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Hello! I own a 1976 Mooney M20F named Loreto. This is my first post on a Mooneyspace forum, so please forgive me if I do it wrong. ◡̈ On 2/17 I heard a slow, deep, repetitive grinding noise coming from my plane after landing that I had never heard before. It was very loud and coming from within the airframe somewhere below and slightly behind the front left seat. The green GEAR DOWN indicator light on the panel was flickering a little. When I turned the master switch off, it stopped. When I turned the master switch back on, the sound and flickering returned. If I sat very still, I could feel my seat vibrating a little in sync with the sound. The DPE sitting next to me in the plane when this occurred suggested it may be an issue with my electric landing gear motor so I took the plane to the only maintenance facility on the airfield, Foothill Aircraft at Cable Airport. The mechanics at Foothill are hypothesizing... "a spring is snapping back and hitting a switch to tell the motor to continue to push the landing gear down even though it is already down and every time the spring extends the problem continues to repeat until the power is cut off." Foothill put the plane on jacks and has still not been able to recreate the problem. This makes sense because during our flight the noise only began after we were on the ground, not in the air. Worth mentioning is that my last flight was an IFR checkride where we shot three approaches in a row and extended and retracted the gear in the air twice with no issues before our final landing which was also totally fine and the landing gear came out and locked correctly. It was only after taxiing and sitting idle during shutdown that the noise began. The sound was so alarming that I do not feel safe to fly my plane again until the issue is properly identified and corrected. I am not a mechanic so my personal knowledge is limited when it comes to understanding this issue. I’m not even entirely sure it is related to the landing gear actuator or motor; or if either of these service documents (SI M20-112 or SB M20-190B) are even connected to this issue since I recently had it removed and shipped to LASAR for a complete overhaul (March 2021) and my actuator is a ITT LA11C2114 which is technically exempt from these service announcements. Have any of you heard this sound / had this problem before? Any feedback/advice would be greatly appreciated. Thank you.

Should be beneficial in the cockpit. I'm curious to what noise levels various Mooneys have in takeoff and cruise. The NIOSH Sound Level Meter mobile application is a tool to measure sound levels in the workplace and provide noise exposure parameters to help reduce occupational noise-induced hearing loss. Key Benefits Raises workers’ awareness about their work environment Helps workers make informed decisions about the potential hazards to their hearing Serves as a research tool to collect noise exposure data Promotes better hearing health and prevention efforts Easy to use https://itunes.apple.com/us/app/niosh-slm/id1096545820?mt=8

Aircraft is a Mooney M20F, engine is a Lycoming IO-360-AIA. It's equipped with a Weldon 8163A electric boost pump (certified replacement for the original Dukes). POH start procedure specifies mixture to idle cut off, boost pump on to pressurize the lines, then advance mixture to prime. When the boost pump is turned on with the mixture at idle cutoff, pressure builds to about 25 PSI and is rock solid. The pump makes a fairly loud hum while it's on, of course, and the frequency of the humming noise (i.e. the speed of the pump) decreases a bit as the fuel line pressurizes. We don't prime for hot starts, but sometimes we prime when the airplane is "sorta" hot, e.g. sat on the ramp for an hour or two during a $100 hamburger run. Sometimes there is still vapor in the lines in these cases. If so, the pump seems to "strain" a little as pressure builds, and the frequency of the humming noise from the pump warbles a little. I've always considered this normal, during the 10+ years this particular pump has been in service. Now, after a recent annual, my airplane partner said he heard the hum from the pump warble a bit even on a cold start. This morning I turned on the pump for a cold start and let it run a full 30 seconds or so before priming. Sure enough, the speed of the pump varied a little after the lines were pressurized. Fuel pressure needle never wiggled, it was rock solid at about 25 PSI as expected. We're now trying to decide if the warbling frequency from the pump is "normal" or not. I confess I've never paid much attention to steady vs. warbling sounds from it, since I know some variation is normal as the lines pressurize (especially if vapor is present). The pump has about 10 years of service on it, and probably somewhere in the neighborhood of 2000 on/off cycles, so I suppose it's possible the brushes on the motor are going. It's also possible the system is sucking air from somewhere. There are no blue stains around the pump or gascolator upstream from it, that would indicate an obvious leak. But the bowl of the gascolator was R&R'd at the recent annual, to inspect and clean the screens. It was reassembled with new gaskets and safety wired, but that doesn't guarantee a good seal of course. What says the collective wisdom of the board? Leave it alone? Inspect the system? Replace the pump now even though it's not obviously defective? We're not necessarily trying to avoid the cost of a new pump. But we are reluctant to replace what may be a perfectly good pump, due to the risk of a maintenence-induced problem in the swap. Any/all opinions appreciated.

Has anyone got a noise certificate for an M20M/Bravo? I've been going through http://www.faa.gov/d...r/AC 91-86 .pdf trying to work out what to put in each of the boxes, but am getting increasing confused with all the various Appendixes, schemes, chapters and sources! So far I've got from http://www.faa.gov/d...36-3H Chg 1.pdf Take off 64.8, Approach 63.3, from http://www.faa.gov/d...36-1H Chg 1.pdf 74.0 and then putting ICAO into it from http://http://www.ea...01-01072009.pdf get Take off 79.0 and maybe overflight at 70.8! The AFM just quotes 74.03 for CFR and 71.0 for ICAO. If anyone has an 'Official' version I'd really like to know which boxes have been filled in, and with what values Ben