On Dec 14, 1:02*am, Jeffrey Bloss wrote:

There's too much jackscrew grease or the lube's spreading too easily if
its getting to the switches. Get it right. Alaskan 261 was running a
failing jackscrew which looked like lube drift.
--

Huh. I wonder if you've ever had anything to do with these things?
Cessna calls for SAE 10 non-detergent oil on the jackscrew every 100
hours. The microswitches are mounted immediately below the jackscrew
and sooner or later the oil gets onto and into them. It's a poor
setup. The older airplanes get moly disulphide grease.

Alaska's problem was too little of the right lube. It was a stab
actuator jackscrew, not a flap jack, and once the screw's nut threads
failed the stab did its own thing. If a flap jackscrew fails it'll
either jam in some position or the flaps will retract. The airplane is
still flyable. Cessna has other flap problems, like the roller sleeves
slipping sideways on their bearings and cutting a disc out of the flap
support arm and causing flap jamming. There was an SB on that in '96
or so. The only bits on the flap itself that need a little oil are the
flap roller bearings, not the tracks. Oiling the tracks attracts dirt
and lets the rollers slip instead of roll and they'll get flat spots.

Dan