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RV-10 Roll Trim Change with Flaps

Hi,

Has anyone dealt with large roll-trim changes with flap deflection?

When deploying flaps for landing, my RV-10 rolls left and requires a significant amount of right stick force. I'm working through a rigging check and checking the flaps for twist, but has anyone else experienced (and fixed) this?


Thanks,
David
N110EE
 
I think rigging is your answer. There's nothing in the airframe that should cause a left roll with flap application. If you told me the airplane was rolling right, I would suggest it could be torque reversal you get when you use the prop for aerobraking, but that isn't the situation as you describe it.
 
Hi,

Has anyone dealt with large roll-trim changes with flap deflection?

When deploying flaps for landing, my RV-10 rolls left and requires a significant amount of right stick force. I'm working through a rigging check and checking the flaps for twist, but has anyone else experienced (and fixed) this?


Thanks,
David
N110EE

That is a bit odd, for sure. If they're at the same position when up (check the alignment at the fuselage), then they should be matched together (trailing edges), when they are deploying down, unless one of the delrin blocks that the actuating bar pivots on is loose or coming apart. Put the flaps at various down positions and check with an angle finder to confirm that they match (and lift on them by hand to check integrity), would be a good sanity check, as a start.
 
Flaps

I get a slight roll trim change when going from 0 degrees to reflex. Both flaps are within 0.5 degrees at all positions fro 0 to full down. The only thing I can figure is the leading edge radius is slightly different. When the flaps are reflexed, the leading edge is against the spar, so it may be that one is contacting and the other is slightly off. It is a small trim change…
 
During fit up testing, I noticed that one QB wing did not allow the flap to reach the correct up position (fully against the rear spar). Had I not noticed this and corrected the issue, one of my flaps would have been at a different angle throughout it's travel, as the starting point of the range would have been off.

IMHO, this is the likely cause and you should be able to pull off the pushrods and confirm similar or different at rest UP positions. In my case, I used a hand seaming tool to manipulate the trailing edge of the top skin to get free movement. I may have also sanded an area of interference. Too long ago for clear recall.

It is also possible that there is no interference, but the builder just didn't adjust the pushrods properly. In the up position, this would barely be noticeable, but would be once deflected at 15 or 30*.

Don't use fuselage position as an up indication. You are looking for firm contact between the flap and the rear wing spar. And you need to be sure that it is not interference that causes the flap to stop moving. Vans support should be able to tell you which specific part of the flap is hitting the spar.

Larry
 
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My plane had a roll input when the flaps were raised. I checked them and found that my right flap was badly misadjusted. After I corrected the adjustment there is no longer a roll input. YMMV

-Marc
 
To follow-up:

At full deflection the flaps were rigged correctly with no applied load (leveled airplane, digital inclinometer on the upper surface).

When I applied load upward on the flaps (hand-force, ~10lbs) to take-out the slop in the system, the right flap was ~0.9 deg different from the left.

I went through the system and checked torques, but the majority of the slop was in the right UHMW plastic block fit-up on the torque tube.

I re-rigged the right flap down, so that the flaps were even when pre-loaded up with hand-pressure. This fixed the roll trim issue.

Recommendations for new builders:
-Get a good digital inclinometer for checking rigging. (I initially missed the rigging difference using a lower quality inclinometer)
-Pre-load the flaps to get the slop out when rigging. 1 deg of difference is enough to create a very annoying roll-trim change at full deflection.

-David
N110EE
 
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