PT20J

Everything went smoothly. All the important stuff is in this thread. My summary is near the end. Skip

^^^^^^^^^^^^^^^THIS!

I think you are right for something TSO'd. I'm not sure about an autopilot though. I think that requires an STC because each installation is different. For instance, there are two plug in modules that program the KC191 computer and they are specific for each airplane.

We discussed this in another thread and IIRC, the result was that the drag of a stopped prop is slightly higher than a windmilling prop set to high pitch. I believe there are some youtube videos about. There's actually quite a bit of blade area to create drag when the prop is stopped but not feathered, and a non-feathering prop will go to flat pitch when stopped. Of course feathered is best. I recall reading somewhere that to get measurements to confirm the B-17 drag polar, Boeing flew one up to 20,000 feet or so and shut down all four engines and feathered all four props and did glide tests. I guess they got them started again Test pilots have all the fun. Skip,

My M20J came from the factory with a KAP150. The KAP150 is not listed on the TC, so I presume that the factory installed it under STC. Legally, to apply an STC you need a letter from the STC holder granting permission to apply the STC to your airplane. Skip

Might be a bad alternator diode.

There's an autopilot trouble shooting guy that hangs about that could help you narrow it down. I blank on his name at the moment but Anthony @carusoam should be along any moment to help us out .

I had this problem with my Aspen and KAP 150. Turned out to be a bad ACU. I believe that the 55X requires an ACU2. When I talked to Aspen tech support, I got the idea that ACU failures were not that uncommon. If that is the problem, Aspen will trade yours for a refurbished one - I don't know the current price. I found a used one on eBay. Skip

Perhaps @Blue on Top can weigh in but I always had the impression that the TC holder had to do a lot more with the FAA than may be required for an STC. At a homecoming factory tour years ago I asked someone why the factory installed speed brakes using the STC instead of just adding them to the TC and was told that the cost that an airframe manufacturer has to go through to get a design change accepted was prohibitive. Back in the day, Mooney always did good engineering and was very conservative. I'm sure that if engineering increased a tube size they thought it necessary to maintain a desired factor of safety. A manufacturer has a lot more on the line than an STC holder, and a lot of STC holders are defunct. Skip

See, that would be my fear: I’d pay $500 for the thing and then every really difficult job would be one where it wouldn’t work.

It’s considered part of the engine, so it would be in the Lycoming engine IPC.

The suction screen was safety cabled at the factory on my A3B6 rebuilt. It looked so pretty, we hated to cut it. Kind of pricey if you’re not doing a lot, but you’d be the envy of every IA that looks at your airplane. https://www.aircraftspruce.com/catalog/appages/nosetool.php?clickkey=27717 Skip

I noticed something interesting about Lycoming SB 480 (excerpt posted above). It has the standard warning that all the Lycoming SBs contain: Incomplete review of all the information in this document can cause errors. Read the entire Service Bulletin to make sure you have a compete understanding of the requirements. Good advice since the oil change procedure includes draining and refilling the sump, and that procedure comes before the procedure to remove, inspect, and replace the suction screen which is located at the bottom of the sump. Skip

Also, note that the torque spec is a 135 degree rotation. I believe it’s standard practice to put the split side of a copper crush gasket toward the engine (non-rotating face) but I don’t know if it really matters. Lycoming calls for food grade anti-seize (I presume that’s because it has no metallic content). Clarence, do you use the anti-sieze? We didn’t have any and figured the threads are soaked in oil anyway, but I’m wondering if I should get some for next time. Here’s the Lycoming SB excerpt.

None of this really matters: The point is that there is no way to get gross weight increases without either complying with the type certificate or an existing STC. If someone thinks it’s a great business proposition to get a new STC to up gross older airframes then I’m all for it. Thus far, Mooney hasn’t wanted to bite that apple, but someone else might make a different ROI calculation. You probably could not get data from Mooney or Rocket — I’m pretty certain that is closely held as proprietary. @Blue on Top might have some idea as to the process and cost to get the data package for FAA approval. For me, it was just cheaper to buy the airplane that fit my mission. Skip

The mechanic at the museum has one of those torque wrenches. They are very cool! I’ve never been able to find a 3/8” drive 1” socket — seems the largest I ever find is 7/8. Is that a Snap-on part also? Skip

The gross weight change happened at S/N 24-1686 which is coincidentally when the wall thickness for the lower tubes was increased. Since these tubes can be prone to internal corrosion (it’s the one called out in SB-208 for inspection with a magnet) perhaps someone has had experience replacing them. Looks to me like the wing might have to come off. Skip

Before changing anything, I’d have someone move the nose wheel with the tow bar while watching the mechanism to try to figure out what’s causing the coupling between the rudder and the brakes. I’d especially watch the pivot point at bolt 8. The brake bell crank and rudder torque tube both pivot at this point. That’s the only obvious source of coupling that I can see. Skip

The biggest problem I have with the A3B6 (which was never a problem with the A3B6D) is getting a wrench on the filter. I use a 1" racheting box end wrench which works fine. I tried all sorts of adapters to get my torque wrench on it (none of which worked) and finally just started tightening 3/4 turn like @jetdriven suggested - just like a car. @M20Doc, How do you torque the darned thing? BTW, it's not that hard to get the suction screen out. It's safety wiring it that will drive you nuts. But experience and practice is everything. My IA did it in less than 5 minutes with no blood and only a little swearing when we did the annual. Same when he safety wired the prop. Point is: after a a couple of oil changes you won't think it's so hard anymore. Just hope you never have to remove the prop governor! Skip

Clarence is correct: The adjustment I showed above will lengthen or shorten the piston rod for the master cylinder to change the pedal angle. It is the only adjustment that I am aware of. I don't really know if it has any effect on your problem, but since replacing the brake cylinders seems to have initiated the issue, it's where I would start. The rudder pedals have two connections: Item 4 for rudder control and item 5 for the brakes. The distance between where the two connect on the pedal is the same as the length of the arm on item 7. So, mechanically, the pedal and items 4, 5, and 7 form a parallelogram such that pushing on a pedal without rotating it will rotate the rudder torque tube without applying the brakes. Another possible way things could have been messed up is if rudder pedal extensions were installed perhaps incorrectly. Skip

Yes

By golly, I think you’ve figured it out! I never would have thought of that. Edit: Sorry, too much eggnog

Paul, Curious to know what magnitude EGT swings you usually see with valve issues. Skip

There is an adjustment to the lengths of the master cylinder piston rods. There is no description of it I could find in the S&MM for my M20J when I had to tweak mine to get the pedal angles right after installing the 3" pedal extensions. There should be some free play in the pedal before the brakes go solid. If you remove the left exhaust cavity an examine the linkages it should be fairly obvious what's gone wrong.

Just email technicalsupport@mooney.com. They are very responsive to specific questions in my experience. Skip