My S92 type rating has at least an inch of dust on it now so that's why I said "some very modern aircraft". Ah I miss the APU!
Didn't want to 'black cat' the discussion but I had the pleasure of a 120nm OEI (full shutdown) transit 2 weeks ago in an Italian machine with starter generators, and that's how I knew the Sat track was wired to a non essential busbar. When I looked afterwards, I could find no mention of this in the RFM supplement or component main manual.