The issue with the flare was the speed control prior to it that led to the aircraft entering Alpha Prot at 150ft. At impact the aircraft was at 125kts config 2 (F speed would have been about 150kts) at a weight of @150,000lbs (68k) doing 750 fpm. It had very low surplus energy. Certainly not enough to significantly reduce the rate of descent but it was at significant risk of stall or would have been had it not been for the fly by wire protections that did their job. The reason the aircraft refused Sully Alpha Max was that at that point it was unsafe to go there at the rate he requested but it did Max Perform for him.
Confiture will continue to insist that the aircraft failed and that trying to trade a couple of knots close to the stall is a smart idea. He fails to understand the speed and energy regime they were in and is wrong. If they had stalled they would have died. The aircraft prevented this as Sully knew it would hence his abrupt full aft stick. The lesson is that if you have to ditch keep your speed up prior to impact so that you have energy to trade.
The NTSB said that the aircraft max performed but did not explain why Alpha Prot did not give Alpha Max. Below are some snippets from Airbus's submission to the NTSB which explain why the aircraft did what it did. The BEA in their comments at the end of the NTSB report highlight the same things in more detail but I cannot paste them for some reason.
During the remaining portion of the flight, the Aircraft remained in Normal
Law, and on occasion was flown within the alpha protection range. Notably
from approximately 150 ft down to the water impact the Aircraft was in
slats/flaps configuration 2. During this time period the Aircraft was in the
alpha protection mode which allowed the flight crew to remain focused on
their priorities, conversely if the Aircraft had been a non fly-by-wire aircraft,
the flight crew would have had to fly in and out of the stick shaker to
maintain the desired descent profile.
All water entries studies performed either by NACA or later by IMFL lead
to the conclusion that for the A320 aircraft on shallow water, the optimum
configuration is to have:
- Landing gear retracted
- Full slats/flaps configuration for minimum speed
- Pitch around 11°
- Slope around -0.5°
These data translate into a 3.5 ft/sec vertical speed at water impact.
It also shows that in case of water impact with an aircraft pitch below ≈ 8°,
or above ≈15° major airframe structural breakage is expected.
In Flight 1549, the Aircraft’s energy just prior to water impact was
insufficient to significantly decrease the vertical speed during flare, leading
to a water impact at around 13ft/s. Despite this rate of descent at water
impact, the extent of aircraft damages did not prevent a safe evacuation for
all persons on board. Aircraft pitch at water impact was close to the
optimum recommended value.
During the flight time in between the birds and the water impacts, the
Aircraft was flown occasionally within the alpha protection range (around 1
minute 7s), notably from about 150 ft RA down to water impact.
As far as aircraft trajectory is concerned, it has to be noted that the flight
control laws in the alpha protection domain do include some additional
features. AoA protection takes also care of the aircraft trajectory and, thus,
looks after phugoid damping as well as AoA control. There are feedbacks
within the AoA protection law aiming at damping the phugoid mode (low
frequency mode). Without these feedbacks, an aircraft upset from its
stabilized flight point up to constant high AoA would enter a phugoid
(which is, by definition, a constant AoA oscillation) without possibility to
stabilize the trajectory. As a consequence, commanded AoA is modulated:
for instance, if aircraft speed is decreasing and/or pitch attitude is increasing,
pilot's commanded AoA is lowered in order to avoid such a situation to
degrade.
Trying to run simulation without such damping features on the very last
seconds of the flight, without considering what could have been the effect
such features brought upstream during the flight on the overall Aircraft
trajectory and management by the crew would be pure speculation, as not
supported by technical facts.
On the last 10 sec in the air of Flight 1549 , DFDR data show that pitch
attitude is increasing and CAS decreasing. Then, the phugoid damping terms
are non null and are acting in the sense to decrease the finally commanded
AoA vs. the stick command, in order to prevent the Aircraft from increasing
the phugoid features.
It is obvious that achieving the optimum water impact configuration when
engine thrust is available (actually setting a Flight Path Angle of -0.5° on the
FCU), is more easily achievable.
However with a loss of engine thrust, as in Flight 1549, the aircraft energy
management significantly increases the pilot workload. Under these
circumstances, aircraft is still able to reach the optimum water impact
configuration, but this is a demanding task which requires time and
significant pilot focus. Typically, the flare initiation height will be critical to
the achievement of the optimum water entry conditions.
As an aside there is a reason the QRH and ECAM do not direct you to use the Yellow Electric Pump in a Green and Yellow Hyd failure. It will overheat and you will lose it very quickly.