PT20J

If the engine is running well, why mess with it until you have to? New and overhauled engines can have infant mortality, so you may or may not get better reliability. I recently replaced a A3B6D (broken oil control ring took out piston skirt and cam was spalling) with a factory rebuilt A3B6 after duscussions with Lycoming and mag overhaulers. Roller tappets are clearly a design improvement worth the extra cost to me. Dual mags are reliable in my experience, but are no longer made, some parts are hard to get and fewer mag shops will work on them. There are numerous internal differences between A3B6D and A3B6 which has more parts commonality with other engines. The A3B6D will likely end up being more expensive to maintain as time goes by. Lycoming will give you a break to retire a A3B6D core which says something (to me) about its commitment to that engine. Lycoming has standardized timing at 20 deg on 360 series engines with the exception of the dual mag engines for many years. Some think this is a big deal, some not so much. I don’t want to open that can if worms, but personslly I haven’t noticed much difference. Hope that helps. Still really currious about the injector lines. I think the newer lines are just thicker walled for fatigue resistance and have the same ID, but I’m really interested to know for sure. And, even if the ID is different, it would be interesting to see if that affects the flow rate through the nozzles since the tubing is so much larger than the nozzle orifice. Skip

When I was contemplating my first airplane purchase many years ago, an airplane owner friend advised that, "The best part of airplane ownership is that the flying is free." "Free?", I asked. He replied, "When you rent, you think about the rental cost per hour. When you own, it's so damn expensive just to have the thing that to put some gas in it and go fly for an hour is essentially free." My wife does't ask anymore. She lives by the belief that you shouldn't ask a question if you can't stand to hear the answer. Skip

Nice - what fabric did you use? Skip

I'm truly sorry that you appear to have taken some of my comments personally; they were not intended that way at all. I merely thought we had a difference in understanding of how RSA fuel injectors work and were discussing it in an open forum so that everyone could benefit. I enjoy hashing out technical subjects with knowledgeable peers -- I learn a lot that way. I won't risk further offending you by commenting on your post other than to say that some of your arguments run counter to my understanding of fluid dynamics. There is a great book that those on the forum with an interest in the subject may wish to track down: Thorner, Robert H., Aircraft Carburetion, John Wiley & Sons, 1946. It explains basic carburetion principles in a very clear manner, as well as going into depth in discussing the fuel metering system used in Bendix-Stromberg pressure injection carburetors, which is exactly the same system used in the later Bendix (now Precision Airmotive) RSA fuel injectors. Peace. Skip

All this wear indicator discussion is interesting, and certainly pads should be replaced when indicated by wear indicator or thickness measurement, but don’t pads generally continue to provide braking until worn to metal contact? The original post was regarding poor braking after wheel maintenance.

Best guess is that the resistance to ground has increased somewhere. Panel lights inside the cluster and the gauges appear to use the same return to ground according to my schematic. If there is resistance in the shared ground, turning up the lights will cause a voltage increase on the ground side of the gauges and decrease their indication. The ground is a wire from the connector on the cluster to a ground plug. Problem could be there or inside the cluster.

This makes sense. I looked up the test cell data from my factory rebuilt IO-360-A3B6. Lycoming specified a maximum fuel flow of 95 pph at an airflow of 1000 pph. Full rated power yielded a measured airflow of 1118.5 pph, but the fuel flow at this test point wasn't measured. Assuming a linear increase in fuel flow, rated power max. fuel flow would be 106 pph or 17.7 gph. Voila! (maybe).

I happen to have a copy of the training manual handy. The first sentence reads: "Precision Airmotive Fuel Injection Systems are designed to meter fuel in direct ratio the volume of air being consumed by the engine at any given time." Some confusion may be that there are several models of RSA 5-series fuel injectors. The RSA-5AD1 is used on the IO-360 and does not include AMC. The RSA-5AB1 is used on the HIO-360 and does include AMC. RSA Operation and Service 15-338e.pdf RSA training 15-812_b.pdf

Slight correction: the RSA fuel injection in the IO-360 Mooneys doesn't have automatic mixture control, so the fuel flow is regulated by the volume of the airflow rather than the mass. That's why we have to lean as we climb (airflow volume stays the same, so fuel flow stays the same, but air density decreases, so mass airflow decreases, and the mixture gets rich). A lot of books get this wrong. I didn't understand it until I was studying the Bendix-Stromberg pressure carburetors (the grand daddy of the RSA fuel injectors) used on the museum's DC-3. These carburetors have essentially the same fuel metering system as the RSA injectors but have AMC, so you just select Auto Rich or Auto Lean and forget about adjusting for altitude. We know, of course, that at high DA we need to lean for max. power before takeoff, but I never thought about the converse (I live on the west coast and have never seen a -2700' DA -- Brrrrr.). So, since we cannot go more rich than "full" rich, the fuel flow at full rich must be really rich (what George Braly calls "gobby rich" - whatever that means - must be an OKey expression :-) to provide detonation margin at really low DA. The Lycoming IO-360 Operator's Manual has a curve for fuel consumption that shows 200 hp/2700 rpm/best power mixture fuel consumption at 94 lb/hr (15.7 gal/hr). I cannot find a specification for full rich fuel flow. I usually see around 18 gph full rich at SL +/- 200 ' DA. I'd be interested in what others see for full rich at takeoff with DA noted. Skip

Interesting question. Really, every horizontal induction IO-360 should have one to drain excess fuel from the induction system to prevent a potential fire hazard. Lycoming makes one (LW 75444) but the Lycoming IPC only shows it on the A1B6 and the A1D6. My factory rebuilt A3B6 didn’t come with one. The Lycoming part won’t work on a M20J, because of the close fit of the muffler which is why Mooney makes the right angle valve.

It’s really hard to blend new paint into the old without it showing. Airbrushing isn’t a bad idea for larger areas but may make a little chip like this more visible. Take the tail access panel to an auto paint store and get a color match. Clean area with solvent, then use a small brush to apply a self etching primer like SEM and then a couple of color costs to fill in.

All I know is what NORCAL TRACON guys told me during a visit a few years ago. Unless it causes them a problem, they don’t care. The last thing they want is extra paperwork. HOWEVER, FAA has a “quality control” group somewhere with a radar feed and nothing to do but watch for things like airspace incursions. If they spot one, they call the TRACON and the TRACON has to investigate it. So, if you aren’t near a TRACON, probably no one cares. And if you are near a TRACON probably nobody cares unless you get flagged by quality control. FWIW, I inadvertantly flew maybe 1/2 mile into Whidbey NAS Class C recently. I called them and confessed my error. The controller hadn’t even noticed me and it took him a minute to locate me once I called. He kinda laughed and said, “We’ll just let it go this time.” I always liked the Navy. Skip

If you just need a binder - Staples, OfficeMax etc. for a plain generic binder. The original is a standard size. If you want a real Mooney binder, bet you could order one from LASAR or your favorite MSC. Probably $$$. Don’t get the entire POH - just the binder. It’s a good idea to copy the content for a backup. Better yet to scan it if you have a scanner. Scan your logbooks, too. If you hand the original to FedEx Office or similar and ask them to copy it they may refuse due to the copyright notice. But, in my experience, they don’t much care what you copy yourself if you use the self service machines. A little Googling will find generic POH online - here’s one. You can just add your airplane specific pages. Skip M20J POH3203B.pdf

Thanks, everyone. I'm currently thinking of using the fiberglass PTFE tape or the 3M 5421 UHMW tape (which is what Mooney uses) on the cowling. For the top leading edge of the flaps where there is some minor rubbing against the wing, I'm thinking of using 3M Polyurethane tape which is UV resistant and specified for helicopter rotor leading edges. Skip

Try Dan Long @ West Coast Governor Service 559-687-1477 danlong@westcoastgovernor.com. Great guy.

The Mooney has some interesting design aspects to the aileron/rudder control system. The ailerons are relatively wide cord and short span and the aileron control system doesn't have a lot of mechanical advantage. This could lead to two undesirable characteristics: high control forces and too much adverse yaw. The first is mitigated by the beveled trailing edges on the ailerons which is a neat aerodynamic trick to reduce the hinge moment. The adverse yaw is mitigated by the rudder/aileron interconnect springs: Left rudder will induce a slight left roll and vice versa. The interconnect also increases the dihedral effect which improves lateral stability and reduces the tendency for spiral divergence. Many years ago I performed the following experiment in a 1978 M20J: Set up at 5000' on a calm day, trimmed clean at 90 KIAS. Hands off pressed slight rudder to initiate a bank. Nose dropped, airspeed increased, bank increased, airplane descended. As airspeed increased, nose rose and airspeed decreased. The airplane completed two to three (don't remember exactly) cycles of this phugoid oscillation and settled into a stable 45-deg banked descending turn at a constant airspeed. It did not end up in the ever tightening, airspeed increasing, descent rate increasing graveyard spiral. I haven't tried this with my '94 J, but would expect the same results. Skip

OK, you win!

I'm looking for a good abrasion resistant tape -- either white or transparent -- to use on the gear doors, cowling, flaps, etc. I have used the teflon tape from Spruce in the past https://www.aircraftspruce.com/catalog/cspages/teflonantichafetape.php but it doesn't stick very well and is pretty expensive. I was thinking of using uhmw-pe tape, but the 3M 54XX tapes are not listed as UV resistant and, unless treated, uhmw-pe material breaks down under UV (per Emco Plastics, manufacturer of uhmw-pe plastics: Sun without protection – depends on thickness and location. The thicker the better. In Florida, Arizona, New Mexico, and other desert areas – less than one year.) Of course, many areas are no continuously exposed to the sun, so maybe the UV resistance doesn't matter. Anyone found anything good? Skip

Here’s a way to think about it. Assume the engine is producing no power and the plane is gliding and the prop control is at the highest rpm position. Spinning the engine at this rpm requires a certain amount of power which creates drag. As you pull the prop control back the power required to rotate the engine at the lower rpm decreases and so does the drag. If you could pull back all the way to feather, the prop would stop and drag would be minimum. For a stopped prop, the first order approximation of the drag is the flat plate area of the blades which obviously depends on the blade size, shape and number. Skip

The transducer is made by Floscan which was purchased by JPI last year. The transducer spec for flow rate accuracy is +/- 0.5% @ 16 gph. It should be good enough if you set the JPI K-factor to match the K-factor written on the transducer which should be around 29K.

Correct. As I now understand it, the fuse pins are designed to shear under excessive load most likely during impact. My original discussion (long ago) with my Boeing friend related to the DC-10 that lost an engine in flight due to maintenance damage to the attachments during engine installation. I may have confused the two issues. The engines are designed to separate but not under the conditions I originally stated.

Clarence has a really good point here. I realize that I don't really know that the eyebolts are designed to break away. I just noticed how easy it was to pop one and assumed that, so my apologies for stating something I didn't know to be fact. BTW on my '78 J, we repaired my goof with a helicoil and noticed that the other side had been previously helicoiled, so that one had probably been popped, too. I was just trying to make the point that we should be circumspect when selecting parts and making modifications to airplanes. Someone mentioned static thrust, and I'll throw in that Rob McDonnell, who was Mooney chief engineer at the time, sent me some data way back in 1991 and it includes an estimated static thrust for the M20M of 1000 lbs. The example of the jet engine attachment is absolutely true. The engines are mounted with fuse pins designed to fail in shear under excessive load. I first learned about this from a friend who is a powerplant flight test engineer for Boeing, but you can easily find references to this with Google. Here's a quote from https://reports.aviation-safety.net/1992/19921004-2_B742_4X-AXG.pdf "1 .6.3 .1 Pylon to Wing Attachment Design. The design of the engine nacelle and pylon incorporates provisions that preclude a wing fuel cell rupture in case of engine separation, by means of structural fuses . A clean breakaway of the nacelle and/or pylon from the wing is ensured when the shear loading of the fuse pins exceeds the design load conditions. The structural fuse concept utilizes hollow shear pins at the four wing attachment fittings between pylon and wing. The wing support structure and fittings have been designed sufficiently stronger than the fuse pins thus safeguarding the wing from structural damage in case of an overload condition . The nacelle and engine are attached to the pylon bulkheads through forward and aft engine mount fittings . The pylon is essentially a two cell torque box containing three bulkheads: a forward engine mount bulkhead, an aft engine mount bulkhead and a rear closure bulkhead . Pylon to wing attachments are made at the aft end of the upper link, the aft end of the diagonal brace and at the two pylon midspar fittings . The fuse pin at the forward end of the upper link, the aft end of the diagonal brace and at both midspar fittings are the primary fuse pins. The fuse pins at the forward end of the upper link and the aft end of the diagonal brace are designed to fail at a slightly lower load than the fuse pins at the other ends in order to assure a controlled separation of the pylon from the wing." Skip

Same stuff was on my '78 J and again on my '94 J. Pretty sure it's just clear vinyl tubing yellowed by oil and time. When we had to remove it, we used a heat gun and it softened just like vinyl. Whenever I've needed to know what material Mooney used for a particular part, I've had good luck emailing the part number to technicalsupport@mooney.com and asking. If that doesn't work, call LASAR or Maxwell -- they have access to the Mooney Parts Portal.

I talked to Bendix-King today regarding the KFC 230. They are still working on the Bonanza certification and have no date for Mooney.

All engineering is a trade off. There really isn't that much force on the eyes when the plane is tied down. They probably won't hold in a hurricane or tornado, but by reducing the break away force they can protect the spar against the more likely occurrence of taxiing away with the wing tied down. Lot's of airplane structures are designed that way; for instance, the engine mounts on jets are designed to break away and let the engine fall if it goes out of balance enough to risk structural damage to the wing. My point is that airplanes incorporate many non-obvious design decisions, and you need to be careful when making changes. Skip