Originally Posted by Owain Glyndwr
What am I missing?
You would probably need to question Airbus as the airplane was in alpha-protection mode from 150 feet to touchdown.
The airplane reached 9 deg of AoA when the alpha-protection threshold value was still at 8 deg.
Obviously the alpha-protection threshold value is dependent of the altitude and configuration.
AFAIK those values are nowhere in the Airbus documentation reserved to the pilot. They only appear in the different incident/accident reports.
Now, how do you call an "
attenuation of pilot's controls that accompanies the alpha prot mode which could limit the ability to get more than 9 deg pitch in the time available for flare starting from 50 ft" if not a restriction ?
Let Sully pull another 2 deg of pitch to obtain the recommended attitude for ditching and benefit from it by decreasing his vertical speed at touchdown.
Adequate margin was in the aerodynamics as alpha max was still 4 deg away.
No immediate risk for stalling.
Originally Posted by Clandestino
Claiming that airbus FBW should provide flight just below Alpha crit, with no margin since this could improve flare (Hudson) or improve climb (that infamous low & slow flyby with trees getting in the way) is cheerfully disregarding that it's not just Cl that rises just below the stall but Cd also.
Margin is already included, that's why alpha max is not set at alpha stall.
Also the benefit from the CI rise over the Cd rise is exactly what is needed for the short term and that's what Airbus figured out by implementing alpha max ... as long they allow to get it.