Originally Posted by
FullWings
Normally I would agree but given the electrical malfunctions that were present, who could say for definite? After all, both IDGs, a backup generator and the APU generator were functional and available but unable to supply power...
It's been many years since I was involved in the 777 development, but IIRC, the RAT generator fed the battery bus directly - if they still had the battery bus they would have still had the RAT generator.
DeeVee - again, a couple decades since I was involved, but based on what I remember, the only way they could have lost all main bus electrical power (with both engines running) would have been either:
latent failures in the electrical bus isolation system (there are regular maintenance checks to confirm such failures are not present), or
the crew didn't correctly follow the QRH procedures after the initiating failure.
(or possibly some combination of the two)