flap rigging

[dedgemon]

I was rigging my first flap today and ran into a clearance issue on the bolt that goes through the pushrod rod end. When drilled to the plan the bolt contacts the weldment with the flap all the way up. This is the hole that is located in the center hinge 2.375 inch from the spar. I moved the hole to 2.1 inch. This seems to work fine with no interference on the weldment.

Anyone else seen this?

[svyolo]

I was trying to adjust the flap pushrod on one wing so that the flap angle was zero but couldn't get to zero. I hadn't noticed it before, but the AN-4 bolt that mounts the flap drive at the root must mate with a hole in the leading edge of the flap, or your flap won't go to zero. I need to clearance the hole about an 1/8 of an inch on one side.

This would be pretty easy to miss, or at least it was for me.

[Mark Goldberg]

We have seen that over the years John. When I was just down at the factory they had one flap doing more or less the same thing. Just took opening that hole a little more. Mark

[Sir Newton]

Mark, Would a flap control "Johnson Bar" mounted on the roof present any flight operation or safety concerns? In your opinion?

[Bcone1381]

On my Patrol the hole to accommodate the AN4 bolt in the rear spar almost co-existed with the bolt on the flat face of the flap's leading edge. I ended up elongating it, ovaling it down until it extended beyond the vertical surface which is parallel to the rear spar to keep the flap from catching on it when they are extended.

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[svyolo]

That is what I did as well. If I was assembling the whole thing for the first time at the airport, I might have not noticed it and thought it was a mechanical stop for the flap.

[nichzimmerman]

Hello all, I have another flap rigging question. Mine is a scratch built 4-place, but I don't see that these issues are specific to specific models or kit vs. scratch.

I started rigging the flaps by installing the springs and resting the pushrod against the rubber tape I have on the steel frame inside the wing. Then, I adjusted the pushrod length so that the "up" position was achieved with the mechanism in this configuration. At this point, I was a little surprised how little force was required to push the flap down. Not a lot of spring tension holding it in the up position. Good so far?

Then, I fabricated the control cables and adjusted the turnbuckles to get 50 degrees on the last notch. This required tightening the left flap cable more than the right, resulting in issue #1: in the "up" position, there is enough tension that the springs on the left flap don't fully pull it up. I can push it up by hand and it will stay there, but the springs don't do it by themselves.

Issue #2: When pulling the flap handle and watching the steel triangle behind the rear bulkhead, the triangle zig-zags a tiny bit on it's way up and down. This results in uneven flaps when the handle is in intermediate positions. I can correct them by hand (and watch the triangle move left or right a little) but this is unlike other planes I've flown.

For Issue #1, I've considered shortening the springs a little.
For Issue #2, will air loads even out the flaps? even if they were perfectly aligned, I can push one up and watch the other go down (as the triangle is moving left and right) which seems like a quirk inherent in the design, but I've never heard of a flight issue associated with this.

Thanks.
Nic, #1217

[svyolo]

I had the wings on a year or so ago and rigged all the cables. I was pretty surprised how many different variables are caused by that triangle piece. I finally got the cables adjusted so that when I raised and lowered the flap cable, the triangle went up and down without rotation, AND verified that both flap actuators were resting on the stops.

[Battson]

This is all normal and air loads will solve it. Cables will stretch a bit once flying, so you need to re-rig at that time.

[Nev]

Nic I think the air loads will solve both of these issues although you may still like to resolve #1 as you've suggested (I'm not the best person to suggest a fix for that). Certainly on mine I can move both of the flaps easily with my hands. Mine do retract mostly up, but usually can still a bit more if I push them further which was something to watch for when rigging them against a wing template.

[Sir Newton]

Nev, Would a flap control "Johnson Bar" mounted on the roof present any flight operation or safety concerns? In your opinion?

[Nev]

I saw something similar today in a Murphy Rebel and quite liked the idea. The only operational issue I could see is the length of the Johnson bar required with the Bearhawk flaps to account for the inflight flap load, and whether it could fit into the space required. Probably if done well it would simplify the flap arrangement, particularly if most of it could be kept above the main crossbars. Safety wise - I noticed on the Rebel the proximity of the flap handle to the pilots heads when deployed was fairly close. With a lap belt, a sudden stop would probably cause the pilots torso to pivot in an arc that may well miss the handle. That would be my main concern if doing it, just to make sure that risk is taken into account. Possibly worth running the idea past Bob just to check if he considered doing it this way.

[Sir Newton]

Thank you for your input.