Apologies if this question has been answered before - I couldn't find it.
A friend of mine asked why vacuum (suction) is used to drive the gyros in small aircraft and not high pressure air. I felt I couldn't give a definitive answer.
Is it because it's lighter? Cheaper? More robust? More tolerant to leaks? And while I'm at it: Why don't we use electric instead? In one of our Cessnas, we have a backup electric gyro but the main in still vacuum-driven.
Thank you for your answers - I'm looking forward to learning something new today.
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