PT20J

That’s a certification requirement to size the battery. I don’t know of any requirement for an owner/operator to perform a capacity test unless the test is required in the limitations section of the ICA or AFM. However, I would not want to fly IFR with a battery that had not been recently tested if it were more than a couple of years old. Skip

According to the TCDS, the change was made with M20C S/N 690001. Along with the change in elevator movement, the stabilizer incidence and trim bungee part number and setting changed. May be related to the increase in Vne and Vno that occurred at the same time. Maybe earlier models were running out of nose down trim at higher speeds. Skip

I recently purchased a 24V Gill LT. Cheaper and higher capacity than the Concord. The ICA only requires it be charged if necessary before installing. No capacity test for 18 months. I replaced the 5 year old Concord because it was marginal on the capacity test and barely passed after a couple of charge/test cycles. It cranked the engine just fine. A lot of people seem to think that it’s good if it cranks. I had a 6 year old battery in my Subaru tested with one of those quickie automotive testers and it tested good. Always started, too. But I left the hatch open for about an hour and that little light bulb in the cargo light ran it completely down so I had to get a jump to start it. Skip

I lubed the cable in my 1978 M20J by removing the connection at the back of the tachometer and pulling the core out. I cleaned it off and used graphite speedometer cable lube from an auto parts store. Skip

There are standard heat treatments once you know the alloy and hardness which could be determined by testing the existing part.

How is the vibration at 2300? If you’re happy with it there, I’d rebalance at the rpm you fly. I assume it was a new prop for the 390 STC so it should have been statically balanced. I know an A&P who claims that removing and remounting the prop 180 deg sometimes makes it smoother. Skip

If it has a curved slot, it’s a Dzus. To open and close them you should use a Dzus tool. The most common version is often referred to as a “Snoopy Tool.” It’s the best tool because it fits all fastener sizes. You can use a screwdriver if the fastener isn’t a tight fit, but if it is tight, the screwdriver blade will chew up the slot. Dzus were popular around WW II. I hate the damn things. The springs break after they work harden. Large panels with Dzus all around the perimeter often will only allow you to tighten the last one if they are tightened is some particular order which is not necessarily the same each time you replace the panel.

The way a controller explained it to me once is that the ARTCCs own all the airspace and turn over operation control of parts of it to TRACONs. When the TRACON is not operational, control reverts to the ARTCC. This happens all the time with TRACONs associated with towers that don’t operate full time. I thing reverting the airspace to G would require a NOTAM. Skip

Ross, I've seen a lot of Dzus fasteners on the museum aircraft, but I've never seen a countersunk one. It sounds more like a Southco. A Dzus stud ties into a S-shaped spring wire retainer. The Southco uses a receptacle. Skip EDIT. Perhaps I spoke too soon. I did a quick web search and apparently there are counter sunk Dzus fasteners. Another way to tell it's a Dzus besides the spring retainer is that the slot depression is curved not flat since it is made for a Dzus tool and not a screwdriver. https://www.specialty-fasteners.com/Dzus-Steel-Countersunk-Flush-p/sku-3345.htm

He’s right, of course, and the amount of damage done here indicates ground handling that might have broken any airplane. The problem with Mooneys is that the turn radius is more limited than many other airplanes and the older ones don’t have turn stops (except for the rudder stops that are in the tail). The later models with turn stops aren’t completely safe either since the stops are not very strong and are fairly easily broken as shown in the pictures. I’ve never found an FBO that doesn’t know about Mooneys. It’s almost impossible not to have them tug it — they are not going to hand tow it out to the north forty when they decide to park it for the night. Most times, I talk to whoever is going to move the plane and make sure they understand. If I’m not comfortable with the situation I just ask them where they want it and park it myself. Skip

I never heard that one either. It’s not in the Pilot-Controller Glossary. I had to resort to Wikipedia.

Mooney will only sell parts through a MSC so it’s best to call your favorite one rather than the factory to check general parts availability. Skip

It took me a long time (and a lot of emails back and forth with Ron Blum) before I understood the bungees. There are lot’s of ways to build a trim system. The most common is the trim tab. Another way is the variable incidence stabilizer like a C-180. Or, you can do it all with bungees like the rudder trim on some Cessna singles. Mooney just used a combination of the latter two methods. Probably no one remembers why the system was changed starting with the K. Bob Kromer told me that he was told that initial flight tests of the K (which were before Bob joined Mooney) showed undesireable characteristics, which apparently were unpredicted, and that required the change. But he didn’t recall anyone ever elaborating on what problem the were trying to solve. The K and all the long bodies have a bob weight and down spring. Bob weights are used to increase maneuvering stability by increasing stick force per g: The harder you pull back, the more g’s you pull and the more the bob weight pulls against you. The down spring might have been to improve low speed airspeed stability: at lower TAS, the elevators are less effective and you have to pull back more on the controls to change pitch which stretches the spring and it pulls against you. Skip

Looks right. If the airplane didn’t have the trim bungees, the stabilizer would have to move through a greater angle to effect the same trim range. The bungees also act as centering springs which improves the airplane’s airspeed stability. Skip