PT20J

One more thing: How to connect the p-lead shields on the Slick mags? My AI and I connected the shields to the ground terminals on the mags. Recently, I was chasing down another issue and found differing opinions on line about how the shields should be grounded. None other than the highly respected Jim Schwaner (formerly of Sacramento Sky Ranch) advocated connecting both ends to ground as we did. This is usually a bad idea as it can create a ground loop. Careful study of the wiring diagram for my s/n shows that Mooney grounded the p-lead shield at the ignition switch and not at the mags. The shields are connected to the GND terminal on the ignition switch, and the GND terminal is in turn connected to airframe ground. I asked Joe Logie at Champion for Slick's recommendation and he said not to ground at the magneto end. So, I'm going to remove the connection at the mag end of the p-leads next time I have the cowling off. Skip

The cables usually don’t wear out but just need lubrication from time to time. Before you replace it try lubing it. Most auto parts stores sell speedometer cable lube. If you unscrew the cable from the tach, you should be able to pull the core out to lube it.

Here are the pertinent pages from the POH/AFM for my '94 J (TOP) and my '78 J (BOTTOM). The newer version doesn't specifically say "ground roll" but that can be inferred by an obstacle height of 0'. For 20-deg C at sea level and 2740 lbs. the '78 version shows a ground roll of 965' and 1831' over the 50' obstacle whereas the -94 version shows a ground roll of 1440' and 2200' over a 50' obstacle. That's a whopping 49% increase in ground roll and a 20% increase in distance to clear a 50' obstacle. All the listed test conditions are the same except that the '78 version notes to lean for smooth operation (which shouldn't make a difference at sea level) and the '94 version references 80% relative humidity. Using an online calculator (https://wahiduddin.net/calc/calc_da.htm), 29.92 in-Hg, 20 deg-C, 80% RH is a DA of 826' whereas the same conditions at 50% RH yields a DA of 737' -- hardly significant. The stated liftoff speeds are about 5 KIAS lower for the later version which I would expect to decrease the ground roll all else being equal. Maybe @mike_elliott or @donkaye or one of the other Mooney instructors has an explanation. Skip

Looking at some of the pictures on this thread, I think we need a prize for the most flat screens installed/mounted in a Mooney. Skip

Don’t mean to be argumentative here, but that is not factually correct. Quoting from the NTSB final report findings: 21. Alaska Airline’s use of Aeroshell 33 for lubrication of the jackscrew assembly, acme screw thread surface finish, foreign debris, and abnormal loading of the acme nut threads were not factors in the excessive wear of the accident acme nut threads. Full report at: https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR0201.pdf Skip

I have caught numerous maintenance goofs over the years. Scariest was the missing cotterpins on the pitch links on a Schweitzer 300. I never blame the mechanic. Humans goof up. If I’m honest, I’ve nearly killed myself many more times than anyone working on the craft I fly. And, who knows how many times they caught and fixed stuff I didn’t even know about on airplanes I rented or flew Part 135? Skip

Actually, now that I think about it, if Mobilgrease 28 was good enough for Douglas to specify for the trim jackscrew on the DC-9 it should be good enough for the ballscrew on the Mooney landing gear actuator. I understand the that the Dukes units with the 20:1 gears are problematic and need the moly-fortified grease, but the ballscrew should get along fine with just Lubriplate 630-AA. As Clarence pointed out, the Service Manual calls out Lubriplate for this application. It says it's permissible to use the Dukes moly compound as LASAR does, but it doesn't say it's required or particularly advantageous. Skip

Here's the short version. There was discussion about incompatible greases but I think the conclusion was that there wasn't much grease at all on the failed jackscrew. A01_41_48.pdf

I discussed this with Robert at LASAR. They mix Aeroshell 5 with 10% MoS2 which is what Dukes specifies for the actuator gearbox. Apparently there are no commercial greases available with greater than 5% MoS2. They use the same grease on the ball screw. They sell the mixture: https://lasar.com/misc-supplies/special-blend-grease-dukes-grease For the landing gear zerks, Mooney specifies MIL-PRF-81322G which is either Aeroshell 22 or Mobilgrease 28. A number of sources I've checked believe that Mobilgrease 28 tends to have less separation of the oil and thickener, but some don't like it because it is dyed red. For wheel bearings, the most commonly used grease is Aeroshell 5. Mooney specifies MIL-G-3545 which is obsolete but Aeroshell 5 met this spec. Cleveland recently switched to recommending SHC 100. Since MIL-G-3545 was superseded by MIL-PRF-81322, either Aeroshell 22 or Mobilgrease should also be acceptable. Ignoring any additive packages, grease comprises oil and thickener. Oil is either mineral-based or synthetic. Thickeners are either clay or soap (most common soap is Lithium). Most older aviation greases are clay thickened because clay provided better high temperature performance. Most non-aviation greases are Lithium soap thickened. There can be compatibility issues, so greases of different oil types and/or different thickener types should not be mixed. If you don't know what grease was used previously, it should be completely removed before adding new grease. Skip

Dot is light side of tire and should be placed at tube valve stem ( heavy side of tube).

After landing my ‘78 J years ago, I noticed gas dripping on the nose wheel tire. The B nut on the output line of the fuel pump was loose. Never smelled gas. Tightened it, checked all the others and Torque Sealed them all. Never had another problem. Plane was ten years old at the time. No indication in the logs that line had been touched since manufacture. Stuff happens. Skip

A quick scan of the overhaul manual didn't show any reference whatsoever to installing one cylinder bored oversize. There are instructions for boring. Anyway, this is a field repair and not an overhaul. I sounds like the cylinders were sent in for reconditioning and the bore on one was worn beyond service limits. The options are: 1) replace the cylinder, 2) plate the cylinder to bring it back up to dimension, 3) bore it oversize. The time on the engine really impacts the economics of the decision. If you are trying to just get a couple of hundred hours until it's going to need an overhaul, then the cheapest route it the probably best. If the engine is low time, then a new cylinder may be a good option. Here's an old article from Mike Busch that goes into a lot of detail about cylinders. It also explains the origins of the head cracking issues of the early 90s that spawned the shock cooling hoopla. https://www.avweb.com/ownership/the-jug-jungle/ Skip

Bore of an IO550 is 5.25" and stroke is 4.25". So volume of one cylinder is 92 in^3. With .010 oversize it is 92.3528 in^3. So the larger cylinder has about 0.4% more volume. Trivial. Boring out a cylinder and installing oversize rings and piston is a common way to rework a cylinder. Skip

Thanks, Clarence! I missed the double entry for the ë symbol. Do you generally prefer Mobilgrease 28 over Aeroshell 22? Skip

Rick, Here's an older one that I like. 100_Hour_Annual2007.pdf Mooney has an updated version on its website: https://cdn2.hubspot.net/hubfs/4147179/TECHNICAL PUBLICATIONS DOCUMENTS/100_Hour_2018.pdf Skip

Didn't really notice any difference in the brakes -- still takes a fair amount of pressure compared to Piper or Cessna. Skip

Google didn't work for me, but I did find the earlier thread:

I'm curious what @mooneydoc and others are using: Wheel bearings: SHC 100 or Aeroshell 5? MIL-PRF-81322G: Aeroshell 22 or Mobilegrease 28? Landing gear actuator ball screw? This is confusing since Mooney used several manufacturers. Mine is an Eaton. The M20J Maintenance Manual calls for GREASE(Dukes) and lists MIL-G-23827 and Mobil #27. Mobilgrease 27 doesn't seem to be made any longer but was lithium soap thickened, so it is probably superseded by Mobilegrease 33 which is a MIL-PRF-2387C Type I grease. Skip

JIm, I installed 1.5" extensions on my '78 J and 3" extensions on my '94 J. I'm also 5'6". The 3" are much better. The 1.5" do not change the brake pedal geometry noticeably, but the 3" tips the top of the pedal aft enough that it is easy to ride the brakes. The fix (which is not described in the maintenance manual) is to adjust the rod length on the brake master cylinders. There is a recent thread describing this if you can get the miserable MS search engine to find it Skip

Good catch. I recalled reading this in connection with the IO-360 years ago and downloaded the current copy from Lycoming's website without noting the effectivity. Attached is an earlier version (245C) that I located on the web that does include the IO-360. It looks like Lycoming updated this SB to 'D' in 1987 to drop a bunch of engines off the effectivity. The remaining affected engines are all geared (the helicopter VO-540 is connected to an external gearbox). This makes sense as it is much more likely for a geared engine to have the propeller overdrive the engine. So, it looks like Lycoming must have figured out that counter weight detuning isn't much of a problem in the IO-360. Thanks for pointing that out. Skip e183.pdf

When you look at the Mooney Maintenance Manuals you will find obsolete Mil Specs called out. MIL-G-81322 is now MIL-PRF-81322G and is Aeroshell 22 (amber color) or Mobilegrease 28 (red color). MIL-G-3545 is now obsolete but is Aeroshell 5 MIL-G-23827 is superseded by MIL-PRF- 23827C Type I (Metallic soap thickener, Aeroshell 33, Mobilegrease 33) and Type II (Clay thickener, Aeroshell 7). Don't mix Type I and Type II, the thickeners are incompatible. Use AS 7. Skip

I think the more meaningful metric would be useful load times mpg. But if you are looking for something much less fuel efficient than your Mooney, try a cruise ship: At its cruising speed of 22.6 knots (26 mph), the Oasis of the Seas cruise ship burns 11,361 gallons of fuel each hour. The fuel efficiency, then, is 0.0023 mpg, or 12.08 feet per gallon! (https://www.brighthubengineering.com/naval-architecture/100758-cruise-ship-fuel-efficiency/)

Regarding the prop driving the engine, Lycoming suggests avoiding high rpm with the MAP less than 15". This isn't going to be a problem unless you're in a high speed dive with the power pulled back. In that case, it would be good to pull the prop back, too. Skip SB245D Detuning Dynamic Counterweight System.pdf

The Airplane Flight Manual Supplement for my '94 J speedbrakes says under Operating Limitations: AIRSPEEDS Same limitations as the basic airplane. So the speed brakes may be used up to Vne. Skip

Interesting point, Don. It works the other way, too. I know a guy that had a few thousand hours flying corporate King Airs. When he bought a Bonanza, the insurance company required 25 hours of dual from an experienced Bonanza CFI. The rationale was that claims history showed that pilots moving down are often at greater risk that when moving up. There is increased risk anytime you are flying something you don't have experience in. I think it is good to remember that the insurance companies are in the business of quantifying and pricing risk. If one pilot's premiums are higher than average it might indicate that there really is more risk there and the pilot might want to think hard about what steps might be taken to minimize the risks. And do make sure to do whatever the insurance company requires. When I was working in Anchorage AK in the mid 80's, a guy bought a Tailorcraft for around $10K. The insurance required 10 hours tailwheel instruction since he had only flown trikes. After about an hour or two, he went off on his own. He lost control of it landing at MRI in a crosswind, ran off the runway into Alyeska Helicopter's ramp and chopped the tail boom off a Jet Ranger. Repairs were north of $100K and guess what happened to the claim when the pilot couldn't show evidence of the ten hours of dual? Skip