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How is the position of the center of pressure affected by different high lift device deployments?

My guesses are:

  • When I use a high lift device that just increases the chord length, it moves backwards so that it stays at the same percentage of the length of the chord - correct?
  • When I use a high lift device that moves downwards, it has the same affect as increasing the AoA (or in fact: it does increase the AoA), so the center of pressure moves forward

Are those two guesses correct? Which other influences are there from high lift devices on the position of the center of pressure?

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When I use a high lift device that just increases the chord length, it moves backwards so that it stays at the same percentage of the length of the chord

Only when the Fowler flap does not change the airfoil's camber, which is rarely the case. Normally, the flap will not only move backwards, but also rotate trailing edge down. A bit only for the take-off setting, but a lot for the landing position. This camber change will move the center of pressure back even if there were no surface increase, and the extension of the wing at the trailing edge will move the center of pressure further back again.

When I use a high lift device that moves downwards, it has the same affect as increasing the AoA, so the center of pressure moves forward

Again, no. The camber change dominates the position of the center of pressure, and it will move back since the wing now sports more rear loading (more lift is created at the rear end of the airfoil due to local camber increase).

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  • $\begingroup$ This means that the movement of the centre of pressure rearwards cos' of downward deflection of aileron will induce more nose down pitching moment at the wing tip.CORRECT? @Peter Kämpf $\endgroup$ – David Teahay Sep 12 '18 at 19:36
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    $\begingroup$ @DavidTeahay: Ailerons move against each other, so the total change in the center of pressure is negligible. For the isolated section with a single aileron flap, you are correct, of course. $\endgroup$ – Peter Kämpf Sep 15 '18 at 9:53

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