Flight conditions included low ceilings, poor visibility, snow, and turbulence. Unless using a simulator, most of us have never been trained in the actual way vacuum pumps fail, so the slow-death routine of most attitude indicators is at first difficult to identify. Attitude indicators die like bad actors in early Western movies, taking forever in order to draw out the scene. When simulated during training, the instructor simply reaches over and slaps a suction cup on the instrument face. HSI failure is often accompanied by a red flag.
Clues come from the other instruments.
The altimeter, airspeed indicator, and vertical speed indicator not to mention engine and wind sounds and the change in air pressure in your ears can help confirm or deny indications of a climb or descent. It all sounds so simple when comfortably seated and reading this magazine. Without partial-panel flying practice, however, such advice is meaningless. The pilot of a Cessna P210 and his friends were killed near Albuquerque in January after the aircraft s two vacuum pumps failed. 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.