PT20J

FWIW, every screw that I've had to drill out has been cad plated. Part of the problem is that the cad plating wears off after a few cycles. I've been replacing any questionable screws with stainless steel, simply because it was easier to buy a kit of screws than to figure out what individual screws I need, and the kits all seem to be stainless. I haven't had any issues with the stainless but I'm careful to tighten by hand so as to not over-torque them and I soak them in WD-40 (or ACF-50, or Boeshield if you prefer) before installing. Skip

Area effect comes into play here. https://corrosion-doctors.org/Corrosion-Forms/area-effects.htm In the case of stainless screws and aluminum skins, the area of the anode (aluminum) is so much greater than the cathode (screw) that the corrosion is negligible.

I’ve had really good results with Mid-Continent.

The lateral-directional motions can get pretty complex. Lets say you are flying along and suddenly decide to stomp on the right rudder and then release it. The nose will yaw to the right. The rate of yaw will increase until you release the rudder and then it will stop and reverse as the natural directional stability wants to reduce the sideslip. The sideslip will cause a rolling moment to the right due to dihedral effect and the yaw rate will cause a rolling moment due to the difference in speeds of the two wings. If you try to correct the roll with aileron, the adverse yaw introduces a yawIng moment and if you use the rudder the fact that the vertical tail is above the CG will introduce a roll. So, in anything but calm air, the airplane is always wallowing around a bit. Some are worse than others especially if the roll-yaw coupling devolves into a Dutch roll. If I get a GFC500, I’m getting a yaw damper. Mooneys aren’t terrible in turbulence, but why not get some help to smooth out the natural dynamics? One trick if you don’t have a yaw damper is to remember that stick-fixed stability is generally greater than stick-free stability. I was getting a terrible ride over the Arizona desert on a warm afternoon in a Duchess when I thought to block the rudder pedals with both feet preventing the rudder from floating. The ride improved considerably. Skip

Let's think this through. Propellers exert various forces on the airframe due to gyroscopic effects, torque, p-factor and spiraling slipstream. If an airplane is flying sideways, there must be a sideways force. Where would this force originate and how is connected to the propeller? Let's consider an airplane in cruising flight. Torque acts axially and cannot generate a side force. P-factor is negligible as the ascending and descending blades are at essentially the same angle of attack in level flight. There is no pitch rate or yaw rate to created gyroscopic precession. Thus, we are left with the spiraling slipstream which, by its impingement on the vertical tail, creates a side force. If unchecked, this would cause the airplane to fly along in a sideslip. However, the pilot would naturally counteract this situation with rudder input nulling out the net side force. This would require constant rudder pressure to keep the ball centered (wings level), and would be tiring on a long flight. Fortunately, engineers have designed means (usually a slight canting of the vertical tail or offset of the engine thrust line) to generate the counterbalancing side force without holding rudder pressure. This solution is exact only for a single speed and power setting, but the optimum is so broad that it works well over the normal range of cruise speeds. Faster speeds, as in a high speed descent, will require compensating left rudder, and slower speeds, as in a climb, will require right rudder. Of course, if you have rudder trim, you can trim for straight flight at any speed. My M20J cruises with the ball centered (feet on the floor) and wings level for several seconds (hands off). Here's a good article about Mooney rigging: 201407 Control Rigging.pdf Skip

I just put one on my M20J. I picked off the #4cylinder. McMaster-Carr has the barbed fittings to attach to the rubber hose supplied by SureFly. https://www.mcmaster.com/53505K111/ Skip

I've owned an 1978 M20J and currently own a 1994 M20J. Here are a few suggestions. Familiarize yourself with the changes Mooney made over time. You don't want to buy a XX year model and then find out that a feature you really wanted was added in XX+1. I consider the 1977s prototypes (there's nothing wrong with them, but there are some differences that got ironed out later). After that, there are important changes along the way such as better landing gear actuators, better corrosion proofing, gross weight increases that are worth considering. I've attached a spreadsheet that is a good starting point. Also, I'd talk to Jimmy Garrison at GMax. He'll share his encyclopedic knowledge of Mooneys even if you're not buying one from him. Some of the long-time Mooney Service Centers can also let you know about any maintenance issue with various vintages: LASAR, DMax, Top Gun are my go to folks and are all very helpful. I've always followed Mike Busch's advice: Buy the newest, lowest time, best cared for airframe you can find. It's the one thing you can't change. Avionics are expensive to upgrade and you never get your money back. Try to buy something with avionics that fit your mission and that you can live with for awhile. After you get used to the setup, you may discover that some of your wants are not truly needs and you can upgrade only what you truly need. I would not worry about the interior. While it is possible to spend a small fortune on interiors, it's also possible to get a very nice looking replacement for a very reasonable price -- especially if you do some or all of the tear out and installation yourself. Paint is expensive, but it's only a cosmetic issue unless there is a corrosion problem in which case you wouldn't buy it anyway. Everyone looks at the engine and prop time because they are expensive. But I always worry about airplanes for sale with newly overhauled or low-time engines. Did the owner spend the money to do a really good overhaul just before sale, or did they take the cheapest route they could find? I would much rather buy a high-time engine (appropriately discounted) than a low-time engine with a questionable overhaul. You may get years of service from the high time engine after which you have complete control over the quality of the replacement. Good hunting, Skip 201hist.xls

The paint looks like it might be epoxy primer applied for corrosion protection. Epoxy primers require mixing with a hardener and then they have a pot life of several hours. You can clean up the area with some Scotchbrite and then brush on two or three coats of primer. Often mechanics keep some around for just such repairs and can mix up a cup for you. You might try the shop that made the goof and see if they'll fix it for you at no charge since it's their mistake. Failing that, you could go to an auto paint supply store. Some NAPA auto parts stores have paint departments. Skip

Mooney uses Camloc fasteners. The Camlocs on the top of the cowl are 4002 series.

I remember going out to look at the scene of a fueling mishap at Lake Hood strip in Anchorage years ago. The pilot was sitting on the wing of a C-180 pouring fuel into the tank filtered by a large funnel and a chamois skin when a static spark lit it off. All that was left was a scorched airplane outline and some oxidized aluminum powder. Skip

And why do we call it a Johnson bar anyway? And, who’s Johnson? https://www.wisegeek.com/what-is-a-johnson-bar.htm

Back in the ‘80’s I instructed at a club in San Jose, CA that had a manual gear Ranger and it managed to land gear up — twice. (No one I checked out - thankfully). That airplane is still flying last I checked. N78888. Skip

Sounds like everyone's having a good experience there. Thanks for your pireps! I had an intermittent issue with my KAP 150 controller a couple of years ago. I phoned David and described the symptoms and he correctly diagnosed the problem as a bad interconnect connection between circuit boards. Skip

The seal shouldn’t stick to the door frame especially if you put silicone on it (I like the 100% silicone plumber’s grease - it spreads around easier than DC-4.) I wonder if the seal is deteriorating? Is it an aircraft seal, or something someone put on from Home Depot. I just replaced the cabin and baggage compartment seals on my plane. It’s a real pain getting the old glue off, but reasonably straightforward. Mooney uses Brown Aircraft T-9088 p seal. Skip

I'm not an expert on this having never done it myself. You are certainly correct that the pressure must be equalized across the airspeed indicator pitot-static ports during the test to avoid driving the ASI way over range and damaging it which could also damage the diaphragm in the gear safety switch. But the test sets have separate systems for leak testing the pitot and static system. My airplane has been recertified every 2 years since it left the factory in 1994, yet I recently discovered a rather significant pitot leak that was apparently created when the Aspen EFD 1000 was installed for a previous owner. Since there is no requirement to test the pitot system for leaks and since there are no log book entries attesting that it has been tested, I don't think it has been. Next time, I'll watch them do the test and see exactly what they do and don't do. Skip

Here's the Concord recommendation. As you can see, the recommended voltage varies from 27.5 to 29 depending on temperature. Mine runs about 28.8. Don Maxwell told me he has adjusted the Mooney regulator, so he must know which pot does what. You might give him a call. It would be a cut and try sort of thing. On the other hand, if you are getting good life from your batteries, maybe it doesn't matter that much. All we have to go on is what the recommended voltage is, but what we don't know is how broad the optimum range is. In other words, what's the effect on battery life by by being 0.1 volt high? Or 0.5 or 1.0 or 1.5? The curve might be fairly flat. Obviously at some high voltage overcharging will cause out-gassing and the battery life will be affected. But these charging systems are pretty basic and my guess is that the optimum is fairly broad.

Also, when you do the next pitot-static check you can have the ASI calibration checked and leak check the pitot system. Usually shops only leak check the static as that's all the regulations require. Skip

Anybody have any pireps? Skip

Something's not right. The master switch should turn off everything (except the clock and the infamous cabin lights that will drain your battery if left on). In your case, it sounds like your alternator field is active when the master is off so that the alternator is supplying power to whatever bus the JPI is connected to. I would get the schematic for your serial number and a good DVM and trace things out to figure out what's going on. Skip

How much debris are you talking about? If it's just a little, keep sampling until it clears up. If it is a lot and/or doesn't clear up, then you will want to have the tanks inspected for deteriorating sealant. But it it's not leaking, it will probably clear up especially if it has been sitting a while. Skip

Well, actually not! In flight, the wing lifts the fuselage. Remember the lift vector? It points upward. These folks are sitting on top of the wing. Their (combined) weight vector points downwards. Another way to think about it is that the wing supports the fuselage in flight. The weak point is where the wing attaches to the fuselage. That's why some airplanes have a zero fuel weight limitation. Some of the gross weight has to be out in the wing or the wing attach bending moment gets too high. Skip

Your MAP sounds about right. My prop gets up to 2700 at rotation speed at sea level (factory rebuilt engine with 200 hours on it). Always a good idea to check the instrument calibration before looking into other issues.

When the breaker pops it generally means that the motor can't turn. As Paul and others noted, this is usually due to the emergency extension lever being engaged. If that's not it, and you've checked out all the rigging and limit switches, then there is the possibility that something inside the gearbox jammed the motor. If that's the case there is a possibility that it could jam again and perhaps with the gear retracted while also rendering the emergency gear extension mechanism inop. If I couldn't find a cause, I would disassemble and inspect the gearbox just to be sure. Maybe it's a good time to replace the noback spring and replace the grease also. Skip

I haven’t worked on this particular valve, but a lot of these type valves are tapered plug (aka cone) valves. They can be disassembled and the plug and mating surfaces VERY lightly lapped together to make them turn freely. Don’t overdo it or you will make the cone undersized and the ports will be misaligned (yes, I’ve made that mistake). All you want to do is remove the surface toughness that is preventing the valve from turning. Replace any o-rings and lube everything with EZ-Turn (aka Fuel Lube). I would remove it from the airplane and get it up on a bench where you can work on it properly. We had to do this recently with a stuck firewall shutoff fuel valve on our Beaver. Any time a metal valve starts getting stiff it’s a good idea to take it apart and lube it. They just get worse until they finally seize up. Good luck. Skip