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Aileron rigging questions

00Dan

Well Known Member
I measured my ailerons the other day and wanted to double check that I’m measuring the right places before I go ahead and look to adjust the mounting brackets.

I have pictures below of one side, basically I measured from the edge of the wing skin down to the aileron nose, then again from the wing skin to the first rivet line. My measurements came out to be as follows:

Left inboard: 5mm up/down, 41mm fore/aft
Left outboard: 8mm up/down, 39 mm fore/aft
Right inboard: 4mm, 39mm
Right outboard: 4mm, 39mm

As I understand it, the absolute value of these measurements isn’t as important as them being consistent. Does it just need to be even for each side or should both sides be equal to each other? At first glance it would seem only my left outboard bracket needs slotted to lower that end slightly, but do I also need to address the fore/aft component?

On a related note: how much, if any, droop would you allow in the rigging on the ground to account for control system elasticity in flight?
 

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There can be variation in where the edge of the top skin ends. Best to lay a straight edge from the main spar all the way back and press down to force it against the rear spar if the skin is curling up a bit. Then observe distance from straight edge to aileron top skin when parallel to straight edge. If the end is curling, use a hand seamer to set it level with the straight edge.

In the end, it is about performance. If one wing is heavy, that aileron needs to go up or down (Forgot which way), though it could also be the opposite problem on the other wing. Which hinge you move should be based upon above observation.

Larry
 
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On a related note: how much, if any, droop would you allow in the rigging on the ground to account for control system elasticity in flight?

I keep adjusting them until they reach the point that I want them while in flight. Not sure there is a standard that can be applied on the ground.
 
There can be variation in where the edge of the top skin ends. Best to lay a straight edge from the main spar all the way back and press down to force it against the rear spar if the skin is curling up a bit. Then observe distance from straight edge to aileron top skin when parallel to straight edge. If the end is curling, use a hand seamer to set it level with the straight edge.

In the end, it is about performance. If one wing is heavy, that aileron needs to go up or down (Forgot which way), though it could also be the opposite problem on the other wing. Which hinge you move should be based upon above observation.

Larry

To restate so I can verify my understanding, the measurement for consistency will then be the gap between the bottom of the straight edge (essentially extending the top wing skin down) with the top skin of the aileron at each end (which is ideally running parallel assuming the trailing edge has the proper radius). Do I have that right?

What about any fore/aft measurements? Do they even make a difference?
 
Daniel,

If this is not FINAL rigging I would not worry about it.

You can worry about it later.

Boomer
 
To restate so I can verify my understanding, the measurement for consistency will then be the gap between the bottom of the straight edge (essentially extending the top wing skin down) with the top skin of the aileron at each end (which is ideally running parallel assuming the trailing edge has the proper radius). Do I have that right?

What about any fore/aft measurements? Do they even make a difference?

With the straight edge in place and the aileron skin parallel to the straight edge, you are measuring the gap between the full, top skin and the straight edge. NOt looking at trailing edge, but the whole skin. Also put a smaller straight edge on the aileron skin. it should be dead flat from forward edge to trailing edge. If this is not the case (concave or convex shape), read section 5 and manipulate your trailing edges to get it flat. This will also affect heavy wings, so test again before addressing the hinges.

Larry
 
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I keep adjusting them until they reach the point that I want them while in flight. Not sure there is a standard that can be applied on the ground.

I found this old post from Scott McDaniels, I’m posting it here for anyone who else who looks at this thread.

Kevin,
I think it actually can. Both ailerons have positive pressure on their bottom surfaces. This exerts a slight load on the aileron control system.
The system is so low in friction (if properly built) that if the bell crank positions are not matched, a difference in moment is developed between the two sides which can allow the pressure of the one aileron to drive the other.
When the two forces equalize it will be with the ailerons positioned for a slight roll.

As a side note...in an RV this can be used to advantage. The very slight elasticity in the RV control system allows this positive pressure on the aileron bottom to push the ailerons up slightly and make the T.E. up compared to ideal alignment.
If the ailerons are rigged very slightly T.E. down (between 1/32 and 1/16 ") the system elasticity will allow them to be properly in trail, in flight.

I totally agree with Kevin in reguards to roll trim checking / adjustments, and trim system. You should disconnect the trim system before working on trim roll trim problems.

https://vansairforce.net/community/showthread.php?t=18617&highlight=aileron+pushrods
 
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To my understanding the round tooling holes in the center of the wing and ailerons ribs should all be perfectly inline. In the blue prints there is a to scale drawing of the aileron to wing dimensions. I built a jig that is simply flat 2"wide × 1/4" thick aluminum bar stock that with holes drilled perfectly inline per tooling hole spacing with roll pins installed. Insert protruding roll pins in jig into tooling holes in the end wing and aileron to hold everything in place. Ill try to get pictures of this uploaded.
 
I worked my trailing edges as near to nominal as I could get them and then went and flew with the aileron trim springs disconnected. The plane exhibited a clear right wing heaviness with a moderate roll rate. I took pictures of the aileron deflections as visible from the cockpit when stick free. All gear fairings were off for this test, for reference.

I attempted to measure with a large straight edge and as far as I could tell my initial measurements were about right, which indicate the left aileron needs to move LE down. Does this in-flight observation back that up?
 

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I placed a large straight edge on the wing and held it at the rear spar. The results were substantially different between the two ailerons and unfortunately I’m still a bit confused on what I’m looking at. The pictures show the straight edge conforming well with the top of the wing skin and the aileron skin on the left wing, but the right the aileron droops away significantly.

Regarding using the tool hole alignment method, my wing tips were riveted on by the builder; I’d like to avoid making work by pulling them if possible.
 

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Dan,
I’d guess you have found the classic “chase you tail” issue for rigging RVs. Rigging is not one and done, it is an iterative process.

The “tooling hole method” is not what you want to do. It does not address the most common rigging problem - ailerons not mounted in the same plane.

For me I try to establish a common reference point, that being the flaps. Once I verify the flaps are really all the way up, and exactly the same on both side, the other measurements tend to make more sense.

If you get the flaps right, check that the flaps have not twist, then align one aileron trailing edge to that side flap (I use a couple of thin pieces of plywood clamped across flap/ailerons trailing edge). Now adjust the other aileron to match - adjusting the linkages to keep the stick in the right place.

At this point the harder stuff needs to be done. You need to verify that the ailerons are in the same vertical plane, inboard and outboard end of each aileron, and left and right ailerons. Here measuring the gap between the the top of the aileron and the trailing edge wing skin and straight edge on the wing are good approaches. Also measure the distance from the wing skin trailing edge and a common line on the ailerons (I use the aileron spar rivet line). Looking at you photos it is hard to tell but it looks like one aileron is lower than the other.

Ignore the wingtips as they are already on the plane. For those building I recommend deferring fitting the wingtips until final assembly (or assembly before paint) as the wingtip trailing edges have a lot of flex.

Fixing aileron hinge problems is done via buying no-hole hinge brackets from Van’s, welding hinge hole closed and re-drilling, slotting hinge to rear spar holes and such.

Good luck,
Carl
 
At this point the harder stuff needs to be done. You need to verify that the ailerons are in the same vertical plane, inboard and outboard end of each aileron, and left and right ailerons. Here measuring the gap between the the top of the aileron and the trailing edge wing skin and straight edge on the wing are good approaches. Also measure the distance from the wing skin trailing edge and a common line on the ailerons (I use the aileron spar rivet line). Looking at you photos it is hard to tell but it looks like one aileron is lower than the other.

This is the step I’m on. I’ve previously verified the flaps are all the way up (the extended skin contacts the fuselage) and any twist is not visually evident. With the elevator clamped neutral the ailerons and stick center were rigged, with the inboard tip of each aileron just slightly below that if the adjacent flap, per Scott’s post I quoted earlier.

As far as measuring, which is the better method for finding tell here, the ruler pictures from my first post or the long straight edge pictures I posted today?
 
SNIP

As far as measuring, which is the better method for finding tell here, the ruler pictures from my first post or the long straight edge pictures I posted today?

As the first step I suggest clamping the ailerons as I discussed. Now measure the gap between the top of the aileron and the bottom of the wing skin. I make up “feeler” gauges of flat aluminum taped together to do this.

Carl
 
I placed a large straight edge on the wing and held it at the rear spar. The results were substantially different between the two ailerons and unfortunately I’m still a bit confused on what I’m looking at. The pictures show the straight edge conforming well with the top of the wing skin and the aileron skin on the left wing, but the right the aileron droops away significantly.

Regarding using the tool hole alignment method, my wing tips were riveted on by the builder; I’d like to avoid making work by pulling them if possible.

First, you manipulate the aileron to have the the top skin to be parallel with the straight edge when measuring. THEN, compare gap sizes. Note pics 3 and 4. Skin parallel to straight edge and gaps not the same size. Need to do this with all four hinge areas and then start deciding which hinge to move.

Assuming your stick was held constant during this measurement exercise, it points to improper rigging at the control stick interface. Note that the elevator must be held in a neutal position when doing that measurement. With the elev clamped neutral, position one aileron neutral and lock. then observe the other. If it is not also neutral, then start adjusting one of the heims at the control sticks. Most be strategic in which heim to adjust, lest your stick will not be vertical at neutral.

Larry
 
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Right wing

The next two posts will show my current measurements and methodology. For all measurements the elevator was locked neutral as shown in picture 1. Picture 2 shows the aileron clamped in place for the first set of measurements; the stick is centered in this configuration. Pictures 3 and 4 show the outboard and inboard bracket of the right aileron. The skins are not parallel in this configuration; the gaps at the trailing edge are 9mm and 11mm, respectively.

With the aileron unclamped I moved it to be parallel with the straight edge and measured both gaps at 2mm, as shown in pictures 5 and 6. The trailing edge on the inboard side is 8mm above the flap in this configuration. Picture 7 shows the flap-fuselage intersection to verify the flap was fully retracted, for reference.

The measurements from the edge of the wing skin to the first row of rivets on the aileron LE were 39mm on each side.
 

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Left wing

On the left wing, picture 1 again shows the aileron clamped to the wing. The inboard side was flush to the straight edge in this configuration, as shown in picture 2. The outboard side was parallel with approximately a 2-3mm gap, as shown in picture 3.

With the clamp removed, the measurements were the same. Picture 4 shows the aileron-flap gap in this configuration; the aileron TE was 3mm below the flap. Picture 5 shows the flap-fuselage intersection to verify the flap was up.

The measurements from the wing skin edge to the first rivet row on the aileron LE were 41mm inboard, and 40mm outboard.
 

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Based on these measurements, my impression is that the entire right aileron assembly needs to translate down approximately 8 mm, which would open the gap to 10mm; the left aileron needs to move down 7mm on both brackets to be equal with the right aileron.

I’m not sure if the fore/aft measurement differences are enough to make a difference. Likewise, the left aileron may be within tolerance despite the small difference between ends.
 
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