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what is that noise?



 
 
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  #21  
Old July 26th 19, 04:57 AM posted to rec.aviation.soaring
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Default what is that noise?

I've heard that in hundreds of videos, more often in two seaters. Watch a few Duo Discus vids, you'll see what it mean. I believe it's almost certainly the spar stubs rubbing.
  #22  
Old July 27th 19, 02:32 PM posted to rec.aviation.soaring
gregv
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Default what is that noise?

Le lundi 22 juillet 2019 12:39:11 UTC+2, gregv a Ă©critÂ*:
Hello, I fly a 1979 Nimbus 2 carbon, and since a few years I hear a cracking noise behind me. That noise occurs more often after a few hours of flight, maybe related to temperature change with altitude. You can hear the cracking noise in this video:

https://www.youtube.com/watch?v=pke-...ature=youtu.be

Did you already hear that noise? how do you think I can fix this ? do you think it is dangerous?

Thank you for help and advice


Ok so I checked carefully the glider on the ground and I seems I could reproduce the noise.

Lift Pins and bearings are ok, no rubbing clue on the spar neither on the fuselage. The noise is not related to outer wings.

When the airbrakes are open, there is no more noise... so it must be related to airbrakes... I can hear the noise coming from the airbrakes / flaps, and if I put my hand on them as they are closed and that I put the wing for and aft I can hear and feel the noise with my hand. When I inspect the airbrakes mechanism everything seems ok. Strange thing is that the noise is symetrical on both wings.
  #23  
Old July 27th 19, 04:15 PM posted to rec.aviation.soaring
Martin Gregorie[_6_]
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Default what is that noise?

On Sat, 27 Jul 2019 06:32:03 -0700, gregv wrote:

Ok so I checked carefully the glider on the ground and I seems I could
reproduce the noise.

Lift Pins and bearings are ok, no rubbing clue on the spar neither on
the fuselage. The noise is not related to outer wings.

When the airbrakes are open, there is no more noise... so it must be
related to airbrakes... I can hear the noise coming from the airbrakes /
flaps, and if I put my hand on them as they are closed and that I put
the wing for and aft I can hear and feel the noise with my hand. When I
inspect the airbrakes mechanism everything seems ok. Strange thing is
that the noise is symetrical on both wings.

If that was my glider (I'm in the UK) I'd being asking the inspector who
does my Annual Inspection to take a look at it. Doing that in the past
has both found problems I've missed and shown that things I asked him
about were non-problems.


--
Martin | martin at
Gregorie | gregorie dot org
  #24  
Old July 28th 19, 01:35 PM posted to rec.aviation.soaring
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Default what is that noise?

if I put my hand on them as they are closed and that I put
the wing for and aft I can hear and feel the noise with my hand. When I
inspect the airbrakes mechanism everything seems ok. Strange thing is


I'm reading this as you pull/push the wing tips for and aft and feel the noise in the airbrake system. If so, how much force, how much do the wing tips move and is there a spec limit for this in the poh or maint manual?
  #25  
Old July 30th 19, 05:00 AM posted to rec.aviation.soaring
Charlie Quebec
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Default what is that noise?

On my DG200 fore and aft play in the wings is eliminated by shimming the lift pins. If a shim has come loose, and dropped of it could cause such issues.
  #26  
Old July 30th 19, 01:53 PM posted to rec.aviation.soaring
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Default what is that noise?

What, if anything is supposed to hold the shims in place when the glider is in the unassembled state?

On Monday, July 29, 2019 at 11:00:28 PM UTC-5, Charlie Quebec wrote:
On my DG200 fore and aft play in the wings is eliminated by shimming the lift pins. If a shim has come loose, and dropped of it could cause such issues.


  #27  
Old July 30th 19, 02:52 PM posted to rec.aviation.soaring
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Default what is that noise?

On Tuesday, July 30, 2019 at 8:53:21 AM UTC-4, wrote:
What, if anything is supposed to hold the shims in place when the glider is in the unassembled state?

On Monday, July 29, 2019 at 11:00:28 PM UTC-5, Charlie Quebec wrote:
On my DG200 fore and aft play in the wings is eliminated by shimming the lift pins. If a shim has come loose, and dropped of it could cause such issues.


Gliders with removable lift pins have the shims under the shoulder of the pin.
UH
  #28  
Old July 31st 19, 05:05 PM posted to rec.aviation.soaring
John Wells[_2_]
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Default what is that noise?

My Mini Nimbus creaks on hot days -- more if it's been left out in the sun

before launch. It sounds like flexing plastic to me, and I've always put it

down to the canopy expanding/contracting a different amount to the fus. I
think it goes away eventually in flight (or at least, I tend to only notice
it at
first).

Your video sounds more like a banging noise, but it's hard to tell from the

video... it could be the same creaking perspex noise I hear.

J

At 13:52 30 July 2019, wrote:
On Tuesday, July 30, 2019 at 8:53:21 AM UTC-4,

wrote:
What, if anything is supposed to hold the shims in place when the

glider
is in the unassembled state?

On Monday, July 29, 2019 at 11:00:28 PM UTC-5, Charlie Quebec

wrote:
On my DG200 fore and aft play in the wings is eliminated by

shimming
the lift pins. If a shim has come loose, and dropped of it could cause

such
issues.

Gliders with removable lift pins have the shims under the shoulder of the
pin.
UH


  #29  
Old July 31st 19, 05:34 PM posted to rec.aviation.soaring
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Default what is that noise?

I agree with a earlier poster that I would look in the airducting system Sounds like a vent cover or something hard but loose in the airflow.
  #30  
Old August 1st 19, 02:51 PM posted to rec.aviation.soaring
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Default what is that noise?

The howling in the tail boom might be from air pressure coming in and it doesn’t have a escape.

You can try leaving the wing tape off at the trailing edge about one inch. It helped on my Lak.
W7
 




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