He had a backup electrically driven attitude indicator, but he reported that it did not seem to be in agreement with a remotely driven compass. A witness saw a wing separate from the aircraft after it emerged from the base of a high overcast. When the turn is stopped, assure that it is stopped by cross-checking with other instruments, and that the plane is not changing altitude. Help may be available from other sources in your aircraft. At Aero-Tech in Lexington, Kentucky, instructors teach students to consider the resources at hand, such as an autopilot that can control the aircraft in the Nav mode and take its information from the VOR or GPS receiver.
Autopilots using turn coordinators as a reference are unaffected by a vacuum failure.
An ADF with a compass card that is slaved to a magnetic heading sensor can replace the heading indicator. A GPS can supply almost instantaneous updates of the aircraft s heading during a turn. Professional Instrument Courses teaches students the configurations and power settings needed for all phases of flight, from climb and cruise to precision approach and nonprecision approach descent, to ease the workload during partial-panel flying. Airline and military pilots will tell you that they practice partial-panel flight and approaches infrequently, if ever. Redundant systems and backup instruments make instrument failure highly unlikely.