REFLECTOR: archives
Richard J. Gentil
richard at naples-air-center.com
Sun Jan 29 12:48:18 CST 2006
Al,
This is what I get:
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charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable 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 =20
Rigging of the ailerons was a bit of a headache, at least for me, on my
SE RG. Referring to the manual helped =96 and hindered; there is the
version in the manual that I got with the plane, and an improved version
in the new manual; neither of which matched reality. Perhaps my
experience will be helpful to someone who hasn=92t been there yet.=20
=20 My experience was aggravated by having push-pull cables with
insufficient travel, so the first thing is to be certain that your
cables have at least 3=94 of travel; and a little more is better. The
ratio of the length of the bellcrank to the length of the aileron from
the hinge to the back edge is very close to 1.6; meaning that in order
to get the total of 5=94 specified, you=92d really like to have a =
minimum cable travel of 3 1/8=94. But Velocity specs the cable at 3=94,
and = that can work because you can gain a bit by the angles between
cable and the bellcrank. =20 =20 As stated in the new manual the
important first step is the get the rigging at the keel bellcrank setup
to get full 3=94 travel, and equal = in both directions from center. It
also says not to change the predrilled holes in the keel plate for the
cable clamp. In my case, these were mutually exclusive. The cable clamp
on the CP side was too close to the bellcrank, so that even with the rod
end threaded fully on (shortest length) it only allowed about 1 =BC
travel to that side. So I had to re-drill and move the clamp further
over. On the other side the angle of the cable clamp was such that it
caused binding of the cable at the extremes of travel, so that needed to
be reworked. My experience may be unique, but don=92t be surprised if
you have to move the clamps. It is unlikely that you can get full/equal
travel in both directions with the rod ends threaded to the midpoint as
suggested. =20 <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.> =20 As has been previously
pointed out; the position of the cable clamps (and configuration of the
keel plate) do not result is a 90 degree approach angle between the
cable and the keel bellcrank. This actually results in slightly larger
movement of the aileron, but makes the down travel of the aileron a bit
greater than the up travel. This we don=92t like; so we compensate the
other way at the aileron bellcrank. =20 The =93old=94 manual says to rig
the aileron bellcrank at the wingroot = 10 degrees forward from vertical
with ailerons neutral; and adds that the objective is to get a 90 degree
angle (approach angle) between the push-pull cable and the bellcrank. Of
course the angle from = =93vertical=94 will depend on the point at which
you bring the cable through the firewall; which was not specified; so
this isn=92t very meaningful. The new manual suggests bringing the cable
through at about the center of the spar, at rigging for a 90 degree
approach angle at neutral aileron. This is more definitive. =20 You can
compensate for the approach angle at the keel by using an approach angle
at the aileron greater than 90 degrees to get slightly more up travel
than down travel in the aileron. However, insuring that you have 2
=BD=94 down is important to good control, and without compromising on
this, the amount of additional up travel that you can reasonable
achieve, I found to be about =BC=94, which is not likely to noticeably
effect affect adverse yaw. =20 I found that an approach angle of about
100 degrees at neutral aileron was about the best I could get and still
get full down travel. You may get a little more than that (positioning
the cable clamp forward) but you are limited by the forward travel
ability of the bell crank. The first photo shows the 100 degree
position. Another way to rig to get a good result is to set the aileron
at about 1=94 down travel with the = cable approach angle of 90 degrees.
=20 Ronnie suggested 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). =20
Apparently he was measureing a different angle (I=92ll guess the outside
included angle of the bellcrank from horizontal =96 giving 30 degrees
forward from vertical) since 120 degrees approach angle (angle between
cable and bellcrank, as shown in second photo) at neutral aileron would
not allow sufficient forward travel to get full up aileron. I=92d also
guess that the VG=92s are the major factor in decreasing adverse yaw at
low speeds, but have no flight experience to back that up. =20 You can
see that I brought the cables through the firewall more toward the top
of the spar to clear over the coolant connections to the wing-root
radiator; obviously a need specific to my case. (Other non-standard
features you will see there are a wing root extended inward to
accommodate my narrower custom cowl; radiator air exit fairing, and an
aileron fence. Tuft-testing by the guys in the local =93EZ = squadron=94
indicated the need for that fence, and Rodney Brim has confirmed it=92s
benefit.) =20 The third photo is full down aileron position. Rigging in
this fashion (vs the 90 degree at neutral) may reduce stick loads just
slightly because you get maximum leverage at a down elevator position
where the loads would be highest. =20 Disclaimer: None of this is to
suggest that you should do anything different than the manual suggests
(well; except where you have to). It is just my approach, factoring in
engineering judgment, analysis (did I hear over-analysis:), and
information gained from the experience of others; and has not been
reviewed by Velocity. =20 Now; back to those cowl fasteners . . . =20 Al
=20 =20
Al Gietzen wrote:
> What am I overlooking? I need to see a message I posted back in Dec,
> 2003. I go to the "new" archives, find the message, click on it; all
> I get is a long blank page with a header:
>
>
> *REFLECTOR:Aileron Rigging *
>
> *Al Gietzen *reflector at tvbf.org <mailto:reflector%40tvbf.org>
> /Thu, //18 Dec 2003// //17:55:54// -0800/
>
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