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Dec 11, 2011, 09:07 AM
Rich
flycracker's Avatar
Discussion

TD sailplanes flap/spoilers


Been too many years since I was into TD. Not sure about the elevator pitch when flaps-down or ailerons up as spoilers. Anybody please?
Thanks,
Rich
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Dec 11, 2011, 09:11 AM
AMA 353531
rdeis's Avatar
*Most* of the time spoilers want some up, is varies with the airplane.

Flaps want some down.
Dec 11, 2011, 11:20 AM
Registered User
Rich,

to be a bit more elaborate ;-) :

- Air brakes usually require not much extra trim
- Flaps down alone(!) as air brakes may require a small down trim
- Ailerons up require a substantial down trim (10% to even 30%) as the intrinsic "nose down" action of a "lifting" airfoil is changed into a "nose up" action due to the resulting "S-shape" airfoil.
- "Butterfly" or "Crow" configuration, flaps down and ailerons up, require the same down trim as for ailerons up alone.

Happy landings
Herbert
Dec 11, 2011, 11:36 AM
Rich
flycracker's Avatar
Quote:
Originally Posted by h.eberbach View Post
Rich,

to be a bit more elaborate ;-) :

- Air brakes usually require not much extra trim
- Flaps down alone(!) as air brakes may require a small down trim
- Ailerons up require a substantial down trim (10% to even 30%) as the intrinsic "nose down" action of a "lifting" airfoil is changed into a "nose up" action due to the resulting "S-shape" airfoil.
- "Butterfly" or "Crow" configuration, flaps down and ailerons up, require the same down trim as for ailerons up alone.

Happy landings
Herbert
Thanks for the response. I think there is a misunderstanding tween ailerons up as spoilers and actual spoilers. Your quote is, I believe, correct.
Rich
Dec 11, 2011, 09:27 PM
Registered User
The pitch response will depend to some extent on the design. I used to have a t tailed glider that had almost no pitch change with spoiler application. (top of wing spoilers) Usually you need a lot of up elevator to compensate for spoilers, especially with an Ava. When using flaps down and ailerons up, the gliders I've flown have all required a fair amount of down elevator to compensate.


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