mh wrote:
The recordings show different frequencies of the noise. Is that based on position? Is the TAS identical in the recordings? Does it change with TAS/AOA/altitude? Is it reproduceable?It could be an aerodynamic buzz.
It used to be a higher pitch noise before last service. It also started at lower altitudes during climb. After last service it seems to start at higher altitudes. Pitch is lower. Intensity is higher. Does not seem TAS related – sounds the same in climb and after leveling off in cruise.
The door seal sound I had would stop quite suddenly.
This does sound like a pressure regulating valve, or a leaky part of a pressurised system, is oscillating.
If you cannot play with DeltaP, maybe try to depressurise (without Pax obviously) and see if it goes away (suggest you record the sound because your ears won’t be very useful for the first couple of minutes)?
If you have an unidentified strange sound in a brand new TBM 930 (?) I would ask the factory right away…
Time flies. Our TBM is now 2.5 yers old and over 800h. Not exactly brand new. Obviously we asked for this to be fixed, but it only got noisier after last service visit.
Possibly unrelated, but about 20 years ago I was taking delivery of a few MD-95’s for my airline at the old McDonnell Douglas plant at Long Beach. One or more production test flights were usually performed before the OEM would tender the aircraft for customer tests.
By far, the most common and difficult to fix test pilot complaint in those flights were inexplicable whistling noises coming from the area of the openable cockpit clearview window…usually only very minor leaks which could be very annoying after a couple of hours with the pilots’ ears inches away from the noise source…
You could tell because manually changing cabin delta p changed or eliminated the whistle. Usually cured by a slight repositioning of window seal or reshaping of window frame, and the most common cause of the need for a refly. They never developed a trustworthy ground check to eliminate the problem. No leaks or noises were usually observed on the ground checks…supposition went that the noise was caused by the interaction between the cabin leak and the external airflow.
Sounds like a pressurisation leak to me.
Another vote for a pressurisation leak somewhere. The issue is finding where! Door seals are usually the first port of call…
As previously suggested, alter the diff and see if the sound changes
You were imc at sea level? Mist Horn? :p
