PT20J

A windmilling prop with an idling engine creates drag. It takes a small amount of throttle -- usually around 12" MAP -- to get zero thrust. This setting is what we use in multi-engine training to simulate a feathered prop at low altitudes (where we might want to bring the engine back on line quickly so that a simulated emergency doesn't become a real one).

A few points to keep in mind: Best glide occurs at the angle of attack (AOA) for L/Dmax which occurs at the point where total drag is a minimum and induced and parasite drag each account for half the total drag. It is not dependent on weight. The speed for best glide does depend on weight, of course. Perhaps the easiest way think about this is to remember that in unaccelerated flight, Lift = Weight and Lift is proportional to TAS2 and AOA. If you keep AOA constant for best glide, then the best glide airspeed varies as the square root of the weight. At higher altitudes, the required TAS increases due to the decrease in air density, however this is compensated by using the same indicated airspeed as at sea level. The descent angel will be constant at best glide, but the vertical speed will vary as the TAS. A stopped prop will always produce the best glide performance regardless of the number of blades. If you keep the prop turning, the best thing is to pull it back to minimum rpm as others have mentioned. A windmilling three bladed prop will theoretically have more drag than a two bladed prop and should reduce the best glide speed a little. If the STC doesn't mention it, the effect was likely pretty small. Vy is the speed where there is maximum excess power available above the power required. Vx is the speed where there is a maximum of excess thrust available above the thrust required (drag). In many high performance aircraft it occurs very near the stall speed in which case a higher (safer) speed will be listed in the POH. Since Vx and Vy depend on the characteristics of the propulsion system as well as aerodynamics, they are not strictly determined by AOA. Skip

The Aspen patent has more details... US20160298985A1.pdf

The coaxial panel connector is standard for JPI. I got tired of dragging my laptop out to the hangar and bought the USB download box which works great. https://www.aircraftspruce.com/catalog/inpages/jpiusbdownload.php Skip

Mooney seems to have moved the VR around a lot over the years. My '78 J had it mounted on the cabin side of the firewall behind the circuit breaker panel -- I haven't found it in my '94 J yet, but I think it's behind the center console. It was a long time ago when I had the VR out of the '78. It was an OECO and it went bad so I removed it and replaced the power transistors and set it to the correct voltage on the workbench. I don't remember if it would have been possible to get to the voltage adjustment without removing the unit. I do remember that it was really, really hard to get it in and out.

In my attempt at brevity, I oversimplified and apologize for creating potential confusion. In a long pipe made up of pipes of varying cross sections, or in a pipe with multiple restrictions, of course all contribute to the flow rate. I was simplifying to the case apropos to the current thread where there are multiple restrictions, but one is considerably smaller than the others. In this case, the smaller restriction will dominate. Precision Airmotive lists the ID for the line to the nozzle as 0.085 to 0.090. The lines are supplied by Lycoming. There are only two part numbers for an IO-360-A3B6(D): LW-12098-0-140 for cylinders 1&3 and LW-12098-0-210 for cylinders 2&4. There are not options for different IDs. Lycoming SI 1275C lists the nozzle flow rate as 32 lb/hr at 12 psi under specified test conditions. From this you should be able to calculate the effect of the lines relative to the nozzles.

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