IFR Vacuum Failure
The Cessna 182S POH (actually all
the new Cessna manuals say pretty much the same thing) also covers emergency
operation in clouds where a total vacuum system failure is suspected and "the
pilot is not completely proficient in instrument flying.
Executing a 180 degree turn in clouds: "Upon inadvertently entering the clouds,
an immediate plan should be made to turn back as follows:
1. Note the compass heading.
2. Using the clock, initiate a standard rate left turn, holding the turn
coordinator symbolic airplane wing opposite the lower left index mark for 60
seconds. Then roll back to level flight by levelling the miniature airplane.
3. Check accuracy of the turn by observing the compass heading which should be
the reciprocal of the original heading.
4. If necessary, adjust heading primarily with skidding motions rather than
rolling motions so that the compass will read more accurately.
5. Maintain altitude and airspeed by cautious application of elevator control.
Avoid over controlling by keeping the hands off the control wheel as much as
possible and steering only with rudder."
IFR Emergency Descent
The procedures for an emergency descent through clouds are similar, using
power to set up a 500 to 800 ft/min rate of descent, trim for 80 KIAS and
keeping the hands off the control wheel, steering only with the rudder, using
the compass for maintaining heading rather than the gyro. Recovery from a spiral
dive into the clouds involves retarding the throttle to idle, using rudder and
aileron to level the wings of the artificial plane on the TC, cautiously
reducing airspeed to 80 KIAS, then keeping hands off the control wheel and
steering using only rudder. Clear the engine occasionally, but avoid using
enough power to disturb your trimmed glide. On breaking out of the clouds,
resume normal flight. For these two procedures Cessna recommends maintaining a
heading of W or E in order to minimize compass error.
Emergency Use of Turn Coordinator
Best to do considerable "rudder
Centre the turn needle with the rudder and keep it centred using only
Hands off the flight controls.
Lower the landing gear.
Reduce the power above a high idle.
Trim to its predetermined airspeed.
Propeller pitch full forward
Power to the predetermined setting.
Expect airspeed oscillations
Check the compass heading.
Turn with the rudder.
Roll out on the desired heading using lead or lag if relying on a magnetic
Altitude is changed using power supplemented by rudder pressure to maintain