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Flaps are not aligned symmetrically

S

Stevehaley

Member
One of my flaps is higher than the other which is causing the plane to roll to the right. If i measure with a vernier from the centre of the line of rivets on the top front of the flap to the trailing edge of the main wing i get 6.78mm on port and 2.96 on starbd.(see pic) I think the port is correct as it aligns and stbd is high as it is 3-4 mm above the aileron when aligned with tip.
but if anyone can give me their equiv measurements would be grateful

As i didnt build the aircraft i dont have the templates to align the ailerons/flaps. However my understanding is that if the flaps are level with ailerons and the ailerons are level with the tips then that is correct?
 

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The ailerons in the neutral position if rigged correctly dictate the tip and flap position.
On a 10 and 14 this should also be very close to the same position as both flaps fully retracted such that the leading edges touch the rear spar.
There is almost no way to mess this bit up.

However, A lot of tips don’t necessarily match this out of the box and require varying levels of surgery to make them match the aileron and flaps. Not everyone does this bit well- if at all. The plans give little guidance here.

So with such a large discrepancy at the flaps then I’d assume that the ailerons and tips are also incorrectly rigged at least on one side, perhaps both.
I’d start by adjusting both flaps up to the spar - then match the ailerons to the flaps. That’ll at least get you going in the right direction.
 
Check for twist

Not flying yet, but I’ve noted that one of my flaps has a slight twist causing it to be about 3/16” low at the aileron when fully retracted. It may or my not impact flight but I’ll likely build a new one.

If you take the flap off the airplane you can confirm if it is twisted or not by laying it on a flat board. Mine rocks a bit.
 
Before you use the flaps as a reference for checking the alignment of the ailerons and wing tips, make sure the flaps don’t have a twist in them.
If you place a digital level cord wise at each end the displayed number should be close to the same (be sure to align the level square to the trailing edge for each check).
 
Where are you based?
As there are a few things to check you might be better off finding someone not too far from you who has some experience...
There is an SB on the Van's website that discusses the problem from a generic perspective.
BTW Scott usually knows what he is talking about.
 
One of my flaps had a twist and it was caused by the lower wing skin touching the leading edge of the flap when retracted. The flap would retract fully close to the fuselage, but not at the aileron side..
 
penguin said:
Where are you based?
As there are a few things to check you might be better off finding someone not too far from you who has some experience...
There is an SB on the Van's website that discusses the problem from a generic perspective.
BTW Scott usually knows what he is talking about.
Click to expand...

In the uk near buckingham.

Can you give me more info on the SB cant seem to find it.
 
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If you're not the original builder and the aircraft has a roll that you would like to get sorted, then I would highly recommend you take the aircraft to your engineer and get him to go through the entire rigging to be sure its correct. If your flaps are straight I doubt that the 3mm difference you have between the left and right side would cause this roll as people have often tried to use flaps to correct a roll problem without success. I'd hazard a guess that this has been induced in an effort to solve a problem elsewhere.

Is the rudder trim set correctly?

Is the aileron rigging correct?

Was there a roll correction made to the ailerons after construction? Do you have the original builders records to be able to read and understand what was done during Phase I to correct any roll moment?

If you get those flaps rigged correctly and then go back and sort out the rest of the rigging you'll probably find you have gained a knot ot two.
 
As suggested, the flap rigging may be an attempt to fix another problem.
Position the ailerons in neutral. To do this you must first lock the elevator horizontal. Stand in front of the wing, sight down the aft part of the wing and onto the aileron. Ideally the airflow will need to go up very slightly (1 mm) to go over the aileron. Check the other side. Is it the same? Even a 1 mm difference in the vertical height will cause a heavy wing.
 
Steve

I see you’re also in the UK. You’ll need to involve your laa inspector if you disconnect any controls.
Sounds like it would be best to check the rigging from the start. You will need an alignment plate but any RV builder will have one. Then follow the manual closely starting with ensuring the ailerons are neutral with the bell crank in the correct position (page 23-9) then with the elevator neutral.
If this is incorrect it would be best to also go back one step and check the inner aileron torque tube is setup correctly (step 3 page 23-8)
Interestingly the neutral point is given with “ the flaps bumps solidly against the W-1007C rear spar doubler plate” then you align the trailing edge of the aileron to flap.
Are both the flaps in the same relative position at the fuselage end. Mine sit exactly even with the bottom of the fuselage at the trailing edge?

I noticed you have Private messages turned off, if you want to chat - message me or email and I’ll send my mobile number.

Regards Peter
 
I went through this madness many years ago. Of importance..

If the airplane seems to want to roll on its own, it used to be that the advice was to pinch down the trailing edge of one of the ailerons. DO NOT do this! This only deforms the desired airfoil shape, lowers the aileron effectiveness, and rarely gets to the real cause of the problem.

Go flying, take your hand off the stick, and watch the ailerons.

The important key here is, if they deflect up or down with no control pressure, that indicates one or both are out of alignment in relation to the chord line. The only "pure" solution is drilling out the aileron mount brackets, moving them up to down as required, then riveting them back on. Probably not a job someone with no building experience will want to take on. You could tape on a wedge to use as a trim tab, but that just builds unwanted drag into the wing.

If the ailerons do not move, but the airplane rolls anyway, only then consider flap alignment or other adjustments. For example, mismatched wheel pant alignment can also make the airplane roll.
 
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