Textron Aviation Cessna 172S NAV III Skyhawk SP, Information Manual

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CESSNA SECTION 3
MODEL 172S NAV III EMERGENCY PROCEDURES
KAP 140 AUTOPILOT
U.S.
EMERGENCY OPERATION IN CLOUDS
(Continued)
EMERGENCY DESCENT THROUGH CLOUDS (AHRS
FAILED)
When returning to VFR flight after a 180° turn is not practical, a descent
through the clouds to VFR conditions below may be appropriate. If
possible, obtain an ATC clearance for an emergency descent through
the clouds.
AHRS FAILURE
Choose an easterly or westerly heading to minimize non-stabilized
magnetic compass card sensitivity. Occasionally check the compass
heading and make minor corrections to hold an approximate course.
The autopilot may be engaged in ROL mode to keep the wings level
and VS mode to control rate-of-descent.
Before descending into the clouds, prepare for a stabilized descent as
follows:
1. Apply full rich mixture.
2. Turn pitot heat on.
3. Set power for a 500 to 800 feet per minute rate of descent.
4. Set the elevator trim for a stabilized descent at 80 KIAS.
5. Use the standby attitude indicator roll pointer and index to keep
wings level.
6. Check trend of compass card movement and make cautious
corrections with rudder to stop the turn.
7. Upon breaking out of clouds, resume normal cruising flight.
172SPHAUS-05 3-29
For
Training
Purposes
Only