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REFLECTOR: Aileron response
In response to Greg's request for followup on sam's aileron fence, I thought
you'd be interesting in test work done by some of our local EZ squadron
guys. It was published in our EZ-Flyer this month and will soon be in the
Central States newsletter.
Basically it is a series of tuft tests at different speeds showing flow
separation and span wise flow over the ailerons at low speeds. Most of the
testing was done on a Vari-eze, which has quite a serious problem in this
regard, but it was also true to a lesser extend on the Long-eze. This
span-wise flow above the aileron is what causes the mushy response and
adverse yaw at lower speeds.
They also showed that spoilers in front of the inboard section on the
aileron made a significant improvement. Additional testing is continuing to
determine how thick this span-wise flow is getting and what is the best
One would expect some tendancy for spilling of air outboard near the leading
edge under the strake (and to a lesser extent the wing) at high angles of
attack, but as tuft-testing showed on the Vari-eze, the flow would be
straight back at the ailerons.
My opinion is (has been) that this flow separation over the aileron also
occurs on the Velocity; to some unknown extent (maybe similar to the
Long-eze). I've noted on Velocitys that any lubricant on the inboard hinges
leaves lines that sweep outboard toward the trailing edge indicating a
tendency for some span-wise flow even at cruise speeds. One would expect
this condition to become more prevalent and extend outward and forward at
higher angles of attack. It would be great if someone would do similar
tuft-testing on a Velocity.
The point of all this is that it is it may be more likely the aileron
response can be improved by strategic use of spoilers on top of the wing in
front of the aileron.
Since the main purpose of the vortilons is to generate a vortex that goes
over the wing at high angles of attack and discourages flow separation and
span-wise flow; one might expect that a vortilon near the outboard end of
the strake may improve flow characteristics over the aileron. Anyone up for
some testing? (Don't wait for me, my plane won't be flying for at least a
year.) Or has someone already done this?
Perhaps some study of the flatbed truck tests that Danny did 10 years ago on
the Velocity could shed some light on flow over the ailerons at low speeds.
Al Gietzen Elite RG