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Are my ailerons rigged right?

BruceMe

Well Known Member
I have the worst flying RV I've ever owned. My stick forces are huge. Now the pitch problems where fixed by swapping to a composite prop and adding some tail weight. That is much better now. Roll is still a problem... Here's what I know by measurement and photos.

Left Aileron 21.3 degrees up, -37.3 degrees down
Right Aileron 22.2 degrees up, -36.1 degrees down

Down aileron is supposed to go less than the up, so that seems backwards.

Here is what the left bellcrank looks like

NOTE: This is not centered, it's actually hard left, which means this aileron is up (21.3 degrees).

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The online RV3B diagrams use the newer "cross-over" bellcrank like modern RVs. My older model RV-3 looks very similar to the RV-4 diagram (no cross over)

I can't tell if this is "as designed" or something got swapped. If anyone has seen this problem and knows the answer, I'd like to hear it.

Also, I do plan to pull the wings and do CN-1-1 and CN-2-1 this winter, so I can update the bellcrank to the cross-over.
 
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I'd dig out the plans (or buy an electronic set from Vans) and verify the aileron throws. Yours seem backwards to me, indicating maybe the bellcrank is reversed or something like that. But I've never seen a set of RV-3 plans, so that's a WAG.

The RV's I'm familiar with all use differential ailerons which have more upward deflection than downward deflection. That minimizes adverse yaw.
 
Yeah, that's WAY off! I don't have the plans here in front of me but typically down aileron should be in the neighborhood of 15° and up should be around 30°.
 
For the RV8….

Max up/down is 32/17 and Min is 25/15.
 
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Induced adverse yaw

Yeah,
as others have said, your differential aileron looks to be reversed. Every turn is inducing opposite yaw in that set-up. I once flew a 1934 Taylor E2, which had zero differential (same up/down) and it was a rudder needy machine to stop the AY. The aileron bell cranks are purposely made to correct the geometry, and it sounds like yours are in backwards. Get them flipped and rigged correct and I'm sure you will be in much better shape. Aileron T/E radius will have some effect on sensitivity (large radius is more sensitive) but I doubt that is what's causing your situation. You should be able to make pretty step turns/circles without much if any rudder input, and I'm guessing you are having to step on it pretty hard to stay coordinated.
 
I'd dig out the plans (or buy an electronic set from Vans) and verify the aileron throws. Yours seem backwards to me, indicating maybe the bellcrank is reversed or something like that. But I've never seen a set of RV-3 plans, so that's a WAG.

The RV's I'm familiar with all use differential ailerons which have more upward deflection than downward deflection. That minimizes adverse yaw.

I have the electronic plans, they are for an rv-3b wing, which is a total redesigned from scratch wing they started making in the 90's after all the spar problems. What I have looks nothing like their geometry.

Does anyone have a scan of the RV-3 (no suffix) wing plans?
 
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RV-3 set up

A couple of pics from my right wing.
 

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I have the electronic plans, they are for an rv-3b wing, which is a total redesigned from scratch wing they started making in the 90's after all the spar problems. What I have looks nothing like their geometry.

Does anyone have a scan of the RV-3 (no suffix) wing plans?

I've got the old paper plans. Will see if I can take some photos of them tonight.
 
max throw being reversed doesn't necessarily mean that the differential alieron is set up wrong IMHO. If I remember correctly, there are stops riveted on for the upward travel limit and the orig builder may have made or installed them incorrectly. You didn't stated whether or not the max throw was done with the control linkage installed or not. Are you seeing the max down at the same time that the max up on the opposite wing is max up (i.e. linkage fully installed) or just measuring throw with them loose? If the measurements were done without linkage installed, then maybe it just means re doing the stops. Max down doesn't have a stop, as it is controlled by the up stop on the opposite aileron. If those are measured with the linkage attached, then agree that something is off with the mixing arrangement - likely bell cranks installed incorrectly. IIRC, the arm connected to the main rod is moving around the 90* point for the up travel and well off 90* for the down travel and this is what gives the differential up/down throws. The manual should give degrees of arm from 90 for the neutral position. Your pic shows it well off 90 at hard up and I believe it is supposed to be close to 90* at full up. Challenge will be whether or not you have enough threads on the arm to stretch it to where it needs to be.
 
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Aileron Bellcrank - Changes Over the Years

I am building a "legacy" RV3 & have two plan sets - one from 1993, and a second one from (around) 2001.

Since the pic from MiserBird's airplane (1980) pre-dates both of these, there must have been an "original" aileron bellcrank I am not familiar with.

It would appear that MiserBird's aileron deflections would be your best resource - at this stage of the game.

Here are the pics from drawings #10 from 1-10-84 & 7-8-98:

HFS
 

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THIS IS SO AWESOME, thank you, everyone!

Here's what I now know... My bellcrank is definitely wrong, it should be 137 degrees per the plans, it's likely 90 or fewer degrees and it's not rigged correctly. When I do the CN-1/2, I will correct it, I like the newer cross-over more, but I need to see what works best.

-Bruce
 
A couple of pics from my right wing.

Miser, this looks exactly like mine, but looking at the plans posted, it should be 137 degrees _AND_ it should be off angle at neutral with the control stick connector closer to the inboard.

When you get a chance, I'd really appreciate it if you measured your deflection angles. You can use any freeby angle measurement app on your phone, it takes 2 minutes.

Thanks!
 
Here are the deflections that I measured, I don't really like the results but my '3 handles really well with very light ailerons. I've got some investigating to do...

Right: 25.4* up and 22.1* down

Left: 22.5* up and 24.8* down

Notice the total deflection for both ailerons for a right roll is 50.2* and for a left roll is 44.6* My '3 has the main spar mod done but for some reason the root / rear spar mod was not done, so no aerobatics are allowed therefore I can't comment on roll rates L vs. R but it seems very balanced in normal flight.

I am wondering if this was compensation for engine torque in roll rate?

FWIW, the wing closure was signed off 6/78.
 
I have the worst flying RV I've ever owned. My stick forces are huge. Now the pitch problems where fixed by swapping to a composite prop and adding some tail weight. That is much better now. Roll is still a problem... Here's what I know by measurement and photos.

Left Aileron 21.3 degrees up, -37.3 degrees down
Right Aileron 22.2 degrees up, -36.1 degrees down

Down aileron is supposed to go less than the up, so that seems backwards.

If these values are the travel in degrees up or down from neutral, then something is definitely wrong.
As already mentioned, the up travel should be about 2X the number of degrees of the down travel.

That is accomplished by the clocking of the bell cranks in the wings when the stick is neutral.

To get less aileron down travel than up travel with a given amount of lateral stick movement, the bellcrank to aileron push/pull tube connection point has to be positioned aft of the pivot point for the bellcrank when the ailerons are neutral as is shown in the drawing Dave's post # 10.

In your photo that point is well fwd. of the bellcrank pivot point (assuming the ailerons are neutral when you took the photo).
I don't have access to photos of your vintage wing but my guess is the lateral pushrod is supposed to be longer than it ism and the longitudinal one, shorter than it is.
 
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To get less aileron up travel than down travel with a given amount of lateral stick movement, the bellcrank to aileron push/pull tube connection point has to be positioned aft of the pivot point for the bellcrank when the ailerons are neutral as is shown in the drawing Dave's post # 10.

Scott,

I'm confused, since the spec calls for more up movement than down, shouldn't this read "To get more aileron up travel than down travel"?

Thanks,
 
Original RV-3 aileron bellcranks

I found this in a post from 2011 by Robert Hughes that I believe describes what I am seeing with almost no differential in my aileron deflection:

"I once owned an RV-3 that was built from the earliest set of plans (it was the 6th airplane completed) and the aileron up and down travel was virtually symmetrical (no differential), suggesting a bellcrank angle close to 90 degrees. I have no hard test data to compare, but the roll rate of that airplane was much higher than my later RV-3 built from the 1984 plans."

While I still need to compare my left and right bellcrank set-ups, I believe the my bellcrank angle is very close to 90* from the pics I took during annual and also the measured deflections.

This would suggest that there exist three bellcrank designs: The original at 90*, the one shown in the 1984 plans at 137*, and the latest (3B?) cross over design.

That said, my RV-3 has delightfully light controls with (for me) no noticeable reverse aileron yaw.

I would love to see the original RV-3 plans, but I seem to remember reading the they no longer exist?
 
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Thinking...

Really great posts all around.

A few clarifying points to add, then I'll sit on this for a few months while I do the CN mods.

- I DO think I have the early 90 degree bellcrank
- The picture I posted earlier was not centered, centered would be near the middle of the bracket.
- I can't explain the differential I measured:

Left Aileron 21.3 degrees up, 37.3 degrees down
Right Aileron 22.2 degrees up, 36.1 degrees down

I built several several examples in CAD and made some pretty big changes to the geometry and I couldn't get it to reproduce that much difference. I think something is off, I just don't know what/where. The previous owner built his own stick gimbal. It appears to deviate from stock in the pitch, with too much arm at the stick (5" instead of 4"). He did not change the roll arm, but I suspect he inadvertently added more control throw angle at the stick and most of the change is happening near the end of the throws where angles get more critical.

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I will say the airplane is very snappy... roll rate is noticeably higher than my rv-4 just control forces are also higher as well. I very well may live with it cause it's honestly mostly in my head.
 
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I will say the airplane is very snappy... roll rate is noticeably higher than my rv-4 just control forces are also higher as well. I very well may live with it cause it's honestly mostly in my head.

It was my understanding that the differential aileron throw was to minimize adverse yaw. Not surprising that the roll rate goes down a bit with this approach. On my 6, I don't need to use rudder in banks under 30* due to this differential throw. I guess it depends on which attribute you prefer. However, your current setup is differential, but in the wrong direction. I suspect it is ADDING adverse yaw even over a neutral throw setup.

Larry
 
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