PPRuNe Forums - View Single Post - Sully's Flare on the Hudson: Airbus Phugoid Feedback
Old 19th May 2017, 02:44
  #18 (permalink)  
QuagmireAirlines
 
Join Date: May 2017
Location: San Diego
Posts: 66
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by vilas
The 19kt deficiency triggered alpha protection mode which pitches the nose down. Isn't that's what it is supposed to do?If aircraft would have been in alternate law it would have stalled. Bilbao was different where alpha protection was not pilot induced but environmental conditions caused the alpha to reach alpha prot.
Going into alpha protection mode is fine, at any altitude, even in flare. I don't think thats the problem here. Also, Sully wouldn't have stalled it since he saw pitch & speed just fine, and could feel the limits, basic skills. Bilboa also was a case where the pilots should have been able to get a few more degrees of pitch to soften the ground impact, but alpha-protect damping terms prevented pitch up in flare. (There was another A320 problem like Bilboa that happened in Canada in 1999.)

I think the solution would be to ONLY have a little pitch rate damping, and do away with any other anti-phugoid mode feedback in alpha-protect below 100' AGL near flare. That way, the pilot isn't allowed to stall while retaining the capability to use all the pitch angle available in flare if the pilot deems it necessary, as Sully requested by full aft stick.

But the greater minds at the NTSB know something I don't since they missed all this stuff that seems obvious.
QuagmireAirlines is offline