DIGITAL COMPLETE.doc

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ELECTRONIC FLIGHT INSTRUMENT SYSTEMS (EFIS)

INTRODUCTION

An electronic flight instrument system, or EFIS, is a flight deck instrument display

system in which the display technology used is electronic rather than

electromechanical. EFIS normally consists of a primary flight display (PFD), multi-

function display (MFD) and Engine Indicating and Crew Alerting System (EICAS)

display. Although cathode ray tube (CRT) displays were used at first, liquid crystal

displays (LCD) are now more common.

The complex electromechanical attitude director indicator (ADI) and horizontal

situation indicator (HSI) were the first candidates for replacement by EFIS. However,

there are now few flight deck instruments for which no electronic display is available.


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AIR DATA SYSTEM - DESCRIPTION AND OPERATION

A. The air data computing system provides air data information to the integrated

display system and other interfacing systems. The system consists of these

components:

MAS ALL; AIRPLANES WITH THREE ADCS

(i) Three air data computers (ADC)

MAS ALL

(ii) Two angle of attack (AOA) sensors

(iii) Two total air temperature (TAT) probes

(iv) Two air data source select relays

(v) Two air data source select switches

(vi) A gear down dispatch switch

MAS 103-110, 201-207, 366-999; MAS 001, 002 POST SB 747-71-2232

(vii) A fifth engine carriage switch


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MAS ALL

i. The inputs to the air data system are pitot and static air pressure from the

pitot-static systemPAGEBLOCK 34-11-00/001, angle of attack from the AOA

sensors, total air temperature (TAT) from the TAT probes, and barometric

pressure correction from the EFIS control panels.

ii. A number of discrete signals are also applied to the air data system. These

discretes perform functions such as selection of SSEC curve, selection of

maximum operating speed curve, definition of status of the air data sensor

heaters, and selection of desired mode of operation.

iii. The air data system outputs are available on four ARINC 429 buses. One test

only data bus, which iselectrically connected to the No. 1 bus, is available on

the ADC front panel. All four of the buses aredentical and contain the same

data.

B. The No. 1 bus supplies data to the following autopilot and flight director

system and warning interfaces:

i. Flap control units (FCU)

ii. Stabilizer trim/rudder ratio modules (SRM)

iii. Flight management computer/thrust management computers (FMC/TMC)

iv. Flight control computers (FCC)

v. Yaw damper modules (YDM)

vi. Modularized avionics and warning electronics assembly (MAWEA) The

MAWEA contains the altitude alert logic, speed tape barber pole logic, and

stall warning functions.


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The No. 2 bus supplies data to the following instrument display interfaces:

i. Inertial reference units (IRU)

ii. EFIS/EICAS interface units (EIU)

iii. MAWEA

iv. The No. 3 bus supplies data to the electronic engine controls (EEC).

v. The No. 4 bus supplies data to the following general purpose and alternate

interfaces:

(a) Cabin Pressure Controllers (CPC)

(b) Ground proximity warning computer (GPWC)

(c) Air traffic contol transponders (ATC)

(d) Data management unit (DMU)

(e) Alternate source input for the following:

1) SRM

2) FMC/TMC

3) EIU

4) FCU

5) YDM

6) IRU


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EFIS control panel control panel controls that are used with the air data

system are the meters (MTRS) button and the baro set control

Pushing the MTRS button adds or removes the altitude display in meters on

the

corresponding PFD.

The baro set control consists of an outer and an inner concentric knob, the

inner knob isalso a push button

The outer knob selects the selected barometric reference to Be displayed in

inches of mercury (IN) or hecto Pascals (hPA) on the corresponding PFD.

Each time the STD barometric reference is selected, 29.92 IN or 1013 hPa

will be displayed just below STD in the preselect readout on the

corresponding PFD

A preselected barometric reference value can be selected by rotating theinner knob. After a preselected value has been set by rotating the inner knob,

pressing the knob will remove the STD barometric reference and replace it

with the preselected barometric reference value.

The altitude in meters and the barometric reference settings can be set using

the CDU in the event that the EFIS control panel fails.

The captains and first officers EFIS control panels are located on the left and

right sides of the pilots light shield


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EFIS/EICAS interface unit (EIU)

The three EIUs receive digital data, on data bus No. 2 and data bus No. 4,

and discrete from each ADC

The EIUs process this information to create air data system displays on the

PFDs and air data system warning, status, and advisory messages for the

EICAS displays.

The left ADC serves as the primary source for the left EIU and an alternate

source for the right and center EIUs.

The right ADC serves as the primary source for the right EIU and an alternate

source for the left and center EIUs

The center ADC serves as the primary source for the center EIU and an

alternate source for the left and right EIUs


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Main and auxiliary EICAS displays

Air data system display presentation on the primary EICAS consists of total air

temperature (TAT). TAT is displayed by a digital readout in degrees Celsius or

degrees Farenheit including sign.


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When the readout indicates zero degrees, the sign is removed. A detected

TAT failure is annunciated by removal of the digital readout including sign andunits.

Air data system warning (red) and advisory (amber) messages are displayed

on the primary EICAS. The latest occurrence message will appear on the top

line of the display.

An advisory message will follow a caution message if a caution message is

displayed and a caution message will follow a warning message if a warning

message is displayed. Air data system status (white) messages are displayed on the secondary

EICAS display. To bring up a status message on the secondary EICAS

display, the STAT button on the EICAS display select panel must be pushed.

Pushing the STAT button will bring up the latest occurrence status message.

A list of air data system EICAS messages are shown inTable 1.


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Components of the inertial reference system that interface with the air data

system are the:

(a) Left inertial reference unit (L-IRU)

(b) Center inertial reference unit (C-IRU)

(c) Right inertial reference unit (R-IRU)

The inertial reference system receives digital data from the left and right

ADCs on data bus No. 2 and data bus No. 4.

The left ADC serves as the primary source for the left and center IRUs and

the alternate source for the right IRU. The right ADC serves as the primary

source for the right IRU and the alternate for the left and center IRUs.

Data will be provided by the center ADC when it is used as an alternate

source for either the left or right ADC.

Selection of the air data input source for the left IRU is controlled by the

captains air data source select switch.

Selection of the air data input for the right IRU is controlled by the first officers

air data source select switch. Selection of the air data input for the center IRU

is controlled by the first officers IRS source select switch


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The vertical speed displayed on the PFDs is baro-inertial vertical speed data

derived by the inertial reference system. The switching arrangement ensures

that vertical speed data is provided from two independent sources when one

IRU is inoperative.

Primary flight display (PFD)

The PFD displays for several electronic systems. The following paragraphs

describe the displays for the air data system

The altitude tape display presented on the right side of the PFD is an

electronic representation of a continuously rotating drum with a fixed readout

box in 20-foot increments.

The altitude tape displays a full scale range of 825.0 feet at any given time

with


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numeric altitude placed at 200-foot intervals.

Indices are placed every 100 feet. Negative values will show a negative sign

immediately to the left of the most significant displayed digit

A detected failure of the displayed altitude information is annunciated by

removal of the altitude tape and the appearance of a yellow boxed ALT where

the altitude tape is normally located

Altitude in meters, when selected, equivalent to feet is digitally displayed

above the fixed altitude readout box. The metric altitude is rounded to the

nearest one meter

The metric readout is removed when an altitude failure is detected

The airspeed tape display presented on the left side of the PFD is an

electronic representation of a continuously rotating drum with a fixed readout

box in 1-knot computed airspeed (CAS) increments

The airspeed tape displays a full-scale range of 123.75 knots at any given

time interval with numeric airspeed placed at every 20-knot intervals starting

at 40 knots.

Indices are placed every 10 knots starting at 30 knots and ending at 420

knots. A detected failure of the displayed airspeed information is annunciated

by removal of the airspeed tape and the appearance of a yellow boxed SPD

where the airspeed tape is normally located.

Current Mach is displayed digitally below the airspeed tape by a period

followed by a 3-digit number. A detected failure of CAS will remove the Mach

readout

A detected Mach failure and not a detected CAS failure is annunciated by

removal of the Mach readout and the appearance of a yellow boxed MACH

where the Mach readout is normally located

The Vmo speed displayed is the smallest value parameter that is received

from the stall warning computer and the air data computer. A detected failure

of CAS will remove the Vmo barber pole symbol.


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The barber pole symbol consists of red squares spaced equally on a black

background. The barber pole symbol will extend from Vmo speed limit to the

upper edge of the airspeed tape (in the direction of larger airspeed values).

If the airspeed values displayed are lower than the Vmo speed limit, the

barber pole symbol will not be displayed

Vertical speed is displayed on the right side of the PFD in digital and analog

representation. The digital readout appears when the vertical speed equals or

exceeds plus or minus 400 feet per minute.

If the vertical speed is negative, the digital readout appears below the analog

display without a minus sign. If the vertical speed exceeds plus or minus 9999

feet per minute, the display will read 9999

The analog display is a fixed scale with a moving pointer. The pointer moves

in a windshield wiper manner about a center point located off the display

along the PFD horizontal centreline

The pointer indicates the value along an analog scale. The scale is positive

for values up from the center line and is negative for values down from the

centerline. The scale is linear between numerics.

The scale defined for the 2000 to 6000 feet per minute range is extended to

the upper or lower display range limit when the vertical speed exceeds the

analog display range limit and the pointer parks in view at the upper or lower

limit.

A detected vertical speed failure is annunciated by removal of the digital

readout and analog display and the appearance of a yellow boxed VERT

where the analog display is normally located.

Selected barometric reference is displayed below the altitude tape full time as

either a numeric value with units or as the letters STD for standard barometric

reference (29.92 in. Hg).

There are two display locations for barometric information, actual barometric

reference used and preselected barometric reference to be used. Preselected

barometric reference is displayed when standard (STD) is selected on the

EFIS control panel for barometric reference used


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When selected barometric reference is displayed, the units legend is IN. for

inches-of-mercury or hPa for Hecto Pascals. The barometric reference display

range is 22.0 to 32.0 inches-of-mercury or 745.0 to 1082.6 Hecto Pascals. A

detected barometric reference failure is annunciated by removal of thatdisplay

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