Originally Posted by
FlyingStone
You're talking about a triple failure to get there, after which the aircraft is still flying normally, albeit for a limited period of time, and is then still controllable with extremely limited instrumentation.
737 has been flying for more than 50 years and I haven't heard of any incidents where all three AC sources have failed. If you know of any, please share, it would be an interesting read.
There have been several events of loss of all normal AC power on the 737NG. Also at least two on the 767 I can recall.
Generator failures are almost never completely independent. Failure of the first one usually causes an increase in load on the remaining generator(s), often to their load limit, which can cause another generator or switching equipment to fail. Also, on an NG the third source is the APU generator. APU inflight start reliability is at best in the 99% range.
Also, adding to the list of what doesn’t work when all normal ac power is lost, add the fuel pumps. You are on suction feed if AC power is lost. If you are at high altitude with warm or unweathered fuel when this happens, you may experience a flame out on both engjnes.