PT20J

Yep, it's been around since the 1930s Good question. When I bought my airplane, the logs said the fluid had been replaced about 5 years before. When I drained some from the calipers, it was quite discolored and noticeably thickened. So, every year during the annual inspection I drain about half a cup out of each caliper and it's always a bit discolored. I suspect the heat from the brakes affects it. The fluid upstream wasn't noticeably thickened when I had everything apart to put new o-rings in the master cylinders and replace the flexible lines. But, since I had been draining some each year it was probably pretty new fluid. I don't know the system capacity but it's probably not much more than a pint. Some posters here have reported that 5606 gets pretty gooey after awhile. I'll be interested in other's comments. The Air Force switched fluids primarily because 5606 is highly flammable.

Yes. The newer spec is MIL-PRF-5606H, but it's the same thing. If you are changing the brake fluid, you might consider Royco 782. It's a newer synthetic MIL-PRF-83282 fluid that won't congeal with age like 5606 which is a mineral oil. It is fully compatible with 5606, so you don't have to flush the system.

I would use 20 AWG two conductor shielded MIL-SPEC wire. https://www.aircraftspruce.com/catalog/elpages/shieldwire.php?clickkey=76643

Often items related to electrical parts (such as your switch) are found at the back of the Service & Maintenance Manual.

No, pilot’s side only.

Assuming that you have the cylindrical reservoir with the pipe plug at the top, the part number for the plug is 850009-000. It appears to be a standard pipe plug with a small hole drilled in it to vent the reservoir. I would call Frank Crawford at Mooney and see if he would share the drawing or at least tell you the size of the plug and the hole. I'm certainly not an expert on Mooney brakes but last year I did remove both master cylinders for rebuild and I replaced all the hoses in the brake system. So, I had all the plumbing pretty well opened. My A&P suggested opening the bleeders on both calipers and letting the system drain by gravity while occasionally slowly exercising the brake pedals. I ran about a pint of fluid through the system this way. Then we bled it bottom up with the A&P at the bleeders and me suctioning out excess fluid at the reservoir with a turkey baster. We did this until there were no more bubbles evident in the plastic line to the reservoir. It didn't take much and the brakes have been rock solid ever since.

As the pads wear the fluid level will drop in the reservoir and air needs to get into the reservoir or suction will be created. The fluid level also drops slightly when the brakes are applied. The plug on the reservoir of my M20J has a small vent hole. It is possible for air to pass through an opening too small for fluid to leak.

My airplane doesn't have a beacon and I only use the nav lights at night.

Great idea. I also do that post flight. I've caught the strobes still flashing because I somehow left the master switch on more than once.

It is certainly possible to "upgrade" a M20D to a M20C using factory parts. The question becomes one of how that gets done and what you are left with afterwards. Mooney doesn't list a kit to convert these on it's list of retrofit kits. Maybe a kit used to exist. If so, it would have all the appropriate paperwork. If there is no kit then it might be possible to make the change with a field approval which again would include the paperwork. Or maybe someone got an STC. But you have to have some basis of approval - you can't just go switching around parts from a different airplane. If the factory did the mod, theoretically they could reissue a new type certificate. This was done with C-47s after the war when Douglas ran a line converting military aircraft to a new commercial type designation DC-3C.

I was thinking of the retractable gear and constant speed prop.

I've only bled brakes on my M20J once when I overhauled the master cylinders and replace all the flexible brake lines. I followed my A&P's suggestion and opened the bleeders and let them drip while occasionally exercising the brake pedals slowly and keeping the reservoir full. I let about a pint of fluid drip through and then we bled them bottom up and it didn't take long to get all remaining air out. I do owner assisted annuals. I usually spend a day forward of the firewall: removing the plugs, borescoping cylinders, removing the fuel servo inlet screen and oil suction screen, removing and opening the oil filter for inspection, removing spinner, removing muffler shroud and tailpipe for inspection, cleaning the engine. The second day is spent opening the airframe, putting it on jacks and lubricating everything. The third day the IA does the inspection and usually I start putting it back together when he's done. On the forth day, I finish putting it all back together, double check everything, run it up and leak check it and adjust idle speed and mixture if necessary. So far, we have never found an airworthiness item that needs repair before return to service because I keep after everything. Any minor issues found are usually fixed at a later date when convenient. Next year will take longer because the mags will be due for 500 hour IRAN.

On my first J back in the late 80's I took off early before work for a short hop from KRHV to the avionics shop at KSJC. Somehow missed the pitot cover on a hurried preflight and noticed it when there was on airspeed on the takeoff roll. Decided to go ahead anyway and got to try out the red button override on the gear retraction system for real. On the same airplane, I can tell you from experience that if you get distracted during preflight and forget a tiedown, and the tiedowns are chains, you will pull the tiedown ring out and you will have to purchase a replacement and your A&P will just laugh at you and hand you a helicoil kit.

You cannot use just any old POH. You need the POH/AFM that goes with your specific airplane serial number. Mooney can supply that if you don't have the correct one. However, since your airplane has been modified, any change in limitations caused by the modifications need to be taken into account. If the mods were done by STC, the documentation would have a AFMS that would list any changes to the limitations. It becomes tricky when multiple modifications are applied because of the potential for interactions between them.

The voltage regulator controls alternator output by sensing the bus voltage and regulating the field current to maintain the proper voltage. So, too high a voltage can be caused by either a failure in the regulator, or a voltage drop where the regulator senses voltage. The latter can be due to an intermittent short or loose connection. When it fails, that momentary surge in current is going somewhere that may not be good for your electronics.

My 1994 M20J KAP 150 roll servo was in the right wing out by the aileron bellcrank. They are a bear to get to. I would have my avionics shop remove it and send it out for repair.

LASAR quit producing this part long before the move to Oregon. I inquired about it six or seven years ago because I thought I might need a new steering horn at some point. Corrine Boatright told me at the time that many of the PMA parts had been made by a local machinist that retired, and since they weren't selling many of these anyway, they decided not to look for another machine shop.

Well, I did sat usually . And, usually, if there are errors, manufacturers try to get it minimized at cruising speeds because that's rally where we care about absolute speeds. At the low end it doesn't really matter what the calibrated airspeed is since we fly by indicated airspeed. Mooney evidently did a good job locating the pitot tube. It's not simple because the upwash ahead of the wing changes with angle of attack. That's why test aircraft often have that long probe out ahead of the airplane so as to place it in the free stream relative wind.

The problem, as we may recall from private pilot ground school, is that that the largest airspeed errors (spread between IAS and CAS) usually occur at low airspeeds because the pitot tube is no longer aligned with the relative wind due to the increased angle of attack.

Interesting. I often find that AI gets things exactly backwards. Recently, it correctly answered a question but then went on and eventually contradicted itself.

It doesn’t matter where along the span you measure the force so long as you accurately measure the distance between the scale and hinge line in order to calculate the moment. I would just put the scale approximately in the center between the two hinges.

I agree with @Vance Harral - you cannot get an meaningful resistance reading with power applied. I would not expect the cabin speaker to be connected directly to ground. I would expect both leads to go to the audio panel. What problem are you trying to correct?

This should really be pretty simple. The Mooney website lists the current revision of the manuals for each airplane. https://mooney.com/wp-content/uploads/2023/04/Mooney-Technical-Publications-1.pdf I would get the version for my airplane and use that. If only IAS values are published, I'd just go with that because there is no other information available from the type certificate holder. If it's close, I would find the closest manual from Mooney that has CAS stall speeds and use that for backup. In the case of a D converted to a C, I would expect that the conversion had some documentation with it, but if not, I would check with the factory for guidance. As long as Mooney backs you up, the FAA won't argue with it. Using other non-certified sources is questionable. The data has to be directly traceable back to Mooney.

I bought a well-equipped 1978 J in 1986 for $40K. Mods were minimal: I put an Airtex interior in it and cleaned up the interior plastic and installed a 4 place intercom and replaced a transponder and an ADF. To keep costs down I did most of the maintenance myself supervised by Vern Miller at RHV in San Jose CA. Vern heartily embraced owner assisted maintenance and was a great teacher. Weekends were always interesting at Vern's hangar as there would be a lot of owners there working on their planes under Vern's tutelage. Several were Silicon Valley execs of companies you've heard of who worked on their planes not out of financial necessity, but as a form or relaxation and decompression from the stress or leading tech companies. My wife and I flew the J for 700 hours and I sold it to Ken Shoupe ( Ken started All American Aircraft Sales which he later sold to Jimmy Garrison) with bad paint and a runout engine seven years later in1993 for ----- $40K. Those were the days. I have learned so much from this site that there is no way I can ever repay it all!

One more thing: Do not power up the transponder with the antenna removed as running without a load causes energy to be reflected back into the final amplifier and can damage it. The old tube types may survive this but the newer solid state transponders claim to be more sensitive. I always pull the transponder breaker when I have the belly panel removed.