Flap Drive Bearing

[Bcone1381]

When Flaps are actuated, the Flap Torque Tube rotates to move the push rod to control flap movement. It is supported by two Flap Support Frames which run parallel to the ribs between and are supported by the two spars. How do we maintain the bearing surface on the Support Frames once wear and tear has caused slop in this fitting and in the torque tube? The bearing on the plans is welded onto the Flap Support Frame. It looks to me like the skin would have to be removed to repair or replace the flap support frame.

The builders manual has us installing grease zircs, but I am thinking that maybe someone has come up with a replaceable bearing that is serviceable without removing the entire Flap Support Frame.

See Patrol Plans p9

[N3UW]

I believe if you keep it lubricated the existing setup should work fine. You are not operating the flaps continuously like the ailerons. It would take a long long time before you should see any wear. The Piper cherokee has a similar setup. I have never seen any problems with that system. athe only problem with the cherokee is they start to stick down when the lubrication needs needs attention. The Cherokees only have a small hole to oil through.

[LukeS]

My frames use sintered bronze oil impregnated bearings. The grease zerk hole obviously goes through the frame and the bronze bearing, which provides additional securement for the bearings. Changing the bearings doesn't require the removal of the frames, but does require an access panel, and the builder to fabricate a simple tool to press out the old bearing, and press in the new one. Time will tell if this system helps or not. The inboard bearing on my 4-place project uses a similar system. The problem with changing that bearing is that the inboard flap lever is supposed to welded on now (originally it was bolted per plans, changed after '97). So with the welded inboard flap lever, I would likely have to remove the entire torque tube to replace that bearing.

[Bcone1381]

Luke, thanks for the photo and the gouge on Sintered Bronze Oil Impregnated Bearings. This $3 modification to help ensure longevity and maintainability is worth consideration. Now, I will have to think about The Patrol's inboard Flap Lever, as it is also welded on.

[LukeS]

A word of warning. This wasn't a change I made, but one that was made by the previous owner of my project, and it does have drawbacks. If you examine the pic I posted, you should be able to see a black sharpie marker line perpendicular to the grease zerk hole. That line represents material that now needs to be removed to clear the bottom wing skin. Also the builder has to be careful to keep the torque tube centerline as designed, or there could be negative consequences resulting from changes in geometry. Bronze is also not light, so there is a weight penalty for the bearings and the larger tubes required for said bearings. The weight penalty isn't huge, but it all adds up. While I feel these changes were well executed by the original builder of my project, I probably would just build it per plans, and focus more on remembering to keep it lubricated with the right grease.