400Hz, three-phase power supply for aviation stuff

[Artlav]

What about a mechanical solution?
Get a BLDC motor, i.e. from an RC plane, spin it with another motor (fixed speed to get the right frequency), wind a transformer to get the right voltage (if not close enough).
Much simpler than trying to build an inverter.

Technical term is Umformer, i think.

[tecman]

Technical term is Umformer, i think.

I believe only in Germany

[james_s]

The term I've heard for those is "rotary converter" many of them have a single armature with a commutator on one end and slip rings on the other. They were made for converting DC to AC as well as converting AC of one frequency to AC of another, or single to polyphase.