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elevator rigging

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Planedude

I'm New Here
I am a new owner of recently purchased RV7A. We are conducting an import inspection for registration in Canada. In doing the inspection we have found that the centre push rod for the elevator control was not properly secured allowing it to rotate and unscrew from the rod end. In further inspection we found that the stick hits the panel and I cannot determine where the control stops are located. The elevator deflection is not correct (23 degrees down and 27 degrees up). Can anyone provide copies of the rigging instructions for the airplane? I have the drawings but they don't have the information on the process for rigging that I am looking for.

Thanks
 
The control stops are part of the aft deck doublers where the elevator contol horn penetrates it (the horn contacts the stops). Don't remember there being a "rig procedure" per se, the stick should be approximately vertical when the elevator is in the neutral position.
 
The measurements (lengths) of the elevator push tubes are in the plans and are good to work with. Make sure you have jam nuts in place as required and that the rod ends are straight.
 
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Walt said:
The control stops are part of the aft deck doublers where the elevator contol horn penetrates it (the horn contacts the stops). Don't remember there being a "rig procedure" per se, the stick should be approximately vertical when the elevator is in the neutral position.
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Just to add the what Walt said, when the elevator is in trail (neutral), the elevator bellcrank should be vertical. Adjust the rod-ends on the aft elevator pushrod to set the bellcrank vertical. The move on to the forward pushrod to set the angle of the stick. Generally the sticks have a slight forward cant when the elevator in neutral. However, the important point is that the elevator hit its stops before the stick hits the spar or the front rod-end binds in th yoke of the control stick. You can adjust the stick to your liking as long as you get full travel.
 
Control stick position at neutral ...

.... is NOT vertical as stated above. I called Vans when I was rigging my elevators ....they said the stick should be 5 degrees forward at the neutral point. You see when you get to making length adjustments on the center p-rod that vertical will cause problems with the other clearances. As soon as you aim for 5 degrees fwd, it all lines up nicely.
 
I made the same call to Vans while building my 7.
Their answer:
Vertical elevator bell crank, streamlined elevator and
front control rod ends threaded in slightly more then half.
This put the stick slightly forward of vertical.
I didn't hear of a measurement in degrees.

It was shown on the plans once I knew to look for it.

Tom
 
RV7A elevator rigging

Thanks for you suggestions and advice. Just spent an afternoon sorting this out. My 6ft 7 inch AME had a fun time crawling around the cockpit making the adjustments!!!
 
Again, just to reinforce, there are two separate steps here. One is the BIG pushrod, whose length and rod-end bearings are adjusted so when the elevator is clamped in its neutral position, the bellcrank is vertical.

The other is the smaller pushrod which connects to your control sticks and is adjusted so that the stick is slightly forward as people indicated.

Also, make sure that shorter, thinner pushrod is not hitting the top of the pass through of the 705 bulkhead (the one just behind the seats). If someone didn't properly secure a rod end bearing on an elevator pushrod, there's a pretty good chance he/she/it wasn't particularly committed to this pushrod either.
 
One other thing to consider, FWIW...I was taught that pushrods should be long enough that with the rod ends screwed on *at least halfway* on both ends, you get the correct geometry and throw. That way, even if a jamb nut loosens AND the rod turns over time, one or the other end will unscrew but *not far enough for the rod end to come off* before the other end is screwed all the way in...thus, the rod cannot physically become disconnected from either of the rod end bearings.
 
LettersFromFlyoverCountry said:
Again, just to reinforce, there are two separate steps here. One is the BIG pushrod, whose length and rod-end bearings are adjusted so when the elevator is clamped in its neutral position, the bellcrank is vertical.

The other is the smaller pushrod which connects to your control sticks and is adjusted so that the stick is slightly forward as people indicated.

Also, make sure that shorter, thinner pushrod is not hitting the top of the pass through of the 705 bulkhead (the one just behind the seats). If someone didn't properly secure a rod end bearing on an elevator pushrod, there's a pretty good chance he/she/it wasn't particularly committed to this pushrod either.
Click to expand...

Installing elevator pushrods tomorrow...just to confirm that there is no measurement other than "vertical" on the elevator bellcrank? I believe that on the -8 there is a measurement called out somewhere, but I couldn't locate any such measurement on the -7 plans.
 
Flying Scotsman said:
Installing elevator pushrods tomorrow...just to confirm that there is no measurement other than "vertical" on the elevator bellcrank? I believe that on the -8 there is a measurement called out somewhere, but I couldn't locate any such measurement on the -7 plans.
Click to expand...

Correct, there's no measurement other than vertical on the elevator bellcrank. The elevator, of course, should be in trail at the time this is set. No other measurement needed in this case.

The other thing here is there should be NO way for any rod end bearing on that push tube to come off if more than half the threads on each rod end bearing are engaged.
 
LettersFromFlyoverCountry said:
Correct, there's no measurement other than vertical on the elevator bellcrank. The elevator, of course, should be in trail at the time this is set. No other measurement needed in this case.
Click to expand...

Thanks...that's what I needed to know.

The other thing here is there should be NO way for any rod end bearing on that push tube to come off if more than half the threads on each rod end bearing are engaged.
Click to expand...

Yep...see my post #10 just above :)
 
Also make sure that the jam nuts are tight before you drop the pushrods in. Not so much with the big rod but with the smaller one that goes forward, it's a giant pain in the neck to get a wrench in there to do it once it's been installed.

I know this is a "duh" advisory, but it's surprising how many times DARs and others find these particular jam nuts loose.
 
ROd ends

It should almost be impossible for any pushrod on a Vans aircraft to unscrew it's self since all the rod ends are threaded like a normal bolt and not like a turnbuckle. You can not turn the pushrod and have both rod ends loosen up.
Smilin' Jack
Ever wonder if you've been building too long... and now might have an answer :)
 
Smilin' Jack said:
It should almost be impossible for any pushrod on a Vans aircraft to unscrew it's self since all the rod ends are threaded like a normal bolt and not like a turnbuckle. You can not turn the pushrod and have both rod ends loosen up.
Click to expand...

Actually it is possible (just not in the way you think).
Since both rod ends are threaded as you describe, if they are both loose and rotating, the push/pull rod would be threading further onto one while it is threading further off the other. The way RV push/pull rods are designed, they should always bottom out onto the jamb nut of the one threading further in, before they fully unscrew off the rod end that is threading out.
 
Never say Never!

Smilin' Jack said:
It should almost be impossible for any pushrod on a Vans aircraft to unscrew it's self since all the rod ends are threaded like a normal bolt and not like a turnbuckle. You can not turn the pushrod and have both rod ends loosen up.
Click to expand...

Anytime you think something can't be done or is "almost impossible", I promise, SOMEONE will prove you wrong.
 
rvbuilder2002 said:
Actually it is possible (just not in the way you think).
Since both rod ends are threaded as you describe, if they are both loose and rotating, the push/pull rod would be threading further onto one while it is threading further off the other. The way RV push/pull rods are designed, they should always bottom out onto the jamb nut of the one threading further in, before they fully unscrew off the rod end that is threading out.
Click to expand...

This depends critically on the length. I was a) careful to make all pushrods to the *exact* length per the plans and b) double-checking each pushrod as we assemble the systems to check for possible backing-out problems (none found so far).
 
Flying Scotsman said:
This depends critically on the length. I was a) careful to make all pushrods to the *exact* length per the plans and b) double-checking each pushrod as we assemble the systems to check for possible backing-out problems (none found so far).
Click to expand...

I guess I should have clarified that if built correctly per plans, it should not be possible.
My post was in response to the comment that it wasn't possible because of the way the rod ends thread, but in reality, if the push/pull rod is of incorrect length, with the wrong amount of thread engagement of the rod ends, it is possible for the tube to thread to one end and separate from the rod end at the other end.
 
rvbuilder2002 said:
I guess I should have clarified that if built correctly per plans, it should not be possible.
My post was in response to the comment that it wasn't possible because of the way the rod ends thread, but in reality, if the push/pull rod is of incorrect length, with the wrong amount of thread engagement of the rod ends, it is possible for the tube to thread to one end and separate from the rod end at the other end.
Click to expand...

I would be very careful about assuming that just building the tube to the exact dimension will eliminate a problem. There are other factors here including how the elevators horns are installed and drilled, for example. If you're off by a 1/8", that pretty much negates the safety of the cut-to-plans push tube. Same with the bellcrank (although I can't recall if that's pre-drilled or not).

There's a reason why in dealing with rod end bearings -- of any kind -- the wisdom has always been make sure AT LEAST half the threads are engaged at both ends. That's the only foolproof guarantee, and it's just good building practice.

That's not to say other methods don't include a margin of safety.
 
Interference

So the large and small pushrods are of the correct length, bellcranck verticle, etc... Problem is,the stick hits the instrument panel when full forward!! Not good...what to do?? Shorten sticks, extend elevator stop, or ??? Anyone else have this issue?
Jim
 
Stick length is critical ...

After I had my elevator controls fully rigged - and was highly pleased with the result - I found just prior to DAR inspection that a fully forward and right stick hit the throttle knob when it was in the full rearward (idle) position. Though I knew that the chances of that control combination (zero power with stick full forward and right) were nearly zero, I was advised that many DARs will not pass any plane that has a control "interference" such as that. My solution was to cut another 1/2" to 3/4" of the stick. Then it cleared the throttle knob by 1/4". And the stick height for me today is totally comfortable.
 
stick length

Terry,
Thanks very much. I'll have to take at least an inch off both sticks to clear everything and it seemed like the logical way to proceed. I just wanted to be sure I wasn't missing something...
Thanks, Jim
 
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