PT20J

Manifold pressure gauges do become inaccurate and, in my experience, they always read low. I used to fly float Beavers for a Part-135 operator. Every year some pilot would remark that a particular airplane was sure a lot faster than the others. We all used 28"/1900 rpm for cruise. I asked if it seemed to burn more fuel and invariably the pilot would admit that it did. At the end of the day, I would check the manifold pressure gauge on the "fast" airplane and find it reading about 1.5 inches low. After the service department replaced the gauge, the pilot would complain that something happened because now the airplane wasn't fast anymore. Skip

My M20J has vents in each footwell sidewall that are attached to NACA scoops. I used the duct seal on the wemac flange to seal where it attaches to the scoop in place of the original sealant.

I just had my M20J boost pump overhauled by Aeromotors ($450). It’s much quieter now though it wasn’t leaking and made pressure before. But, after 30 years, I figured it was time. Sounds like a new manifold pressure gauge is in order. First thing I would try is replacing the batteries in the headset. If that doesn’t fix it I would reset the software by telling the phone to forget the Bose. Then turn the phone off (not just locked; power it down) and restart it and the pair it with the Bose again.

There are thousands of Mooneys with these springs and millions of gear operations and only a handful of documented failures mostly in Plessey actuators. The Eatons seem pretty sound except for maybe one bad lot of springs maybe 30 years ago. I think this is like the dual mag - everyone worries about it out of proportion to the risk. Historically, pilots are many times more likely to belly in because they didn’t put the gear down than to have a mechanical failure of the actuator. Skip

If it is a true PMA part, it will have gone through FAA Design Approval to show that it is identical or equivalent to the original. https://www.faa.gov/aircraft/air_cert/design_approvals/pma/pma_des: "The design approval phase of PMA certifies that a replacement or modification article complies with the airworthiness standards of eligible products (aircraft, engine, or propeller). The applicant shows this compliance through tests and computations unless the article is identical to the article design on a type-certificated product. Identicality means that an article is the same in all respects to an article design in a type-certificated product. Evidence of license agreement shows this identicality."

Well, if you've ever read any of the articles about how TurboTax has effectively lobbied for years to prevent funding for the IRS to develop a free tax program, then you'll understand how we have already begun traveling down that road

Although the accessory case is the most obvious external difference, there are many other differences. Even the crankshaft is different. Check the parts catalog. They are really different engines and since relatively few A3B6Ds were built, Lycoming would really like to retire them which is why they will take a A3B6D core in exchange for an A3B6 (Lycoming's usual core policy is that you have to exchange like for like). In fact, when I got my rebuilt engine in late 2018, Lycoming gave me a discount to order an A3B6 instead of an A3B6D. So, bottom line is that the only reasonable way to change a A3B6D to an A3B6 is to use the A3B6D core when ordering a rebuilt A3B6 from Lycoming. Fortunately, both engines are listed on the TCDS for the M20J and the IPC lists all the parts necessary for the conversion. Another option is to convert by STC to the IO-390. Skip

I’ve used Rectorseal 81880 HVAC duct seal for a lot of things like sealing Wemac vents and plugging the hole where the cables run through the rear bulkhead into the tail. It’s easily mold to shape and doesn’t harden or dry out and is easily removed.

The over voltage protection is built into modern voltage regulators. It sounds like the regulator has a problem with the over voltage circuit. It sounds like it is tripping at too low a voltage and not latching. To troubleshoot, I would measure bus voltage versus rpm. Also, most regulators have an output to indicate that the over voltage protection has tripped and I would monitor that.

Another option: https://www.aircraftspruce.com/catalog/inpages/mech_tachs.php?clickkey=19141

But my point is that it works as advertised with Transition to Approach disabled. Enable it and it’s anyone’s guess because we don’t know why Garmin required it be disabled.

It seems that the whole issue hinges on enabling Transition to Approach. When disabled per the STC, the VNAV appears to work as described in the documentation (at least for my G3X). Frankly, the only value I see in Transition to Approach would be for approaches without vertical guidance. With Garmin adding +V advisory glidepaths to LNAV and VOR approaches, these are becoming rare. For an approach with vertical guidance, I never descend to the GP/GS altitude on the intermediate segment because I don't see any advantage in descending lower than necessary earlier than necessary. I just remain to the IF altitude (or vector altitude restriction if on a vector) until I capture the GP/GS. Skip

Well, it's kind of interesting, so I looked it up. Manufacturers communicate their maintenance recommendations in an Instructions for Continued Airworthiness (ICA) document which the FAA requires. However, for Part 91 operators, most of this stuff is not legally required -- just like service bulletins. However, the ICA contains a section called Airworthiness Limitations which is approved by the FAA and becomes a legal requirement under FAR. Most manufacturers take pains to write NONE in this section. However, Power Flow included the disassembly and lubrication in this section, so technically your airplane is not airworthy if you don't comply. Your only way out is to get Power Flow and the FAA to agree that using an alternate method is acceptable. Good luck with that . 6.2 AIRWORTHINESS LIMITATIONS “The Airworthiness Limitations section is FAA approved and specifies maintenance required under §§43.16 and 91.403 of the Federal Aviation Regulations unless an alternative program has been FAA approved.” 6.2.1 Mandatory Replacement Time – None. Any collector assembly that is damaged and/or fails the pressure test described below must be rebuilt or replaced. 6.2.2 Structural Inspection Interval – At 100 hour or Annual intervals, depending on the service regime of the aircraft. WARNING: Carbon Monoxide gas present in exhaust gases can lead to pilot incapacitation and/or death. A damaged exhaust system has the potential to allow Carbon Monoxide into the aircraft cabin. To prevent such an occurrence, it is imperative that the exhaust system is inspected using the intervals and procedures described in this report. It is recommended that in-cabin carbon monoxide levels be measured periodically. Concentrations of greater than 50ppm will require immediate exhaust system inspection and repair or replacement as necessary. 6.2.3 All slip joints must be disassembled and lubricated with a high-temperature anti-seize compound (MIL-A-907E or equivalent) at 500hr or Annual intervals (whichever comes first). While disassembled, inspect for wear or galling. This should be performed more frequently if headers seize between inspections. 6.2.4 Structural Inspection Procedure – See Section 6.6.

@Marc_B, first of all, good for you to go out and experiment to really understand how all this works. It looks like the behavior is what would be expected when Transition to Approach is not enabled. In other words, VNAV stops at WELDS (the fix before the FAF). It crosses WELDS at 7000 because that's its endpoint -- it's not looking at the 6600 constraint at BUFFS. Why? Who knows? I have not had much success with anyone at Garmin answering why questions. (Thirty years ago, when Garmin was so much smaller, I could get to talk to an engineer sometimes and get an answer to a why question. But those folks are well insulated from customers these days). But, I have a hunch. The G3X, G5 and GFC 500 were developed together by the Team-X experimental group. The G3X has a VFR GPS and it's own VNAV. At the time that the GFC 500 was designed, the Garmin IFR navigator would have been the GNS 430W. This navigator had a rudimentary VNAV which is similar to VCALC in the GTN. The GTN Xi is developed by an entirely different group. When the GTN Xi enhanced VNAV came out it had VNAV capability all the way to the FAF with certain Garmin autopilots. This appears to work on the simulator in both GPS and ILS. For some reason, the GTN Xi STC requires that this feature be disabled for the GFC 500. This information is included in both the GTN Xi Installation Manual and the Pilot's Guide. There must be a reason for this decision. Perhaps it is because it doesn't work properly on an ILS. Anyway, I understand that Garmin is working on a change to allow Transition to Approach to be enabled with the GFC 500. We'll have to see if and when this is released if it changes any behavior. Skip

PS Engineering has good tech support. I would call them. Or maybe @Mscheuer will drop by.

People have used that forever. But, it's a penetrating oil. I doubt is survives vaporization the first flight after application. But it might unstick a slip joint that was stuck when it was applied.

McFarlane sells a low viscosity moly lube for exhaust joints. I'll bet that will seep in without tearing it apart every year. https://www.mcfarlaneaviation.com/products/product/DAM20-4.0/

Here’s the manual for the KFC 150 in case that’s what you have. KFC150 Installation Manual.pdf

When I was at the Lycoming factory last fall, the biggest hold up was cylinders. They brought head machining in house and are also doing all the barrel machining and nitriding in house and they had start up issues with the automated head milling lines at the same time demand went through the roof (apparently, during Covid a lot of people decided to buy engines and cylinders). So, I would ask a field overhauler what they are going to use for cylinders because there is a long wait for new. There are other options, but you probably want to weigh the pros and cons carefully. Personally, I would not want an overhauled jug that had been through more than one TBO run because aluminum work hardens (the heads expand and contract slightly with each power pulse) and the IO-360 heads do sometimes crack. The DLC lifters seem to be a good option -- maybe as good as roller tappets -- and they fit an existing crankcase. One thing that's interesting is that Van's was Lycoming's biggest customer and who knows how Van's bankruptcy will affect orders. Maybe it will help Lycoming catch up if Van's has to cut back significantly. Skip

I wonder if it really makes a difference whether you switch the CDI source manually or it autoswitches? I think the key is probably that the autopilot must be in APR before changing the CDI. But, what I'm curious about is why it seems to cancel out VNAV when the CDI changes. It would seem to make sense for the vertical mode to remain unchanged and the GS to arm waiting for capture. I asked Joey Ferrerya a while back why the GTN Xi STC doesn't permit Transition to Approach for the GFC 500 when other Garmin autopilots allow it. There must be a reason why they left it out. He never said why, but did say that they were actively working on a change to permit it. So, perhaps it's related to the issue that @Marc_B raised and maybe there is more software that needs to be changed to get all the logic right.

OK, so say you have the following setup: 1. An ILS approach is active in the flight plan and you are at the IAF. VNAV altitude constraints have been set/verified and the altitude bug is set at or below the FAF altitude and you have previously enabled Transition to Approach in the GTN configuration mode. The localizer frequency is active in the GTN nav. 2. Lateral mode is GPS (green), Vertical is VNAV (green) with ALTV armed (white). Airplane is tracking the procedure course and descending via VNAV. 3. You select APR. Lateral mode is now GPS (green) with LOC armed (white), vertical mode is VNAV (green) with ALTV armed (white). 4. The GTN autoswitches the CDI from GPS to VLOC. The autopilot intercepts the localizer. Lateral mode is now LOC (green) What is the vertical mode annunciation? Skip

Well, I really am going to have to go flying. Like I said, I haven’t done many ILS approaches for a long time, and they’ve all been vectors to final when I have. Looking at my G3X Pilot’s Guide, it appears that the GFC 500 should not revert to ROL upon CDI autoswitch if APR is set before the switch.

Just don't forget that the GFC 500 will not couple a LOC or ILS without a valid GPS signal.

I bought a Gill 7243-16 because it was on sale and had slightly higher capacity than the Concorde and I figured by now Gill had figured out how to make good AGM batteries. I kept it on a BatteryMINDer in the hangar. It failed the first capacity check at about 18 months. I went back to Concorde. Skip

I think @donkaye has a great point. The problem with automation is that it is very disorienting if it doesn’t do what you expected. And, it is easy to fail to get something right, like setting the altitude bug before selecting VNAV or not making the localizer frequency active before an ILS approach, that will cause the automation to fail to do what you expect. The more things you have to do manually, the more you stay “in the loop.” The best use of automation, IMO, is to avoid task saturation by letting it do some of the work. Just because it can do something doesn’t mean you should let it. In Don’s example, he knows that APR must be selected after changing the CDI source to VLOC. But, if it auto switches, he’d have to notice that it switched and then select APR or it goes into la la land (ROL). And, unless you memorize the diagram and description in the manual, you don’t know exactly when this will happen. Skip