Aileron pushrod bellcrank

Hi All,

Question regarding aileron rigging on an RV6

Before I start ? have checked that the bellcranks are in the right way round and understand differential ailerons etc. I have also verified that ailerons are neutral and all seems nice.

I have got 30 degrees up and 16.8 degrees down on one and 15.8 degrees down on the other with enough threads engaged (1/2 of the rod ends on the small pushrods engaging in the pushrod and all of the threads on the long pushrods engaged) ? so she should be safe.

However to get to this state, I had to adjust out (lengthen) the small pushrods leading to the ailerons by about ?? to ?? from the standard bellcrank neutral position otherwise I would have only had 14 to a maximum 15 degrees of aileron down travel. Obviously I then had to adjust-in the long pushrods by a similar amount in order to get the ailerons neutral at rest again (checked neutral by using long straight edge across the tooling holes in the ribs).

Also in the standard position it felt as if the down-aileron pushrod was over-centering on the bellcrank when fully extended.

Is it normal to have to lengthen the small pushrods to change the bell crank position? Also am I the only one to feel as if in standard set-up, the bellcrank was over-centering when installed as per plans?

I and my inspector are happy with how they now sit, but as first flight is this week, for peace of mind, I just wanted to sound out if others have found the need to adjust-out the small pushrod?

Thanks

15 degrees of down travel is sufficient.
You DO NOT want the belcrank to go "over center". That has the potential of locking the controls.

Aileron bellcrank jig?

My RV-9A wing kit came with a factory-made bellcrank jig from Van's Aircraft. I am guessing the RV-6 did not have this jig included. Look at the second photo on this web page to see the jig. Although I am posting the photos in this thread, I am also providing the links to the pages where they are on my web site in case you want to see what I was doing on that day of construction.
http://www.n2prise.org/rv9a013.htm


The photo above was taken on the first day I used it. I had just peeled off the blue plastic and it was shiny like a mirror, and is somewhat hard to see because it is reflecting the anodized surface of the wing spar. This jig rests against the surface of the wing spar when it is in its proper position as it is seen here.

You can see it better on this page when I was installing the wing leveler servo. This jig has a cutout area to clear the aileron bellcrank where it is bolted to the steel angle plates. There is one hole drilled in it which as you can see has the bolt that secures the rod end bearing of the smaller push rod that goes to the aileron itself.
http://www.n2prise.org/rv9a015.htm


The day I did the final adjustments of all the linkages is on this web page. The last two photos show the result while the aileron bellcrank was held in position by the jig supplied as part of the wing kit.
http://www.n2prise.org/rv9a125.htm


The photo above and the one below shows a piece of aluminum also labeled by me as "aileron jig" I made to align the trailing edge of the ailerons with the tooling holes in the wing rib that define the chord line of the wing. This thing was in my plans and was made with two holes on the centerline of one side of the angle that are spaced to match the tooling holes in the wing rib. I also drew a line on the center line with the holes I drilled on the side of the angle. The line faces the aileron to show precise alignment of the trailing edge of the aileron.


The RV-9 wing flaps and ailerons have a sharp trailing edge not a rolled edge as in your RV-6. The theory is the same for alignment. Although the RV-6, -7, and -8 builders need to check for a "heavy" wing in test flights. The ailerons may visually look as if they are in precise alignment according to all the things I have described above. The difference is the thickness of the rolled trailing edge of the aileron. There are guys here who can tell about gently squeezing the the trailing edge of the aileron to trim out the heavy wing condition.

As for my first flight, I tested the aileron alignment by putting the airplane into a standard rate turn with the wings banked at 30 degrees, adjusted the elevator trim to hold the altitude in the turn, and then let go of the joy stick. The airplane continued the turn without any tendency to roll out or to increase the bank angle. After completing a 360-degree turn to the left, I rolled the airplane to the 30-degree bank angle to the right without changing the elevator trim, and it made the turn with hands off the stick, again without a change in bank angle or altitude change. I had seen that done in a 1966 Piper Comanche B with the wheels up. I also rode in an RV-9A that did the same thing. I wanted to see if it would work in my RV and it did! That proved to me that my wings were straight and the rigging was correct.

This is the web page where I posted photos and text about my first flight. Keep reading until you complete page 138. It is the reward for building your very own airplane.
http://www.n2prise.org/rv9a136.htm

It's been too long, since I fitted the aileron pushrods & made final adjustments. But I know, that the small aileron pushrods were too short if going by the plans. I ended up using one for the oil cooler reinforcement that's attached to the engine.

Two things for sure, that I did with all pushrods; is to make sure that nothing comes close to over-centering, and that there is more than 1/2 threads after all adjustments, so that no pushrod can completely backout before fully tightening at the other end. I did end up making several new rods because of this.

On this mornings AOPA Internet magazine, there is a report of a Glasair Sportsman that crashed about 7 hours into it's test flight, because the elevator pushrod backed out. The jam nut hadn't been tightened after it was partially disassembled after the two weeks to taxi program at the factory.
He probably could have been somewhat successful by trying to use trim, but that didn't happen either.

L.Adamson --- RV6A

One other item. On the six, the plans called for drilling a small hole through both sides of the aileron bell crank, in which you insert a drill bit, that lays against the support angles. This is the "neutral" position. All adjustments & pushrod lenghts are taken from that neutral setup. But perhaps, you've already seen this.

L.Adamson --- RV6A

Thanks for posting Larry!

I was hoping a 6-builder would post on this topic. After reading your post above, I know why Van's made and supplied the bellcrank jig for the models that came after the RV-6.

Thanks Larry,

That is what I meant by saying that I had the bellcrank neutral position. With the bellcrank in that neutral position, I could not get 15 degrees down and it felt as if the controls could over-center. However by taking the bellcrank slight out of that position by adjusting-out the small pushrod (and also having to adjust-in the long pushrod), I got 16-17 degrees and am no longer in danger of over-centering the controls.

It seems to me that the danger of over-centering the controls comes when the small pushrod is too short and the long pushrod is too long. The bell crank is then too far round its axis and you also do not get enough down travel on the aileron.

All good fun this rigging...