No question that Sully was wrong to fly the approach way to slow. The NTSB report and pilots here know that. That said, he had a little pitch-up room i flare which was denied. Next time, or when other landing events trigger alpha-protect as we've seen in the past, is when changes will benefit passengers.
Originally Posted by
zzuf
It seems to me that because of the low speed Sully was lucky to have been able to achieve the flare that he did - it was at the edge of having enough manoeuvre capability.
Sully still had 3.5 degrees of pitch before alpha-max, and actual stall doesn't even happen until CL-max at around 5 degrees more than his A320 got. Remember, while close to the ground, with a descent rate, going right to stall in those final 2 seconds would be fine right before impact. Right to the edge, maybe even hitting CL-max and ground effect at the same time, knowing the water was very close. IF Sully would have been able to get 11 or 12 degrees pitch in flare like he was asking for, his descent rate would have been less, and his deck angle would be right at ideal for water impact.
From the Aircraft Performance Study document:
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Figure 7 shows that between 15:30:36 and the touchdown at 15:30:43, the pitch angle increases from 9.5° to 11° and then settles back to 9.5°, even though in the last two seconds the left longitudinal side stick is at its aft limit, and α is below αmax. "
Originally Posted by
zzuf
This thread started with the claim being made that it was all caused by the phugoid damping term in the flight control laws.
Straight from the Aircraft Performance Study:
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A phugoid damping feedback term in the flight control laws, that is active in α−protection mode, attenuated the airplane’s nose-up pitch response to progressively larger aft side stick inputs made below 100 ft radio altitude. "
Originally Posted by
zzuf
Perhaps some one can tell me how phugoid damping is important in this accident but it is not during general handling of the A320?
That damping doesn't belong there so close to the ground in flare.
It lowered the nose a bit when he needed a bit of nose-up. Above about 100 ft AGL (RA), its good to have the damping. The damping is there in alpha-protection "general handling" and usually pilots aren't aware of it or almost never use it, which is OK. Its only there in general handling to help out in low airspeed situations.