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Old 11-06-2018, 09:45 PM
rvbuilder2002 rvbuilder2002 is offline
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 8,176

Originally Posted by simpkinsona View Post
I was intrigued by this thread. Id heard of stall buffet being caused by the tail but never investigated it. My 9A has a noticeable buffet just as it breaks in the stall. Today I went out to investigate and sure enough the buffet is from the tail. I watched the tail over my shoulder during the stalls and it definitely shakes and is causing the buffet. It was more pronounced with the flaps up, but present either way.

The stall induced buffet felt in the stick and airframe is generally caused by the disturbed flow rolling off the wing and striking the tail.

That is why it can be different between different airplanes depending on the relative vertical position of the horizontal tail surfaces to the wing.

It is also why the buffet can be different depending on flaps up or flaps down... the physical angle of attack of the aircraft will differ between the two which will result in the wake of the wing striking the tail differently.

I think this is also why the trim change (nose up vs nose down) with flap deployment is typically different between low wing airplanes and high wing airplanes because the wake of the wing is in a different position and thus has a different influence on the horizontal tail.
Any opinions expressed in this message are my own and not necessarily those of my employer.

Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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