In small "general aviation" type aircraft commonly built for decades, the
vacuum pump is engine driven through a mount on the engine. This vacuum
pumo typically drives the attitude indicator and directional gyro. Another
instrument called turn coordinator is typically a self-contained,
electrically-driven gyro. If the engine-driven vacuum pump fails pilots
learn how to fly with reference to the turn coordinator, compas, airspeed
indicators.

There is a section of the vacuump pump shaft that is designed to fail should
the vanes of the pump, or some other cause, cause the pump to seize. This
can protect the rest of the pump and/or prevent damage to the engine
accessory drive gears.

Owners/pilots that foresee a lot of flying by reference to instruments will
sometimes install an electrically-driven attitude indicator as a redundant
instrument to the vacuum driven indicator. There are devices some
owners/pilots install which can be used in an emergency which will tap into
the vacuum in the intake manifold of the engine and provide instrument
vacuum power.

--

Scott

"a community that allows a large number of young men to grow up in broken
homes, dominated by women, never acquiring any stable relationship to male
authority, never acquiring any rational expectation about the future - that
community asks for and gets chaos."
Daniel Patrick Moynihan


"Terence Wilson" wrote in message
...
Hello,

I was wondering how the primary vacuum is powered in a single engined
aircraft. If it was powered directly by the engine, a engine failure
would result in the immediate loss of attitude indicator and heading
indicator. So I guess most aircraft use an electrical pump that can be
driven by the alternator or battery, is this the case?

Thanks in advance,

Terence