I have been fussing over my flap setup on my Skymaster L-39, and I'm at a standstill. No matter what the orientation of the servo arm I still get servo buzzing at the 'up'/flaps retracted position. There is no buzzing at mid (1/2) and full-flap extension. I'm using a JR x9303 TX, with the 3-position toggle for Norm/Mid/Land, and each flap servo is a Futaba S9155.

The flap control horn has only one hole. Due to the mounting in the wing, only the end hole of the servo arm protrudes enough from the bottom wing skin to be useable. Both the servo arm and control horn are on the bottom of the wing, with the servo arm moving toward the nose as the flaps are 'pulled' down. Right now I've got the servo arm positioned where at full flaps the servo arm/linkage clevis just barely clear to wing skin, to try and get the servo arm, spindle, and linkage as close to "in line" as possible. This puts the servo control arm a bit less than perpendicular to the linkage rod.

When I physically reposition the servo arm on the spindle to have it more in-line when the flaps are up, the buzzing is still there, but seems less intense. However, this puts the arm at 90 degress to the linkage when the flaps are full down. Seems like this will cause the servo to work hard to hold the flaps in the full-down position.

Should I widen the slot where the servo arm protrudes so that I can use a hole closer to the spindle? I hate the thought of this, since the slot would be kind of ugly if wide enough to allow the clevis end to go down below skin-level.

I'm a turbine newbie...maybe I'm making too much fuss over this.

Thanks,
Sluggo