Primarily for general aviation discussion, but other aviation topics are also welcome.
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By Dodo
#1784231
My aircraft (with a continental O-200) has been making odd noises in flight. I have been unable to reproduce it on the ground.

All is in the hands of my LAA inspector, but in the meantime can anyone identify what the clattering noise is?

I was not flying through rain or hail. There were no seatbelt straps dangling outside, nor any loose bits of trim.

Suggestions gratefully received.



Please ignore the video itself. If I knew how to publish a sound only file I would.
D
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By Rob L
#1784234
I'd suggest it's not engine-related, Dodo.

What aircraft is it? (It really sounds like something loose/flapping in the slipstream), close enough to the microphone to be recorded.

PM if needs be.
Rob (also an LAA Inspector)
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#1784241
Acoustics in a cockpit are a nightmare!

I have an electronic stethoscope system that you could move around the cockpit in order to pinpoint the loudest area of the noise source.

That's usually a good place to start jiggling or cable tying stuff.

Where are you located?
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By Rob P
#1784253
I get exactly that with a passenger and the squelch not quite turned down enough. More noticeable when they turn their head to look out of the side window.

Rob P
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#1784256
Rob P wrote:I get exactly that with a passenger and the squelch not quite turned down enough. More noticeable when they turn their head to look out of the side window.

Rob P


But that would be through the headset wouldnt it? I had thought the video sound was direct from the camera - @Dodo ?
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#1784258
Is the engine fitted with a dry vac pump for instrument suction? as I see you have an AH and DI, or do you have a venturi.
Does it change frequency with a change in RPM
Is it noticeable on climb, cruise and descent to land
Last edited by Flying_john on Fri Jul 17, 2020 9:47 pm, edited 1 time in total.
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By Dodo
#1784260
Thanks all. I shall re-investigate. Thanks also for suggestion re electronic stethoscope @ flyingeeza I am at Shoreham. At the moment a/c is grounded for investigation, but when flying again, if it continues, that might be the way to go.

But that would be through the headset wouldnt it? I had thought the video sound was direct from the camera - @Dodo ?


Yes , direct from camera, not through headset.

Is the engine fitted with a dry vac pump for instrument suction?


No, no such luxury, it has a venturi system.
Last edited by Dodo on Fri Jul 17, 2020 9:50 pm, edited 1 time in total.
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By Dodo
#1784266
Flying_john wrote:Change with Revs ?
Change with climb, descent or cruise ?


Seemed more marked at high engine power rather than airspeed related. Audible in climb and cruise.
I really didn't think I could hear it on the ground but here is a video of a high power ground run after landing, and on reflection, I think it is there but not as noticeable. Again the video is incidental, it was really just recording the sound. If I had thought more sensibly I would have kept it on the tacho (which I didn't think was causing the noise, but could have been).
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By Rob L
#1784273
I don't think it's acoustics in the cockpit; it's more like an exterior sound. It also sounds close to the microphone (it's "flapping", not "drumming" if it was further away on a wooden structure)

In your second "video" I hear the "flapping" diminish with RPM (or perhaps airspeed). It's something close to the cockpit. Cowl chafe tape come loose, perhaps? Windscreen tape/seal (if fitted) come loose?

Just suggestions.
Rob
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