Port-side flap pulley in the wing root

[Battson]

Hi everyone, I have a question about the last pulley (in the wing-root) on the port-side flap cable system.

The pulley is mounted on an angle, and depending on the position of the flap drive arm, there is sometimes a noticable change in direction (of the cable-run) at that pulley. I positioned my flap drive so that the cable was straight at about the mid-point, but there's almost no other option given the tight spaces involved. Now that all the holes are drilled etc and I've been using the flaps for a while, a rubbing noise started coming from the pulley with full flap. Upon investigation, when the last notch of flap is added, the cable is being forced to change direction significantly enough that is makes contact with the side of the pulley's channel. This, combined with the very high cable tension at full flap, is causing the cable to gradually eat away at the side of the pulley (making the "rubbing" noise). Obviously this isn't ideal.

Because the plane is fully covered, wings fitted, etc - I can't repositon easily reposition the whole arrangement. I had some questions:

Has anyone else had this problem?

Would it be worth putting a stong bolt or steel rod through the pulley's mounting hole and trying to bend the mounting bracket, to re-align the pulley?

[Mark Goldberg]

The way you describe how you set it up is correct. With maybe two notches to three notches of flaps the cable should be centered in the pulley. With the flaps all the way the cable should ride on one side of the pulley, and at full flaps it should move to the other side. I have never heard of it making a noise though. And any wear on the pulley should not be noticeable for about a jillion years with the small amount of time that the flaps are used. Are you really seeing wear on the pulley already? That would be unusual. Mark

[Battson]

Hi Mark, glad to hear it's intentional. Mine works exactly as you describe. But yes, we are seeing noticeable wear on the pulley after maybe 50 operations of the flaps. Small flakes of the phenolic material can be found on the cable, and the pulley has lost a little shape on the inboard side (very minor). It will probably need to be changed after a few hundred hours of frequent landings. The noise it makes isn't loud, just something I noticed on the ground. For anyone who's inspecting it each annual, I am sure it's no risk.

[Enewton57]

Could you move the pulley outboard a bit using a couple of washers between the mount and the pulley?

[Battson]

Yes that is certainly possible and a good suggestion; the difficulty is it's rubbing on the inboard side at full flaps - but that point wasn't implicity clear in the posts above.

[Enewton57]

Oh ok, well then could you file or remove some material from the pulley mount? I would think the cable is under greater strain at full flaps than at 10 degrees so I would prefer it to rub on the side of the pulley near 10 degrees instead of rubbing at near full flaps.

[Battson]

I don't have a great deal of access behind the fabric, but your suggestion has given me an idea. The right bit on the Dremel tool might be able to get in there.