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adverseyaw last won the day on January 14 2018

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  1. It took me a bit longer than I'd like, but I was finally able to gather enough performance data on this STC to put together an assessment. I've got a summary posted at the link below. The short version is that above about 9k feet, I get lower fuel consumption than what the POH specifies, or better speeds, or both. Below that, I tend to get neutral or slightly worse numbers. (Most of the POH's I've used depict best-case performance achieved by test pilots, and achieving them can be spotty. So I don't necessarily take the neutral/worse numbers as a performance deficit, just a lack of improvement over stock.)
  2. I've got a 1978 M20J with the Firewall Forward "Horsepower Plus" STC SE2741NM. This is an IO-360-A3B6D with the stock dual magnetos and no other engine performance upgrades of note. I do have GAMI injectors which got me to a spread of 0.2GPH and reduces tendency to run rough, especially at altitude. This STC limits propellers to the stock McCauley so that's what I'm running. This engine has about 350 hours on it since overhaul by FF. No real issues with the engine so far. The airframe only has a couple of speed mods, notably flap/aileron seals, but it still has the multi-piece belly. Usually I fly this airplane at Economy Cruise (low altitudes, up to about 9000 feet) and Best Power Cruise above that. Ram air is open on all runs. I keep the cowl flaps closed and make sure the CHTs don't get out of hand, and in all cases below I've let the airspeed and temps settle for at least 20 minutes before recording numbers. I haven't been writing down degrees ROP/LOP. Weight on these speed runs is around 2500 pounds so I'm averaging the 2300 and 2740 speeds in the POH. RPM, MP, and fuel flow are measured with a JPI 800. I've got more runs than this but picked 4 that I could match to the POH. The TL;DR on this performance for this STC is that starting around 9k feet, it gives me lower fuel burn, and sometimes better speed. Below that, it performs like a stock engine: at or slightly below factory numbers.
  3. Oh man, this is cool -- sadly it isn't solving a problem that I happen to have right now I even redid the fiberglass on my upper cowl at the end of last year. @xcrmckenna do you know if Sam from CA is on here? He has that cowl with a lump on it and may want a upgrade...
  4. Any of the ones listed on the event are fine, they're all on the same block so transit is easy. Anecdotally I heard people were happier with the Holiday Inn than the Best Western. I'm a simple traveler and the Motel 6 worked great for me.
  5. Very confusing. ROL mode is described independently of wings-level mode (see below). The Garmin tech confirmed that ROL mode would maintain bank. What you're describing is intuitively what I would expect the autopilot to do, although the sources say otherwise. Do you have a page number for that? I'd like to take back to Garmin for clarification.
  6. I have a GFC 500 and fly in an area with lots of low overcast and a few military GPS interruptions every year. So I called pulled out my AFMS and called Garmin pilot support for clarification. TL; DR: the autopilot gives up when GPS is lost. Here's the page of the AFMS for M20J and M20K: Roll mode (ROL) maintains current bank. It is not a wing-leveler. Garmin pilot support confirmed this is the mode the 500 will enter on GPS loss when on GPS, VOR, localizer, and backcourse approaches. Pitch mode (PIT) maintains current pitch. Although the AFMS says the 500 reverts to PIT on ILS tracking, Garmin pilot support clarified that both the ROL and PIT modes are applied. When the autopilot mode switches due to GPS loss, the pilot can select a new mode, although Garmin pilot support says reselecting approach mode will kick it back into ROL or PIT. My interpretation is that when GPS interruption occurs while on a radio approach, the GFC 500 gives up and keeps the aircraft in its current attitude. Three things that are not clear to me (and which I plan to ask Garmin support if I have time this week): This limitation only applies if a GPS navigator is installed. Is the 500 capable of working without a GPS nav head? If so, why does this limitation exist? Which autopilot modes are usable during a GPS interruption? What annunciations accompany GPS loss and reversion to ROL/PIT? I assume it's just the tiny icons on the G5 but want to clarify.
  7. @M20C_AV8R here's our May formation clinic -- come join! Odds are good @amillet will make it :-)
  8. So much to respond to! @aeroHAWK 100 that's such a neat story. Would love to meet up sometime if you're game. Will PM you. @flyboy0681 I still don't have a lot of great data. One recent flight at 8,000 has me at 9.2GPH at 2350RPM, and I believe my TAS was around 145. One of my goals for 2020 is to record these numbers, and I've since bumped up my cruise RPM so should see an increase above those numbers. Note that this is with the stock prop. The STC requires the factory propeller -- it isn't authorized with an aftermarket prop. @exM20K the mod definitely helps, but I do find that keeping the CHTs in check on hot days is a real challenge. It's also placarded to 28.2"/28.5" of MP down low, which prevents use on the runway. The engine builders tell me that running it above those pressures at sea-level is the main cause for excess oil consumption. @Mooney217RN the Powerflow is on my list! Probably sometime this year, and I heard from Buzz that it really helps with CHTs, which would be a big improvement. I talked with both the Firewall Forward and the Powerflow folks and both felt the STCs were compatible.
  9. @rcwagner and others, the 2020 schedule is now available.
  10. I have bladders in my 1978 M20J and the caps are labeled Shaw Aero No. 457, Assy Code 99321
  11. Yep, our mains are further aft of our CG than most other aircraft. This presents problems at low and at high airspeeds. At low airspeeds, we need comparatively more elevator authority to keep the nose high than, say, a Cessna. I find it's harder to modulate at the edge. At high airspeeds, above the stalling speed of the aircraft, it's really hard to get the airplane to stick to the runway unless you plant it on the pavement. Planting it means the airplane is descending (we'll say at 50-100FPM at time of touchdown) and the CG, which is way far out in front of the mains, continues downward after the mains touch, thereby causing the aircraft to pitch down and slam the nose before the descent is halted. Anecdotally, I've observed that flying with pilots who land fast will tend to hit the nosewheel harder than those who land substantially slower. The geometry is what really gets you in the high-speed landing. A by-the-numbers approach with touchdown right before stall results in the cleanest landings. One advantage of having mains that far back: I've never seen a Mooney tipped onto its tail after a snowstorm.
  12. Is this a recent change in the way the autopilot performs? My IIB wandered a bit and my avionics shop ran adjusted a few pots on the controller to dial up/down the gain on the various signals inside the unit. The adjustment process is fairly simple and is described in the maintenance manual. There could also be a component failure happening (in the autopilot or the DG/HSI encoder) but you can at least try the adjustment first. When I had my IIB fully adjusted, it would still wander a few degrees after a turn or encountering a crosswind in cruise. It usually took 10-20 miles for the oscillation to settle down. Like carusoam mentions, there are other threads on this.
  13. @rcwagner stay tuned as we assemble the schedule. I'll post back here when we have it. @amillet great flying with you today
  14. ;-) Likely my CFII on the radio. We had a glider on the runway at Wenatchee as well. P.S. I checked the roster at the B2OSH clinic coming up, saw your name there, so looks like I'll see you soon!
  15. I've been chasing the induction leak theory and have had some success so far. After changing the intake gaskets and o-rings, and cleaning up the Precise Flight standby vacuum line and valve, we got the popping to stop at much lower RPMs and get the mixture to richen way up (so much that it barely ran). Clearly, I had big leak(s). I'll be testing the sniffle valve again this weekend to see if that's leaking further air. We only have a few more possibilities. One thing that tipped me off is that I can only pull down to 12-13" MP with the throttle at idle and 600rpm. I found a few YouTube videos showing IO-360s pulling more vacuum at idle. It may be I can only get it this low but high numbers indicate a leak is possible (not guaranteed, but worth investigating).