Flap Issue Take 2...

ViperDriver · #1 12-06-2008, 07:09 PM

Howdy,

Yesterday in hour 33 of phase one on our 7A, I had the inboard third of the right flap pop over the wing skin and do some damage. I was running the flaps to full up for takeoff when the 'pop-crunch' was heard. Slid the canopy back to take a look and confirm. Flaps were then lowered and they popped back into the proper position but left the wing skin bent and deformed, see pics. The flaps were part of the QB kit so I am pretty sure they are to spec. I am also confident that the install was correct (rechecked this with the plans and some trusted builders after the incident yesterday). The temp was extremely cold yesterday, 15 degrees and I had taxied with the flaps in the full down position. We are going to adjust the flap push rod and recheck everything another ten times after the wing is repaired.

Has this happened to anyone? What else can contribute to this?

I'm pretty sure the push rod fix will do it but wanted opinion just the same.

(Attempted this post yesterday but it seemed not to be working, new to posting on here. If an admin can mort out that other post that would be great. THANKS TO flyinmonque for your help.

)

wing skin deformed where flap came out

Garage Guy · #2 12-06-2008, 07:29 PM

Quote:

Originally Posted by ViperDriver

Has this happened to anyone?

Oh yes.

http://www.vansairforce.com/communit...ad.php?t=29183
http://www.vansairforce.com/communit...ad.php?t=25360

--Paul

ViperDriver · #3 12-06-2008, 07:33 PM

Thanks Ill be better about searching!

Sorry for posting something that has been hit already but on that note I hope everyone looks at the pics and thinks about it so they can avoid having this happen. Just went through all that posts in the links and got quite an education on both the problem and what can be done thanks. I guess this is a common thing.

rv9aviator · #4 12-06-2008, 08:11 PM

Is this problem only on the 6-7-8 models or can it also happen to a 9.

Thanks

pierre smith · #5 12-07-2008, 04:55 AM

.......since the -9's fowler flaps are hinged differently than the 6,7,8. They're hinged by a long piano hinge and the upper surface is real close, sometimes touching the trailing edge of the upper skin and barely tucked under. A little extra travel and the flap leading edge jumps up, interfering with the top skin as they retract.

Regards,

N941WR · #6 12-07-2008, 06:04 AM

Quote:

Originally Posted by rv9aviator

Is this problem only on the 6-7-8 models or can it also happen to a 9.

Thanks

Quote:

Originally Posted by pierre smith

.......since the -9's fowler flaps are hinged differently than the 6,7,8. They're hinged by a long piano hinge and the upper surface is real close, sometimes touching the trailing edge of the upper skin and barely tucked under. A little extra travel and the flap leading edge jumps up, interfering with the top skin as they retract.

Regards,

Jim,

In addition to what Pierre said, the skin on the forward edge of the -9's flaps are riveted to the spar top and bottom. On the -6 & -7 (I don't know about the -8) the bottom of the leading edge on their flaps is not secured, just bent into position.

See this picture from Dan C's web site:

rv9aviator · #7 12-07-2008, 06:19 AM

I feel better now. I'll check the operation anyway but looks like the 9 is made substantially different than the others.
Thanks

RV7ator · #8 12-07-2008, 07:59 AM

I curled the right outboard top skin and tweaked the flap leading edge a week ago. First clue was the plane not flying straight or as fast. Reading other posts, I think my bumping the fully extended flap while loading set up the problem. Ex post facto, it takes a whole lot of force to pop the flap leading edge to where it will bind.

I read where others have set the travel to less than the usual 45degrees the drive screw allows when built to plans (RV-7). My concern is not allowing the full range means the up stop becomes the flap skin overlap with the fuse. (During construction, the pushrod attachment to the flap could be moved further away from the hinge to reduce motion, but that's not possible now.) I asked Van's about how the internal clutch works, could it be adjusted, how strong is it, etc.; they didn't know. Recommendation was install limit switches.

So my question for those of you who let the flap/fuse overlap limit up travel rather than the clutch in the drive mechanism, what's been the effect on the flap skin, and how repeatable is the up limit?

John Siebold

Brantel · #9 12-07-2008, 08:44 AM

I would never use the flap skin as a stop for the up travel. Doing so stalls the motor each time you put the flaps up and could damage the motor or kill the screw/nut inside the linear actuator. You might also pull the threads out of the pushrod tubes.

If your going to do anything, put in a down limit switch to kill the power early before the linear actuator decouples at the end of the stroke.

roee · #10 12-07-2008, 04:02 PM

Quote:

Originally Posted by Brantel

I would never use the flap skin as a stop for the up travel. Doing so stalls the motor each time you put the flaps up and could damage the motor or kill the screw/nut inside the linear actuator. You might also pull the threads out of the pushrod tubes.

... or you might even bend your flaps and/or fuselage. That actuator has a lot of torque... Anyway, something's gonna give.

Quote:

Originally Posted by Brantel

If your going to do anything, put in a down limit switch to kill the power early before the linear actuator decouples at the end of the stroke.

Exactly. Section 15 of the builder's manual specifies a maximum down travel on the flaps of between 40 and 45 degrees. Set it to 40 degrees using a limit switch and you're good to go.