Additional interesting observation:
When I initially start up the A330 with the GPU, the VOR is active, but as soon as it is OFF, the VOR is inactive.
So as follows:
- Start plane from cold and dark with GPU on and APU on. VOR works.
- Disengage external batteries with APU on - VOR do NOT work
- Turn on external batteries - VOR works
- Start engines and then turn off external batteries. VOR does NOT work
- Turn on external power when the engines are running. VOR works
So this is very strange. I have not tried this, but if I could turn on external power in the air, I bet the VOR comes back working.