PT20J

I bought a J a year ago. Engine ran fine, lowest compression was #4 72/80. Filter was clean, last oil analysis was OK, borescope inspection by Don Maxwell himself was OK. But... it was burning a quart every 2 hours. I flew it for about 30 hours, still running fine and put it in for annual. Compression #4 58/80, metal in the filter, part of an oil ring in the suction screen. Pulled #4, found the oil control ring broke and took out part of the piston skirt and scored the cylinder. Metal had contaminated the rod big end bearing so it must have gotten around the engine pretty well. Oh yeah, and the cam was spalled. Moral: probably not a good idea to continue running it if you think an oil ring is stuck, because if it breaks, it makes a mess. Better to pull the jug and have a look. My bottom plugs were not very oily and there wasn’t a lot of black soot in the tailpipe and the belly was clean. Skip

It's in the tail immediately aft of the avionics tray. It's the carrier bearing to support the trim torque tube at the point where the trim servo sprocket attaches. I believe it's a Bendix-King part. The maintenance manual calls for yearly inspection and lubrication (but I think it's often overlooked). Skip

Is it in the illustrated Parts Catalog? If not, is there a logbook entry for its installation? Can you read the numbers on the label? If so, you should be able to look up the part number and find out what kind of a sensor it is. If it's not in the IPC, not part of an STC and unused, it should be removed.

And, for the final word on what controllers can and cannot do w/r/t speed assignments, here's the appropriate sections of 7110.65. Thanks everyone for helping clarify the matter (And watch those high speed low passes!) Skip

I've given this more thought. I have never personally heard ATC assign speeds greater than 250 below 10K or greater than 200 below class B. I have heard ATC assign speeds greater than 200 in class C and D. I experienced many times in the San Francisco Bay area being instructed, both IFR and VFR, to maintain an altitude contrary to 91.159 and 179. Many years ago, a former FAA lawyer who used to speak at AOPA FIRCs mentioned that the "Administrator" clause in many FARs is intended to allow the FAA to grant broad powers to FAA staff through internal letters. I do not know for certain whether this applies to ATC. Looking at the language in the FARs (see below) it seems pretty clear that ATC can assign non-91.159-compliant altitudes, and speeds above 200 in class C and D airspace. It also seems unlikely that airspeeds greater than 200 below class B or 250 below 10K are permitted by the regulations. If a controller clears or instructs you to do something you don't think is right, the best course is to question it. If the controller insists, you should comply (unless, of course, they are vectoring you into terrain or something similarly hazardous) assuming that the controller has a good reason, and to avoid violating 91.123. You can always file an ASRS report and/or contact the facility after the fact. §91.117 Aircraft speed. (a) Unless otherwise authorized by the Administrator, no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 m.p.h.). (b) Unless otherwise authorized or required by ATC, no person may operate an aircraft at or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class C or Class D airspace area at an indicated airspeed of more than 200 knots (230 mph.). This paragraph (b) does not apply to any operations within a Class B airspace area. Such operations shall comply with paragraph (a) of this section. (c) No person may operate an aircraft in the airspace underlying a Class B airspace area designated for an airport or in a VFR corridor designated through such a Class B airspace area, at an indicated airspeed of more than 200 knots (230 mph). (d) If the minimum safe airspeed for any particular operation is greater than the maximum speed prescribed in this section, the aircraft may be operated at that minimum speed. §91.123 Compliance with ATC clearances and instructions. (a) When an ATC clearance has been obtained, no pilot in command may deviate from that clearance unless an amended clearance is obtained, an emergency exists, or the deviation is in response to a traffic alert and collision avoidance system resolution advisory. However, except in Class A airspace, a pilot may cancel an IFR flight plan if the operation is being conducted in VFR weather conditions. When a pilot is uncertain of an ATC clearance, that pilot shall immediately request clarification from ATC. (b) Except in an emergency, no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised. (c) Each pilot in command who, in an emergency, or in response to a traffic alert and collision avoidance system resolution advisory, deviates from an ATC clearance or instruction shall notify ATC of that deviation as soon as possible. (d) Each pilot in command who (though not deviating from a rule of this subpart) is given priority by ATC in an emergency, shall submit a detailed report of that emergency within 48 hours to the manager of that ATC facility, if requested by ATC. (e) Unless otherwise authorized by ATC, no person operating an aircraft may operate that aircraft according to any clearance or instruction that has been issued to the pilot of another aircraft for radar air traffic control purposes. §91.159 VFR cruising altitude or flight level. Except while holding in a holding pattern of 2 minutes or less, or while turning, each person operating an aircraft under VFR in level cruising flight more than 3,000 feet above the surface shall maintain the appropriate altitude or flight level prescribed below, unless otherwise authorized by ATC: (a) When operating below 18,000 feet MSL and— (1) On a magnetic course of zero degrees through 179 degrees, any odd thousand foot MSL altitude + 500 feet (such as 3,500, 5,500, or 7,500); or (2) On a magnetic course of 180 degrees through 359 degrees, any even thousand foot MSL altitude + 500 feet (such as 4,500, 6,500, or 8,500). (b) When operating above 18,000 feet MSL, maintain the altitude or flight level assigned by ATC. §91.179 IFR cruising altitude or flight level. Unless otherwise authorized by ATC, the following rules apply— (a) In controlled airspace. Each person operating an aircraft under IFR in level cruising flight in controlled airspace shall maintain the altitude or flight level assigned that aircraft by ATC. However, if the ATC clearance assigns “VFR conditions on-top,” that person shall maintain an altitude or flight level as prescribed by §91.159. (b) In uncontrolled airspace. Except while in a holding pattern of 2 minutes or less or while turning, each person operating an aircraft under IFR in level cruising flight in uncontrolled airspace shall maintain an appropriate altitude as follows: (1) When operating below 18,000 feet MSL and— (i) On a magnetic course of zero degrees through 179 degrees, any odd thousand foot MSL altitude (such as 3,000, 5,000, or 7,000); or (ii) On a magnetic course of 180 degrees through 359 degrees, any even thousand foot MSL altitude (such as 2,000, 4,000, or 6,000). (2) When operating at or above 18,000 feet MSL but below flight level 290, and— (i) On a magnetic course of zero degrees through 179 degrees, any odd flight level (such as 190, 210, or 230); or (ii) On a magnetic course of 180 degrees through 359 degrees, any even flight level (such as 180, 200, or 220). (3) When operating at flight level 290 and above in non-RVSM airspace, and— (i) On a magnetic course of zero degrees through 179 degrees, any flight level, at 4,000-foot intervals, beginning at and including flight level 290 (such as flight level 290, 330, or 370); or (ii) On a magnetic course of 180 degrees through 359 degrees, any flight level, at 4,000-foot intervals, beginning at and including flight level 310 (such as flight level 310, 350, or 390). (4) When operating at flight level 290 and above in airspace designated as Reduced Vertical Separation Minimum (RVSM) airspace and— (i) On a magnetic course of zero degrees through 179 degrees, any odd flight level, at 2,000-foot intervals beginning at and including flight level 290 (such as flight level 290, 310, 330, 350, 370, 390, 410); or (ii) On a magnetic course of 180 degrees through 359 degrees, any even flight level, at 2000-foot intervals beginning at and including flight level 300 (such as 300, 320, 340, 360, 380, 400).

91.117 Aircraft speed. (a) Unless otherwise authorized by the Administrator, no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 m.p.h.). The Administrator has delegated authority to ATC to assogn speed as required to sequence and separate aircraft within controlled airspace.

Oh, they know the regs. But, controllers have authority to deviate from them when separating traffic in airspace they own. They issue altitude clearances contrary to the hemispheric altitude rule all the time in busy terminal areas, for instance. The authority is in 91.123 (b) Except in an emergency, no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised. Skip

I've got Frank's contact info and I'll try to chase it down at Mooney. But, still...

So where are all the MAPA PPP instructors? I thought you’d be all over this with an explanation by now. With all the pilots flying different year Js attending the classes over the years, this can’t be the first time this has ever been noticed, can it?

Flying the DC-3 back from an airshow to the museum at KPAE at 2000 feet. Realized we would fly through KRNT’s delta so we gave them a call and requested transit south to north directly over the field at 2000’. Reply came back, “Approved as requested (pause), ah, could we talk you into a low pass?” So is it legal if the tower requests it? And, yes, we accommodated them and added a nice 2g pull up at the end Skip

Preplanning an abort point is an excellent idea. The first time I ran across the 50/70 notion was in the late Sparky Imeson's excellent Mountain Flying book back in the 80's. However, I did some calculations (attached) and I don't think this is conservative enough. First, assuming constant acceleration, 70% of lift off speed at the midpoint gets you to lift off speed at the very end of the runway. This doesn't allow for any margin and it also doesn't allow for any obstacles whatsoever. Also, the assumption of constant acceleration is probably generous. The propeller thrust is highest when standing still and decreases with increasing speed, and the aerodynamic drag, zero when standing still, will increase with increasing speed. Perhaps 80% of lift off speed at the mid point would be a better choice, unless there is a headwind (the calculations assume calm wind). Skip 50-70_20190704_0002.pdf

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