Indications: Steady off flags in the ADI, HSI and CONTR AUG caution light with master alert (when less
than 217 KIAS and flaps other than up).
The procedure for dealing with a SAHRS failure is:
Use the standby AI and standby compass for attitude and heading information.
Select COMP on the SAHRS control unit.
Maintain VFR flight conditions, if possible.
Report the instrument failure to ATC.
Land as soon as practicable.
Transition to standby AI and wet compass: if NAV flag is not visible, TACAN/VOR bearing and TACAN
range will be accurate. However, the HSI card will freeze. #1 and #2 bearing pointers will no longer point
to the station; but the tails will properly indicate correct radial. ILS will be inoperative.
When able, inform ATC of primary attitude and heading indicator failure, request a no-gyro ground
controlled approach. If this service is unavailable, use tail of bearing pointer to ascertain position and
perform timed turns to predetermined headings on the magnetic compass. Remember, the magnetic
compass gives erroneous indications during turns. Check magnetic compass heading during wings level,
balanced flight with zero VSI for most accurate reading.
Stuck HSI Card TACAN Arcing
To arc, note radial and make a 90 degree timed turn (30 second SRT) left or right. To determine heading,
add 90 degrees for clockwise arc or radial minus 90 degrees to arc counter clockwise. To maintain arc,
hold AOB that keeps range at desired DME. Watch for tail to rise to lead radial and perform timed turn to