R44 odd noise

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with altitude
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R44 odd noise

Postby with altitude » Sat Apr 26 2014, 05:59

This is an odd one, for the R44 pilots or engineers etc....

We have an R44 Clipper II which has approx. 550 hours and it has been making this odd noise for most of its life - we have spoken to Robinson about it and they are not able to help... Maybe someone else is or has experienced the same thing?? We have 2-3 other R44 Clipper II's that we operate and never had this noise/issue...

The noise sounds similar to the seat in the R44 being open and then dropped shut. It has been doing it for most of its life and it will only do it once during the course of a flight of any length from 5 minutes to 2 hours, and if it happens again will only happen after it has landed and taken off again.

When this noise occurs there are no symptoms, no yaw, no rpm change and no manifold psi change, no loss of power, there is nothing that changes at all, some times at is worst it sounds like a shot gun shot out side the back right side of the helicopter. Where ever we are operating at different heights/load etc the same noises occurs. We have checked for any visual signs like a panel cracked or loose rivets. Could it be fuel coming back into the air filter? Could the M/R blade be giving of this noise? It is coming from the same spot each time just different loudness.

Any help would be much appreciated!!

:shock:
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iPilot
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Re: R44 odd noise

Postby iPilot » Sat Apr 26 2014, 06:11

Any idea where it's generating from? Might be something loose under one of the seats, also check the yoke flanges, I've seen that they can hit the induction fan cowl internally. All bolts on the sprag clutch ok and no fractures?
Anything under the mast cowl?

Could really be anything. Hope it doesn't cause an issue.
DoorsOff
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Re: R44 odd noise

Postby DoorsOff » Sat Apr 26 2014, 06:32

If you have or know someone with a gopro camera, i would mount it close to where the noise appears to be comming from and hit record!
whats the worst? you might see or hear something that could help.

DoorsOff :o
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Kiwieng
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Re: R44 odd noise

Postby Kiwieng » Sat Apr 26 2014, 06:40

Have the skids been off?, Its possible there is something rolling around in the skid tubes. Something hitting the inside of those tubes could send a decent noise right through the airframe.
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Mongrel Dog
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Re: R44 odd noise

Postby Mongrel Dog » Sat Apr 26 2014, 07:06

Could also be something unloading in the skids after the weight comes off them. Maybe where the cross tubes go into the elbows. Possibly a crack. Wouldn't hurt to remove them and have an NDI carried out on the assembly. You could have a good look at the fuselage mounts as well when it's in bits.
The Scarlett Harlot
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Re: R44 odd noise

Postby The Scarlett Harlot » Sat Apr 26 2014, 08:55

Even the aircraft itself is telling you that you shouldn't be flying it! Lol!
torque effect
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Re: R44 odd noise

Postby torque effect » Sat Apr 26 2014, 10:01

I flew an R44 Clipper II a few times which seemed to have something similar.. I think it was just one of the panels on the rhs expanding on climb out.. used to happen at different times on different days, although it happened regularly I never got used to it.. it always gave me a fright
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Freewheeling
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Re: R44 odd noise

Postby Freewheeling » Sat Apr 26 2014, 10:48

Is it air speed sensitive?
Air vent on the nose can slam shut and be quite scary!
harrisonheli
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Re: R44 odd noise

Postby harrisonheli » Sat Apr 26 2014, 11:30

Could be the flat portions of sheet metal that forms the rear firewall and transmission deck.
I reckon there is an area that is slightly deformed and pops in and out similar to the test button on a baby food lid.
When you land it resets and then at some point during the flight it pops back out.

Would still go over all the tube frame mounting points to check the bolt toques and any signs of fretting.
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Leethallee
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Re: R44 odd noise

Postby Leethallee » Sun Apr 27 2014, 01:34

Sounds like a panel might be "Oil Canning"

might be worth a few GoPro' mounted where you can see the airframe skins ?
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Always Out Of Balance
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Re: R44 odd noise

Postby Always Out Of Balance » Sun Apr 27 2014, 04:17

Does it happen when you go through a certain altitude, could it be a change in pressure that is causing a panel to pop out or change shape? Like when you pass through a certain height the door sounds like its going to fly open.

AoB
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hand in pants
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Re: R44 odd noise

Postby hand in pants » Sun Apr 27 2014, 22:35

Not someone small trying to get out from under a back seat.............................
Hand in Pants, I'm thinking, my god, that IS huge!!!!!!!!
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froginasock
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Re: R44 odd noise

Postby froginasock » Sun Apr 27 2014, 23:08

harrisonheli wrote:Could be the flat portions of sheet metal that forms the rear firewall and transmission deck.
I reckon there is an area that is slightly deformed and pops in and out similar to the test button on a baby food lid.
When you land it resets and then at some point during the flight it pops back out.

Would still go over all the tube frame mounting points to check the bolt toques and any signs of fretting.


I think HHeli might be on to it here ... try to get the machine a little out of balance on the deck (flat pitch) with some cyclic and pedal positions until you get the robbie shudder/shake and listen for the 'popping' sound of the transmission deck. It's worth going over all other areas mentioned in this thread (and any other engineering input) regardless. Things that 'pop' also fatigue.
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with altitude
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Re: R44 odd noise

Postby with altitude » Mon Apr 28 2014, 00:41

Thank you for the funny replies - gave me a Monday laugh!!!

I will however, take on the serious posts and check some of them out! - strangely enough I flew it for about 3 hours yesterday and did not hear it at all!! Maybe the little person under the seat escaped!!! 8)
Never take life seriously. Nobody gets out alive anyway.
MaccaM
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Re: R44 odd noise

Postby MaccaM » Mon Apr 28 2014, 04:31

Freewheeling wrote:Is it air speed sensitive?
Air vent on the nose can slam shut and be quite scary!


Also the vents on the doors. Happened all the time with the Raven 1 I used to fly. The difference in outside and inside air pressure would cause the door vents to slam shut, making a nose that does sound very similar to the seats being slammed shut. I knew what it was, but still scared the crap out of me each time it happened. Will only happen once in the flight, and if you are opening them up again while on the ground, your just setting it up to happen on the next one.

Macca

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