REFLECTOR: Aileron balance - again

[Al Gietzen]

Al 

I also used a one piece torque tube and have just a small amount of flex
(0.5 inches in the 4 ft from the aileron to the bell crank) in the tube.

 

I talked to Brendan about balance and he said to use the same published
balance procedure with nose down incidence line. The torque tube is parallel
to the hinge line and slightly forward and below so has a little, to neutral
balance effect.  

 

Thanks Bob.  I started out to do that, but I guess my tube is bent just a
bit more forward (acts like counterweight when just hanging by the hinge),
and of course it is supported in the bearing when installed which changes
things.  So proper balancing of the aileron with the long bent tube is
problematic.

 

After extensive inertial and aerodynamic analysis of flutter conditions
(meaning I thought about for a while), I concluded that the objective is to
achieve the condition where; with the aileron in a neutral position at level
top-speed condition there is no induced rotational moment if the hinge line
is accelerated up or down. (Just a way of looking at it that eliminates the
amplified oscillation in a flutter condition.) Trying to achieve this with
the aileron suspended by wires requires taking the best shot at applying a
supporting force at the end of the tube to counteract the slight moment it
adds, and with the aileron installed you have the friction of the hinges and
the slight moment due to the bending of the out-of- alignment tube fixed in
the bearing when the aileron is rotated.  Anybody still with me?

 

The other thing I concluded (if I may be so bold to say) balancing the
aileron to a level chord line as stated in the manual is not quite correct
because that is not the neutral position in flight.  Balancing to chord line
level gives trailing edge up with the wing in level flight orientation.
Perhaps there is some reason for this being a good thing that I am missing
here; and I'd be happy for someone to correct me on this.

 

Solutions are to use the standard stub tube, or, if using the single long
tube, balance the aileron (including final paint) before putting the slight
bend in the tube.  As far as balancing to chord line level, or flight-
neutral position, I would choose the latter unless someone can explain to me
why not - or it may not matter.

 

I'm guessing that a close approximation to flight-neutral position would be
with the wing incidence gauge showing level and the aileron trailing edge
aligned with wing trailing edge.

 

Al  

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