Lexy
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MD-11 Nose Wheel

Tue Jul 15, 2008 4:53 am

I have seen some shots here on ANet of the nose wheel on the DC10/MD10/MD11 bending backwards with the weight of the aircraft when they are taxing and turning. But while I was out at the airport this morning here in Nashville I saw something I had never EVER seen before from a FedEx MD11. Check this picture out and tell me what's happening with the nose wheel.

LINK: http://www.flickr.com/photos/perspectivephotography/2670208918/

My thanks in advance!

Michael
Nashville, Tennessee KBNA
 
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jetmech
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RE: MD-11 Nose Wheel

Tue Jul 15, 2008 5:19 am

Quoting Lexy (Thread starter):

G'day Lexy,

Check out reply 13 in the following thread,

http://www.airliners.net/aviation-forums/tech_ops/read.main/231525/

It outlines why MD-11 landing gear legs are tilted back. If you imagine the geometry carefully, you can also picture why one of the wheels lifts during extreme nose wheel steering angle situations. The best way to do this, is imagine the extreme situation where the nose-leg is parallel to the ground. The phenomenon in the photo is due to the nose landing gear geometry only, and not due to flexing from weight.


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Photo © Shotaro Shimizu



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Photo © Massimiliano terzaghi
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Photo © Bob Groenendijk



Regards, JetMech

[Edited 2008-07-14 22:28:15]
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
dl757md
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RE: MD-11 Nose Wheel

Tue Jul 15, 2008 8:27 am

All Douglas civilian jets (not sure about the DC-8) do this and is as Jetmech said it's due to the geometry or angle of the the nose gear strut. It's actually helpful to mtc as you can change a nosewheel without a jack. Simply turn the nose wheel tiller in the direction opposite of the wheel you want to change and turn off hydraulics. The nose gear will remain turned and the wheel needing changing will remain off the ground.

DL757Md
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CosmicCruiser
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RE: MD-11 Nose Wheel

Tue Jul 15, 2008 12:58 pm



Quoting Lexy (Thread starter):
have seen some shots here on ANet of the nose wheel on the DC10/MD10/MD11 bending backwards with the weight of the aircraft when they are taxing and turning.

I don't think the MD-11 nose gear strut bends backwards. It better not. The tilt you illustrate with this pic is normal and well explained already.
 
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jetmech
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RE: MD-11 Nose Wheel

Tue Jul 15, 2008 1:22 pm



Quoting CosmicCruiser (Reply 3):
I don't think the MD-11 nose gear strut bends backwards. It better not.

If you want to see a nose gear bending, try to observe an A340 or A330 that gets turned onto bay with any sort of vigour. The amount of bend is simply amazing.

Regards, JetMech
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Lexy
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RE: MD-11 Nose Wheel

Tue Jul 15, 2008 3:08 pm

Many thanks to those that have explained this to me. When I saw this, I thought it was something unique. Thanks again everyone!!!
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jetmech
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RE: MD-11 Nose Wheel

Wed Jul 16, 2008 6:22 am



Quoting Dl757md (Reply 2):
Simply turn the nose wheel tiller in the direction opposite of the wheel you want to change and turn off hydraulics. The nose gear will remain turned and the wheel needing changing will remain off the ground.

What is the exact mechanism that keeps the nose gear in the displaced position as you change tyres? Is the geometry stable enough by itself, or does it rely on some sort of hydraulic lock being formed?

Regards, JetMech
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HAWK21M
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RE: MD-11 Nose Wheel

Wed Jul 16, 2008 7:30 am



Quoting JetMech (Reply 6):
What is the exact mechanism that keeps the nose gear in the displaced position as you change tyres? Is the geometry stable enough by itself, or does it rely on some sort of hydraulic lock being formed?

Exactly what I was thinking.What stops the NLG from moving while using the Torque wrench.
regds
MEL
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dl757md
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RE: MD-11 Nose Wheel

Wed Jul 16, 2008 8:45 am



Quoting JetMech (Reply 6):
What is the exact mechanism that keeps the nose gear in the displaced position as you change tyres? Is the geometry stable enough by itself, or does it rely on some sort of hydraulic lock being formed?



Quoting HAWK21M (Reply 7):
What stops the NLG from moving while using the Torque wrench.

It doesn't hydraulic lock but it doesn't return to center by itself either. You can easily turn the nose gear with a towbar for leverage with hydraulics off but your talking about a large lever arm created by the towbar and hence a lot of torque moving around the center axis of the nose strut. Changing a nose wheel doesn't require much torque (50ft-lbs initial torque on an MD-88) and most of that is in line with the center axis of the nose strut rather than around it so you're not going to turn the nose gear by simply changing a wheel assembly.

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113312
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RE: MD-11 Nose Wheel

Wed Jul 16, 2008 12:44 pm

Every Douglas jet has been designed that way. There is less tire scrub in maximum effort turns.
 
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jetmech
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RE: MD-11 Nose Wheel

Wed Jul 16, 2008 2:02 pm

Quoting Dl757md (Reply 8):

I see. Thanks for the info! I presume that the geometry of the MD-11 nose-leg is mild enough, that even if the axle did turn with a nose-wheel off, it wouldn't make contact with the ground?

Quoting 113312 (Reply 9):
There is less tire scrub in maximum effort turns.

Yep, I imagine that this would be another benefit of canting the nose-leg. I suppose the idea behind it is similar to the significant camber you see on the front wheels of some racing cars?



Regards, JetMech

[Edited 2008-07-16 07:06:13]
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
Viscount724
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RE: MD-11 Nose Wheel

Wed Jul 16, 2008 9:10 pm

Somewhat related question I've always been curious about -- why are the nosegear wheels on the Lockheed Constellation not parallel to each other? There is a larger gap between the top of the tires than the bottom. It's noticeable in the following photos when you enlarge them.


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Photo © Craig Murray
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Photo © Tom Turner


[Edited 2008-07-16 14:14:19]
 
dl757md
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RE: MD-11 Nose Wheel

Wed Jul 16, 2008 9:49 pm



Quoting JetMech (Reply 10):
I presume that the geometry of the MD-11 nose-leg is mild enough, that even if the axle did turn with a nose-wheel off, it wouldn't make contact with the ground?

That is correct.
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474218
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RE: MD-11 Nose Wheel

Wed Jul 16, 2008 11:16 pm



Quoting Lexy (Thread starter):
I have seen some shots here on ANet of the nose wheel on the DC10/MD10/MD11 bending backwards with the weight of the aircraft when they are taxing and turning.



Quoting CosmicCruiser (Reply 3):
I don't think the MD-11 nose gear strut bends backwards.



Quoting JetMech (Reply 4):
If you want to see a nose gear bending,

The DC-10/MD-10/MD-11 nose landing gear does not bend backwards and it does not bend under the weight of the airframe. When their nose landing gear is fully down and lock it does no reach a full 90 degrees like most aircraft. This picture clearly shows the down and locked position in the air with no weight on the gear.

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Photo © Andrew Hunt - AirTeamImages



If you look at the Constallation the nose landing gear when it is down and locked it is actually over 90 degrees.

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Photo © Ralf Manteufel

 
CosmicCruiser
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RE: MD-11 Nose Wheel

Wed Jul 16, 2008 11:31 pm



Quoting 474218 (Reply 13):
When their nose landing gear is fully down and lock it does no reach a full 90 degrees like most aircraft.

I'm going to have to call you on this one. I just checked my MD-11 CFM and it doesn't really say but I can bet it is more than 90 deg. I may call maint and see what they say but it "ain't" less than 90.
 
wingscrubber
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RE: MD-11 Nose Wheel

Thu Jul 17, 2008 2:06 am

That angle also helps reduce nosewheel shimmy, if it was angled the other way it would be inclined to caster like a shopping cart, usually this is only used on small GA aircraft which steer with differential braking alone.
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dl757md
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RE: MD-11 Nose Wheel

Thu Jul 17, 2008 2:09 am



Quoting CosmicCruiser (Reply 14):
I may call maint and see what they say but it "ain't" less than 90.

I think what 474218 meant is that the gear extends less than 90 deg from the longitudinal axis of the airplane. On the DC-10/MD-11 the nose gear strut extends down and back and never reaches full vertical. It may extend 90 deg from the stowed angle but again as 474218 implied it is not 90 deg from the longitudinal axis of the aircraft. The Connie nose strut on the other hand extends forward past vertical and therefor extends more than 90 deg.

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HAWK21M
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RE: MD-11 Nose Wheel

Thu Jul 17, 2008 3:29 am



Quoting Dl757md (Reply 8):
It doesn't hydraulic lock but it doesn't return to center by itself either. You can easily turn the nose gear with a towbar for leverage with hydraulics off but your talking about a large lever arm created by the towbar and hence a lot of torque moving around the center axis of the nose strut.

Thanks.But is the Wheel change without the Jack a company approved procedure on this type....or just an alternative.
regds
MEL
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dl757md
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RE: MD-11 Nose Wheel

Thu Jul 17, 2008 5:38 am



Quoting HAWK21M (Reply 17):
But is the Wheel change without the Jack a company approved procedure on this type....or just an alternative.
regds

C'mon Hawk you don't think I'd use an unapproved mtc. method do ya?  Wink
It is listed in the MD-88 and MD-90 AMM as an alternative method of lifting each nose wheel for wheel assy change.

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HAWK21M
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RE: MD-11 Nose Wheel

Thu Jul 17, 2008 6:28 am



Quoting Dl757md (Reply 18):
C'mon Hawk you don't think I'd use an unapproved mtc. method do ya?

Never ever  wink 

Quoting Dl757md (Reply 18):
It is listed in the MD-88 and MD-90 AMM as an alternative method of lifting each nose wheel for wheel assy change.

Interesting.

regds
MEL
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CosmicCruiser
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RE: MD-11 Nose Wheel

Thu Jul 17, 2008 12:55 pm



Quoting Dl757md (Reply 16):
think what 474218 meant is that the gear extends less than 90 deg from the longitudinal axis of the airplane

Yeah, I realized that after I hit the "post" button; he got me thinking wrong using the Connie as the example. I was about to post a correction.
 
ex52tech
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RE: MD-11 Nose Wheel

Sat Jul 19, 2008 8:35 pm



Quoting Dl757md (Reply 8):
It doesn't hydraulic lock but it doesn't return to center by itself either. You can easily turn the nose gear with a towbar for leverage with hydraulics off but your talking about a large lever arm created by the towbar and hence a lot of torque moving around the center axis of the nose strut.

I never trusted the steering bypass enough to leave the tow bar attached, not to mention the DC-10 MD-11 tow bar is one heavy tow bar, I don't think I could pick one of them up to swing the nose wheel.

I always wrapped the seat belt around the tiller with the hydraulics on to keep it in place.
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