Originally Posted by
vilas
Am I missing something? APU gets you out of ELEC EMER that brings CM2 instruments, it can take over pressurization, main use is starter assisted relight which wasn't going to happen. None of this would change PK8303 fate. Sully started APU from memory as good airmanship to get an engine going but once that didn't happen he also got no other help from APU. It doesn't get you out of G+Y. In PK8303 once they lowered the gear they were done in. Even if they could raise it they would've lost more height.
From the Flight 1549 accident report:
Starting the APU early in the accident sequence proved to be critical because it improved the outcome of the ditching by ensuring that electrical power was available to the airplane. Further, if the captain had not started the APU, the airplane would not have remained in normal law mode.
[...]
The NTSB concludes that, despite being unable to complete the Engine Dual Failure checklist, the captain started the APU, which improved the outcome of the ditching by ensuring that a primary source of electrical power was available to the airplane and that the airplane remained in normal law and maintained the flight envelope protections, one of which protects against a stall.
Full report:
https://www.ntsb.gov/investigations/...ts/aar1003.pdf