Flap Connection Worn

[2356]

The slot allows/accommodates the wing dihedral during flap operation. I’ve never seen a bushing in the torque tube.

[aviacs]

I’ve never seen a bushing in the torque tube.

Curiouser and curiouser.

You note implies that the bolt shank is the fit as well as the bearing surface in the slot.
And that it can be tightened to pinch the torque tube?

In the one i'm looking at, the bushing is the bearing in the slot, and is coaxial with the bolt.
As previously noted, it also seems to provide the function (by being slightly longer than the OD of the torque tube) of preventing the bolt from pinching the torque tube, which would constrain the bracket stub from sliding.

What size is the cross bolt shank?
What is the slot size width in the bracket?

smt

[2356]

The bolt is an AN 4 or 1/4 inch. It shouldn’t be tightened so as to crush the torque tube.

[aviacs]

Looking at the online catalogs, which are clearer and easier to blow up, there is no bushing showing, either.
Hmmmmmm.

Thanks for that data point.

smt

[aviacs]

I called Univair and they confirmed slot dimensions from prints as '.25" x .5" '
It seems we will be ordering those parts, and making repairs to the torque tube ends per our AI's specification.

Hopefully this will be useful to others in future.
The process was helpful for me.

Thanks!
smt

[6643]

I'm left with one question, is the slot in the flap bracket there to allow for a change in geometry as the flaps are moved though their range of motion - the bracket would slide in and out of the torque tube in flight?...

Not so much in flight as when deployed. The wings are at an angle to the carry-through spar (dihedreal). When you deploy the flaps the whole assembly (torque tube , flap fittings and flaps rotates, but the angles have to stay the same. The slot allows a sort of universal joint action. The cracked fitting above probably comes from inadequate flex. I've also seek cracked inboard hinges from the same problem.

There is no bushing, and the bolt should not be tightened enough to distort the tube. The parts should be free to slide.

A little slop between the bolt, tube and fitting is not a problem, as long as you have the same slop on both sides. Otherwise you get uneven flap deployment.

[7133]

Just latching on to this old topic re flap brackets and cracking due to a solid connection between the flap bracket and torque tube.
Does anyone know what thickness the 0.75 torque tube is meant to be to give the correct clearance. I am thinking .065 4130 tube giving an id of 0.62
I have a new flap bracket which measures 0.5625 od so this would be a clearance of 0.06. Does this seem correct?
Michael Sheppard
VH-TMO

[6643]

I tried to measure mine today. It's tough to get an exact measurement without taking one of the flaps off, but I am confident it is between .060 and .070, which implies it's .065 wall tubing.

[2356]

I measured an old one and came up with .070.