PT20J

The electric system is more complicated, so I would expect it to have more issues. But, mechanically, it is very similar and the emergency gear extension system will protect you from electrical failures. If everyone had upgraded to the 40:1 gears in the Dukes and lubricated them properly, the actuators would probably outlast the airframe. Similarly, the Eaton noback springs are really a non-issue as far as I can tell. So, that leaves the Plessey actuators. There have been several documented failures. It is known only to Mooney how many of these actuators were installed, but my guess is not many which would make the failure rate higher, and you cannot get parts for them. Some will say you cannot get parts for Dukes or Eatons either, but at least Eaton is still in business making it a possibility.

Many people use too much glue.

There are two relays: one turns the motor on one way to retract the gear and the other turns the motor on in the opposite direction to lower the gear. If the relay coil is shorted (or the flyback diode) it would pop the Gear Cont CB (not the Gear Act CB) which is why I asked which breaker popped.

None. Which is really the point. The number of gear up landings caused by mechanical failures (J-bar or electric) is very small compared to pilot errors. Just like driving, the nut behind the wheel is the most likely component to fail. I don't worry about the gear failing to come down (although since I had a relay and then a microswitch fail, I have some concern about it going up); but I do very much worry about getting distracted by unusual ATC requests, traffic or some unrelated emergency.

I used to instruct at a club that had a M20C with manual gear. Over a period of about fifteen years, it landed gear up three times.

Which breaker popped? If it was the gear actuator breaker, it sure sounds like the emergency gear extension system became engaged. I would check the rigging. It's unlikely to be electrical unless the wiring has a short, but you said that the actuator was "locked up" which would not indicate an electrical problem.

Sounds like you did this with the airplane on jacks and the belly opened so that you could watch the jackscrew. If the jackscrew stops, of course the gear will stop retracting. There is not, to my knowledge, a slip clutch in the actuator, and the fact that there is also a problem with cranking the gear down manually leads me to think that something is stripped, especially if the gear stops moving but the motor keeps turning. If it's happening at the same point retracting with the actuator and extending with the crank, I might look closely at the jack screw for a damaged spot.

During prepurchase the airplane will be opened up. Witness or have the inspector take pictures of the actuator including the ID plates. Examine the logbooks for what's been done to the actuator: Dukes: 40:1 gear installed? Periodic lubrication, AD compliance?; Eaton: noback spring replacement; Plessey, well, I wouldn't buy it with a Plessey personally.

Another option https://www.aircraftspruce.com/catalog/topages/pointers.php

3M Dual Lock has much stronger adhesive.

I'm 5'6". With no rudder extensions, I put the seat one notch back. With 1.5" extensions, I put the seat 2 notches back. With 3" extensions (which I now have), I put it three notches back. The articulated seats also move back when lowered and forward when raised.

Maybe this will help.

Did he blow them out with an air hose afterwards? If there are deposits, the solvent can soften them but they may remain within the nozzle and clog it unless blown out. I found this out once when I forgot to blow them out. Also, some manuals (AvStar) recommend rinsing with hot water after soaking in solvent. This works with acetone or MEK, but Hoppes reacts with water and makes a white goo.

FAA AIN https://www.asias.faa.gov/apex/f?p=100:96:1300354096487::::P96_ENTRY_DATE,P96_MAKE_NAME,P96_FATAL_FLG:20-JUN-24,MOONEY It's classified as an INCIDENT which means no substantial damage, but that can't be right. It also says that AIRCRAFT CONDUCTING TOUCH-AND-GOS AND VEERED OF (SIC) RUNWAY. That's not right either.

But, that never happens

The 20:1 / 40:1 ONLY applies to the Dukes (and similar ITT) actuators which use a worm and wheel gear arrangement. The problem with them is that the gears are small and heavily loaded. The moly grease helps reduce friction and thus wear, and the 40:1 retrofit gears are less heavily loaded than the original 20:1 gears to further reduce wear. Eventually the gears will wear out and there are currently no replacement parts available. The Eaton (a.k.a Avionics Products, Vickers) and the similar Plessey actuators use a spur gear train that is less heavily loaded and I have not heard of issues with gear wear on these actuators. The Mooney electric gear has no mechanical up locks. Something has to keep the gear from falling back down when in the retracted position. The worm and wheel gear arrangement cannot be back driven, so the Dukes/ITT actuators naturally hold the gear retracted. But the spur gear arrangement on the Eaton/Vickers actuator needs a brake which is the infamous noback spring. There have been a handful of noback spring failures in the field, most in Plessey actuators. There was one bad batch of Eaton noback springs that was recalled long ago and probably none exist in the field today. Don Maxwell told me that the Eaton noback spring is rated for 20,000 cycles. The 1000 hour replacement interval seems arbitrary and chosen because of a couple of failures or Plessey springs at around that time in service. But, time in service is meaningless. It is cycles that is important. Currently there are no new noback springs available. If it were my airplane, I'd keep the Vickers because I believe its a more robust design. It would also probably be a lot of work to source the parts and switch to the Dukes emergency retraction crank system.

I'm confused. Are those pictures of the Vickers that was removed and the Dukes you are considering installing? The Vickers in the picture is not a 20:1 gear actuator. It is a later model design as used in airplanes built after 1978. It has been built under various names: Avionics Products, Vickers, Eaton. It has a more robust gear train and has a noback spring and a completely different emergency gear extension mechanism than the Dukes. I believe that parts for the Dukes emergency gear extension system are difficult to obtain.

Hardly ever makes sense to buy a new engine. What's the lead time and cost on a factory rebuilt engine?

My two M20Js both required about 4 seconds of prime when cold. Make sure the throttle is open when priming - it affects the fuel flow when near idle.

Depending on the amount of corrosion, it is often more economical to replace the wing with a salvaged one.

I agree with @EricJ. If it was repaired correctly, it should be good as new. I think people make way too much fuss over damage history. These airplanes are old and stuff happens. Airplane sales are a negotiation between buyer and seller. Your case is special because you are selling a share to partners. If I were in your position, I would pay for one or more written appraisals and agree to sell your share for an amount based on the appraisals. Jimmy Garrison https://www.gmaxamericanaircraft.com/ would be a good place to start.

The cotter pin is way too long.

Single mags from Bendix and Slick are available with 15 degree lag angles, which means that when the mag is timed to the engine at 20 deg the impulse coupling will fire at 5 deg BTDC. The Bendix dual mag is not available in different lag angles and was designed for mag to engine timing of 25 deg BTDC. Here is the original Lycoming Service Instruction. SI 1325 Timing Change for IO-360 Series Engines.pdf Also, the note in the Operator's Manual begins, "On the following model engines..." The first engine listed is "IO-360-A Series (Except -A1B6D)". You have an -A3B6D. The difference between the 3 and the 1 is just the propeller indexing, so the parenthetical note applies to your engine. The D signifies dual mags.

Anything can be repaired. It’s a matter of time and money. It’s just like a car. Get in a major crash with a 20 year old car and the insurance company is going total it because the cost to repair exceeds the value of the vehicle.

The procedure is in the service manual. Essentially, loosen the screws, move the stall vane assembly, tighten the screws, test fly. Repeat until you get it correct.