CGinSD

Sadly this lead did not play out... it turns out that the brake screw was only added to the trim wheel in '64; 62-64 models of C, D and Es had none. With a second warm body it was also fairly easy to verify the effect with one of us standing at back jiggling the tail up and down and the other observing the trim wheel rolling back at 16th of a turn per 10 jiggles. It could be stopped pretty easily and I have a strong suspicion that the brake screw was added to 64+ models precisely because of this issue. Our mechanic reckons that the jack screw is just worn enough to allow the extra play necessary to wiggle the trim wheel back and should be replaced. Any thoughts or experiences? How expensive is this likely to be? Anyone with a 62-63 C,D or E who wants to try the jiggle test? Had to replace the trim rods?

Everyone has an... opinion. And here is mine for buying old Mooneys: figure out the value of the engine uninstalled, look up the uninstalled avionics prices on ebay and add the 2 numbers together. These days the hull should be free and the bits are already installed. I think you have about 25K worth of engine and 3k worth of avionics here. Add on something if it looks pretty. Pay very little when you buy as you'll be plunging money into the sweetheart for the rest of your days...

Got it. Thanks very much (in particular for the parts PDF 47U) that sounds feasible, I'll give it a try and then find another crappy day to go flying to test it and let you know.

It was in your neighbourhood too: SDL -> RNM via Buckeye and Blythe. And um... what are brake screws?

Ah! this sounds like a lead, thanks very much.

Yes. Yesterday was particularly choppy but for an hour it was trying to give me over 500'pm of climb in under 2 minutes of reseting it at 8,500'... tiring

Tempting, or kicking a door wedge under the trim wheel Seriously though it needs something doing: as you can imagine being forced to fly one hand off the yolk in turbulence is sub-optimal

Ah. Did that and it seems normal. If I understand correctly though, the diagnosis for me is a bit different than this as the trim wheel itself turns as part of the nosing up so it is not just the slack in the linkage. So if I extrapolate, you would say then that the friction on the trim wheel is just to light? Would be the kind of Doh! solution that wouldn't surprise me but I was not aware there was a specific way of tuning it.

OK, so its not just me! Now my trim slipping is by no means subtle, yesterday I was having to work it down every 30 second or so for over an hour of flight but I was coming to the same theory that the tail 'waggling' was just unwinding the screw. Thanks

Yep - will check, thanks

I'll ask our mechanic to look again at the assembly and check the joints. The problem with testing the trim limits is that in smooth air or on the ground the trim stays where it is, but I find the idea of flying around in turbulence with the trim set to the stops a bit hair-raising Is there a quantitative way to set the friction? I'm not a mechanic in any sense, but this sounds like a concrete test of what could be wrong if there is.

Thanks for all the thoughts: I guess there are enough people who don't have to do this tells me it can be fixed... which is nice.

Thanks Marauder and 95W for confirming the weirdness. First time I squawked this our mechanic tested the tensions and reported all normal but there has to be something in that whole trim contraption that is loose or slippy. Just hoping someone point me to a likely culprit... its gotten old dealing with the problem and I really don't want to take out an 'exploratory maintenance' mortgage

Hello all, I've noticed that during turbulence I'm continually correcting for increased nose-up trim in my 1962 M20C. The more turbulence the more often I have to roll the wheel forward to correct. Love to hear anyone's ideas, similar experiences, cautionary tales or estimated costs of repair?