Rotors making clapping noise at low speed and level flight/very slow descent - ED Forums
 


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Old 12-28-2018, 06:21 PM   #1
DanielNL
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Question Rotors making clapping noise at low speed and level flight/very slow descent

Does anyone know what exactly causes the rotors to make that strange (frightening) clapping sound? I keep an eye on my rotor RPM and it's totally fine.

All I could find about it in the doc is
Quote:
page 274
At airspeeds below 50 kph, the helicopter develops
vibrations, which disappear as airspeed is reduced further.
What causes these rotor-vibrations? (Which aerodynamics phenomenon?)

The Gazelle rotor doesn't make such sound for example...
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Old 12-28-2018, 06:54 PM   #2
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is this what you were searching for? https://en.wikipedia.org/wiki/Helico...oise_reduction
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Old 12-28-2018, 07:06 PM   #3
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Yes, thanks, my guess it's the "Blade-vortex interaction noise" in the Mi-8, but I still wonder why it occurs specifically at around 50 km/h.
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Old 12-28-2018, 10:36 PM   #4
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Quote:
Originally Posted by DanielNL View Post
Yes, thanks, my guess it's the "Blade-vortex interaction noise" in the Mi-8, but I still wonder why it occurs specifically at around 50 km/h.


Transition Effekt.
This occurs when you come out of forward flight slowly into Hover and from Hover into forward flight aswell. And is absolutely normal but a more critical Flight phase, because on some Helicopters this Transition can be relative short and the Pilot needs a bunch of attention especialy on the Collective and the pedals.

The Wikipedia link Razor linked to you is more about Noise reduction overall to make Helicopters inflight less Noisy…The EC-155 is a good example on how Noisy Helicopters can be.
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Old 12-29-2018, 12:13 AM   #5
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Weird the DCS Gazelle doesn't have that transition
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Old 12-29-2018, 12:26 AM   #6
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Quote:
Originally Posted by DanielNL View Post
Weird the DCS Gazelle doesn't have that transition
It does it's just not as loud but it is still there.
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Old 12-29-2018, 12:29 AM   #7
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Hmmmm okay. I turned cockpit vibration to 0% now (default was 50%), now it should be fine. thanks.
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Old 12-29-2018, 01:01 AM   #8
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Great :-)

Don't start a thread about falling out of the sky as you slow and descend though - above the speed at which the vibrations occur you can descend as fast as you want (within reason), below that speed you're at risk of VRS and a quick exit from the game.
The shudder's a useful reminder...
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Old 12-29-2018, 01:08 AM   #9
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shudder always appears in Mi-8, it's inevitable (as stated on page 274). DCSKa-50 just doesn't have it that bad.
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Old 12-29-2018, 08:52 AM   #10
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Quote:
I turned cockpit vibration to 0% now
Shouldn't do that. Not realistic and you'll lose a useful cue for catching the vertical as well.
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