Instrument power sources
Vacuum and electricity split the gyroscopic instruments on purpose, so that one failed source never takes every reference at once.
12 min read · Flight instruments
After this lesson you can
- Name which instruments typically run on vacuum and which run on electricity, and explain why they are split that way.
- Recognize the signs of a failing vacuum pump before the gyros become obviously wrong.
- Fly the remaining instruments correctly after losing the vacuum-driven gyros (partial panel).
- Explain how the redundancy strategy changes on an all-electric, glass-panel aircraft.
Gyroscopic instruments need energy to spin their rotor up and keep it there. Most light aircraft draw on two separate sources for that energy: vacuum, produced by an engine-driven pump, and the aircraft's electrical system. That split is not an accident of manufacturing; it exists so that a single failure can never take out every attitude and heading reference at the same moment.
Knowing the split only pays off if you can also recognize when it has failed, and what to do about it. A vacuum pump rarely quits with a bang; it fades, and a fading gyro keeps producing a believable, wrong picture for several minutes. This lesson covers both halves: what depends on what, and how to fly once part of it is gone.
The rest of this lesson
- 1.Who is powered by what
- 2.How the vacuum system works
- 3.Catching a failing pump before the gyros lie
- 4.Flying partial panel
- 5.A different kind of redundancy on glass panels
These 5 sections, their figures, the checks along the way and the end-of-lesson quiz come with the PPL track. Paid once, yours for good.
Key terms
Try to recall each definition before turning the card.