and record compass reading in column 2, line3, of DD Form 1613. Assume that the reading is 86degrees.

3 Turn aircraft to the south magnetheading and record compass reading in column 2, line5, of DD Form 1613. Assume that reading is 176degrees.

4 Turn aircraft to the west magneticheading and record compass reading in column 2, line7, of DD Form 1613. Assume that compass reading is278 degrees.

5 Fill in the column headed DEV; ifaircraft COM P is greater than the actual heading, DEVnumber will be positive; if aircraft COMP is smaller thanthe actual heading, DEV number will be negative. Alladditions and subtractions are algebraic.

Compensating Residual Computation TableSwing Swing

Comp Actual Aircraft Actual Aircraft ActualRose Head (M) Comp. (C) Dev. Head (M) Comp. (C) C to M Head (M) M to C

N 000 000 008 +8 000 002 -2 000 +2NE 045 045 046 -1 045 +1E 090 090 086 -4 090 092 -2 090 +2SE 135 135 135 0 135 0S 180 180 176 -4 180 182 -2 180 +2SW 225 225 224 +1 225 -1W 270 270 278 +8 270 272 -2 270 +2NW 315 315 315 0 315 0

COL NO. (1) (2) (2)-(1) (3) (4) (3)-(4) (3) (4)-(3)

Figure 4-22. DD Form 1613 (Compass Correction Card)

4-27

TM 1-1500-204-23-4

6 Return aircraft to the north magneticheading. Add coefficient C, shown below, algebraicallyto compass reading on that heading to determine whatcompass should read when compensated. Adjust MScompensating screw (of polyplane compensator) orinsert magnets in compensating drawer, which is at rightvalue angles to needle, until compass indicatescompensated value.

Coefficient C= N-S = (+8) - (-4) = 12 = +62 2 2

7 Head aircraft east. Add coefficientB, as shown below, algebraically to compass reading onthat heading. Adjust EW compensating screw (or insertmagnets in that chamber of compensating drawer atright angles to needle) until compass indicatescompensated value.

Coefficient B= E-W = (-4) - (+8) = -12 = -62 2 2

NOTE

• The spread between maximumpositive and maximum negativedeviation after compensation shallnot exceed 5 degrees.

• Coefficient A represents totaldeviation from the formula givenon DD Form 1613. All additionsand subtractions are algebraic.

Coefficient A = N + E + S +W =4

(+8) + (-4) + (-4) + (+8) = 8 = 24 4

8 After adjustment has been made,residual swing can begin on any heading. Record actualheading (M) Column 3, and aircraft compass reading (c)Column 4; repeat every 45 degrees around the circle.As indicated in the example in figure 4-22, C to M DEVis calculated by (3) - (4) or M to C by (4) - (3).

NOTE

The spread between maximumpositive deviation and the maximumnegative deviation after compensationshall not exceed 5 degrees.

9 Fill in back of the DD Form 1613.Detach heading correction card portion of the DD Form1613 at the perforation and place in the cockpit. Thelocation for the card may vary due to night vision gogglerequirements. See applicable aircraft manual forlocation of Compass Correction Card.

10 Place the balance of the form withthe aircraft historical record as a record of compassswing until completion of the next compass swing.Upon transfer of aircraft, this portion of the form willaccompany the aircraft with other records.

(d) B16 master sighting compassmethod of compensating. The compensator assembly isremoved from the compass and a special sightingdevice fitting is substituted. During compensatingprocedure with this instrument, aircraft is turned todesired heading as indicated by aircraft compass. Asight is then taken by the swinging compass 2 points onthe fore-and-aft axis of aircraft being lined up withhairline in collimator lens, as shown in figure 4-23. Thecompass used for this purpose will be painted red,indicating that it has been remagnetized 180 degreesfrom normal. This permits observer to read magneticheading of aircraft directly when sighting from in front ofaircraft. When a compass drawn from stock is used asa swinging sight, 180 degrees must be added tocompass reading to obtain magnetic heading of aircraft.Corrections, as indicated by master compass, are madeon each of the cardinal headings in the conventionalmanner. In every other respect, compensation isexactly the same as in the use of the compass rose.

NOTE

When using a sight compass onhelicopters, line up with any twoobjects that are parallel with thecenterline of the aircraft.

(e) Using AHRS and INS tocompensate compasses. If the aircraft is equipped witha functional Attitude and Heading References System(AHRS) or an Inertial Navigation System (INS) and thevariation is known to within 0. 2 degree, the standbycompass system may be swung using either of thesesystems as a heading reference in place of a compassrose. The standby compass system is thencompensated by using the procedures in paragraph (c).Special care must be exercised in the alignment ofaircraft and the use of nonmagnetic materials.

4-28

TM 1-1500-204-23-4

Figure 4-23. B-16 Master Sighting Compass Alignment Method.

NOTE

When using the Attitude and HeadingReference System (AHRS) or theInertial Navigation System, locate theaircraft away from magnetic buildings,materials and other structures.

(f) Checking compass while flying. Thecompass may be checked for deviation while flying bycomparing the compass heading with a known heading.

NOTE

Do not compensate compass while inflight.

(g) Calibrator set method of compensating. Amore precise method for checking the compass isreflected in TM 11-4920-292-15. It may be used ifdesired and necessary test equipment is available.

(4) Replacement criteria. Line maintenance onmagnetic compasses consists primarily of compassswinging, replacing burned out light bulbs, andreplacement of defective compasses. Compasses willbe replaced for any of the following:

• Clouded or discolored liquid

• Illegible card markings, fading, or lossof luminous paint

• Failure of card to rotate freely in ahorizontal plane when aircraft is in anormal flying position

• Cracked bowl, broken mounting frame,or broken lugs

• Erratic action, or failure of compass torespond after proper efforts tocompensate

• Lubber line loose or misaligned

• Air visible in bowl of compass

• If the total deviation of the eightheadings exceeds 8 degrees

p. Remote Indicating Compass. Remote indicatingcompass compensation, testing, and replacementcriteria are explained in the following paragraphs.

4-29

TM 1-1500-204-23-4

(1) Compass compensation. Remoteindicating compass compensation procedures are thesame as the magnetic compass, except that whencompensating, the power supply to the compass mustbe turned on.

(2) Testing and replacement criteria. Do notreplace components of remote indicating compasswithout first testing wiring for proper continuity (seefigure 4-24), and the indicator for correct operation.Test indicator by using the following procedures:

(a) Using P-1, ANASM61, orANASM339V1 tester, test indicator and transmitter forproper operation. Refer to applicable tester technicalmanual for operation and connection of tester, andapplicable wiring diagram for location of transmitter.

(b) When the remote magneticcompass does not read within specified tolerances,check applied voltage. If power supply is functioningproperly, troubleshoot system in accordance withapplicable TM 11 series maintenance manual.

(c) Replace either indicator ortransmitter when faulty.

q. Electrical Liquid Indicating Systems andIndicators. Electrical liquid indicating systems are usedfor fuel quantity and anti-icing fluid quantity. Atransmitter in the liquid tanks transmits an electricalsignal to position the pointer of a gauge in the cockpit.

Refer to applicable aircraft maintenance manual fortesting and troubleshooting procedures.

r. Position Indicating Systems and Indicators.Position indicating systems are used to indicate positionof landing gear and flaps. A cockpit indicator showsrelative position of landing gear and flaps. Refer toapplicable aircraft maintenance manual for testing andtroubleshooting procedures.

s. Repair and Replacements. The followingparagraphs describe repair and replacement ofinstruments and instrument system components that canbe accomplished on the flight line.

(1) Repair. Line repair is limited primarily tothe following:

• Resoldering broken leads

• Replacing tubing, hose, andfittings

• Removing obstructions fromrigid or flexible tubing

• Recompensating compasssystems

• Removal and replacement ofcomponents

Figure 4-24. Remote Indicating Compass Wiring Diagram

4-30

TM 1-1500-204-23-4

(2) Replacement. Instruments (indicators ortransmitters) will be removed and replaced for any ofthe following reasons:

• Failure to indicate (excludingsystem failures)

• Inaccurate indicators (excludingsystem failure)

• Damage case

• Loose or distorted pointers

• Cracked or loose cover glass

• Cracked or broken mountinglugs

• Damaged lamp receptacles • Defective setting or caging

mechanisms • Defective binding posts • Defective connecting nipples

and AN/MS connectors • Dull or discolored luminous or

fluorescent markings • Electrical connectors for bent or

damaged pins, stripped,crossed or excessively wornthreads, or visual damage to theshell

4-31/(4-32 blank)

TM 1-1500-204-234

APPENDIX A

REFERENCES

A-1 ARMY REGULATIONS (AR):

AR 385-10 Army Safety Program

AR 385-30 Safety Color Code Markings and Signs

AR 385-32 Protective Clothing and Equipment

A-2 FEDERAL HANDBOOK:

A-3 TECHNICAL BULLETINS (TB):

TB 385-4 Safety Precautions for Maintenance of Electrical/Electronic Equipment

A-4 TECHNICAL MANUALS (TM):

TM 1-1500-204-23-6 Aviation Unit Maintenance (AVUM) and Aviation Intermediate Mainte-nance (AVIM) Manual for General Aircraft Maintenance (Hardware andConsumable Materials) Volume 6

TM 1-1500-343-23 Avionic Cleaning and Corrosion Prevention/Control

TM 1-1500-344-23 Aircraft Weapons Systems Cleaning and Corrosion

TM 11-4920-229-12 Scorsby Table Assembly

TM 11-6130-385-34 Inverter Static Power

TM 11-6140-203-23 Aircraft Nickel-Cadmium Batteries E

TM 55-1500-323-24 Instrument Practices for Aircraft Electric and Electronic Wiring

TM 55-1500-345-23 Painting and Marking of Army Aircraft

TM 55-4920-229-12 Scorsby Table Assembly

TM 55-4920-231-14 Tester, Pilot and Static Systems

TM 55-4920-377-13&P Tumtable Gyro Instrument Testing

TM 55-6685-201-12 Manometer

A-5 LEGAL AND CONSENSUS STANDARDS

NFPA 410 Aircraft Maintenance

OSHA 1910.251 Occupational Safety and Health Act of 1971

A-6 MILITARY SPECIFICATIONS

MIL-W-5088 Wiring, Aerospace Vehicle

QQ-S-571 Solder, Electronic (96 to 486 degrees C)

A-7 DEPARTMENT OF DEFENSE (DD) FORMS

DD Form 1613 Compass Correction Card

Change 3 A-1/(A-2 blank)

TM 1-1500-204-23-4

GLOSSARY

AMMETER An instrument that measures either ac or dc current.

CONDUCTOR A bare or insulated wire or combination of wires not insulated from oneanother, suitable for carrying electrical current. They usually are copper,aluminum, steel or silver.

FREQUENCY The number of complete cycles in one second of alternating current,voltage, or electromagnetic pressure waves.

HYSTERESIS The difference obtained on measuring instruments containing iron whenthe current is increased to a definite value and when the current isreduced from a higher value to the same definite value.

LOAD The power consumed by a machine or circuit in performing its function.

POLARITY Having two opposite charges, one positive and the other negative.

VOLTAGE Electrical pressure; the force which causes current to flow through anelectrical conductor.

VOLTMETER A current measuring instrument designed to indicate voltage bymeasuring the current flow through a resistance of known value.

WAVE An activity that rises and falls, or advances and retreats, as it travelsthrough a medium.

Glossary-1 /(Glossary-2 blank)

TM 1-1500-204-23-4

INDEX

Subject Paragraph,Figure, Table

Number

A

Airspeed Indicator ...................................................................................................................................... F4-11Test Tolerances ................................................................................................................................... T4-1

Alternating Current, Basic Principles and Theory for ................................................................................... 2-3Alternating Current, Cycle .......................................................................................................................... F2-2Altimeter .................................................................................................................................................... 4-3, F4-13Ammeter ..................................................................................................................................................... 2-6dAutomatic Wire Marking Machines ............................................................................................................. F3-2

B

B-16 Master Sighting Compass Alignment Method ..................................................................................... F4-23Basic Circuits ............................................................................................................................................. 2-5

Compound ........................................................................................................................................... 2-5c, F2-7Parallel ................................................................................................................................................ 2-5b, F2-6Series .................................................................................................................................................. 2-5a, F2-5

Basic Principles and Theory for Alternating Current .................................................................................... 2-3Basic Principles and Theory for Direct Current ........................................................................................... 2-2Bonds ......................................................................................................................................................... 3-lk

C

Centigrade-Fahrenheit Conversion Chart ................................................................................................... T413Circuit Breakers ......................................................................................................................................... 3-1 nCircuit, Thermocouple ................................................................................................................................ F3-13Circuits, Basic ............................................................................................................................................ 2-5Cleaning Apparatus, Mercury ..................................................................................................................... F4-3Compass

Alignment, B-16 Master Sighting Method ............................................................................................. F4-23Correction Card ................................................................................................................................... F4-20Rose ..................................................................................................................................................... F4-21

Components, of Electrical Systems ............................................................................................................ 3-4Compound Circuits ..................................................................................................................................... 2-5c, F2-7Conduits...................................................................................................................................................... 3-ljConnectors

Inspection of ........................................................................................................................................ 3-3bInstallation of (on Wires) ...................................................................................................................... 3-3cMS ....................................................................................................................................................... F3-4Potting .................................................................................................................................................. F3-7Rectangular Shell ................................................................................................................................ F3-6Subminiature ....................................................................................................................................... F3-5

Consumable Materials ................................................................................................................................ 1-3

Change 3 Index 1

TM 1-1500-204-23-4

INDEX - CONT


Number

C - Continued

Continuity Tester ........................................................................................................................................ 2-6b, F2-8Copper Wire Strippers ................................................................................................................................ . T3-1Correction Card, Compass ......................................................................................................................... . F4-20Counter Drum Pointer Altimeter ................................................................................................................. . F413

Friction Stop and Jump Error ............................................................................................................... . T4-8Pressure Altitude Difference ................................................................................................................ . T4-10Scale Error ........................................................................................................................................... T4-6Static Friction Error (Vibrator Inoperative) ............................................................................................ T4-9Test Tolerances ................................................................................................................................... T4-7

Cycle of Alliterating Current ....................................................................................................................... F2-2

D

D'Arsonval Meter ........................................................................................................................................ 2-6c, F2-9DD Form 1613 (Pilot Compass Correction Card) ........................................................................................ F422Direct Current Wave Form .......................................................................................................................... F2-1Direct Current, Basic Principles and Theory for .......................................................................................... 2-2Direct Reading Pressure Indicator ............................................................................................................... 4-3h

Tolerances ........................................................................................................................................... T4-11Dual Synchronous Rotor Tachometer Wiring Diagram (Grounded Two-Wire System) ................................ F4-17Dual Synchronous Rotor Tachometer Wiring Diagram (Ungrounded Three-Wire System) .......................... F4-16

E

Electrical Connectors and Common Plugs, Installation of ........................................................................... 3-3Electrical Liquid Indicating Systems and Indicators .................................................................................... 4-3pElectrical Resistance Temperature Indicators ............................................................................................. 4-3kElectrical System Components ................................................................................................................... 3-4

Built-In Test Equipment ........................................................................................................................ 3-4fElectronic Control Units ....................................................................................................................... 3-4gIgnition Systems .................................................................................................................................. 3-4jInverters .............................................................................................................................................. 3-4c, F3-9Lighting Systems ................................................................................................................................. 3-4kMotors ................................................................................................................................................. 3-4hRelays ................................................................................................................................................. 3-4bStarters ................................................................................................................................................ 3-4dStorage Battery .................................................................................................................................... 3-4aSwitches .............................................................................................................................................. 34eThermocouples .................................................................................................................................... . 3-4i

Change 3 Index 2

TM 1-1500-204-23-4

INDEX - CONT


Number

E - Continued

Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Thermocouples.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Electrical System Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Electrodynamometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Equipment, Measuring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Equipment Safety

ElectricShop.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .InstrumentShop.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F

Fahrenheit-Centigrade Conversion Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Fire Safety

ElectricShop.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .InstrumentShop.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Frequency Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Friction Stop and Jump Error, Counter Drum Pointer Altimeter . . . . . . . . . . . . . . . . . . . . . . . . . .Friction Test Tolerances, Three Pointer Altimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Fuse and Fuse Holders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

G

Gauge,Wire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F3-1General Shop Rules, Electric Shop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

EquipmentSafety.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1cFireSafety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1dMaintenance of Shop Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1eResponsibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1aShop Housekeeping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1b

General Shop Rules, Instrument Shop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1Equipmentsafety.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1cFireSafety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1dResponsibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1aShopHousekeeping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1b

3-4e3-4i3-2

2-6h2-6

2-1c4-1c

T4-13

2-1d4-1d2-6kT4-8T4-43-1h

H

Hand Wire Marking Machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F3-3

I

Ignition System Troubleshooting Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T3-3Indicator, Airspeed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3e, F4-11

Change 4 Index-3

TM 1-1500-204-23-4

Subject

INDEX - CONT

Paragraph,Figure, Table

Number

I - ContinuedIndicator, Tolerances

Direct Reading Pressure Indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Remote Reading Pressure Indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Inspection of Installations of Wires and Cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Inspection of Instrument Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .lnspectfon Requirements for Installations of Wires and Cables . . . . . . . . . . . . . . . . . . . . . . . . . .Inspection Requirements, Instruments and Instrument SystemsInstallation Inspection of Wires and Cables

Bonds.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .CircuitBreakers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Conduits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Fuses and Fuse Holders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Inspection Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Junctions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Kapton Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Marking of Wires with Marking Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Replacement Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Splices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .TerminalsandTerminalBlocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ToggleSwitches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Wire Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .WireSizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .WireStripping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Installation of Electrical Connectors and Common Plugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Inspection of Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Installation of Connectors on Wires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .TypesofConnectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Instruments and Instrument System Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Airspeedlndicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Altimeters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Direct Reading Pressure Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Electrical Liquid Indicating Systems and Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Electrical Resistance Temperature Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Inspection of Instrument Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Inspection Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MagneticCompass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Outside Air Temperature Gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PitotStaticSystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Pitot Static System Heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Position Indicating Systems and Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Remote Indicating Compass. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Remote Reading Pressure Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Repair and Replacements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .TachometerSystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Thermocouple Temperature Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Vertical Speed Indicators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Inverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

T4-11T4-12

3-14-3a3-1a4-3b

3-13-1k3-1n3-1j

3-1h3-1a3-1l

3-1o3-1 f

3-1b3-1i

3-1g3-1m3-1d3-1c3-1e3-3

3-3b3-3c3-3a

4-34-3e

4-39, F4-134-3h4-3q4-3k43a4-3b

4-30, F4-194-3m

4-3c, F4-74-3d4-3r4-3p4-3i

4-3s43j4-31

43f, F4-12F3-9

Index-4 Change 3

TM 1-1500-204-23-4

INDEX - CONT


Number

J

Junctions.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .K

Kapton Wiring.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .L

Leak Test ConnectionsPitot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Static . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Lighting System Troubleshooting Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .M

MagneticCompass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Maintenance of Instruments and Instrument Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Maintenance of Shop Equipment, Electrical Shop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Maintenance of Shop Equipment, Instrument Shop. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

JetCalSystemTester . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Manometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Pitot Static System Tester . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Scorsby Base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Turntable Instrument Tester . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VacuumChambers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Manometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ManometerReading Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Marking of Wires with Marking Machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Materials, Consumable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MeasuringEquipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Ammeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Continuity Tester . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .D’ArsonvalMeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Electrodynamometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Frequency Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Meter Safety Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Multimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Ohmmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .RectifierMeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .TestLights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-1I

3-1o

F4-8F4-9T3-4

4-3n, F4-194-3

2-1e4-2

4-2f, F4-64-2a, F4-1

4-2e4-2d, F4-54-2c-F4-4

4-2b4-2a, F4-1

F4-23-1f1-32-6

2-6d2-6b2-6c2-6h2-6k2-61

F2-10, 2-692-6f2-6i

2-6a

Change 4 Index-5

TM 1-1500-204-23-4

INDEX - CONT


Number

2-6e2-6j

F4-32-6c, F2-9

2-61F3-11F3-4

F2-10, 2-69

2-613-2a

43m, F4-18

2-5b, F2-6F4-22

F4-84-3c, F4-7

4-3d4-2e

F4-104-3qF3-73-2b

T4-10T45

1-1

F4-2T3-2F3-62-6i

F3-84-3o

F4-244-3i

T4-12

M - Continued

Voltmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Wattmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mercury Cleaning Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Meter,D’Arsonval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Meter Safety Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Microswitch.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MSConnectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Multimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

O

Ohmmeter.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Operational Check (of Electrical Systems) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Outside Air Temperature Gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P

ParallelCircuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Pilot Compass Correction Cards, DD Form 1613 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Pitot

LeakTestConnections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .StaticSystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Static System Heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .StaticSystemTester . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Position Indicating Systems and Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Potting Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Precautions (for Troubleshooting Electrical Systems) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Pressure Altitude Difference

Counter Drum Pointer Altimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Three Pointer Altimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Purpose(ofManual) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .R

Reading Level, Manometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Recommended Sizes oi Marking Tape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Rectangular Shell Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .RectifierMeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Relays, Typical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Remote Indicating Compass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

WiringDiagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Remote Reading Pressure Indicator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Tolerances.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Index-6 Change 3 PIN: 070463-004

TM 1-1500-204-23-4

INDEX - CONT

Subject Paragraph,Figure, TableNumber

R - Continued

Repair and Replacements, Instruments and Instrument Systems ............................................................... 4-3sReplacement Criteria for Wires and Cables ................................................................................................ 3-lbResponsibility

for Electric Shop Rules ........................................................................................................................ 2-1 afor Instrument Shop Rules ................................................................................................................... 4-la

Rose, Compass .......................................................................................................................................... F4-21Rotary-Selector Switch................................................................................................................................ F3-12

S

Scale ErrorCounter Drum Pointer Altimeter ........................................................................................................... T4-6Three Pointer Altimeter ........................................................................................................................ T4-3

Schematic, of Typical Electrical System ..................................................................................................... F2-4Scope (of Manual) ...................................................................................................................................... 1-2Scorsby Base ............................................................................................................................................. 4-2g, F4-5Series Circuits ............................................................................................................................................ 2-5a, F2-5Shop Housekeeping

Electrical Shop ..................................................................................................................................... 2-1 bInstrument Shop .................................................................................................................................. 4-1 b

Sizes of Marking Type, Recommended ...................................................................................................... T3-2Splices ....................................................................................................................................................... 3-1iStatic Friction Error (Vibrator Inoperative), Counter Drum Pointer Altimeter ............................................... . T4-9Subminiature Connectors ........................................................................................................................... F3-5Switch

Rotary-Selector..................................................................................................................................... F3-12Toggle ................................................................................................................................................. F3-10

Symbols, Charts, and Schematics for Wiring Diagrams .............................................................................. 2-4Symbols, Wiring Diagram ........................................................................................................................... F2-3Synchronous Rotor Tachometer Wiring Diagram (Grounded Two-Wire System) ........................................ F4-1 5Synchronous Rotor Tachometer Wiring Diagram (Ungrounded Three-Wire System) .................................. F4-14

T

Tachometer Systems ................................................................................................................................. 4-3jTachometer Wiring Diagram

Dual Synchronous Rotor (Grounded Two-Wire System) ....................................................................... . F4-17Dual Synchronous Rotor (Ungrounded Three-Wire System) ................................................................. F4-16Synchronous Rotor (Grounded Two-Wire System) ............................................................................... F4-15Synchronous Rotor (Ungrounded Three-Wire System) ......................................................................... F4-14

Terminals and Terminal Blocks .................................................................................................................. 3-1g

Index 7

TM 1-1500-204-23-4

INDEX - CONT


Number

T - Continued

Test Lights ................................................................................................................................................. 2-6aTest Tolerances Airspeed Indicator

Airspeed Indicator ................................................................................................................................ T4Counter Drum Pointer Altimeter ........................................................................................................... T4-7Three Pointer Altimeter ........................................................................................................................ T4-3

Tester, Continuity ....................................................................................................................................... 2-6b, F2-8Thermocouple Circuit ................................................................................................................................. F3-13Thermocouple Temperature Indicators ....................................................................................................... 4-31Three Point Altimeter ................................................................................................................................. F4-13

Friction Test Tolerances ....................................................................................................................... T4-4Pressure Altitude Difference ................................................................................................................ T4-5Scale Error ........................................................................................................................................... T4-2Test Tolerances ................................................................................................................................... T4-3

Toggle Switch ............................................................................................................................................ F3-10Toggle Switches ......................................................................................................................................... 3-1 mTroubleshooting Electrical Systems ............................................................................................................ 3-2

Operational Check ............................................................................................................................... 3-2aPrecautions .......................................................................................................................................... 3-2b

Tube, Pilot ................................................................................................................................................. F4-10Turntable Instrument Tester ....................................................................................................................... 4-2f, F4-4Typical Electrical System Schematic .......................................................................................................... F2-4Typical Ignition System Troubleshooting Chart ........................................................................................... T3-3Typical Lighting System Troubleshooting Chart .......................................................................................... T3-4Typical Relays ............................................................................................................................................ F3-8

V

Vacuum Chambers .................................................................................................................................... 4-2dVertical System Indicators ..........................................................................................................................4-3f, F4-12Voltmeter .................................................................................................................................................... 2-6e

W

Wattmeter................................................................................................................................................... 2-6jWave Form, of Direct Current .................................................................................................................... F2-1Wire Gauge ............................................................................................................................................... F3-1Wire Identification ...................................................................................................................................... 3-1dWire Marking Machines

Automatic ............................................................................................................................................ F3-2Hand .................................................................................................................................................... F3-3

Change 3 Index 8

TM 1-1500-204-23-4

INDEX - CONT


Number

W - Continued

Wire Sizes ................................................................................................................................................. 3-1cWire Strippers, for Copper Wire ................................................................................................................. T3-1Wire Stripping ............................................................................................................................................ 3-1eWiring Diagram, Remote Indicating Compass ............................................................................................ F4-24Wiring Diagram Symbols, Charts, and Schematics .................................................................................... F2-3, 2-4

U· .S. GOVERNMENT PRINTING OFFICE: 1996-755-025/40086

Change3 Index 9/(Index 10 blank)



Chief of Staff

Official:



Distribution:

To be distributed in accordance with DA Form 12-31-E, block no. 3226, requirements for TM 1-1500-204-23-4

U.S. GOVERNMENT PRINTING OFFICE: 1995-388-421 42233

These are the instructions for sending an electronic 2028The following format must be used if submitting an electronic 2028. The subject line must beexactly the same and all fields must be included; however only the following fields aremandatory: 1, 3, 4, 5, 6, 7, 8, 9, 10, 13, 15, 16, 17, and 27.

From: “Whomever” <[email protected]>To: [email protected]

Subject: DA Form 20281. From: Joe Smith2. Unit: home3. Address: 4300 Park4. City: Hometown5. St: MO6. Zip: 777777. Date Sent: 19--OCT--938. Pub no: 55--2840--229--239. Pub Title: TM10. Publication Date: 04--JUL--8511. Change Number: 712. Submitter Rank: MSG13. Submitter FName: Joe14. Submitter MName: T15. Submitter LName: Smith16. Submitter Phone: 123--123--123417. Problem: 118. Page: 219. Paragraph: 320. Line: 421. NSN: 522. Reference: 623. Figure: 724. Table: 825. Item: 926. Total: 12327. Text:This is the text for the problem below line 27.

RECOMMENDED CHANGES TO PUBLICATIONS AND

BLANK FORMSFor use of this form, see AR 25--30; the proponent agency is ODISC4.

Use Part II (reverse) for Repair Parts and Spe-cial Tool Lists (RPSTL) and Supply Catalogs/Supply Manuals (SC/SM)

DATE

8/30/02

TO: (Forward to proponent of publication or form)(Include ZIP Code)

Commander, U.S. Army Aviation and Missile Command

ATTN: AMSAM--MMC--MA--NP

R eds t one A r s enal, AL. 35898

FROM: (Activity and location)(Include ZIP Code)

MSG, Jane Q. Doe

1234 Any Street

Nowhere Town, AL 34565

PART 1 -- ALL PUBLICATIONS (EXCEPT RPSTL AND SC/SM) AND BLANK FORMS

PUBLICATION/FORM NUMBER

TM 9--1005--433--24DATE

16 Sep 2002TITLE Organizational, Direct Support, And GeneralSupport Maintenance Manual for Machine Gun, .50Caliber M3P and M3P Machine Gun Electrical Test SetUsed On Avenger Air Defense Weapon System

ITEM

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1 WP0005

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* Reference to line numbers within the paragraph or subparagraph.

TYPED NAME, GRADE OR TITLE

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TELEPHONE EXCHANGE/AUTOVON, PLUS EXTEN-SION

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DA FORM 2028, FEB 74 REPLACES DA FORM 2028, 1 DEC 68, WHICH WILL BE USED. USAPA V3.01

TO: (Forward direct to addressee listed in publication)

Commander, U.S. Army Aviation and Missile Command

ATTN: AMSAM--MMC--MA--NP

R eds t one A r s enal, AL. 35898

FROM: (Activity and location) (Include ZIP Code)

MSG, Jane Q. Doe

1234 Any Street

Nowhere Town, AL 34565

DATE

8/30/02

PART II -- REPAIR PARTS AND SPECIAL TOOL LISTS AND SUPPLY CATALOGS/SUPPLY MANUALS

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PART III -- REMARKS (Any general remarks or recommendations, or suggestions for improvement of publications and

blank forms. Additional blank sheets may be used if more space is needed.)

TYPED NAME, GRADE OR TITLE

MSG, Jane Q. Doe, SFC

TELEPHONE EXCHANGE/AUTOVON,PLUS EXTENSION

788--1234

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Commander, U.S. Army Aviation and Missile CommandATTN: AMSAM-MMC-MA-NPRedstone Arsenal, AL 35898

TM 1-1500-204-23-4 13 July 1992 (AVUM) and (AVIM) Manual for GeneralAircraft Maintenance

TO: (Forward direct to addressee listed in publication) FROM: (Activity and location) (Include ZIP Code) DATE



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TM 1-1500-204-23-4 13 July 1992(AVUM) and (AVIM) Manual for GeneralAircraft Maintenance




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The Metric System and Equivalents

Linear Measure Liquid Measure

1 centiliter = 10 milliters = .34 fl. ounce1 centimeter = 10 millimeters = .39 inch 1 deciliter = 10 centiliters = 3.38 fl. ounces1 decimeter = 10 centimeters = 3.94 inches 1 liter = 10 deciliters = 33.81 fl. ounces1 meter = 10 decimeters = 39.37 inches 1 dekaliter = 10 liters = 2.64 gallons1 dekameter = 10 meters = 32.8 feet 1 hectoliter = 10 dekaliters = 26.42 gallons1 hectometer = 10 dekameters = 328.08 feet 1 kiloliter = 10 hectoliters = 264.18 gallons1 kilometer = 10 hectometers = 3,280.8 feet

Square MeasureWeights

1 sq. centimeter = 100 sq. millimeters = .155 sq. inch1 centigram = 10 milligrams = .15 grain 1 sq. decimeter = 100 sq. centimeters = 15.5 sq. inches1 decigram = 10 centigrams = 1.54 grains 1 sq. meter (centare) = 100 sq. decimeters = 10.76 sq. feet1 gram = 10 decigram = .035 ounce 1 sq. dekameter (are) = 100 sq. meters = 1,076.4 sq. feet1 decagram = 10 grams = .35 ounce 1 sq. hectometer (hectare) = 100 sq. dekameters = 2.47 acres1 hectogram = 10 decagrams = 3.52 ounces 1 sq. kilometer = 100 sq. hectometers = .386 sq. mile1 kilogram = 10 hectograms = 2.2 pounds1 quintal = 100 kilograms = 220.46 pounds Cubic Measure1 metric ton = 10 quintals = 1.1 short tons

1 cu. centimeter = 1000 cu. millimeters = .06 cu. inch1 cu. decimeter = 1000 cu. centimeters = 61.02 cu. inches1 cu. meter = 1000 cu. decimeters = 35.31 cu. feet

Approximate Conversion Factors

To change To Multiply by To change To Multiply by

inches centimeters 2.540 ounce-inches Newton-meters .007062feet meters .305 centimeters inches .394yards meters .914 meters feet 3.280miles kilometers 1.609 meters yards 1.094square inches square centimeters 6.451 kilometers miles .621square feet square meters .093 square centimeters square inches .155square yards square meters .836 square meters square feet 10.764square miles square kilometers 2.590 square meters square yards 1.196acres square hectometers .405 square kilometers square miles .386cubic feet cubic meters .028 square hectometers acres 2.471cubic yards cubic meters .765 cubic meters cubic feet 35.315fluid ounces milliliters 29,573 cubic meters cubic yards 1.308pints liters .473 milliliters fluid ounces .034quarts liters .946 liters pints 2.113gallons liters 3.785 liters quarts 1.057ounces grams 28.349 liters gallons .264pounds kilograms .454 grams ounces .035short tons metric tons .907 kilograms pounds 2.205pound-feet Newton-meters 1.356 metric tons short tons 1.102pound-inches Newton-meters .11296

Temperature (Exact)

°F Fahrenheit 5/9 (after Celsius °Ctemperature subtracting 32) temperature

PIN: 070463-000

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