PT20J

Keep in mind when comparing legroom that Mooney makes 1.5” and 3” rudder pedal extensions. At some point, they started putting the 1.5” extensions in J’s at the factory. My ‘78 didn’t have them, but my ‘94 came with them. Check the equipment list. Or, someone may have added extensions later. If done by hangar fairies, it may not be in the logbook.

Shouldn’t be an issue if it was done as well as you say. If parts were just replaced rather than repaired, it wouldn’t even be considered a major repair and wouldn’t need a 337.

Pacific overhauled mine for $267.92 last fall. Looks like new.

I agree. But some of the claims made around MS about operating LOP or ROP boggle my mind. I use both depending on what I'm trying to accomplish - I have no bias one way or the other. I've also instructed and flown at several operators of rental fleets comprising mainly Lycoming normally aspirated four-bangers, and they are very reliable. And, aircraft rented at wet hourly hobbs rates fly WOT and best power mixture a lot. Some of us are obsessing over cylinder pressures and red boxes too much, I think. Of course these exist, but they are taken into account in the engine and airframe installation design. The primary parameter to watch when operating these engines is head temperature which is why I like Mike Busch's red box that starts at CHTs 400F and above - it fits with experience. So, let's stop scaring the OP that his operating technique caused the damage. As you said, sometimes these things just happen.

Help me understand some things, because I’m confused. I know what heat is, and I know what mass is, but what is heat mass and how does ICP affect it? If I fly a M20J at 3000’ density altitude at 75% BHP and 50F ROP with CHT of 360F, exactly what damage would you expect that would shorten cylinder life and how do you know that?

RPM rise will be as the mixture passes best power

For all you LOP fans, I dug this out of the archives. It's from the POH for a Piper Warrior powered by a Lycoming carburetored O-320 with a fixed-pitch prop. Turns out the mixture distribution was so even that it would run LOP and they put the procedure in the manual. And you thought all this stuff was new.

If you do ever make a mold for the top section, maybe you can figure out how to get the raised section over the annunciator panel to sit flat. Mooney never could.

You won't cook a cylinder running LOP that way, but every documented, instrumented, scientific analysis done since the 1930's says you will running 100 ROP. I use LOP and ROP depending on what I'm trying to accomplish, so I don't claim to have any bias. That's a pretty strong statement you made there. Can you back it up with copies of every (or even some) "documented, instrumented, scientific analysis done since the 1930's" that shows running a normally aspirated engine at 7500' at 100 ROP will "cook" (very scientific term, BTW) a cylinder?

Since the plane didn't have an EGT, I used Walter's suggestion. Here's the quote from his email, "If you lean till roughness and richen to smoothness on an R-985 you will end up about 50dF LOP. " Frankly, I never found real "roughness". The power just fell off with reduced mixture strength until it either backfired or stopped. The way I ended up doing it was moving the mixture control toward lean fairly rapidly by a fixed amount (the throttle quadrant has the word M I X T U R E written on it vertically next to the lever, so I used the letters as an index) and noting if there was a noticeable power drop. If not, I'd go to full rich, wait a bit, and do it again moving it further lean. Once I got to a perceptible power drop I'd leave it there or sometimes enrich slightly and watch the CHT. On some planes this would work out fine and the the CHT would stay below 200 deg C (392 F). On others, it would get too hot. I think the variation was in the cooling airflow. The air exits an annular area between the cowling and the firewall dishpan. These planes were all built in the '50s and '60s and the cowlings have been banged around over the years. I noticed that the gap is tighter in places around the circumference on some planes than on others and this likely restricts the cooling airflow a bit. But, that's just a guess.

So, did I understand that you are using a fast blow fuse in a slow blow application? If so, does a slow blow fuse also blow? Have you tried seeing if it blows if you run the engine with the alternator off?

Compression checks are notoriously unreliable and a single check doesn't mean much. You want to look for trends and sudden changes in a cylinder. When they all go the same way at once there has to be a common element - either equipment or operator. You can fly it for a few hours and then do another check with the engine warm if you are worried about it.

I can think of a couple of cases where it is possible to be too lean: 1. The BSFC curve has a minimum that is pretty constant over a range of LOP EGTs. But, if you get leaner than that, the fuel flow continues to decrease, and your MPG actually decreases. Doesn't hurt anything, but it's not as efficient -- you'll burn more gas to get to the destination later. 2. I experimented with LOP in a Beaver on floats with a R-985. The mixture distribution on this engine is about the best you could get -- single row of cylinders with a central supercharger and equal length intake tubes to each cylinder. You can pull it back and just feel the power decrease until it gets so lean that there is still fire when the intake valve opens and it backfires. That's almost idle cutoff! I had an interesting discussion with Walter Atkinson on leaning this engine (he used to own a Beech 18 with R-985s). Just shy of very slight roughness is about 50 LOP (the planes I was flying didn't have EGTs). But you can't always operate the float Beaver there on a hot day. The airspeed is so low (around 90 Kts) that the engine won't stay cool LOP. Apparently as the airspeed falls off, the cooling decreases faster than the combustion chamber heat decreases. The Beaver doesn't have cowl flaps. Skip

I know that the G500 pitch and bank information comes from the G5. I'm wondering though if it has outputs to drive the flight director display on an Aspen PFD and if it will accept lateral mode inputs from the Aspen PFD.

RSA fuel injection systems meter fuel according to the volume of air passing through the venturi. The density of the air is lower at higher altitudes, so fewer molecules of air per given volume as you go up means the mixture gets richer as you climb. This is why we have to lean. When landing at high altitude airports, I leave the mixture at cruise or may enrich it slightly in case of a go around. Idle mixture may still be too rich with this setting and the engine may still die at a high altitude airport if you close the throttle. The idle mixture is controlled for about the first half inch of throttle travel by the idle mixture valve which is mechanically linked to the throttle. You set the idle mixture by adjusting the length of the connecting linkage. Normally, this will be set for the elevation you normally operate. If that's sea level and you go to a high altitude airport, the idle mixture is going to be too rich and you may have to pull the manual mixture out quite a bit to get the engine to run properly. Also on startup, you don't want to go to full rich, or it will probably die on you. Skip

Thanks, Lance.

Still fighting autopilot problems. KC 191 computer intermittant self test trim issue has been fixed by Mid-Continent. But, now HDG and NAV modes don’t work. I checked some voltages and I think the problem is somewhere between the Aspen PFD/ACU and the KC 191. I probably need to take the whole airplane to someone who knows what they’re doing. I’m based in the Seattle area and would prefer a west coast shop in case it has to make more than one trip. Anyone have any experience with Executive Autopilots in Sacramento CA? Any other recommendations? Thanks, Skip

Mooneys were originally certificated under CAR 3 and the empty weight did not include oil. At some point (for sure by the time the M20J was introduced) Mooney started using the GAMA empty weight definition which includes full oil. You can use either empty weight in your calculations so long as you use the correct corresponding empty CG/moment. It’s a simple matter to add a station for oil in Foreflight. Just select Setup and then Edit. Skip

Rod's a good friend. I really enjoy discussing this stuff with him, but I still can't see this effect, so don't feel bad. Judging height to a few inches is very difficult. Even Bob Hoover said he sometimes had landings he wasn't proud of. I do know from experience with my own flying and instructing that the biggest problem is looking too close to the nose. When I started flying seaplanes, I had trouble judging height because there are fewer cues. I found that looking far into the distance and keeping the eyes moving around to take in the whole landing area helps. It keeps you from fixating on a spot and gives your brain more visual cues to work with.

Let's see... It's not on the TCDS. It's not in the IPC. It's not in the POH. No one here has ever seen such a placard before. The placard is homemade. What was the question?

Exactly! Frankly, I think a lot of people make it sound like there is something exotic or unusual about many aspects of flying a Mooney. It's just another single engine, four place, low wing, retractable gear airplane. As I tried to point out earlier, the range of approach speeds varies with weight - the same as any airplane - but not nearly so much as some seem to believe. Low wing planes float more than high wing, and Mooney's float more than most low wings because the wing is closer to the ground. My observation as a CFI has been that many people try to land too fast regardless of type. Mooneys just float more when you do that making them seem different. A really good exercise is to cover the airspeed indicator and fly around the pattern without it. It's not that hard and will cure you of fixating on the airspeed once you get comfortable with it. Find an experienced instructor and try it if you've never done it before. Skip

Anthony, Yep. Although at a MSC I once saw a prop shimmed with blue painter's tape Skip

This isn’t taped per the Service Manual. Teflon tape is supposed to be wrapped around prop hub. That way you can adjust amount of tape for a good fit. This way might work, but I’d put the next one on by the book. BTW, IPC calls out part as a bulkhead assy, spinner (fwd).

I just completed some repairs on my 1994 M20J glare shield. It was warped and starting to develop some cracks. Here are techniques that I found helpful: The glareshield is made from ABS plastic and is really easy to work with. I first separated the two pieces that form the glareshield assembly by using a long bladed knife and a thin putty knife to work the upper and lower pieces apart at the glue joint. Then I used a heat gun to soften and flatten some portions that had been warped by the sun. I got some 1/16" thick sheet ABS from a local plastic store and used this to reinforce some cracked areas from the bottom side on flat parts of the glareshield. ABS cement used for gluing plumbing pipe together works great. Small cracks can be glued back together by dribbling some MEK (which is a solvent for ABS) into the crack with a toothpick or other device and then pressing the two sides of the crack together. Just use it sparingly. Some areas needed reinforcing, and for these I used two or three layers of glass cloth embedded in ABS cement. Don't get carried away reinforcing - the glareshield needs some flex to be able to install it. After completing the repairs, I glued the two parts of the glareshield together using RTV. This will hold them securely, but make it possible to get them apart in the future if necessary. To hide the repaired cracks on the top of the glareshield, I filled in some voids with a little ABS cement and then sanded smooth. Then I used SEM Texture Coating and Trim Black sprays to finish. SEM has a good Youtube video on this. I also put some UHMW PE tape on the back edge to make it less likely to scratch the windshield during installation and removal. Final touch was to install Bruce Jaegar's Easy-out glareshield repair kit to allow enlarging the slot around the center post (I think forcing the old part around the post is what caused a lot of the cracks). Skip

Careful... At 400°F it’s closer to 20%, you need to get to 475° to lose 50%, they drop off quickly after around 425° and that’s for standard aluminum alloys, I assume they use a more heat resistant alloys. Here for quick reference:  I believe the numbers that get bandied about the Internet for aluminum strength vs temperature originated with APS and John Deakin originally got if from a Pratt & Whitney publication titled The Aircraft Engine and its Operation. Th Since the ordinate axis isn't scaled, and we don't even know if it starts at zero, it is pretty meaningless other than to say not to operate P&W engines above 450-500 deg F CHT. Lycoming has long recommended 435 F max for high performance cruise and 400 F max for economy cruise. As a practical matter, keeping temps below 400 F seems prudent. I'm not sure that obsessing on really low CHTs buys anything on a Lycoming IO-360.