PT20J

I've always liked King autopilots, but I recently went through several month's effort resolving an intermittent problem with the computer for a KAP 150. All the King autopilots are getting old, some parts are scarce, and there are fewer options for repair. I would look for a plane with an S-TEC, even though I agree with many that the rate-based autopilots don't fly nearly as precisely as the attitude based autopilots. Why? Because there are more upgrade options on the horizon (namely the S-TEC 3100 and the Avidyne DFC90) to upgrade the installation to a modern, digital, attitude-based autopilot without ripping out all the servos and wiring. Some interesting history: Ed King took the best engineers from Collins to form King Radio. Years later, the best engineers left King to start Garmin. EDO morphed into Century after an employee buyout. A group of engineers left Century to form S-TEC to exploit the idea of rate-based autopilots. The idea was that the vacuum system/gyros were the most failure prone system and the fatal accident rate after an IMC vacuum failure was very high. On the other hand, turn coordinators had low failure rates. So, after a vacuum failure, the S-TEC would be able to bring you home safely. Not a bad idea, but they just never were as responsive as the attitude based autopilots. Skip

I'm a retired electrical engineer. The only aviation project I worked on during my career was a flight simulator back in the early '90's. I owned a 1978 J at the time and we used it as a test bed. I got to know the VP of Engineering and a couple of engineers at Mooney at the time and we shared some data. I also had several consultants working on the project. I learned a lot on that project and it and started a fascination with aerodynamics and flight dynamics.

I think certified version of TruTrak doesn’t have trim.

I believe the impulse coupling spins the common mechanism that turns both mags.

OK, so at 2500 lb GW, that’s a ROC decrease of 3.7 * (550/2500) * 60 = 48.8 ft/min. At 100 kts that’s about 30 ft/nm.

Actually, it depends on whether you have the jumper on the ignition switch or not. No jumper = both mags for start.

One mag except Bendix dual mag engines that start on both.

If it doesn’t start after a couple of attempts, prime enough so you are sure it’s flooded and do a flooded start procedure. Works every time. When priming an engine with a RSA injector, it’s important to open the throttle about an inch or so. Idle mixture is controlled by the idle valve connected to the throttle. If the throttle is set too low, the valve limits the fuel flow and you will get an inconsistent amount of prime depending on the throttle position. Skip

Hey, thanks, Clarence. I didn’t know that. Now I know better. Skip

Search youtube for Don Maxwell hot start.

You probably mean the oil suction screen. If you have an oil filter, most mechanics only pull it if metal is found in the filter. It’s a pain to get to and it’s a pretty coarse screen, so if there’s no metal in the filter, it’s pretty rare to find anything in the screen. Continentals have one too, but it’s internal and you can’t get to it.

What melted at what EGT?

Try this: https://youtu.be/jbRYqS-fRo0

I used a Tempest oil filter for the first time recently and it’s supposed to go on dry. Has anyone run into any problems with that? Now, what am I going to do with that half tube of DC-4 that I’ve had for 25 years?

+1 for PHT. Ashley Wilson was very helpful. OEM style hoses have 5 yr. life. I got PTFE hoses with crimped stainless fittings and molded on firesleves that have unlimited life. Just under $1K for complete set for M20J. The molded firesleves look nice and are smaller overall diameter, but are stiffer and a bit more difficult to install when you have a bend in the hose. I believe Guy @GEE-BEE also makes the same style hoses. Compare prices.

Interesting question. A few points to consider: 1. Propeller efficiency varies as both TAS and RPM, and propeller efficiency is generally plotted as a function of advance ratio J = V/nD, where V is TAS, n is RPM and D is diameter. So, the optimum rpm varies with airspeed. Generally, lower rpms for lower airspeeds and higher rpms for higher airspeeds should yield the greatest efficiency. 2. The purpose of a constant speed propeller is to broaden the peak of the efficiency curve over a wider range of advance ratios. This means that at normal cruise speed, the efficiency isn't overly sensitive to rpm. 3. Any rpm/map combination that is in the engine manual is okay to use. For the Lycoming IO-360A, the range at sea level is 1800/25" to 2700/28.5" depending on power output desired. 4. When comparing different rpm/map settings, it is important that the airspeed be the same for both. This is the only way to know that the power output is the same. 5. As noted, rpm/map combinations affect engine power and efficiency as well as the propeller. 6. Often it comes down to finding a rpm/map combination where the engine runs smoothest. A lot of Lycoming four-bangers don't run as smoothly at lower rpms. 7. On a normally aspirated engine, as you climb you will run out of manifold pressure at WOT and then will have to increase rpm to maintain power.

I'd get a good DVM and check the bus voltage to verify that the JPI is reading right. You mentioned that pulling the alt CB didn't affect the headsets. Did you pull the alt FIELD CB? That will turn off the alternator. Check if that changes the headset noise or has any effect on the voltage. With the alternator off, you are just measuring the battery voltage. If that fluctuates, you have a bad gauge or a bad connection somewhere. Check all that before digging into the alternator/regulator.

I've been doing some research and I've decided that the Mooney transducer mounting is all wrong. It's difficult to get any good technical support now since JPI bought Floscan. I can't find anyone at JPI that knows anything about the transducers, and the Floscan phone number just rings a salesman. Shadin tech support just defers to Floscan. There is actually some pretty good info on Floscan's website for the marine versions (most of their business). The marine version is essentially the same design but it's cast from zinc instead of aluminum and they don't come with calibration data according to the Floscan salesman. So, combining information from the marine installation instructions and the aviation installation instructions and some installation instructions from Van's, here's where I think Mooney got it wrong: Per Floscan marine installation instructions: "Flow Sensors must be placed in a horizontal section of fuel line at a low point in the fuel system. Fuel should travel, “Up-hill” when exiting the sensor. Its outlet should be at least 1 or 2 inches lower than the fuel pump inlet." This is, I believe, why it's supposed to be mounted with the wires coming out the top. The outlet is slightly higher than the inlet when mounted this way. Mooney mounts it upside down. The Mooney location also puts the transducer outlet at about the same height as the injector inlet. The instructions that come with the aviation version say this is OK, but I think lower would probably be better. Other less severe mounting issues with the Mooney design are that it is mounted to the engine whereas the instructions that come with the transducer suggest not mounting it to the engine to reduce vibration. Also, it's a good idea to mount it in a straight section of fuel line - Van's suggests at least 6" of straight line on either side - and Mooney puts a 45 degree fitting on the input. Speaking of fittings, Mooney IPC calls out aluminum fittings. Bad idea to put aluminum NPT fittings into an aluminum casting as it can gall. Steel fittings are specified by Floscan and should be used. All Floscan installation instructions (marine and aviation) say not to use Teflon tape which certainly is appropriate since you don't want strands of tape clogging the transducer and injector inlet screen. However, the marine instructions say to use a fuel proof sealant on the NPT threads whereas the aviation instructions say not to use any sealant or you will void the warranty. This makes no sense. Pipe threads aren't designed to seal without some sort of sealer as there's a spiral channel between the mating threads. I'll take a voided warranty over a fuel leak under the cowling any day. Byron did a very nice installation that seems to meet all the Floscan requirements. Look toward the end of this thread: Skip

Great test. I can’t do that in my J because the KAP 150 has autotrim and I can’t fly it precisely enough when it’s that far out of trim to note any airspeed change. It’s kind of interesting that the bungees align the elevator at the takeoff trim setting rather than cruise. As @carusoam noted, we never run out of nose up trim.

Knots2U bought out Aircraft Door Seals so they are the same thing.

A lot of folks on BeechTalk recommend it with no ill effects, so I thought I'd give it a try. Since the transducer wasn't working reliably anyway, I didn't have much to lose. As one of the BeechTalk guys pointed out, Hoppes comes in a plastic bottle .

Here's an interesting paper I ran across. It explains a few things I never understood, especially the mechanism that causes the "vertical" scratches in new cylinders. Skip 10.1.1.851.7750.pdf

Certainly the tail down force is a function of weight, CG and TAS, and if you didn't adjust the trim, the elevator position would vary with these parameters also. However, when you trim, you're changing the angle of incidence of the stabilizer. If there were no trim assist bungees, the stabilizer angle would trim the airplane and the elevator would trail in its neutral position. However, the trim assist bungees on the J and previous models bias the elevator to move along with the stabilizer to reduce the amount of stabilizer travel required to effect the full trim range (that's likely why Mooney called them trim assist bungees). This spring pressure causes the elevator to be slightly out of trail when trimmed at cruise speed.

Yep, that’s the down spring that started with the K.

Here’s a link where someone took one apart. Forgot one more thing: Instructions that came with transducer said not to mount it to the engine. I might try removing it from the engine mounting and rotating it 180 degrees. Still interested if others have run into this problem with the Mooney design. https://www.euroga.org/forums/maintenance-avionics/3929-shadin-floscan-201-fuel-flow-transducer-internals