What can you tell me about lubrication of the Anti-Servo Tab actuator?
Search strings: tab actuator, trim tab cartridge, trim tab actuator, tab jackscrew, tab jack-screw.
Technical Editor:
There are several versions of the tab actuator cartridge, though only one part number. Most have to be removed from the plane for disassembly, as they come apart only from the forward end. There is a very large but thin locknut, which retains a big, fine-thread barrel nut. That BN is what holds everything in place, and is the way that the end play is adjusted out. If you are lucky enough to have the style with an aft snap ring rather than a rolled end with a center hole, you can remove the snap ring. That will allow you to take out the aft bearing surface, and unscrew the trim rod with the Acme threads. Those threads, and the mating threads inside the big barrel nut, are the location of most wear (and need the most servicing). If you take it completely apart, you can grease everything. But if you can only get the aft end apart, you can wick LPS-2 into the joint between the barrel nut and housing. It gets virtually no wear, as there is almost no rotation of that part during trim operations. The jackscrew has a coarser Acme thread pitch and travels more. It is also subject to fretting wear related to Tab ‘buzz’; that’s the area that most needs re-greasing, in part just to take out some clearance. I would use only a Lithium-based grease on the jackscrew, as in the landing gear pins; and for the same reasons.
Please note that the adjustment of this jackscrew is quite critical. Just getting it reassembled only one-half turn off, too far in or out, can surprise the heck out of you during a take-off attempt. If you disconnect the tab drive link, and turn it for any reason, be darn sure that you use some method of keeping track of the tab, link, and jackscrew positioning for reassembly. I don’t recall whether you are an A&P; officially, one is required for this work. But you are unlikely to find one who has done this before anyway.