PPRuNe Forums - View Single Post - AF447 final crew conversation - Thread No. 1
Old 13th Feb 2012, 00:17
  #1320 (permalink)  
infrequentflyer789
 
Join Date: Jan 2008
Location: uk
Posts: 806
Originally Posted by Smilin_Ed View Post
With a century of flight experience under our belts, why did AB decide to alter the flight control philosophy? Good question.
They didn't. The "philosophy" and control laws they used were already tried and tested in military a/c (and the odd NASA vehicle I believe...). The behaviour you are referring to is apparent neutral speed stablity, and is (I think) a fairly fundamental characteristic of the c* ("c-star") control law. Airbus just applied existing FBW control knowledge to a civilian a/c.

Boeing, on the other hand, for the 777, invented a completely new control law, c*U, to give the effect/illusion of speed stability. As far as I know this was completely new control law/philosophy, never tried on any previous a/c, and arguably therefore much higher risk.

As to which turns out "better", I guess maybe we'll see as FBW spreads beyond A&B - already in Embraer I think, and filtering down to the bizjets. Have they chosen A-style or B-style ? [I don't know, haven't looked].

[There might be another complication - I vaguely recall Boeing having patented the whole c*U concept, in which case they might be able to keep it Boeing-only even if it is "better". Love the patent system...]
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