Originally Posted by
Allegheny
If you have seen the Tom Hanks movie, it is accurate to a T because they used flight and cockpit voice recorder data. The simulator scenes were flown by US Airways check-airmen.
In one scene in the cabin, the lights went out. That was the generators dropping off line. The engines were windmilling enough to give erratic power and hydraulics. Starting the APU guaranteed good computers and Alpha protection. Erratic power and hydraulics could have led to an Alternate Law situation where you lose Alpha Floor protection. With the APU on it also guaranteed blue hydraulics at full power, which supports normal flight controls.
Alpha Floor protection enabled Sully to hold full aft stick prior to impact and it allowed the aircraft to settle into the water without stalling. There is not a great deal of technique required, just keep the wings level and the aircraft will land at the slowest possible speed with a nose up attitude.
Sure sounds good. But this is absolutely not what alpha floor does... Do you have an Airbus type? First, it's wrong. Alpha floor is an auto thrust only function. Second, it's inhibited below a certain altitude (although the gear being up might have blocked that inhibition, been off the plane for a while).
My understanding was that the airplane was in alternate law at impact, due to the hydraulic issues and being single generator. I could be wrong, sure. But, you're throwing alpha floor around like someone who hasn't flown the bus, which casts doubt on the rest of your "analysis."
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