PT20J

I echo what others have said about the first year... or two. Put off upgrades and save the money for unexpected expenses. The previous owner may have deferred nonessential maintenance as they were thinking about selling, and/or may not have been flying much anymore which might be the motivation to sell. Funny things happen when the new owner starts flying the airplane a lot, and they always expensive.

The chrome comes from the rings being abraded by the rough cylinder walls. Those cylinders are steel as evidenced by the cross hatch honing pattern.

Hard to tell without earlier borescope pictures.

Mooney steering is a weak point. They all have some slop, even when new, and it gets worse as things wear. The slop manifests as a dead zone in the center of the steering range which causes a lot of footwork when taxiing to keep it straight. At higher speeds, it centers better because of the caster in the nose gear geometry provides a self-centering effect that increases with speed. The caster should cause the nose wheel to center on touchdown unless you hold rudder pressure. Since this only happened twice rather than consistently, it may not be the airplane. I would go out on a clam day and shoot some landings and see if I could figure out if it were me or the airplane. Skip

Lycoming brought cylinder head machining in house just before Covid and was working through start up issues when the factory shut down for Covid. Then, during Covid owners decided it was a good time to overhaul and homebuilders decided it was a good time to order engines (Lycoming told me that Van’s is by far their largest customer now). Orders spiked and production was halted. They are still trying to catch up although they have 6 automated head machining lines running 24/7. Lead time was a year when I visited the factory last fall. Not sure what it is now. Skip

I believe those bearings are made by Timken. According to aircraftsupply.com, the Timken part numbers are: 214-00300 = 08231-20629 214-00400 = 08125-20629 Skip

CAR 3 cooling requirements: § 3.586 Cooling test procedure for singleengine airplanes. This test shall be conducted by stabilizing engine temperatures in flight and then starting at the lowest practicable altitude and climbing for 1 minute at take-off power. At the end of 1 minute, the climb shall be continued at maximum continuous power until at least 5 minutes after the occurrence of the highest temperature recorded. The climb shall not be conducted at a speed greater than the best rateof-climb speed with maximum continuous power unless: (a) The slope of the flight path at the speed chosen for the cooling test is equal to or greater than the minimum required angle of climb (see § 3.85 (a)), and (b) A cylinder head temperature indicator is provided as specified in § 3.675. § 3.675 Cylinder head temperature indicating system for air-cooled engines. A cylinder head temperature indicator shall be provided for each engine on airplanes equipped with cowl flaps. In the case of airplanes which do not have cowl flaps, an indicator shall be provided if compliance with the provisions of § 3.581 is demonstrated at a speed in excess of the speed of best rate of climb.

George Braly once told me that all the engine monitors he looked at were inaccurate in %power calculations. He did a proprietary algorithm for Cirrus for their Perspective system and it leaked out to other Garmin products. My G3X seems pretty accurate LOP and ROP. I don't know about the current versions of other monitors -- perhaps they have improved.

Galvanic corrosion occurs when an less noble metal (anode) is in contact with a more noble metal (cathode) in the presence of an electrolyte (e.g., water with salt or other impurities). The corrosion removes material from the anode. So, in the case of stainless steel in contact with aluminum, the aluminum is the anode and would corrode. So, why is it that you can get away with stainless screws on an aluminum airplane without damage? There are two reasons: 1) If the airplane is mostly hangared and not subject to warm, moist, salty air then there is no electrolyte which is a necessary ingredient for corrosion. 2) There is an area rule: If the area of the anode (aluminum skin) is much greater than the area of the cathode (screw heads) then the corrosion proceeds at such a slow rate as to be essentially unmeasurable. Skip

The mail is slow and sometimes things get lost, so if it is really important to you to get quick turnaround, I’d pay to send it UPS red or blue. Personally, I change oil two or three times a year and so it is months between samples and I don’t sweat a few weeks getting the results. Skip

You should be able to figure out how to reverse it if you reference the drawing. Rudder Extension Drawing 720115.pdf

I shouldn't have included Vx and Vy because they are affected by more than aerodynamics as is the wing. They are also affected by power and thrust available. Vy decreases with altitude because it is the speed at which there is the maximum excess power available and that speed is the difference between the power available and the power required. Due to the shape of the curves, the speed for maximum excess power decreases with altitude. Vx is the speed where there is maximum excess thrust available and it increases somewhat with altitude. The two speeds, Vx and Vy meet at the absolute altitude and this is the only speed for which the airplane will maintain altitude. When I'm flying a normally aspirated airplane at high altitudes, I just climb at a speed half way between S.L. Vx and Vy. It's east to remember and it is pretty close to the optimum speed. Sorry for the confusion, Skip

Lift is a function of dynamic pressure, q, where q = 1/2pV^2, p being air density and V being TAS. As altitude increases, p decreases, and at the same configuration, weight and angle of attack. TAS must increase to make up the difference. The airspeed indicator actually measures q, but it is calibrated in knots. Since the TAS increases to make up for the loss of density, q stays the same and that's why the IAS performance numbers (Vs, Vx, Vy, etc.) don't change. But the wing is going through the air faster and you see this in increased groundspeed during landing and takeoff. Skip

@jetdriven probably knows.

Power is always a function of fuel flow; after all, no fuel flow, no power. Brake Specific Fuel Consumption is gallons per hour per horsepower. So, if you have a BSFC formula for your engine, you just divide the fuel flow by the BSFC and you have your horsepower. The problem is that the BSFC curve is not linear and there is no simple relation between it and the MAP, rpm and fuel flow over the entire range of mixtures that the engine will operate. ROP, it's simplest to use the power charts in the POH. Many have simplified this to "key numbers" noting that, to good approximation, MAP + rpm/100 is nearly constant for any particular power (say 65%) in the chart. It's not exact, but it's simple enough and who really cares if you are set at 64% or 66% anyway? LOP, the BSFC reaches a minimum and is then relatively constant over a range of mixture until the mixture gets so weak that the engine begins to misbehave. This allows a simple estimate of power. I'll attach an article that goes through the details, but for an IO-360 you can just take the fuel flow and multiply by 15 (technically it might be 14.9, but it's an approximation anyway, and 15 is easier to do in my head ) Skip Determining Engine Power.pdf

Best power mixture is pretty clearly the mixture that produces the most power. But there is no standard definition for economy mixture. A lot of manufacturers use peak because that may be the leanest mixture where the engine runs smoothly. Some may cite leaner, some richer. When these Mooney manuals were written, Mooney's selling point was speed. Gas was cheaper and economy was not as much of a concern, though leaner mixtures allowed advertising an increased range. Mooney probably chose 25 ROP as a compromise between economy and speed. Some get worried about the dreaded red box at this mixture, but it's not a problem at cruise powers as long as the CHTs are in check.

There’s pressure in the line so a loose connection will leak. I’d tighten it and see if that fixes it. It’s going to get removed with the G3X EIS installation.

My 1994 M20J had the same installation. The hose Mooney used had a red inner layer and a black outer layer and no reinforcing cords. The section in the tailcone deteriorated and cracked which is undoubtably why yours has been patched. To replace it you have to remove the left interior side panels. The hole in the tailcone bulkhead is large because most of the wiring runs through it. Mooney used some sort of putty to seal it. I just used commercial duct seal.

Also, keep in mind that the system manually rotates the motor so it only protects against electrical component failures. It won’t help if the failure is mechanical.

Good for you. If you go to SAF, grab a crew car and get lunch at Maria's. I think the terminal is still under (re)construction, but Signature always has taken good care of me and they have self serve fuel.

That's correct. The Dukes uses a wheel and worm gear train like the flap actuator. This is inherently locking. The Plessey and Eaton units use a ball screw driven by a spur gear chain that can be back driven and since there are no mechanical up locks on an electric gear Mooney, it needs a brake keep the weight of the gear from back driving the actuator. The spring acts as wrap spring brake in one direction and a wrap spring clutch in the other.

Good point about checking the spark plugs. A preignition source can be a cracked nose insulator. Happened to me. It only showed up at takeoff power, so the preignition could be separated from e valve failure by quite some time. It takes hours for the deposits to build back up on the head and piston.

I sent the latest photos to George Braly. He replied: The piston appears to evidence pre-ignition or fairly heavy detonation damage. The fact that the valve is “clean” of deposits goes along with it having suffered the scrubbing effect from pre-ignition. THAT is why having routine ongoing engine monitor data stored can “tell the whole story”. I would check the timing and would consider changing both spark plugs in that cylinder if you just replace/overhaul that cylinder.

That’s I use and what the M20J manual calls for.

My 28V plane has relays -- perhaps the 12V ones do not. The switches don't really get dirty. What happens is that the arcing from breaking an inductive load eventually penetrates the plating on the contacts and then the base metal oxidizes. Many switches are designed to open and close with a mechanical wiping action to help clean the contacts if the switch is exercised often enough. But, these switches don't get used often enough for there to be much wiping.