REFLECTOR: Aileron Torque Tube

Thu Jun 7 06:52:31 CDT 2007

Good morning Jim,

OK, now I think you are talking about wallow on final when flying slowly.  In my RC modeling days and learning to fly, I discovered adverse yaw.  I crashed a couple of times (could have been more than that), when first taking off, and trying to climb too quickly and too slowly,  The model would turn right when I gave it left aileron.  This is caused by much more drag by the aileron that is deflected down than the one on the other side which is deflected up.  The increased drag of the downward deflected aileron on the right wing causing the plane to yaw right instead of banking left as commanded.

This can be corrected by having differential aileron travel.  We need more up travel than down travel.  Even though our Velocities have Frise ailerons (the nose of the aileron sticks down in the airflow when the aileron is up which provides more drag on this wing), we have a design flaw in that the way the push pull cables attach at the rear of the keel, produces even worse adverse yaw.  As brother Dave (Black - where are you? - flying yet???) pointed out some time ago when I was having a hard time getting my aileron geometry figured out, the angles that the cables attach to the bell crank at the back of the keel are the cause of this problem.  For equal travel up and down, the bellcrank at the keel would need to be made much wider and have two attachment points - each 90 degrees to the cable.  

Or, alternately, the approach angle at the aileron bell crank next to the engine needs to be changed.  My approach angle is 90 degrees when the aileron is all the way down.  The angle when the aileron is up is more like 135 degrees.  This recovers the error at the keel and does indeed provides more up aileron travel than down.  This does away with the adverse yaw and my plane (Long wing - 173 Elite)  flies the pattern and final very nicely with minimum rudder inputs.  I do use rudder on occasion, just like I used to on my 172 when a gusty crosswind would lift a wing or otherwise disturb the approach.  But otherwise I can fly down to 75-80 knot finals with nice control authority and directional control with just ailerons.

I posted pictures and write ups at http://www.tvbf.org/gallery/?dir=airframe_construction%2Fwings%2F173%2Faileron%20travel 

IMHO,
Ronnie Brown
173 Elite RG - N713MR - 350 fantastic flying hours!!! 

  ----- Original Message ----- 
  From: Jim Agnew 
  To: Velocity Aircraft Owners and Builders list 
  Sent: Wednesday, June 06, 2007 10:35 PM
  Subject: Re: REFLECTOR: Aileron Torque Tube

  Ron, 

  The problem is not at high speeds, but at low speeds when aileron deflection is large.

  Jim

  James F. Agnew
  Jim_Agnew_2 at Yahoo.Com
  Tampa, FL
  Velocity 173 Elite Aircraft Completed & Flying 

  ----- Original Message ----
  From: Ron Brown <romott at roadrunner.com>
  To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
  Sent: Wednesday, June 6, 2007 8:59:54 PM
  Subject: Re: REFLECTOR: Aileron Torque Tube

  I used the factory aluminum tubes but did not use the connector - I mated my long tubes directly to the ailerons and allowed for the swing of the tube while the ailerons moved through their travel.  It is possible to install the tubes so that the end of the tube at the bellcrank does not go through an arc.  My ailerons work great - but I do not do rolls so I don't need anything stiffer.  (I am a mechanical engineer and I really doubt that there is enough aerodynamic force at 200 knots on the ailerons to cause any significant deflection on a length of 6-7'  3/4" diameter aluminum tubing. - Don't make me get out my slide rule!!!)

  Ronnie    
    ----- Original Message ----- 
    From: Milehitaz at aol.com 
    To: reflector at tvbf.org 
    Sent: Wednesday, June 06, 2007 2:38 PM
    Subject: REFLECTOR: Aileron Torque Tube

    Question for the collective,

    The original aluminum torque tube stock I received with my kit was badly bent in a Bi-fold hangar door incident a while back and I need to order new stock. 

    I vaguely remember something about folks going to steel tubing VS the Aluminum between the bearing and the connection to the Aileron. 

    If memory serves me the modification was because there was a belief the Aluminum was "twisting or flexing" at high speeds and not providing all intended input. I see in the newest version of the construction manual the factory still lists the Aluminum tube.... Anyone flying have input here?

    Thank you in advance for your help.

    Larry Lambert
    XL/RG 

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