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FLAP TRAVEL ASYMMETRY

G

Graham

Active Member
I have finally managed to complete the instn of the Electric Flaps in my very sloooow RV6 build in remote New Zealand.

My Flap travel measures out at 40 degrees RHS, & 43.5 LHS.

Has anybody else experienced this amount of difference in travel, on ANY RV model?

After exhaustive measurements I suspect that it is due to small geometry differences between the two flaps. Ideally a simple Jig or template should have been required to be used to locate the pushrod attach hole at identical positions, wrt the hinge, on both sides.

I shall ask VANS but I would be very grateful for any feedback from Team RV who have "been there done that".

Thanks in advance.
Graham
 
Difficult to identify the problem based on your description but does it seem like lengthening the RH pushrod and/or shortening the LH pushrod might bring those measurements closer together?
 
Nope, haven't experienced asymmetrical flap travel on my -6A, both sides are the same when retracted and fully extended...
Assuming both of yours are the same measurement when retracted? What is the relative difference at half flaps?
3 degrees sounds like a lot, due to a minor difference in the radial dimension from the hinge line to the rod end bolt, some rough calcs indicate that the dimension to the holes would need to differ by more than 0.25".
As for remedy, it would probably be not too difficult to remove and replace one of the FL-606 plates if you have some 2024 .125" thick and can measure carefully.
 
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How are you measuring that? Are they even when retracted?

Make sure you're rigged correctly beginning with the ailerons. I'm assuming the 6 is like the 7 in this regard, as Van's tells you how to make an alignment jig using the tooling holes in the end wing rib. That should be your starting place. Once the ailerons are fixed in position, the flap pushrods can be adjusted so that the flaps in the retracted position are flush with the ailerons. Use that as your "datum" and measure the extension angle of the flaps from there.
 
The proper way to measure travel is to start with them fully retracted and a digital inclinometer or level zeroed out. You also need to make sure you're measuring the up and down measurements from the same spot on the flap in both up and down positions.

Assuming that's your process and you're getting 40 on one and 43 on the other, about the only causes I can think of are that either the point where the pushrod attaches to the flap isn't the same on both of them or the weldment from vans is slightly longer on one side than the other.

Either of these conditions would cause what you're seeing.
 
While you're in the process of working on the flaps, you might consider reducing the down travel to something less than 40°.

At just slightly more than 40° there's a good chance that the top skin (gap seal) will pop out from under the wing skin thereby making it impossible to retract the flaps.

I always set the maximum flap travel on the -6 at about 38°.
 
I suggest you find a way to make the flaps equal at all positions.
On my RV-10, I initially had mine adjusted with about 1.5 deg. difference at full flaps. When I tested stalls (at altitude) during early phase 1, I found the with zero flaps stall was straight ahead and easy to control, but at full flaps there was a major wing drop at stall, making control and recovery exciting!

Used 1/2 flaps on the landing, and adjusted them to zero difference before the next flight. Tested and found the handling in a stall was easily controlled with no tendency to drop a wing even with full flaps.

I don't know how they are attached/adjusted on the RV-6, but strongly recommend you don't fly it until you have figured it out and corrected it.

Cheers,
 
FLAP TRAVEL ASSYMMETRY

FOLKS,

Thanks for all your effort & kind thoughts in replying.

It transpires that my RH Pushrod was very heavily preloaded with Flaps fully up. Well spotted Fred Magare.

When released and pushrod adjusted my flaps now both travel 44 degrees. I shall reduce this to 40 degrees. to ensure a goof overlap of the wing top skin & Flap top skins. Under air loads this will prob become about 38 deg.

It transpires that there is sufficient flexibility in the flap T Tube & arms, plus the lower skin overlap, to deflect the arm to pushrod connection point down to an extent corresponding to 3 deg of flap travel. So for the first 3 deg of flap travel the flap pushrod attach point doesn't actually move.


Not sure how I managed to assemble that pushrod with such a preload. I suspect the flap was not quite fully up when the bolt was installed.

Vans advise that many builders use the RV9 flap pushrod. Can anybody advise me of its P.No.

I was intrigued by the response from DRMA that with only 1.5 deg mismatch he had a significant wig drop stall with full flap, & an "exciting" recovery. Anybody else seen that??

Thanks Team
Graham.
Way down in the South Pacific.
 
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