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larywil(at)comcast.net
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 Posted: Wed Jan 27, 2010 4:40 pm Post subject: roll trim/aileron trim |
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Hi gang,
It's good to see some real RV-list questions and answers. I would
like to add a very relevant piece of info to this subject.
Years ago, there were numerous discussions regarding roll trim
control on the RV series. I learned a lot ( and forgot some of it)
On my second RV-4, I found that I was constantly pushing over to the
left to compensate for a heavy wing. This, of course changed in
magnitude as the right tank was depleted. But, no matter how much
aileron pinching I did, my honey always wanted to lean to the right
more often than to the left. Now, this was not always the case. My
first flight across the continent never showed a trim problem. After
this 2400 mile trip (16 flying hours over two days) someone pointed
out that my left main gear leg fairing was split open at the back.
Signs of blood and guts, as well as a small dent in the leading edge
of the fairing pointed to a small bird strike. A relatively easy
repair was completed and the fairing was re-installed. That's when
the problem started. But I didn't realize I had a problem for several
months. When I did, I certainly didn't think of my fairing repair as
the culprit!! Where is this all going? Well, I never really aligned
the fairing perfectly, and after my first Anual Inspection, my
mechanic asked me how to align the fairings. Well I did the old
string trick, and noticed that the tabs on the left fairing didn't
match the crud marks left on the leg prior to removal. Voila! The
plane was now a much more balanced machine. So I decided to do a few
experiments. I twisted the fairing a little bit, took it back into
the air. Twisted it past center in the other direction, took it into
the air. The results were that a small twist or misalignment was like
having an off-center rudder under the engine. Boy, does this affect
roll/yaw balance. I removed Van's roll trim for good ( It did work
well, but I was in new territory with my aileron misaligned). So, my
point is: for those of you just into your first flights, check your
fairings' alignment before bending rudder trim tabs and squeezing ailerons.
P.S.
I added a Digitrak a few months later to give me a break (when the
shit hits the fan), but not to control a bad roll condition. My
feeling is that all RV's should have an A/P if you are going on
serious trips - even if you never turn it on. When turned off, I
hardly notice my "well balanced" RV-4 when the tank are uneven.
Louis I Willig
1640 Oakwood Dr.
Penn Valley, PA 19072
610 668-4964
RV-4, N180PF
190HP IO-360, C/S prop
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rhdudley1(at)bellsouth.ne
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| Posted: Wed Jan 27, 2010 5:11 pm Post subject: roll trim/aileron trim |
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First flighter,
Here is another suggestion I learned from somewhere or someone before my
first flight of my RV-6A. Make your first flight and other early flights
WITHOUT your gear leg fairings or wheel fairings. Do your rudder trim
adjustments and heavy wing adjustments BEFORE mounting your leg or wheel
farinigs or installing your aileron trim. Then, you will know what effects
result from leg or wheel fairings. You will also learn how much airspeed
improvement you get from those fairings. My results were like 20 mph gain
(per 3 heading gps measurements) after mounting those fairings.
Happy first flights!!
Richard Dudley
RV-6A
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jfogarty(at)tds.net
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| Posted: Thu Jan 28, 2010 7:53 am Post subject: roll trim/aileron trim |
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Louis, That is a great post. Thanks for give us another side to the story
of roll trim/aileron trim/roll yaw. I apprecate your knowledge.
Jim
RV9a building, MN
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dan.pat.b(at)gmail.com
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| Posted: Thu Jan 28, 2010 11:15 am Post subject: roll trim/aileron trim |
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Good Morning All:Nice to be discussing RV issues.
First flight of my RV-7A, was 8/4/09. The tach went over 90 hours yesterday. Thus far all "issues" have been minor and easily dealth with.
If you're a "newbie" to homebuilding the most important thing before you even begin is to find yourself a good mentor, someone who has "been there - done that." I was lucky - I got the best. (I'm doubly lucky I guess - I have a wife who loves to fly in small airplanes.)
Re aileron trim - a comment based entirely on my own experience.
1. I have electric aileron trim - it's not expensive; installation is easy; it does not get in the way; it's not heavy; it works. Yes - I'd do it again.
2. Do not install wheel pants and gear leg fairings prior to first flight, it will only complicate things.
3. Without the pants and fairings installed, I had a heavy left wing, attributable, I think, to a barely noticeable (You can feel it with your fingers more than you can see it.) airfoil difference between the two wings. Solution: I bonded a plastic "rudder trim tab," part # 9883, $13.50, from Avery Tools, to the bottom, outboard trailing edge of the right aileron. It moves the right aileron up ever so slightly (You can't even see the difference in flight.), keeping the right wing down where it belongs. Problem solved.
4. I optimized my plane for cross-country flying and installed Jon Johanssen, 9.5 gal tip tanks. I've only used them once so far but noticed that with four gallons burned off out of one tank there was a noticeable tendency for the plane to dip toward the opposite wing; a 24 lb weight differential on the end of a long lever does have an effect. It trimmed out easily with the aileron trim.
5. I have a Grand Rapids Technology single AHARS, dual screen system, an all Garmin avionics stack (The 480 is on top - (not user friendly but, when you learn how to use it, the capablity is phenomenal.)) and a Tru Trak a/p slaved to the Garmin. Virtually all my flights since the 40 test hours were flown off have been x/c, and, with an RV - an a/p makes all the difference in the world on a long flight. I flew several of my first x/c flights with the a/p turned off (Yes - I'm a slow learner.) and found, once I learned how to use it, that the a/p makes all the difference in the world in terms of fatigue, ease of navigation, enjoyment, communication, and, most importantly, safety. (I'm instrument rated (not current at the moment) and intend to use this airplane for instrument flying - some might disagree but, I feel an a/p is essential with an RV in the clouds.)
6. I used the string method when lining up my leg fairings and wheel pants. I put the main gear fairings on first and noticed the ball was a bit out of the cage. I had to adjust them several times, using the eyeball method, with test flights in between, before getting it right. The nose gear fairing was no problem. The wheel pants and upper intersection fairings took me three or four days to install but came out fine. Take your time and measure everything repeatedly. (Dad's old plumb-bob came in handy. (Think about that folks - probably the oldest precision instrument on the planet being used to build an airplane)).
7. I Typically cruise at 2300 RPM, leaned to 50 degrees LOP. The difference in airspeed at that power setting w/ vs w/o fairings and pants is between 14 and 16 knots.
Dan Bergeron
RV-7A, N307TB, Spero II
90 hours since 8/4/09
On Thu, Jan 28, 2010 at 10:52 AM, Jim Fogarty, Lakes & Leisure Realty, Inc. <jfogarty(at)tds.net (jfogarty(at)tds.net)> wrote:
[quote]--> RV-List message posted by: "Jim Fogarty, Lakes & Leisure Realty, Inc." <jfogarty(at)tds.net (jfogarty(at)tds.net)>
Louis, That is a great post. Thanks for give us another side to the story of roll trim/aileron trim/roll yaw. I apprecate your knowledge.
Jim
RV9a building, MN
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timb
Joined: 16 Apr 2008
Posts: 77
Location: Frankston, Texas
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| Posted: Thu Jan 28, 2010 1:40 pm Post subject: roll trim/aileron trim |
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I agree. I flew for months without the leg or wheel fairings. Finally got
all the minor tweaks to the ailerons and rudder tab to get the plane flying
straight and level. OK, that only took a few flights but it took longer to
really have a feel for the feel and speed of the plane. Then when putting
the wheel fairings and gear fairings on I knew for sure when they were
straight. Improvement in speed but no other adverse affect. I can fly
straight and level without the auto pilot but I rarely go anywhere without
using it.
Tim
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_________________
Tim Bryan
RV-6 Flying
N616TB |
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