No subject

ailerons should go up more than they go down.  Although we have Frieze 
ailerons (the nose sticks down when the aileron is up), there is still a 
tendency toward adverse yaw.  Especially since the attach point for the 
aileron cables at the back of the keel is not 90 degrees.

So, to improve the situation, I installed my aileron bell cranks beside the 
engine with a good bit of bias toward the front.  I also lowered the attach 
point for the aileron cable jacket.  This helps relieve the "error" at the 
keel as well as move the bellcranks away from the engine (but your rotary is 
narrower than the Lycoming so not an issue).  The aileron bell crank is more 
like 90 degrees to the cable when the aileron is down.

Here's a note that I wrote in 2003 that is repetitive but adds some more 
info:

When I rigged my ailerons, I found it difficult to obtain the equal 2.5" up 
and 2.5" down that is called for in the manuals - for my 173 Elite RG. 
Since the push/pull cables at the rear of the keel do not have a 90 degree 
approach angle, the connection of the push/pull cable at the aileron torque 
tube on the wing, results in ailerons that travel down more than they do up. 
This causes an adverse yaw condition which will lead to wallowing at low 
speeds.

I learned this lesson a long time ago when flying RC models.  If you take 
off at just above stall speed, the model would turn the opposite direction 
from that commanded.  This is because the aileron that is going down has 
more drag than the one going up. This causes the left wing to slow down if 
you are commanding a right turn at slow speeds.  This is called adverse yaw 
and is common in older airplanes.  To get a coordinated turn, even at speed, 
you need to lead with a lot of rudder before applying aileron deflection. 
Or, you rig the ailerons so that there is more up travel than there is down 
travel, which will reduce this yaw effect.

Cessnas and some other planes (including our Velocities) have a Frieze 
aileron, which features a lip that hangs down below the wing when the 
aileron is deflected upwards.  This helps balance the drag from the other 
aileron which is hanging down in the airstream.

Velocities handle fine at higher speeds even with no rudder input.  But at 
lower speeds, if the ailerons are rigged with the 90 degree approach angle 
at the wing, then this results in more down than up aileron travel, and the 
adverse yaw condition that some folks have called "wallowing" on final.

A while back, Dave Black pointed out the problem at the keel.  One fix is to 
build a wide bellcrank at the back of the keel so that the aileron cables 
could be attached at a 90 degree approach angle while in the neutral 
(centered) condition.

The other way is to attach the aileron cable at the wing so that the 
approach angle is more than 90 degrees.  Mine are attached at about 120 
degrees, which results in more up travel than down travel.  My Velocity 
handles fine at low speeds, with just aileron control, similar to my Cessna 
172.  If I need a sharper turn, I'll kick in more rudder, just like in my 
172.  But normally, no rudder is needed, all the way down to the runway. 
(But I also installed VG's before my first flight, these also improve low 
speed aileron control).

Ronnie Brown




----- Original Message ----- 
From: <jewen at comporium.net>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Saturday, July 05, 2008 11:42 AM
Subject: REFLECTOR: Aileron Rigging


>I am rigging up my aileron this weekend (173RG.)  I recall several threads 
>on the subject in the past, but can't find my notes.  Does anyone mind 
>refreshing me on the nuances that the manual does not address.
>
> Thanks,
> Joe
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