On 2009-02-06, wrote:

[ ... ]

Most aircraft inverters were 12 or 24VDC in and 115 volt 400hz out,
for radio and instrumentation use. I believe some were 400Hz 3 phase
to run gyros.

Yes. I have one -- somewhere. 14 VDC in, 115 V 400 Hz three
phase -- and a couple of instruments (gyrocompass and artificial
horizon) which spin the rotor up using the 400 Hz three phase. They
also use some liquid level sensors to control current to torque motors
to precess the devices to horizontal gyro orientation when they first
spin up. (And I think that they apply very slow correction during
flight, too. Slow enough so if you do a loop you won't confuse it. :-)

These were in the surplus market around 1960, so are certainly
well out of date by now.

Enjoy,
DoN.

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