PPRuNe Forums - View Single Post - Positive Stability in Fly by Wire Aircraft
Old 26th Feb 2019, 16:52
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FlightDetent

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Join Date: Apr 2003
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Airmann i think it is safe to say that the aircraft, as a result of a closed feedback loop of the Normal Law FCS function, behaves like a one with neutral stability. After a disturbance it is not diverging, nor coming back but stays steady instead.

I just did a search of the FCOM and the term “positive stability” shows up few times only where the protections are described. I.e. if you are getting near an edge of the envelope, some positive stability (various types) is re-introduced to support staying inside.

Without the FCS interfering at all, in the so called Direct Law, the aircraft has all the usual and appropriate stability characteristics by the virtue of its aeromechanical design.

Gums’ covered it actually.
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