P

prkaye

Well Known Member
I've been playing around with my ailerons tonight, trying to figure some things out. The thing that's puzzling me now is that there is more upward travel allowed (before hitting the stops) than there is possible downward travel (before the bellcrank is completely vertical, and LE skin of aileron contacts trailing edge skin of wing). When the ailerons are linked, this means that one aileron will reach the limit of its downward travel (bellcrank fully extended) before the opposite aileron hits the stop. This means it will be impossible for an upgoing aileron to ever reach the control stop, and aileron travel will really only be limited by the bellcrank (which, when aligned vertically with the pushrod, has the aileron at the maximum downward deflection possible).
Have I misunderstood something? If the stops can't be reached when the ailerons are linked together, why are they even there?
 
travel stops

Somethjing is wrong with your rigging, or the stops are not in the correct
location, is the R belcrank in the left wing ? mine had that and confused me
at 1st till I doulble checked the plans.. my 9a hits the stops on both wings
onced rigged properly.. double check it..


Danny..
 
clarification

Just to clarify, I'm not at the stage of doing a full rigging yet. In fact, the wings are still in the cradle. What I did was use the aileron alignment bar (long straight piece with two holes drilled into it that align with tooling holes on the outboard rib) to set the aileron in the neutral position, use the bellcrank jig (the one supplied by vans) to set the bellcrank neutral, and connected the pushrod. Just as described in the plans for "attaching the aileron to the wing". Then, when I manually deflect the aileron up and down by hand, there is more upward travel allowed (from the neutral position) than there is downward travel (also from the neutral position). The only possible explanations I can see are:

1) this is some kind of illusion, and it just *appears* that there's more freedom of upward travel

2) The neutral position is set wrong.

3) The control stops are in the totally wrong place.

As for (1), I really doubt it. It seems clear to me that I can delflect the aileron further upwards than downwards. For (2), I also doubt it... I used the jigs as per plans, and visually the neutral aileron looks like it follows the contour of the wing skin. As for (3), the holes in the attach bracket were pre-punched in position, so there's very little room to get these control stops very far off.

So I'm baffled... I guess one solution is wait till the plane is done and I do a full rigging, and worry about it then.
 
aileron limits

The ailerons do deflect up more than down. When properly set, the up aileron hits it's stop before the down aileron reaches it's limit. Obviously this can only be set & checked with the ailerons installed.
One thing the DAR found on my inspection is that I had just a smidge too much up deflection in one aileron, and the bellcrank was contacting the aileron pushrod. I'm using a 'delron bushing' over the aluminum spacer as my stop, so I just wrapped a couple of thicknesses of UHMW tape (the stuff used to protect the flaps) over the delron and the problem was solved.
 
Having the ailerons deflect up more than they deflect down is a technique used to limit adverse yaw and is found on many airplanes.

I installed the aileron stops per plans and all come out, well, as per plans.

Check with Van's but it sounds like you are doing everything correct.
 
Thanks Dennis!

The ailerons do deflect up more than down. When properly set, the up aileron hits it's stop before the down aileron reaches it's limit.
Click to expand...

I'm confused by this... it sounds like a contradiction. If the up aileron deflects more than the down aileron, how could it hit the stop before the down aileron reaches its limit? How is this possible? Does the geometry of the bellcranks somehow make it so that for a given deflection of the control stick, the upgoing aileron travels through a greater angle than the downgoing aileron? I'm having a very hard time visualizing how this could be possible.
 
Phil,

Check out section 15 page 2 of your build instructions. There is a chart there which shows min and max values for deflections of control surfaces. You will see that the ailerons travel upwards almost twice the angle than downwards. This action is built into the geometry of the bellcranks.
 
Thanks guys! I should have remembered that from my groundschool days. Glad to know I haven't messed something up!
 
It's the geometry

prkaye said:
Thanks Dennis!

I'm confused by this... it sounds like a contradiction. If the up aileron deflects more than the down aileron, how could it hit the stop before the down aileron reaches its limit? How is this possible? Does the geometry of the bellcranks somehow make it so that for a given deflection of the control stick, the upgoing aileron travels through a greater angle than the downgoing aileron? I'm having a very hard time visualizing how this could be possible.
Click to expand...

You are exactly correct. The geometry of the bellcranks is how the magic is done. The position of the aileron pushrod on the bellcrank arc is the 'secret' to allowing more travel in one direction than the other.
The fact that the down aileron doesn't travel as far means the other aileron's up-stop will always be the limiting factor.
 
Because of the aileron design, you will find when you get to your transition training that very little rudder is used in normal flight conditions. It will be particularly evident when you start practicing stalls. You won't have to step on the ball - the ball will be centered!

keith
RV9A
N355RW
 
You must log in or register to reply here.