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Why is there a nose-up change in moment after leaving ground effect?

Asked by: 485 views General Aviation

The Airplane Flight Handbook states:
The aircraft leaving ground effect will
1) Require an increase in AOA to maintain the same CL
2) Experience an increase in induced drag and thrust required
3) Experience a decrease in stability and a nose-up change in moment
4) Experience a reduction in static source pressure and increase in indicated airspeed

I'm having a hard time understanding the number 3 here. What's the aerodynamical reasons you experience a nose-up change in moment right after leaving the ground effect?

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1 Answers



  1. JDJ on Apr 18, 2017

    The opposite reason that you get a nose down pitching moment when you enter ground effect (assuming conventional horizontal stabilizer, not T-Tail). In ground effect, the downwash from air flowing over the wing is reduced because of the disruption of airflow close to the ground. When you enter ground effect, you lose some of the downwash flow over the horizontal stabilizer (downward force on tail plane), resulting in nose down pitching moment. Vice versa, as you depart ground effect, the downwash then takes place acting with greater force over the tail plane. You then experience a nose up pitching moment as a result.

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