Precise Flight SVS uses induction manifold differential to power vacuuum gyros. A manually controlled valve activates the system.

Of all the things pilots worry about—and that’s plenty, if you ask us—they seem to worry most about gyro instruments or, specifically, the vacuum systems which power those gyros. We get more letters and e-mails on this subject than on any other, suggesting that owners sweat gyro failures but don’t exactly know what to do to forestall them or what kind of back-up to rely on when the worst happens.

There’s no easy, all-purpose answer to this dilemma. Owners want cost-effective solutions to the instrument back-up challenge but “cost effective” is another word for compromised. You can pay a lot and get a lot or you can pay nearly as…