Flight Instruments

Question 1

EFIS Data Sharing

Answer 1

The Avionics Standard Communications Bus allows data travel between the various computers of the aircraft. It is controlled by the AFCS computer.

The Private Line links the AHRU to the SGU in the event of ASCB failure.

The Video Bus distributes signals fro the SGU to the various CRTs in the system.

Question 2

AFCS

Answer 2

The Auto Flight Control System receives data from the two ADC, AHRS, SGU, the radio altimeter, the GNSS and from some sensors. It generates commands to the flight control actuators and to the FD bars. The AFCS is the ASCB controller too.

Question 3

AHRU

Answer 3

Attitude and Heading Reference Unit includes an Inertial measurement unit (INU) composed of three gyrometers and three accelerometers. The AHRU receives inputs from its associated flux valve and the TAS, fed by both ADC, is used to compute gyro erection and also sends attitude and heading signals to indicators, AFCS, Wx Radar, and FDAU. Vert. accuracy +/-1.4* Heading accuracy +/-2*

Question 4

AHRU1 supplies

Answer 4

SGU 1- attitude and heading
FO RMI- heading
FDAU- attitude and heading 
Radar- attitude 
ASCB 
GPS

Question 5

AHRU2 supplies

Answer 5

SGU2- attitude and heading
CA RMI- heading
ASCB

Question 6

ADC

Answer 6

Air Data Computers is supplied with static air pressure (static ports), total air pressure (pitot ports), total air temperature (TAT probe). With these inputs, the ADC computes pressure altitude, VS, IAS, TAS, TAT, SAT.

Question 7

SGU

Answer 7

Symbols Generator Unit:
– collects all the data, coming
* from the ASCB (AFCS, AHRU, ADC)
* from navigation sources (VOR, ILS, DME, ADF, GNSS)
* from the remote controller (CRS, HDG)
– converts the data in video format, for the EFIS (EADI, EHSI)
– transfers the video data, from the weather radar or the EGPWS to the EHSI

Question 8

EADI Alerts

Answer 8

AHRS and ILS systems are monitored by the SGUs an amber alert and EFIS COMP CCAS is generated for:
HDG- >6* and bank 12* and bank >6*
PIT- >6* pitch 
ROL- >6* roll
ATT- both pitch and roll disagree 
LOC- >0.6* localizer 
GS- >0.2* glide slope
ILS- both loc and gs disagree

Question 9

EFIS Components

Answer 9

ASCB
Private Line
Video Bus

AFCS
2 AHRU
2 ADC
2 SGU

Question 10

EADI/EHSI Failures

Answer 10

SGU FAILURE alert
A and B part failure and all information disappears from EADI and EHSI

AHRS FAILURE
the associated information immediatly disappear from both CRTs. ATT FAIL message is displayed

SGU FAILURE alert
C part failure and a red cross appears on EADI and EHSI

AHRS FAILURE
the associated information immediatly disappear from both CRTs. HDG FAIL message is displayed

Question 11

EADI/EHSI Failures

Answer 11

SGU FAILURE alert
A and B part failure and all information disappears from EADI and EHSI

AHRS FAILURE
the associated information immediatly disappear from both CRTs. ATT FAIL message is displayed

SGU FAILURE alert
C part failure and a red cross appears on EADI and EHSI

AHRS FAILURE
the associated information immediatly disappear from both CRTs. HDG FAIL message is displayed