TaromA380
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Posts: 275
Joined: Sun Sep 11, 2005 12:35 am

Why Not Accelerate Wheels On Landing?

Mon Sep 12, 2005 10:35 pm

Hello everybody,

When big airliners are landing, the gear wheels are immobile, thus the tires will get significant stress when touching the runway at ~150 knots, with such a mass pressure upon them. Everyone knows the dark rubber smoke which appears on each landing. The result is that the tires will need to be replaced after a few (or more) dozen landings.

Now, I ask you : why not putting a small electrical motor on the gear, to accelerate the wheels near the landing speed just before touching down, avoiding the abrasive contact shock thereby the degradation of the tires ?

I think it would be economically wise on long term. Just think about how many times an airliner needs to change the tires because of repeated landing shocks that reduce their size until the security limit. Moreover, tires would be much economical to acquire, not needing to be specially reinforced to support dozens highly abrasive landings.

I bet you'll come with the "weight" motive, but I think those electrical motors doesn't need to be big, the accelerating of the wheels would be in the air, without friction, so no need to huge power. How heavy two main devices plus one smaller device for the nose wheel would be ? 100 kg overall ? What is 100 kg besides the 560.000 kg of the A380 ? Not even talking about the tires weight save.

And remember, a big airliner like the A380 needs not less than 22 tires replacement !!

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FredT
Posts: 2166
Joined: Thu Feb 07, 2002 9:51 pm

RE: Why Not Accelerate Wheels On Landing?

Mon Sep 12, 2005 10:44 pm

This has been discussed numerous times and thoroughly beaten to death. Try searching the forum.
I thought I was doing good trying to avoid those airport hotels... and look at me now.
 
TedTAce
Posts: 9098
Joined: Sun Mar 27, 2005 12:31 am

RE: Why Not Accelerate Wheels On Landing?

Mon Sep 12, 2005 10:47 pm

I think it comes down to weight/complexity/cost issue. I'm POSITIVE that tire wear, when compared to additional fuel burn and complexity/cost of such a system, makes burning rubber a more appealing option.
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HAWK21M
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Joined: Fri Jan 05, 2001 10:05 pm

RE: Why Not Accelerate Wheels On Landing?

Mon Sep 12, 2005 10:47 pm

I may not win often, but I damn well never lose!!! ;)
 
SlamClick
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Joined: Sun Nov 23, 2003 7:09 am

RE: Why Not Accelerate Wheels On Landing?

Tue Sep 13, 2005 3:16 am

To reduce unsprung weight for cornering.

Oh, wait, that was the answer in a car forum.
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ZSOFN
Posts: 1379
Joined: Fri Jun 24, 2005 5:20 pm

RE: Why Not Accelerate Wheels On Landing?

Tue Sep 13, 2005 3:48 am

The main reason is actually due to the large gyroscopic effect the spinning tyres would have, making the aircraft very difficult to manouvre on final approach. I found this out from an SAA technician in JNB.
 
FredT
Posts: 2166
Joined: Thu Feb 07, 2002 9:51 pm

RE: Why Not Accelerate Wheels On Landing?

Tue Sep 13, 2005 4:04 am

Yes, especially significant compared to the low mass and low RPM of other rotating objects on the aircraft... such as the engine fans. Hangar tale, that one. The aircraft aren't hard to manouever after taking off, are they? Even before the gear is retracted/the wheels braked.

Most tire wear is during taxi anyway. There's just not much wear to be saved. Read the previous thread, you are reiterating things which were said there.
I thought I was doing good trying to avoid those airport hotels... and look at me now.
 
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ZSOFN
Posts: 1379
Joined: Fri Jun 24, 2005 5:20 pm

RE: Why Not Accelerate Wheels On Landing?

Tue Sep 13, 2005 5:37 am

Quoting FredT (Reply 6):
Yes, especially significant compared to the low mass and low RPM of other rotating objects on the aircraft... such as the engine fans

You might be right, but surely the orientation of the wheels is important, being side-on to direction of travel. I'll stand corrected if this is not the case though!
 
GRZ-AIR
Posts: 540
Joined: Sat Apr 14, 2001 3:02 am

RE: Why Not Accelerate Wheels On Landing?

Thu Sep 15, 2005 1:25 pm

Tire wear is good for economy... there are many ways how tires could be improved to withstand more ldgs and t/o's..but then fewer would be needed which is of no interest to the tire manufacturers.

The best solution I came accross once was a tire which had a little "hump" going around the outside of the tire...thus building up friction agains the air which resulted in accelerating the tire up to landing speed...tests showed that the lifetime of these tires were much higher than the ones used today..

The idea was however (for obvious above stated reasons) turned down by the large aircraft tire corporations..

Good idea though! And far better than any "electrical" motor and other crap..

cheers GRZ
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