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CA 12-12a 20 NOVEMBER 2015 Page 1 of 19
Section/division Accident and Incident Investigations Division Form Number: CA 12-12a
AIRCRAFT ACCIDENT REPORT AND EXECUTIVE SUMMARY
Reference: CA18/2/3/9624
Aircraft Registration
ZT-RAC Date of Accident 14 June 2017 Time of Accident 1030Z
Type of Aircraft MD 500E Type of Operation
Private (Part 91)
Pilot-in-command Licence Type PPL Helicopter Age 28 Licence Valid Yes
Pilot-in-command Flying Experience
Total Flying Hours
1030 Hours on Type 2.9
Last point of departure Welkom Airport (FAWM)-Free State Province
Next point of intended landing Christiana-North West Province
Location of the accident site with reference to easily defined geographical points (GPS readings if
possible)
Bultfontein area on a national road at GPS: 28°13'32.18"S, 26° 7'28.70"E and a field elevation of 4491ft
Meteorological Information Wind direction:195°; wind speed: 2-6kt; wind temperature:20°C: Visibility: CAVOK
Number of people on board 1+2 No. of people injured 0 No. of people killed 0
Synopsis
The pilot accompanied by two passengers was engaged on a private flight from FAWM to Christiana in the North West Province. According to the pilot they had also planned to fly over the area where his company was conducting road constructions on the regional road R700 in the area of Bultfontein for progress observation. Upon reaching the area, the pilot flew over the area as planned at approximately 80ft above ground level (AGL). He then made a turn to the right and the helicopter experienced an engine power loss and began spinning to the right. The pilot maintained control by stopping the spin and decided to execute a forced landing on a road. During a flare, the helicopter cushioning caused lot of dust which obscured the pilot vision and made it difficult to judge the height to the ground. Prior to contacting the ground it began to swing violently to the right due to the loss of tail rotor effectiveness. The helicopter contacted the ground hard with the right skid gear first which broke off., The aircraft was substantially damaged and neither the pilot nor passengers sustained injuries. The investigation revealed that the helicopter power loss was due to the pilot inadvertently cutting off the engine power, resulting in a rapid loss of height, a spin to the right followed by a hard impact with the road surface.
Probable Cause
Unsuccessful forced landing following a power loss due to the pilot inadvertent cutting off the engine power resulting in a rapid loss of height, a spin to the right followed by a hard impact with the road surface. Contributory factor: The Pilot used incorrect (Robinson R44) recovery technique instead of a correct (MD500E) recovery technique.
SRP Date 10 October 2017 Release Date 08 January 2018
CA 12-12a 20 NOVEMBER 2015 Page 2 of 19
Section/division Accident and Incident Investigation Division Form Number: CA 12-12a
AIRCRAFT ACCIDENT REPORT
Name of Owner : Aircraft Assets Finance Corporation
Name of Operator : Private
Manufacturer : Macdonnel Douglas Helicopter INC
Model : MD 500E
Nationality : South African
Registration Marks : ZT-RAC
Place : Bultfontein area on a national road at GPS:
28°13'32.18"S, 26° 7'28.70"E and a field elevation of
4491ft
Date : 14 June 2017
Time : 1030Z
All times given in this report are Co-ordinated Universal Time (UTC) and will be denoted by (Z). South
African Standard Time is UTC plus 2 hours.
Purpose of the Investigation:
In terms of Regulation 12.03.1 of the Civil Aviation Regulations (2011) this report was compiled in the
interest of the promotion of aviation safety and the reduction of the risk of aviation accidents or incidents and
not to establish blame or liability.
Disclaimer:
This report is produced without prejudice to the rights of the CAA, which are reserved.
1. FACTUAL INFORMATION
1.1 History of Flight
1.1.1 The pilot accompanied by two passengers was engaged on a private flight to
Christiana in the North West Province. According to the pilot, they had planned to
fly pass the Bultfontein area where his company was conducting road constructions
on R700 to observe the progress. Upon reaching the area the pilot descended to
about 80ft AGL and commenced with his fly pass as planned and then made a right
CA 12-12a 20 NOVEMBER 2015 Page 3 of 19
hand turn to follow the road. According to the pilot, during a turn the helicopter
engine out light illuminated associated with an audible sound through the
earphones and was followed by a loss of power. The helicopter then started
pitching the nose up and down and pulling left and right. The pilot immediately
rolled the throttle in an attempt to increase engine power and increased the
collective control without success. The pilot then entered into an autorotation
whereby the helicopter entered into a spin to the right. However the pilot was able
to contain the situation and regain control of the aircraft and stopped the spin. He
then further made a turn to the right as he passed a gravel road.
Figure 1: Shows the google view of the accident site and planned route
According to the eye-witnesses who was at the accident site at the time observed a
black helicopter flying pass on the left hand side along the road at a low height of
approximately 80ft AGL. When the helicopter was passing a T-junction, It was
observed making a turn to the right then suddenly it entered a spin before impacting
the ground.
1.1.2 According to the pilot he opted to execute a forced landing on a gravel road which
was perpendicular to R700. The aircraft came down at a high rate of descent while
rotating to the right. During a flare the aircraft entered a cloud of dust that was
caused by aircraft rotor downwash. The aircraft impacted the ground at high vertical
velocity and the right hand skid gear broke off on impact.
1.1.3 The main rotor blades also made contact with the ground while the aircraft was
skidding until it stopped at 2 meters before the road information board. The
helicopter sustained substantial damages to the right hand skid gear, bottom right
CA 12-12a 20 NOVEMBER 2015 Page 4 of 19
edge of the fuselage and all five main rotor blades were also damaged.
1.1.4 The accident occurred during day light conditions on the road R700 facing in the
direction North West next to the road information board with GPS position
determined to be 28°13'32.18"S, 26° 7'28.70"E and a field elevation of 4491ft
Above mean sea level
1.2 Injuries to Persons
1.2.1 None of the occupants sustained any injuries during the accident sequence.
Injuries Pilot Crew Pass. Other
Fatal - - - -
Serious - - - -
Minor - - - -
None 1- - 2- -
1.3 Damage to Aircraft
Figure 2: Shows damages to the helicopter
1.3.1 The helicopter sustained substantial damages to the right hand skid gear, bottom
right edge of the fuselage and all five main rotor blades were also damaged
CA 12-12a 20 NOVEMBER 2015 Page 5 of 19
1.4 Other Damage
1.4.1 None
1.5 Personnel Information
Nationality South African Gender Male Age 28
Licence Number 0272349499 Licence Type PPL
Licence valid Yes Type Endorsed Yes
Ratings Instrument
Medical Expiry Date 30 November 2017
Restrictions Corrective lenses
Previous Accidents None
Flying Experience:
Total Hours 1030.0
Total Past 90 Days 26.8
Total on Type Past 90 Days 2.9
Total on Type 2.9
1.5.1 The pilot is also a commercial pilot license holder on aeroplanes. According to the
available information, the pilot began his private pilot license on helicopter in 2015
on which he attained 60.1 hours on both R22/R44 helicopter types to date. On the
9th of June 2017 he then began with his conversion on the MD helicopter type and
accumulating 2.2hours when he was signed off on the 10th June 2017 by a qualified
type rated instructor allowing him to fly solo to build hours. The aircraft endorsement
records applications were submitted to SACAA on 14 June 2017. At the time of the
accident the application was still pending.
1.5.2 According to the pilot’s logbook the following were the hours accumulated as per
aircraft type flown:
Helicopter type Hours on type
Robinson R22 24.8
Kiss K-209 8.8
Robinson R44 35.3
MD500E 369E 2.9
CA 12-12a 20 NOVEMBER 2015 Page 6 of 19
1.6 Aircraft Information
The information is extracted from: Rotorcraft Flight Manual: MD 500E (Model 369E)
Figure 3: Show three view dimensions of the helicopter type
1.6.1 The aircraft is an import from Namibia and was initially registered in the SACAA
register in 2016. The MD 500E, model 369E helicopter is a 5 seater, rotary wing
aircraft constructed primarily of aluminium alloy. The airframe structure is egg-
shaped and provides very clean aerodynamic lines. The fuselage is a semi-
monocoque structure that is divided into three sections. It is powered by Rolls
Royce model 250-C20B gas turbine engine. The main rotor is a fully articulated five
bladed system, with anti-torque provided by a 2 bladed semi-rigid type tail rotor.
Power from the turbo shaft engine is transmitted through the main drive shaft to the
main rotor transmission and from the main transmission through a drive shaft to the
tail rotor.
An overrunning (one way) clutch, placed between the engine and main rotor
transmission permits free-wheeling of the rotor system during autorotation. The
landing gear is a skid-type attached to the fuselage at 12 points and is not
retractable. Aerodynamic fairing covers the struts. Nitrogen charged landing gear
dampers act as spring and shock absorbers to cushion landings and provide ground
resonance stability. Provisions for ground handling wheels are incorporated on the
skid tubes.
CA 12-12a 20 NOVEMBER 2015 Page 7 of 19
Airframe:
Type MD 500E (369E)
Serial Number 0210E
Manufacturer Macdonnel Douglas Helicopter Inc
Date of Manufacture 1998
Total Airframe Hours (At time of Accident) 3659.1
Last MPI (Date & Hours) 03 June 2017 3655.7
Hours since Last MPI 4.6
C of A (Issue Date/Expiry Date) 14June 2016/ 13 June 2018
C of R (Issue Date) (Present owner) 25 November 2016
Operating Categories Standard Part 127
Engine:
Type 250-C20B
Serial Number CAE-835774
Hours since New 3659.1
Hours since Overhaul Modular
Main Rotor:
Type 369D21100 (X5)
Serial Numbers H970;H971;H973;H974;H978
Hours since New 1805.1
Hours since Overhaul TBO not yet reached
Tail Rotor:
Type 369D21600-503 (X2)
Serial Numbers C244/ C245
Hours since New 5143.4
Hours since Overhaul TBO not yet reached
1.6.3 . The helicopter was involved in a main rotor incident strike at airframe hours 1854,4
on 14 February 1995 in the country of origin. All five main rotor blades were
changed with the currently installed. According to the available maintenance
records, the helicopter was maintained and equipped in accordance with
manufacture’s approved procedure by the regulator approved AMO. At the time of
the accident flight, the helicopter was just transferred from FALA to FAWM to the
new owner whose owner paperwork was still under process at CAA offices.
CA 12-12a 20 NOVEMBER 2015 Page 8 of 19
1.7 Meteorological Information
1.7.1 The meteorological conditions as obtained from the pilot’s questionnaire
Wind direction 195° Wind speed (2-6)kt Visibility CAVOK
Temperature 20°C Cloud cover Unknown Cloud base Unknown
Dew point Unknown
1.8 Aids to Navigation
1.8.1 The helicopter was equipped with standard navigation equipment that meets the
requirement of the regulator. There were no reported defects with the navigation
equipment at the time of the accident.
1.9 Communications.
1.9.1 The helicopter was equipped with standard communication equipment that meets
the requirement of the regulator. There were no reported defects with the
communication equipment at the time of the accident.
1.10 Aerodrome Information
1.10.1 The accident occurred on the regional road R700 facing in the direction North
Westerly next to the road information board with GPS position of: 28°13'32.18"S,
26° 7'28.70"E and a field elevation of 4491ft.
1.11 Flight Recorders
1.11.1 The helicopter was not fitted with a cockpit voice recorder (CVR) or a flight data
recorder (FDR) and neither was required by the regulation to be fitted to this type of
helicopter.
CA 12-12a 20 NOVEMBER 2015 Page 9 of 19
1.12 Wreckage and Impact Information
1.12.1 The helicopter accident occurred on a Regional road R700 which was under
construction (Refer to Figure 1). The area surrounding the accident site is private
farms with vegetation. According to the pilot, the flight was planned for them to fly
pass over the region to observe the progress on the road works and then proceed
to the landing destination. According to the pilot, the helicopter’s approach was at a
1000ft AGL and then descended to approximately 80ft AGL. Moments after a turn to
the right the engine experienced power loss.
Figure 4: Shows the ground scars caused by impact sequence
The helicopter impacted hard with the ground as a result of loss of control. The
impact marks on the road surface began at 1 to 2 meter from the helicopter
wreckage on the right hand side. According to the pilot, the helicopter at close
proximity to the ground whilst been cushioned caused lot of dust which obscured
him from making a clear judgement of the distance to the ground. The helicopter
began rotation to the right hand side direction due to loss of tail rotor effect and
suddenly contacted the ground hard where after it bounced on towards the tar road.
At the time the pilot noticed collision was evitable with the road signage on the side
of the road and then turned the helicopter toward the right hand side. The helicopter
contacted hard with the right hand skid gear first and began skidding where after it
broke off. The helicopter fuselage dropped to the right and began skidding along
with the main rotor contacting the ground. The helicopter came to a full stop 2m
from the road signage.
CA 12-12a 20 NOVEMBER 2015 Page 10 of 19
Figure 5: Wreckage as it was found
Wreckage examination as it was found:
There was hard contact and skidding marks on the tar road edge leading
towards the right hand side of the wreckage.
The right landing skid gear broke-off from the root attachment points.
The right hand fuselage bottom edge was damaged due to scrapping along
the tar road.
All five main rotor blades made contact with the ground and got damaged.
The damage on the rotor blades are consistent with the damage caused by
auto-rotation.
All annunciating audible and warning lighting were serviceable.
The left front door was damaged by the main rotor during the accident
sequence.
1.13 Medical and Pathological Information
1.13.1 N/A
1.14 Fire
1.14.1 There was no evidence of pre or post impact fire during the accident.
CA 12-12a 20 NOVEMBER 2015 Page 11 of 19
1.15 Survival Aspects
1.15.1 The accident was considered survivable. The cockpit was intact with no damages
sustained. The ELT did trigger following the accident in which the Search and
Rescue made some follow-up and then advised the AIID regarding the situation. A
location and time of the activation was provided to the investigating personnel.
1.16 Tests and Research
1.16.1 Following the reporting of the alleged engine power loss. The MD helicopter and the
engine manufacturers were invited to test both the fuel system on the airframe and
on the engine. None of the tests revealed any anomalies that could have
contributed to the accident.
Research (Refer to the Annexure A)
1.17 Organizational and Management Information
1.17.1 This was a private flight under provision of Part 91
1.17.2 According to the maintenance records, the helicopter was equipped and maintained
in accordance with the manufacture’s prescribed procedures by a regulator approved
aircraft maintenance organisation.
1.17.3 According to the available records, the helicopter was recently bought by a new
owner who resides in the area of Welkom in the Free State Province. The helicopter
was transferred on the 10th of June by the accident pilot and the instructor as part of
the training. The pilot was the only person available with helicopter flying
experience upon its transfer. His helicopter training conversion was conducted to
make him ready to operate the machine.
1.18 Additional Information
1.18.1 Pilot statement
According to the pilot during the reported power loss, he stated that he rolled the
throttle in an attempt to increase power on the helicopter engine however it was
unsuccessful.
CA 12-12a 20 NOVEMBER 2015 Page 12 of 19
According to the manufacturer’s pilot, the use of throttle during normal operation is
not advisable. This is in relation with the helicopter type operating hand book which
only indicate the use of throttle twisting (rolling) during engine starting and engine
switching off.N1 and N2 governor control switches are provided to increase engine
power on demand during operation.
1.18.2 The pilot is more qualified on the piston engine helicopter type. The helicopter type
he was flying at the time of the accident was equipped with a turbine engine.
Throttle control differential as compared on both helicopters
Robinson R44 Helicopter: Information is extracted from Robinson POH Model
R44 II Page 3-2
Power failure between 8ft and 500ft AGL
Procedure:
Lower collective immediately to maintain rotor RPM
Adjust collective to keep RPM between 97 and 108 or apply fully down
collective if weight prevents attaining above 97
Maintain airspeed until ground approached then begin cyclic flare to reduce
rate of descent and forward speed.
At about 8feet AGL, apply forward cyclic to level ship and raise collective just
before touchdown to cushion landing. Touchdown in level attitude and nose
straight ahead.
Loss of tail rotor thrust during hover
1. Failure is usually indicated by right yaw which cannot be stopped by applying
left pedal.
2. Immediately roll throttle off into detent spring and allow aircraft to settle.
3. Raise collective just before touchdown to cushion landing.
1.18.3 UNANTICIPATED YAW / LOSS OF TAIL ROTOR EFFECTIVENESS (LTE)
Unanticipated yaw is the occurrence of an un-commanded yaw rate that does not
subside of its own accord and, which, if not corrected, can result in the loss of
helicopter control. This un-commanded yaw rate is referred to as loss of tail rotor
effectiveness (LTE) and occurs to the right in helicopters with a counter clockwise
rotating main rotor and to the left in helicopters with a clockwise main rotor rotation.
CA 12-12a 20 NOVEMBER 2015 Page 13 of 19
Again, this discussion covers a helicopter with a counter-clockwise rotor system and
an anti-torque rotor. LTE is not related to an equipment or maintenance malfunction
and may occur in all single-rotor helicopters at airspeeds less than 30 knots. It is the
result of the tail rotor not providing adequate thrust to maintain directional control,
and is usually caused by either certain wind azimuths (directions) while hovering, or
by an insufficient tail rotor thrust for a given power setting at higher altitudes.
For any given main rotor torque setting in perfectly steady air, there is an exact
amount of tail rotor thrust required to prevent the helicopter from yawing either left
or right. This is known as tail rotor trim thrust. In order to maintain a constant
heading while hovering, you should maintain tail rotor thrust equal to trim thrust.
The required tail rotor thrust is modified by the effects of the wind. The wind can
cause an un-commanded yaw by changing tail rotor effective thrust. Certain relative
wind directions are more likely to cause tail rotor thrust variations than others. Flight
and wind tunnel tests have identified three relative wind azimuth regions that can
either singularly, or in combination, create an LTE conducive environment. These
regions can overlap, and thrust variations may be more pronounced. Also, flight
testing has determined that the tail rotor does not actually stall during the period.
When operating in these areas at less than 30 knots, pilot workload increases
dramatically.
1.19 Useful or Effective Investigation Techniques
1.19.1 None
2. ANALYSIS
2.1 According to the available information, the pilot is a private pilot license holder on
helicopter with 2.9 hours on the helicopter type. Prior to the accident flight, the pilot
flew the helicopter on two occasions during his helicopter type conversion and
accumulated 2.2 flying hours. He was then signed off to fly unsupervised by a
helicopter type rated instructor allowing him to building hours. It is the investigator’s
opinion that the insufficient training offered to the pilot was influenced by the
operational matters. The pilot was the only person who has helicopter flying
experience in which the helicopter was recently purchased and was delivered to
their facility. It is evident that the pilot training insufficient as per hours accumulated
by the pilot.
CA 12-12a 20 NOVEMBER 2015 Page 14 of 19
2.2 The pilot was more experienced on flying a reciprocating engine equipped
helicopters (R44’s) which had a difference of engine power increase settings on
demand operations. On the R44 which is also fitted with a governor switch, raising a
collective control will increase engine power and also adjusting the blade pitch
symmetrically to maintain minimum required power to sustain lift. However on the
MD helicopter type to increase engine power demands are controlled by adjusting
either N1 or N2 governor switch allocated on the collective control column raising the
collective on the MD will only increase the pitch and not the power. The pilot stated
that during a turn, the helicopter commenced an un-commanded yaw to the right in
which afterwards he started operating the twist grip in an attempt to increase engine
power however was unsuccessful.
The recovery (procedure) technique used by the pilot to increase engine power on
the helicopter type by using twist grip either than the allocated governor switches N2
is used on an R 44 and not in the case of MD helicopter.
2.3 The pilot stated that during a turn to the right hand side, the helicopter experienced
an un-commanded yaw to the right. These actions are indicative to an unanticipated
yaw relating to the loss of tail rotor effectiveness. The helicopter is equipped with
five main rotor blade system that rotate counter clockwise. This will cause the nose
of the aircraft to have a turning effect to the right, therefore to counter act this
turning effect the use of the left anti-torque pedal will be required to compensate
this movement.
2.4 The manufacturer was invited to assist with the investigation of fuel system and
engine. The engine was removed and bench tested on a test cell. The engine was
performing in accordance with the manufacture’s specification. No anomalies were
noticed during any of the tests relating to the fuel system and reported engine
power loss and the flight control systems.
2.5 The reported weather condition at the time leading to the accident did not have any
contributions towards this accident.
3. CONCLUSION
3.1 Findings
3.1.1 The pilot was signed off to fly the helicopter solo for hour building by a helicopter
type rated instructor at approximately 2.2hours flying experience. The pilot’s flying
experience and familiarisation on the helicopter type was found to be insufficient at
CA 12-12a 20 NOVEMBER 2015 Page 15 of 19
the time of the flight.
3.1.2 The helicopter type was not yet endorsed on his license at the time of the accident.
The application was submitted on the same date of the accident, however, he was
signed off by a type rated instructor allowing him to build hours unsupervised.
3.1.3 The pilot had more flying hours on the piston engine helicopters as compared to the
turbine engine equipped helicopters.
3.1.4 The helicopter was maintained and equipped by the regulator approved AMO in
accordance with manufacture’s approved procedures. The helicopter had enough
fuel at the time of the accident.
3.1.5 Good weather conditions prevailed in the surrounding area and it cannot be
attributed to the cause of the accident.
3.1.6 The pilot only had accumulated 2.9 hours on type which was inadequate to handle
any emergencies that may occur and control the situation safely.
3.1.7 The engine was removed and tested on test cell and it was running in accordance
with manufactures specification.
3.2 Probable Cause/s
3.2.1 The helicopter experienced engine power loss due to the pilot inadvertently cutting
off the engine power resulting in a rapid loss of height, a spin to the right followed by a
hard impact with the road surface.
Contributory factor:
3.2.2 The Pilot used incorrect (Robinson R44) recovery technique instead of a correct
(MD500E) recovery technique.
CA 12-12a 20 NOVEMBER 2015 Page 16 of 19
4. SAFETY RECOMMENDATIONS
4.1 It is recommended to the DCA in the interest of aviation safety to review and
possibly impose the minimum hours required for conversation training of piston
helicopter to turbine powered helicopter. The turbine engine helicopter has more
functions and very complex systems and the pilot had only 2.2 hours for conversion
and it was evident during this accident that he had difficulties in handling the
emergencies and to land the helicopter safely.
5. APPENDICES
5.1 The information is extracted from: Rotorcraft Flight Manual: MD 500E (Model 369E)
Section 4 Pages (4-23, 4-24)
CA 12-12a 20 NOVEMBER 2015 Page 17 of 19
5.1 Annexure A
5.1.1 The information is extracted from: Rotorcraft Flight Manual: MD 500E (Model 369E)
Section 4 Pages (4-23, 4-24)
Low rotor Speed
Indications: Red [Engine out] warning indicator ON and Audible warning in headset
Drop in RPM/ Change in noise level
Note: The LOW ROTOR warning is activated when Nr falls below 468.
Conditions: Low rotor RPM will most commonly be associated with the following
Engine failure
Transient rotor droops during large, rapid increases in power.
Governor failure producing an under speed.
Procedure:
Respond immediately to the low rotor RPM warning by adjusting collective to
maintain rotor RPM within limits.
Check other Caution/ Warning indicators and engine instruments to confirm
engine trouble and respond in accordance with appropriate procedures in
this section.
Low speed Manoeuvring
Manoeuvers that exceed thrust capability of the tail rotor should be avoided.
Note: Conditions where thrust limits may be approached are: High density altitude,
high gross weight, rapid pedal turns and placing the helicopter in a down wind
conditions. These conditions may exceed the thrust capability of the tail rotor.
Extreme aircraft attitudes and manoeuvres at low speeds should be avoided.
Warning: Un-coordinated turns/ manoeuvers may cause fuel starvation with less
than 35 pounds of fuel on board.
Warning: Observe the cross-hatched region of Height Velocity Diagram (Ref
Section V). These represent airspeed / altitude combinations from which a
successful autorotation may be difficult to perform. Operation within the cross
hatched area is not prohibited but should be avoided.
CA 12-12a 20 NOVEMBER 2015 Page 18 of 19
Practice Autorotation
Warning Performance throttle rigging check prior to attempting practice auto
rotations. Mis-rigging of the throttle control may result in inadvertent
flameout during rapid closing twist grip to the ground idle position.
Uncoordinated turns/ manoeuvres may cause fuel starvation with less
than 35 LBS of fuel. Do not practice autorotation if the FUEL LEVEL
LOW caution indicator is ON.
Caution : Do not perform intentional full touchdown autorotation with blade
tracking reflectors installed on blade tips.
For autorotation decent, the twist-grip should be in the full open/ ground idle
position. However, if a practice autorotation landing (minimum engine power) is
desired, rotate the twist-grip to the ground idle position. Increase collective pitch
after establishing autorotation to prevent rotor over speed if flight is at high gross
weight or high density altitude. To reduce rate of descent or to extend gliding
distance, operate at minimum rotor rpm. Restore ROTOR RPM (NR) by lowering
collective prior to flare out. If a power recovery is desired, lower collective to full
down, rotate the twist-grip to the full open position, verify that N2 is between 102%
and 103% percent and that full engine power is available prior to increasing
collective.
Conduct practice autorotation at 131knots IAS or below (see Vne placards). Maintain
rotor between 420 and 523 by use of the collective control.
Note: Keeping the rotor above 420RPM will place the engine above the N2 speed
avoid range.
Caution: Refer to Section II “Power turbine (N2) speeds avoid ranges”.
Maximum glide distance is attained at 80knots and 410 rotor RPM.
Minimum rate of descent is attained at 60knots and 410 rotor RPM
Note: Glide distance attained during an actual engine autorotation may be less than
the glide distances achieved during practice autorotation’s when operating at
reduced RPM (N2/Nr needles joined).
Touchdown in a level attitude
Avoid use of aft cyclic control or rapid lowering of collective pitch during initial
ground contact or during ground slide.
CA 12-12a 20 NOVEMBER 2015 Page 19 of 19
Autorotation RPM
Normal rotor RPM (collective fully down) is 485±5 RPM at 2250 pound gross weight
at sea level, 60knots. Rotor speed will decrease approximately 10RPM for each 100
pounds reduction in gross weight and increase approximately 6.5 RPM for each
1000 foot increase in density altitude. For gross weights greater than 2250 pounds,
increase collective control as required to maintain approximately 485 RPM.
Recommended