Le lundi 22 juillet 2019 12:39:11 UTC+2, gregv a écritÂ*:
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.