744lover
Topic Author
Posts: 169
Joined: Mon Nov 06, 2000 5:29 am

Creaking Sounds On 747-400 Nose Gear

Sun Mar 25, 2007 12:58 am

Hello everybody


During the last month I've been working in Argentina for my company. I've flown on LH 747-400 (D-ABVS) from GRU to EZE on Feb 25th and on D-ABVT from EZE to GRU on March 22nd.

Since I was at the Business class I was near the nose gear and I could hear, when the captain steared it, a creaking noise comming from it. I could hear it on both planes that I've flown, so I think that it was not a isolated problem in one aircraft only.

BTW I recorded the backtrack procedure at RWY 35 at EZE and you can hear that creaking sound in it.

http://www.youtube.com/watch?v=5Y_a4gjhnmM

and here you can see the takeoff: http://www.youtube.com/watch?v=NKnB-gBgrW0

So, what is this creaking sound and why is it produced???

Thanks and best regards!
GHN
 
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Jetlagged
Posts: 2562
Joined: Sun Jan 23, 2005 3:00 pm

RE: Creaking Sounds On 747-400 Nose Gear

Sun Mar 25, 2007 10:01 am

The "creaking" noises are vibrations in the hydraulic system which drives the nosewheel steering. It is normal, not a problem. These kind of vibrations occur especially when a servo valve hits an endstop, like when the nosewheel is at maximum deflection. It can also be caused by a resonant frequency in the system, or a servo valve slightly out of adjustment.

I'm talking very generally. A hydraulics expert would be able to provide much better information.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
nonfirm
Posts: 426
Joined: Mon Sep 12, 2005 3:04 pm

RE: Creaking Sounds On 747-400 Nose Gear

Sun Mar 25, 2007 4:32 pm

I am not sure about the 747 but in the 737 we get a moaning or popping noise from the nose gear and it comes from the trunnion bearings.It is deferable item per Boeing for up to 25 flt hrs (for the airline i work for) after you check the bearings.Then to repair the noise you need to jack the nose spray the bearings with dry lube and swing the gear. airplane 

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