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flaperon droop

GatorsR1

Well Known Member
Patron
Early KAI pg 32-10 (rev 0) specified aligning & clamping wing and flaperon edges prior to drilling torque tubes, but a later revision (rev 1) added shims to provide for 1/8" flaperon droop on both sides.
Just wondering what caused that change?
In trying to think it through, wouldn't that be akin to having a small amount of flaps down (with associated increase of lift & drag)?
The runup to this question occurred during the ongoing 1st Condition Inspection.
I had built to the rev but sometimes wonder about my precision in some measurements.
So I took the flap pushrods out just to doublecheck (38 3/4).
Both were a skosh short so adjusted the rod ends out (left 1/2 & right 1 turn) to meet the spec length.
Anxiously awaiting getting back in the air to see what change in flight characteristic there may be.
 
Early KAI pg 32-10 (rev 0) specified aligning & clamping wing and flaperon edges prior to drilling torque tubes, but a later revision (rev 1) added shims to provide for 1/8" flaperon droop on both sides.
Just wondering what caused that change?

There is a bit of elasticity in the system. With the higher pressure that is present in flight, on the bottom of the flapperons, it is enough to deflect the flapperons upward slightly so they are no longer in neutral trail to the wing.
Making the adjustment specified, compensates for the slight deflection that will occur.
 
As always, many thanks to Scott.
I was hoping he'd chime in & give The Van's answer.
Simple & makes perfect sense (now).
Now get back to work on that prototype, we're all waiting to see it ;)
 
There is a bit of elasticity in the system. With the higher pressure that is present in flight, on the bottom of the flapperons, it is enough to deflect the flapperons upward slightly so they are no longer in neutral trail to the wing.
Making the adjustment specified, compensates for the slight deflection that will occur.

Thanks Scott. Great information like always.
 
Has anybody experienced a dropping wing when you raise flaps? Mine rolls right as I raise flaps, but flies straight when they are raised or down.
 
I have noticed that if I push the flap handle all the way to the floor (below the lowest detent), the resulting flaperon position is nearly neutral to the wing tips. In that position the plane is much more sensitive in roll, to the point that it is very tiring to fly for more than a few minutes. Also, the autopilot can not maintain a steady attitude and it constantly rolls from side to side. I came to the conclusion that the flaperon droop was thus introduced to increase the stability in the roll axis.

-dbh
 
I have noticed that if I push the flap handle all the way to the floor (below the lowest detent), the resulting flaperon position is nearly neutral to the wing tips. In that position the plane is much more sensitive in roll, to the point that it is very tiring to fly for more than a few minutes. Also, the autopilot can not maintain a steady attitude and it constantly rolls from side to side. I came to the conclusion that the flaperon droop was thus introduced to increase the stability in the roll axis.

-dbh

By all the way to the floor I assume you mean past the flaps fully retracted detent notch?

If so, that position is not intended to be used. The flaps are supposed to be adjusted positioned trailing edge slightly below nominal with the flap hand in the bottom detent notch.
 
Hands off !

Got some hours in this weekend after completing the 1st Condition Inspection and then waiting for field to reopen (resurfacing).
Adjusting the tube lengths to exactly 38 3/4 made a world of difference.
No more "heavy" wing and having to maintain (slight) stick pressure against roll.
Another bonus improvement - loosened nose gear castellated nut to reduce the fork pressure (per KAI rev) and taxiing is great, much less differential braking required.
This 12 is becoming even more of a dream machine !
(all I had to do was follow directions!)
 
By all the way to the floor I assume you mean past the flaps fully retracted detent notch?

If so, that position is not intended to be used. The flaps are supposed to be adjusted positioned trailing edge slightly below nominal with the flap hand in the bottom detent notch.

Correct, but it is not a position that I use. It was an accidental placement that baffled me as to why my plane suddenly felt different. Now that I know about it, I am more careful to ensure that I engage the detent when I retract the flaps.
 
Nosewheel Fork pressure

Gators R1, Bob, I note that you have reduced your nosewheel Fork pressure,
"Per KAI Rev", and have better ground handling and less differential braking.
Can you please tell me where that Revision is, (I can't find it on Van's website) and/or what the new pressure is, as I have lots of ground handling problems and anything that makes it easier
for me would be wonderful!
Cheers & thanks, Dean Wallace,
RV12 120679.
 
Hi Dean
My book (KAI) is at the office (hangar) so I have to guess at the published values for nose wheel deflection (as measured with scale affixed to fork per instructions).
But originally the number was like 26 lb. (I think) and was revised to an 18 to 20 lb. range (again, guessing - check the official KAI update).

The latest rev/change can be found at

www.vansaircraft.com/service-information-and-revisions

Select your aircraft model and drill down the page (after all the service directives, alerts, bulletins, letters & notes) to the appropriate KAI Section (1st/left column).

I was SO pleased with the improvement in taxiing after adjusting the rotating force at the nosewheel.
Another factor, not to be ignored, is that I had removed the fork, cleaned all and applied fresh grease.

P.S. I also have the improved fork (installed prior to 1st flight) but not the new leg (yet). Also have wheel pants/fairings.
 
Nose Fork Pressure

Hi Bob, Yes, found it! Thanks for your help, It's on page 35-07, revision 3, Dated 09/21/16. I found a note to myself in my KAI on a previous revision, that I had reduced the force to 19lbs, (originally 26lbs) so it may be that I need to disassemble, clean, regrease & reset. Hopefully that will reduce my embarrassment when turning on the taxiway... Thanks again, Dean
 
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