mrstl
Posts: 353
Joined: Fri Sep 09, 2005 9:58 am

Question For AA MD80 Pilots

Wed Sep 28, 2005 12:37 pm

I apologize in advance if this has already been asked as I am fairly new to the board but it is a question I have been wanting ask and I was reminded of it on a flight yesterday . Upon take off on an MD80 from LAX-STL yesterday we experienced pretty severe vibrations and shuddering ( I tend to feel it more in the first class cabin). It seems to a novice like the plane is under extreme strain, is this a weight issue, simply a nose gear retraction deal, headwinds or something else. This does not happen on every flight as some takeoffs are vibration free. What is causing this?
 
2H4
Posts: 7960
Joined: Tue Oct 19, 2004 11:11 pm

RE: Question For AA MD80 Pilots

Wed Sep 28, 2005 2:07 pm



I'm certainly no MD80 pilot, nor did I stay at a Holiday Inn Express last night, but if the shuddering/vibrations occured shortly after leaving the ground, and dissipated somewhat gradually, I suspect it could be an unbalanced nosewheel spinning down.

Any more knowledgeable folks care to shed some light on this?




2H4

[Edited 2005-09-28 07:11:20]
Intentionally Left Blank
 
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Starlionblue
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Joined: Fri Feb 27, 2004 9:54 pm

RE: Question For AA MD80 Pilots

Wed Sep 28, 2005 8:46 pm

Having flown this plane a large number of times, and often in the front cabin, I would say 2H4 is correct. This happens often and always just around the time you hear the nosegear thunk into position in the well.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Goldenshield
Posts: 5005
Joined: Sun Jan 14, 2001 3:45 pm

RE: Question For AA MD80 Pilots

Wed Sep 28, 2005 10:38 pm

I concur. This will happen with any aircraft. I've noticed that the vibrations tend to stop once the wheels hit the snubbers. On small, non-retractable aircraft, the wheel vibrations will get lower in frequency until it stops as you climb out.
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MX757
Posts: 495
Joined: Wed Aug 17, 2005 5:38 pm

RE: Question For AA MD80 Pilots

Fri Sep 30, 2005 8:56 pm

I have flown the cockpit jump seat on MD-80's a few times. On take off I could feel and hear the NLG retract into the wheel well. It makes a the nose of the aircraft shudder a little but not enough to bother the pax in 1st class. The nose wheel spin brakes stop the tires spinning within a few seconds if they not to worn out. I have had pireps about this. I have flown in 1st class a few times on MD-80's also and I never felt a shudder from the nose gear coming up.

The fuselage extends quite a bit foreward from the wings and I think that makes it more susceptable to vibrations. I think an MD-80 pilot would be alot more helpful on this topic. I'm basing my opinion from a MX tech stand point.
Is it broke...? Yeah I'll fix it.
 
AAR90
Posts: 3140
Joined: Fri Jan 21, 2000 11:51 am

RE: Question For AA MD80 Pilots

Sat Oct 01, 2005 1:18 pm

From what you describe, best guess is imperfectly balanced nose wheels/tires. The MD's nose gear is not vertical and the tires get worn on the sides during tight turns causing the imbalance. Combine that with the relatively light airframe structure on that long fuselage and the tight nose wheel well compartment close to the cabin floor and the MD's reputation for nose gear vibration becomes apparent. There are other possibilities, but that is the most likely one.
*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
mandala499
Posts: 6458
Joined: Wed Aug 29, 2001 8:47 pm

RE: Question For AA MD80 Pilots

Sat Oct 01, 2005 7:52 pm

U can hear it in the front of an F100 too! Something about long t-tailed aircrafts I suppose...

Mandala499
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
LMP737
Posts: 4800
Joined: Wed May 08, 2002 4:06 pm

RE: Question For AA MD80 Pilots

Sun Oct 02, 2005 7:37 am

Quoting AAR90 (Reply 5):
The MD's nose gear is not vertical and the tires get worn on the sides during tight turns causing the imbalance. Combine that with the relatively light airframe structure on that long fuselage and the tight nose wheel well compartment close to the cabin floor and the MD's reputation for nose gear vibration becomes apparent.

Like AAR90 said the MD-80 in a tight turn has the wheel opposite of the turn come up off the ground and ride on the edge of the other one. Makes for some interesting handling characteristics in the rain or snow. The DC-10 does this as well.



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