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https://aviation-safety.net/wikibase/237728 Does anyone know more? M.

74 " in Diameter= 187,96 cm in Diameter. At 2700 RPM speed tip is: 3,14*1,8796*2700/60= 265,59 m/s. Sound travels at 343 m/s in air. lg, M

Hi, From Hartzell I got a link to EASA database https://www.easa.europa.eu/domains/environment/easa-certification-noise-levels and explanation: "Whatever the reason, for the listings in the EASA noise level archives, you can bet that we had nothing to do with it. Here’s what I can tell you about it Prior to 1988 noise was measured at 1000’ AGL (overflight). In FAA speak, this was FAR 36, Appendix G. EASA, or more specifically the Authorities that preceded EASA called in ICAO Annex 16, Chapter 6. After 1988 both organizations changed to a noise measuring system that took take-off and climb performance into account. The better a plane climbed, the higher it would be at 8200’ from where the airplane started rolling, and the microphone is set up. This Take-off method is called FAR 36, appendix G, or ICAO Annex 16, Chapter 10. I can tell you that Hartzell never tested a M20C with any prop on it for the FAA or EASA. Both of these prop TC/STC’s were validated in Europe well before EASA was established. Hence they were grand-fathered in without any noise testing on our part. The note that EASA has pertaining to the three blade entry is “”9/24/201 Engine designation revised”. Looking at the numbers themselves, the Chapter 6 numbers are on props that were TC’ed. Maybe these numbers came from Mooney from the TC process? I can only guess. The 7282 three blade is approved on an older STC. In 2010 we added eligibility for the Powerflow exhaust to the STC. The only thing I can think of is that when Powerflow applied to validate their STC it must have initiated some noise discussion. If you will note, 85.5 dB(a) is the maximum allowable under Chapter 10. That seems like allot for un untested unit that is the same diameter as the two blade?? So, to get to the bottom of your questions, The props are the same diameter. They should be about the same noise-wise, except the 3 blade climbs better (CHAPTER 10). The numbers in the archive compare two 74” props at the same RPM, using two different methods, one of which may be considerably closer to the mic, and the Chapter 10 listing is as high as it can be to pass. It seems almost arbitrary?? The three blade certainly is not 10 dB(a) louder than the two blade." lg, m

Hi, Please, what should be a Take -Off Noise Level for M20C with Lycoming O 360A1D and new 3 Bladed Hartzell (HC-C3YR-1RF/F7282) Prop? I replaced the original, old 2 bladed Hartzell HC-C2YK-1BF/F7666A-2 with the new 3 blade Prop. Unpleasant surprise for me is a new Noise Certificate (Foto) with 85,5 dBA, while in the old one there was 75 dBA. According the Hartzell Page new prop. should dramatically decrease noise. lg,m.

Hi, Unfortunately during engine overhaul (Lycoming O360 A1D) the old (I think) Prestolite starter motor was not overhauled. Last time worked at "second attempt" and now is not working any more. Please advice regarding replacement. Thanks, M.

AOA is difference between where the plane points and were it flyes. Just a battle of the words. For me, the biggest problem is, that people take their two dimensional 1 G world in air and consider the turn as a a change in heading over the ground. Something like to drive a car, they want to fly "level". For a plane a turn is any change in the velocity vector of the airplane. When we pull up the nose, that is a turn because the airplane is now flying in a different direction. When we push, that s also a turn. A turn is always accomplished by changing the lift being produced by the wing. And here is, where problem arises. lg,m,

Hi, when you are in descent, relative wind is from below, AOA rise. lg,m

Good analysis of one accident from AvWeb. m

Thanks, I found this: http://donmaxwell.com/fuel-tank-repairs-how-we-fix-them/ what should I use to prime wheel wells after cleaning? m

Hi. I have fuel in the right wheel well (co-pilot site, picture below), but only when right tank is completely full. There is no leak "symptom", when I refuel right tank approx. 1,5-2 inches less. From pictures it is clear, that right tank has already been repaired. Where should I start? How "acute" is the problem? Thanks in advance for your opinion/experiences lg,m.

Citat from Langenwiesche's Stick$Rudder: Epitaph: "He did not know he was pulling the stalling lever." It is easy to be safe.

Wind contition at the time of the accident? Tailwind on base leg? RIP airmann.. m

So look my freshly modified cowling with Lasar Cowl enclosure. I have to confirm, that it was good invested money. CHT are definitely better. I can't comment on speed gain, because motor was overhauled & new prop (I do not know what contributed more). lg,.m

Hi. Need an advice. Trying to fix a problem. My EGT shows only last 75 F from the Peek. The Engine is fresh after TBO. The same numbers were before engine overhaul. Suppose the Probe has not been replaced. Any suggestions? thanks, lg,m