When in normal Law are Airbus aircraft now protected from the types of excessive rudder input that caused the crash of American Airlines 587 (as dramatized in Mayday, S13E05)?

  • 3
    $\begingroup$ There seems to be a misunderstanding here; the A300-600 uses a mechanical hydraulic link between the foot pedals and the rudder, and so flight envelope protection could not hope to do anything. $\endgroup$ Apr 12 '15 at 22:58
  • $\begingroup$ @raptortech97: Note the word "now". I think this is asking about the A320 and newer Airbus models which do have flight envelope protection, unlike the A300. $\endgroup$ Apr 13 '15 at 1:41
  • $\begingroup$ @NateEldredge could be $\endgroup$ Apr 13 '15 at 1:41

Yes, A320 and all newer models have rudder travel limiter that limits the maximum rudder deflection depending on speed.

It should be noted, that this has nothing to do with normal law. Normal law governs pitch and roll. Rudder is controlled by (hydro)mechanically connected¹ pedals and yaw damper, which is independent from the system controlling pitch and roll and simply reacts to side-slip (lateral acceleration actually, only A350 will have side-slip vanes) induced by the roll.

¹ Different Airbus models have different subset of controls with direct hydromechanical link as a backup in case of electric failure, so I am not sure rudder pedals have it on all models. They do on A320.

  • 1
    $\begingroup$ I am not sure that rudder travel limiting based on speed would be able to prevent the type of structural failure that caused the crash of AA587. The vertical tailplane sheared of because of extreme sideslip angles caused by multiple cycles of alternating rudder input. $\endgroup$
    – DeltaLima
    Apr 13 '15 at 20:50
  • $\begingroup$ @DeltaLima: I understood it so that the limit should be such as to not allow so large excitation. But now that you say it, I am not completely sure either. $\endgroup$
    – Jan Hudec
    Apr 14 '15 at 5:52

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