REFLECTOR: Aileron Rigging (Reflexing)
Reiff Lorenz
Reiff at Lorenz.com
Thu Apr 26 15:29:42 CDT 2012
Ron,
I'm not an aeronautical engineer, but I like to pretend from time to time. Here is my understanding of the aileron-reflex issue. If anyone knows better, I'd love to hear from you.
There are many tradeoffs when designing an airplane. The angle of incidence of the wing needs to be a compromise between slow flight and cruise speed. The wing is initially set at some angle that isn't optimal at either end of the speed spectrum, but gives acceptable performance throughout the range.
Optimal flight occurs when the fuselage is pointed directly ahead, straight into the relative wind. When flying really slow, the wings need more angle of attack (AOA) and the plane must be pointed up (above the horizon) in order to provide enough lift. When flying really fast, the wings on most planes provide too much lift, and the nose must be pointed down a few degrees in order to maintain level flight.
On a conventional GA airplane, the flaps effectively increase the incidence of the wing. Put the flaps down and you no longer have to point the nose so high in order to get the AOA; you have improved slow-speed performance. In some planes, the flaps can be put UP (raised above 0 degrees). This decreases the AOA and you no longer have to point the nose down; you get better high-speed performance.
[Of course, instead of using flaps, you could adjust the 'neutral' position of your ailerons to achieve the same thing. If you can do this in flight, they become flaperons. If you're making ground adjustments, then you're changing the designer's point-of-compromise between high- and low-speed flight.]
A canard aircraft is much the same. The fact that the main wing is lifting 85% of the weight instead of 110% of the weight doesn't change the analysis. The main wing incidence is set such that it strikes a balance between fast flight and slow landings. When flying slowly, the elevator on the canard is way down (stick back), thus lifting the canard enough to get the extra AOA that the main wing needs. In cruise flight, the elevators are way up in order to push the nose down enough to "unload" the main wing through decreased AOA. In this cruise attitude you have two inefficiencies: the fuselage is pointed slightly down and the elevators are fighting against the lift of the canard.
So . . . *IF* the following assumptions are correct (I don't pretend to be an expert here):
1. The Velocity main wing incidence is a compromise between cruise speed and slow performance.
2. The Velocity cruises with its elevator mostly up (stick down) and the fuselage pointed down a few degrees.
3. The ailerons are initially rigged at 0 degrees (in line with the trailing edge of the wing)
THEN:
You might be able to get a more efficient (higher-speed) cruise attitude by raising both ailerons. Unless you invent a way to adjust them in flight, you would pay a penalty in the form of a higher stall speed. (The canard, of course, doesn't know how your ailerons are rigged, but because the AOA of the main wing is effectively decreased by raising the ailerons, the canard reaches its stall AOA at a higher speed.)
This is a much more complex topic than I can do justice to, and there are many ramifications to messing with the rigging of an airplane. (Read the article in this month's Kitplanes that describes how adding a camera to stunt plane prevented it from recovering from an intentional flat spin.) Depending on the configuration of the canard and main wing, changing the rigging of an aircraft can cause the canard wake to pass over the main wing and kill its lift. Also, I'm told there can be flutter issues with rigging the Velocity's ailerons at 0 degrees, so most builders may already have their ailerons 'reflexed' to the optimal cruise configuration. There are probably 100 other aerodynamic issues that I'm overlooking. Please chime in if you know what these are. I'm anxious to learn.
As for how to make in-flight aileron adjustments, here's how you could (theoretically) change your wing-root aileron torque tube attachment to mix in some flaps.
[cid:image002.jpg at 01CD23C9.C8582170]
The image shows a push-rod connecting to the aileron, but you can imagine the torque-tube version of this same setup. I don't recommend this; I'm just including it to satisfy intellectual curiosity over how it could be done.
Hope this helps!
Reiff Lorenz, Dayton, OH
XL-RG, 31% complete
Trying to finish all the canard tasks
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Ron VelocityXLFG
Sent: Thursday, April 26, 2012 10:59 AM
To: Velocity Aircraft Owners and Builders list
Subject: REFLECTOR: Aileron Rigging (Reflexing)
http://www.angelfire.com/on/dragonflyaircraft/reflexing.html
I know there are people with way more understanding of this than me . I only entertain the idea
because the web sit speaks of gaining 10- 60 knots in theory . Reflexing the ailerons
would be a fairly easy modification . If you could gain this kind of speed with the same HP
and set the system up so as to remove the reflex of the ailerons as the plane slows down why not
give it a try.
Yes deep stall is very possible and maybe the whole reason not to do this but what if you could
rig the system to remove the reflex in the system quickly and would also automatically removed
the reflex if the plane is under some predetermined speed. With a gain of 10 knots with the same
HP sounds real enticing.
No I am not trying this just entertaining the idea. I do not own a Parachute so I will only entertain the idea
for now. Has any one looked into this and would like to share.
Ron
From: Alex Balic<mailto:velocity_pilot at verizon.net>
Sent: Friday, December 02, 2011 9:27 PM
To: 'Velocity Aircraft Owners and Builders list'<mailto:reflector at tvbf.org>
Subject: REFLECTOR: Aileron Rigging (was another Velocity in the air)
Reflexing the ailerons will reduce drag- for a more detailed explanation of why this is see this:
http://www.angelfire.com/on/dragonflyaircraft/reflexing.html
it uses a Dragonfly canard aircraft to illustrate the aerodynamics, but it is the same with the Velocity.
Having the ailerons drooped is like flying with flaps deployed all of the time-
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Scott Baker
Sent: Friday, December 02, 2011 6:34 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Another Velo in the air
Looks like contributions to this discussion are dealing with two issues ...
the first deals with aileron balancing (trailing edge up is good; trailing edge down is bad) ...
the other deals with aileron rigging (trailing edge down offers better stable handling; trailing edge up offers lively roll response).
Scott B.
----- Original Message -----
From: Michael Watson<mailto:mikewatsspg at gmail.com>
To: Velocity Aircraft Owners and Builders list<mailto:reflector at tvbf.org>
Sent: Friday, December 02, 2011 6:37 PM
Subject: Re: REFLECTOR: Another Velo in the air
Mine has been down a 1/4 inch for over twelve years and I have had no problems with stability.
When the test pilot came up from Velocity to do my first flight, the first thing he had me change
was to move them from level with the wings to 1/4 inch down. He claimed that if they were up,
the leading edge would protrude below the wing and cause yawing.
Joel who owned a XL was having problems with unstable landings. I re-adjusted his ailerons
to 1/4 inch down and that solved his problem.
John, I think you are referring to initial balancing of the ailerons without the cables connected
On Fri, Dec 2, 2011 at 4:59 PM, Scott Derrick <scott at tnstaafl.net<mailto:scott at tnstaafl.net>> wrote:
Mine are rigged up also, per two different velocity factory a&p's
aminetech at bluefrog.com<mailto:aminetech at bluefrog.com> wrote:
Mine are both 1/4" UP with no issues. Rigging them both up was mentioned several years ago (see below). Should I change them?
Subject:
Re: REFLECTOR:AILERON CONTROL FORCE
Date:
Tue, 9 Mar 2004 19:57:26 -0500
From:
"Scott Baker" <sbakr at comcast.net<mailto:sbakr at comcast.net>>
Reply-To:
reflector at tvbf.org<mailto:reflector at tvbf.org>
To:
<reflector at tvbf.org<mailto:reflector at tvbf.org>>
References:
1 , 2
I wanted to offer a clarification to an earlier post where I said ...
"How are the ailerons balanced? Do they droop below the
trailing edge of the wings and is their movement almost
'frictionless'?"
When properly balanced, the trailing edge of the ailerons should rise
slightly above the trailing edge of the wings. I was wanting to say
that IF
the ailerons on Tom's aircraft drooped below the trailing edge of the
main
wings, then this is a problem. Besides inviting flutter, an aileron
that is
not balanced may also contribute to greater stick forces - which is
what we
are trying to trouble shoot from Tom's message.
Scott B.
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--- john at velocityaircraft.com<mailto:john at velocityaircraft.com> wrote:
From: "John Abraham" <john at velocityaircraft.com<mailto:john at velocityaircraft.com>>
To: "'Velocity Aircraft Owners and Builders list'" <reflector at tvbf.org<mailto:reflector at tvbf.org>>
Subject: Re: REFLECTOR: Another Velo in the air
Date: Thu, 1 Dec 2011 07:49:54 -0500
Dave,
SE and XL’s should have ailerons drooped 1/8” down. What your pilot was experiencing was the leading edge of the ailerons grabbing the air and pulling on the stick. You can’t find the centering point very well with this. The other thing to look at is if the leading edge has any sharp edges on it. You want the leading edge to be rounded so it doesn’t grab the air.
John
From: reflector-bounces at tvbf.org<mailto:reflector-bounces at tvbf.org> [mailto:reflector-bounces at tvbf.org<mailto:reflector-bounces at tvbf.org>] On Behalf Of Dennis Martin
Sent: Wednesday, November 30, 2011 10:54 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Another Velo in the air
I hired John Abraham, Velocity Chief Pilot, to conduct my first flights. He and I spent a couple hours doing fine tuning on the aileron and elevator rigging. I think you should talk with John about your dutch roll and any fine tuning you might do to make sure the ailerons are rigged properly. I also had some nose wheel shimmy - we kept tightening the castle nut until it went away. We went well past the 15 lbs recommended - perhaps as much as 20-25 lbs. on my fixed gear.
Good luck - I'm sure the factory team can help you figure it out.
Dennis
On Wed, Nov 30, 2011 at 8:42 PM, David Ullman <ullman at robustdecisions.com<mailto:ullman at robustdecisions.com>> wrote:
N-444DX, an SEFG took to the air for its first flight today after 5+ years
of work. With Jorge Bujanda's flight, that makes two planes this week. I
hired a test pilot, Robin Reid (30,000+ hours in over 300 types of aircraft,
owner of a VarEZ for 5 years, and he flew a Velocity (Thanks Mel Rudin) just
two weeks ago) and I am glad I did. Most everything worked well which was a
relief since I had been concerned about the engine that I built from a
basket case, brakes heating, and nose wheel shimmy, but none of these were a
problem. But,I do seem to have a roll control problem that I will work out
over the next couple of days (starting with a call to Velocity tomorrow AM).
It seems that right after take-off Robin experienced a severe Dutch roll
problem whenever he input any aileron control. This seemed to increase with
speed so he went around a big circle with rudder only and the ailerons
locked neutral. He kept the speed under 120kts and landed at about 100kts.
After taxiing it bask to the hangar I measured the following:
If I push down and let go, both ailerons fare even with the wings.
If I push up on one, it will stay up due to friction about .35" above the
wing when the other is even with its wing.
If I push up hard on one I can flex it to .550"
The reason for this test is the thought that the air loads are pushing them
both up, but this does not explain the Dutch roll (maybe?).
I measured the incidence of both wings at five different locations with an
angle measuring device and found that most values were within a degree of
each other (within the tolerance of the device).
I had a colleague put a resisting force on the ailerons and moved the
control stick and all seemed normal.
One thing I haven't checked is the gap between the wing and the aileron.
This was on spec early on, but there has been paint and other finishing
since then. I will measure that tomorrow.
Anyone else have a Dutch Roll problem? I am calling Velocity tomorrow AM to
get their input on this, but other ideas are more than welcome.
David Ullman
N-444DX Velocity
EAA 292 President
david at davidullman.com<mailto:david at davidullman.com>
541-754-3609
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--
All the best,
Dennis
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--
Mike W.
1997 Velocity Elite RG
Franklin /IVO Electric CS
Dual GRT EFIS HX Synthetic Vision
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