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4 Answers

Why does a nose-down pitch change result from the extension of flaps

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Why does a nose-down pitch change result from the extension of flaps?

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4 Answers

  1. Nathan Parker on Sep 07, 2012

    Flaps move the center of pressure of the wing more rearward. Since the CG stays put, this produces a more nose down pitching moment.

    Note that this effect isn’t dominant in many airplanes. Depending on the airplane wing/tail configuration, flap deployment may increase the downward airflow on the horizontal tail, producing a pitch up moment which overcomes the intrinsic nose down moment of the wing.

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  2. Bob Watson on Sep 07, 2012

    Another aerodynamic consideration is that as the flaps go down, the camber of the wing changes which rotates the wing’s angle of incidence up causing an increase in the angle of attack. If left uncorrected, the additional lift will cause the airplane to climb. Because of this, the natural pilot reaction is to push the nose down to restore the previous flight attitude.

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  3. Pete Kemble on Sep 07, 2012

    This depends on the airplane; in a Cessna 172, a pitch up moment will occur with the first extension of flaps because of the change in downwash on the elevator: namely it is deflected more downward, creating a larger angle of attack on the elevator (it would look “upside-down”) which causes greater downward force, thus lifting the nose. A similar thing happens in a Piper Warrior.

    In a Piper Tomahawk, which is a T-tail airplane, the elevator is removed from the equation as it is unaffected by the air-stream around the wings (unless stalling…) a pitch down moment occurs because of the increase in lift on the wings, with no increase in downward force on the elevator, due to the change in angle of attack by extending the flaps. The same happens in the first two planes mentioned, but it is more or less canceled out due to the downwash’s effect on the tailplane.

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  4. Ehsan on Apr 16, 2017

    Why does some aircraf first nose up and then nose down from extension of flaps?? Please answer my question

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