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Planes are stable by design. Instabilities have causes: >a rudder power control unit malfunction led to a Dutch roll oscillatory instability >a Dutch roll inc
by jonsen 7y ago
Planes are stable by design.
Instabilities have causes:
>a rudder power control unit malfunction led to a Dutch roll oscillatory instability
>a Dutch roll incident following structural failure of the rudder
>a trainee pilot's actions violently exacerbated the Dutch roll motion and caused three of the four engines to be torn from the wings
- WalterBright 7y agoStability, in a technical sense, means if you push something off of equilibrium, it will return to equilibrium after some time has passed. It is unstable if it does not return to equilibrium. Less stable means it takes longer to return to equilibrium, more unstable means it diverges quicker from equilibrium. My understanding of dutch roll is it takes only a small perturbation to push it off of equilibrium and into oscillation, the oscillation is sickening to people, and it doesn't return to equilibrium without active correction (by the pilot or an active system). A small perturbation means it happens more or less continuously. Correcting the oscillation rather than making it catastrophically worse is something only a well trained pilot can do successfully. The stable point is not straight and level, it's lurching around sickeningly. I mean that literally, at Boeing I was told about a 707 crossing the Atlantic when the yaw damper failed. The pilot didn't crash it, but the airplane was full of vomit by the time it arrived. To be technical, it is not stable flying straight and level. The stability point is dutch roll, like a carbureted car does when the engine rpm "hunts" at idle.