REFLECTOR:Gap Seals - Aileron Rigging
Ronnie Brown
reflector@tvbf.org
Tue, 25 Nov 2003 14:50:08 -0500
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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. =20
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
173 Elite RG with 101 hours of Fantastic Flight!!!!
----- Original Message -----=20
From: OddJ@aol.com=20
To: reflector@tvbf.org=20
Sent: Tuesday, November 25, 2003 1:51 PM
Subject: Re: REFLECTOR:Gap Seals
Re static: It was the strangest thing. It happened only when reaching =
speeds of 120+ knots. In rain or mist it was non-existant at any =
airspeed. I have had a lot of discussions with people in NASA, radio =
labs in CA, tech councillors in EAA etc., but have not gotten any firm =
explanation for the phenomenon. After trying miscellaneous suggestions =
which didn't improve the situation, I just removed the tape. I have =
"reasonable" control with my ailerons on crosswind landings after taping =
the gaps and don't really need more rudder authority than what I have =
now anyway.
Odd=20
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<BODY bgColor=3D#ffffff>
<DIV><FONT size=3D2>When I rigged my ailerons, I found it difficult to =
obtain the=20
equal 2.5" up and 2.5" down that is called for in the manuals - for my =
173 Elite=20
RG. Since the push/pull cables at the rear of the keel do not have =
a 90=20
degree approach angle, the connection of the push/pull cable at the =
aileron=20
torque tube on the wing, results in ailerons that travel down more than =
they do=20
up. This causes an adverse yaw condition which will lead to =
wallowing at=20
low speeds. </FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>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=20
the opposite direction from that commanded. This is because the =
aileron=20
that is going down has more drag than the one going up. This=20
causes the left wing to slow down if you are commanding a right =
turn at=20
slow speeds. This is called adverse yaw and is common in older=20
airplanes. To get a coordinated turn, even at speed, you need to =
lead with=20
a lot of rudder before applying aileron deflection. Or, you =
rig the=20
ailerons so that there is more up travel than there is down travel, =
which will=20
reduce this yaw effect.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>Cessnas and some other planes (including our =
Velocities)=20
have a Frieze aileron, which features a lip that hangs down below the =
wing when=20
the aileron is deflected upwards. This helps balance the drag from =
the=20
other aileron which is hanging down in the airstream.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Velocities handle fine at higher speeds even with no =
rudder=20
input. But at lower speeds, if the ailerons are rigged with the 90 =
degree=20
approach angle at the wing, then this results in more down than up =
aileron=20
travel, and the adverse yaw condition that some folks have called =
"wallowing" on=20
final.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>A while back, Dave Black pointed out the problem at =
the=20
keel. One fix is to build a wide bellcrank at the back of the keel =
so that=20
the aileron cables could be attached at a 90 degree approach angle while =
in the=20
neutral (centered) condition.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>The other way is to attach the aileron cable at the =
wing so=20
that the approach angle is more than 90 degrees. Mine are attached =
at=20
about 120 degrees, which results in more up travel than down =
travel. My=20
Velocity handles fine at low speeds, with just aileron control, similar =
to my=20
Cessna 172. If I need a sharper turn, I'll kick in more =
rudder,=20
just like in my 172. But normally, no rudder is needed, all the =
way down=20
to the runway. (But I also installed VG's before my first=20
flight, these also improve low speed aileron =
control).</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Ronnie Brown</FONT></DIV>
<DIV><FONT size=3D2>173 Elite RG with 101 hours of Fantastic=20
Flight!!!!</FONT></DIV>
<BLOCKQUOTE=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3DOddJ@aol.com href=3D"mailto:OddJ@aol.com">OddJ@aol.com</A> =
</DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dreflector@tvbf.org=20
href=3D"mailto:reflector@tvbf.org">reflector@tvbf.org</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Tuesday, November 25, =
2003 1:51=20
PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> Re: REFLECTOR:Gap =
Seals</DIV>
<DIV><BR></DIV><FONT face=3Darial,helvetica><FONT lang=3D0 =
face=3DArial size=3D2=20
FAMILY=3D"SANSSERIF">Re static: It was the strangest thing. It =
happened only=20
when reaching speeds of 120+ knots. In rain or mist it was =
non-existant at any=20
airspeed. I have had a lot of discussions with people in NASA, radio =
labs in=20
CA, tech councillors in EAA etc., but have not gotten any firm =
explanation for=20
the phenomenon. After trying miscellaneous suggestions which didn't =
improve=20
the situation, I just removed the tape. I have "reasonable" control =
with my=20
ailerons on crosswind landings after taping the gaps and don't really =
need=20
more rudder authority than what I have now anyway.<BR>Odd</FONT>=20
</FONT></BLOCKQUOTE></BODY></HTML>
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