PT20J

Fuel injection systems and carburetors are based on a couple of principles: 1) The flow rate across an orifice is a function of the pressure change across it. 2) In a pipe having multiple restrictions along it's length, the flow rate is determined by the smallest orifice. The fuel flow rate to the engine is determined by the main jet. The fuel injector measures airflow and controls the pressure across the main jet to match the fuel flow to the air flow. Equal distribution to the cylinders is determined by the nozzles. The rest is just plumbing. Bendix RSA fuel injectors are based on design principles from Bendix-Stromberg pressure carburetors used on the big radials. A great explanation of how these work (written by the man that designed them) is found in Aircraft Carburetion by Robert H. Thorner.

Things don’t add up here. Engine roughness is caused by the cylinders delivering unequal power. Conversely, if it runs smoothly, especially LOP, the cylinder power, and thus the fuel flows, are balanced. The lines from the flow divider to the injectors are much larger than the injector nozzle and are not a factor unless severely clogged. It is possible for the valve in the flow divider to be damaged or hang up and cause unequal flows, but this should cause roughness or shut down issues. It seems your engine operates normally, but you are concerned about what your instruments (EGT & FF) are telling you. Perhaps it’s an instrumentation issue. You could eliminate one source of confusion by cleaning and re-installing the stock injectors and rerunning the bottle test. Skip

I notice that Precise Flight says to remove them annually for inspection and lube. Does anybody actually do that? Also curious how much others use their speed brakes. I find that I rarely use them unless I’m helping out ATC or I screwed up my descent planning. But then my previous ‘78 J which I flew for seven years, and the C I flew before that, didn’t have them. So, maybe I’m missing something. Skip

Likely a B nut on a fuel line wasn’t tightened properly during installation and backed off. It’s not a bad idea idea to change the oil at 10 hrs on a new engine and check security of everything. You won’t know for sure until someone removes the cowlings and looks.

Check bus voltgage with an accurate digital multimeter before changing anything.

Thanks!! Great pictures worth a few thousand words at least, and really helpful. It makes me long for the Aspen MFD, though. But I can see advantages with just the PFD for now.

My panel currently has a GNS 430W and an Aspen PFD with synthetic vision. I’m about to install a GTX 345 for ADS-B in/out. ADS-B in will display on the 430W and my iPAD (via Bluetooth). The ADS-B in display capability on the PFD seems pretty limited, so I’m thinking of not connecting the Aspen to the GTX 345. Wondering if anyone has experience with the ADS-B traffic and weather displays on an Aspen PFD with or without synthetic vision, and how useful it is. Will I be sorry if I don’t hook it up? Skip

Agree epoxy is probably best. My Mooney Service Manual calls for cleaning bare aluminum with solvent, then using a wash primer, then epoxy primer, then the top coat. The wash primer is a low build etch primer. That’s a lot of work for a touch up. You have to mix the epoxy primer and use a spray gun. You can get it in a rattle can, but once you push the button you have a limited time to use it. So, for a touch up, you’ll waste most of the can. Since you need to use an etch primer of some sort to get good adhesion, I like to keep it as simple as possible. So, I just go for an etch primer and a top coat. But that’s just me. I know guys at museums that will go all out on a chip.

Zinc chromate has fallen out of favor since it is highly toxic and a carcinogen. Interesting, since FED SPEC TT-P-1757A says: "3.3.2 Toxicity. The manufacturer shall certify that the primer contains no substances of known toxicity under normal conditions of usage." Guess it never meet spec ;-) TT-P-1757A.pdf

Well, actually zinc phosphate is an etch primer. https://www.aircraftspruce.com/catalog/pdf/09-02128tds.pdf I've tried a couple of brands zinc phosphate in spray cans without good results. Both took over a day to dry and spit out little blobs of paint mixed with the spray no matter how long I shook the can. SEM lists its etch primer as an aerospace product. https://www.semproducts.com/manage/html/public/content/techsheets/sem_tds_self_etching_primer.pdf I'm not a paint expert, but I've had good results with this for touch ups.

Back to the original point, if you want to hear how easy it is to forget the gear, read this: https://www.avweb.com/news/pelican/188536-1.html

Curious how much play a blade should have. The McCauley Owner/Operator manual says up to 1/8” at the tip is normal, but doesn’t mention a minimum.

Sand to remove corrosion and feather paint edges. Prime with etch primer (better adhesion than zinc phosphate). Take the access panel from the tailcone to an auto paint shop and they can color match it and put it in a spray can.

There's an old saying: A man with one watch knows what time it is. A man with two watches is never sure. In my plane I got the following voltage measurements (engine stopped, master and avionics ON): Aspen PFD: 23.6V EDM 700: 24.9V Mooney voltmeter: 25V (best guess - not enough graduations to read accurately) Fluke DVM at main bus: 24.35V Fluke DVM at battery terminals: 24.4V The DVM is, of course, the most accurate. So, be careful where and how you measure your voltage.

Just curious... what incorrect basic aerodynamic concept did an instructor teach you?

Check on insurance costs. Turbos may be a challenge to insure economically without an instrument rating.

Jimmy Garrison @ All American is a straight shooter. They’ve been around since 1991 - can’t last that long if you don’t treat people right. I have both sold and bought planes there and was treated honestly and fairly on both transactions. The PPI is important, but don’t expect it to catch more than deal breaker defects. Budget for lots of deferred maintenance surprises at your first annual. I think a lot of folks put too much faith in MSCs. I have used both well known MSCs and non-MSC shops. Some of the things MSCs have missed or screwed up were surprising. It really comes down to the knowledge and experience of the mechanic that works on your plane Find a good Mooney mechanic - MSC or not - and stick with him. Best is to be directly involved (owner assist) during any major maintenance. Good luck, it’s a great adventure. Skip

I think you are saying that the gear down light on the annunciator panel did not illuminate, but the floor indicator was in alignment and the floor indicator light was on. I don't have a wiring diagram for an M, but the gear system is likely the same as my J. The down limit switch in the belly is a double pole switch. One pole shuts off the actuator motor when the gear is down and the other pole controls the light. It could be a loose connection between the switch and the annunciator panel, or a bad switch. It's probably not a switch adjustment since the motor apparently shuts off OK. Also, the annunciator light dims when the NAV lights are on and this can make it hard to see in the daytime. Skip

Actually, Lycoming will still overhaul or rebuild the dual mag engines. I discussed this with Lycoming when I recently replaced an IO-360-A3B6D with a -A3B6. You will get an overhauled mag since the dual mags are no longer in production. Since Continental bought the Bendix magneto line, Lycoming has switched to Slicks wherever possible. There are a lot of internal dufferences between the A3B6D and the A3B6 - its not just the mags - and Lycoming will make it worth your while to switch. Skip

On my ‘78 J it was a switch for the Davtron clock flight time function.

Good idea to check the aiming when you replace the bulb.

Thanks. Any idea what rpm it’s calibrated for?

According to the wiring diagram, the hour meter is fed from the electric tachometer on my M20J. Does anyone know how this works? Is there a cut-in rpm below which it doesn’t record, or does the tach pilse modulate to simulate the hour meter on a mechanical tach? Skip

Should be possible to determine if the flaps are closing by noting CHTs.

Here's what I got from Mooney - they told me this is all they have. Skip Mooney Service Manuel M20J Vol. 2 of 2.pdf