Aircraft tyres: Air or nitrogen?
Joined: May 2004
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From: Balmullo,Scotland
The DC-8 nationair crash was nothing to do with what the tyre was inflated with it was caused by underinflation coupled with a very long taxi in hot conditions, the tyre overheated and caused it to explode on retraction resulting in a massive fire in the wheel well, further cause was the inability of the saudi controller to understand the gravity of the situation, the aircraft made it to approach but the damage was so great due to the fire when the gear was extended the aerodynamic forces caused the tail to break off resulting in the crash. I actually visited the crash site, very tragic indeed but a lesson to us all.
Joined: Oct 2000
Posts: 49
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From: Heathrow
Hi Guys
I had the old AWN 70 so heres what it says >>>>>>>
A fatal accident involving cabin decompression and fire has highlighted another mode of
tyre failure in flight where a tyre may fail explosively without any significant prior
degradation. A tyre inflated with air and subjected to excessive heating, possibly caused
by a dragging brake, can experience a chemical reaction resulting in release of volatile
gases. Such a chemical reaction in the presence of the oxygen in the contained air may
result in a tyre explosion in a landing gear bay and/or an in-flight fire since it appears that
the protection normally afforded by conventional pressure relief devices in the wheel
would be incapable of responding adequately to the rapid increases in temperature and gas
pressure associated with auto-ignition.
2.4 Laboratory material and tyre burst testing indicates that the risk of auto-ignition can be
reduced by using an inert gas for tyre inflation and servicing.
2.5 Other potential benefits may accrue from the use of Nitrogen as it will tend to reduce
wheel corrosion, tyre fatigue and the risk of fire when fusible plugs melt due to brake
overheating.
Sure the CAA wont mind its been moved now anyway.
I had the old AWN 70 so heres what it says >>>>>>>
A fatal accident involving cabin decompression and fire has highlighted another mode of
tyre failure in flight where a tyre may fail explosively without any significant prior
degradation. A tyre inflated with air and subjected to excessive heating, possibly caused
by a dragging brake, can experience a chemical reaction resulting in release of volatile
gases. Such a chemical reaction in the presence of the oxygen in the contained air may
result in a tyre explosion in a landing gear bay and/or an in-flight fire since it appears that
the protection normally afforded by conventional pressure relief devices in the wheel
would be incapable of responding adequately to the rapid increases in temperature and gas
pressure associated with auto-ignition.
2.4 Laboratory material and tyre burst testing indicates that the risk of auto-ignition can be
reduced by using an inert gas for tyre inflation and servicing.
2.5 Other potential benefits may accrue from the use of Nitrogen as it will tend to reduce
wheel corrosion, tyre fatigue and the risk of fire when fusible plugs melt due to brake
overheating.
Sure the CAA wont mind its been moved now anyway.
Joined: Sep 2006
Posts: 638
Likes: 18
From: South Oxfordshire
I may have misunderstood something here, please tell me if I have (I'm sure someone will).
Given that there is approx 21% oxygen in atmospheric air surrounding everything, how does inflating a tyre with N2 reduce the risk of fire caused by an overheating brake?
Given that there is approx 21% oxygen in atmospheric air surrounding everything, how does inflating a tyre with N2 reduce the risk of fire caused by an overheating brake?
Joined: Oct 2000
Posts: 49
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From: Heathrow
Blues&twos
Dont forget the air we are talking about is inside the tyre and at hundreds of degrees centigrade, it interacts with the tyre makeup and contributes to an explosive mix, the surrounding air is cool and safe
Dont forget the air we are talking about is inside the tyre and at hundreds of degrees centigrade, it interacts with the tyre makeup and contributes to an explosive mix, the surrounding air is cool and safe
Joined: Sep 2006
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From: South Oxfordshire
Spanners - I know N2 is inert, I'm not that daft! Mind you, you weren't to know that.....
Joined: Feb 2004
Posts: 64
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From: Cornwall
Air in Tyres
The Partial Pressure of Oxygen in a Tyre filled air is much greater. This causes the problem by making O2 a much improved oxidisation agent. They have a similar problem in dive recompression chambers.
Cheers
snips
Cheers
snips
Last edited by snips; 27th January 2007 at 22:39. Reason: Finger Problems
Joined: Feb 2007
Posts: 23
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From: USA
Dry N2
Most of the reasons are correct. We use DRY nitrogen
mainly because of the possible water contamination.
Corrosion and also on an overheated tire it will turn to steam
and react with the tire & tire pressure. Heat is the main cause
of premature tire failure.
mainly because of the possible water contamination.
Corrosion and also on an overheated tire it will turn to steam
and react with the tire & tire pressure. Heat is the main cause
of premature tire failure.
Joined: Jan 2004
Posts: 121
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From: Hemel Hempstead
I think this young engineer has misunderstood, the terms we use over our 2way radios and what is now a colloquial term for a nitrogen bottle and regulator trolley. When asking our maintenance workers to deliver a set of "air bottles" to a stand we mean nitrogen bottles. Nitrogen and Oxygen sound very similar on a crackly often breaking up radio. No confusion when asking for a set of oxygen or a set of air bottles.
Joined: Jan 2006
Posts: 454
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From: Georgia, USA
The Saudia incident had nothing to do with a tire (tyre). It was the bead on the rim that failed and holed the pressure deck over the main landing gear wheel well, the tire never lost pressure. The accident investigation revealed undersized beads on some of the L-1011 MLG wheels.
Addtionally, I was in the USAF from 1965 to 1969 and we used nitrogen to service tires at that time.
Addtionally, I was in the USAF from 1965 to 1969 and we used nitrogen to service tires at that time.
Joined: Dec 2001
Posts: 782
Likes: 2
From: UK.
This reminds me of a post I put in the spectator section some weeks back never did get the answer I was looking for maybe some of you guys could tell me, I drive a 44 ton truck it has 16 wheels inflated to 110psi, I remember when being close up to a 737 looking at the main bogies and thinking how on earth can just 4 main wheel take all the weight of a fully loaded 737 from what I gather this can be 75.000kgs, I know there a 2 wheels at the nose but I would think the mains carry most of the weight but how on earth can such a small number of wheels carry that weight without even bulging.
Nick.
Nick.
Joined: Dec 2004
Posts: 733
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From: Andalucia
Have a look at the references quoted in this thread posts 18 & 19 the definitive guides.
A/C tyres, while of similar construction to vehicle tyres, are incredibly rigid even when deflated. It needs a trained eye to spot a low pressure or deflated tyre visually, a gauge is normally required. When you throw in the typical inflation pressure of about 200psi (dependent on type) I think you find the answer.
A/C tyres, while of similar construction to vehicle tyres, are incredibly rigid even when deflated. It needs a trained eye to spot a low pressure or deflated tyre visually, a gauge is normally required. When you throw in the typical inflation pressure of about 200psi (dependent on type) I think you find the answer.
Joined: Mar 2007
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From: FL410
And in Iran...I don't know about western fleet , but I was working with an Airline for a short time and they all used air to fill Tu154Ms tires . Good to know that Tu154 tires are not Tubeless.
Last edited by mmrassi; 12th March 2007 at 18:21.
Tell me your Englihsh is limited please. 
Joined: Jun 2000
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From: Wherever I lay my hat
Magpienja, aircraft tyres run at a deflection of about 30% as opposed to automotive ones typically 10%, and are not designed to be continuously run. As they roll, the heat builds up. They do not reach an equilibrium temperature as ground tyres do. If you taxied an aircraft for long enough, its tyres would overheat and burst. The same is true for underinflated tyres, the rapid heat build-up kills them very quickly.
If you designed aircraft tyres to be capable of continuous running the weight would increase massively.
If you designed aircraft tyres to be capable of continuous running the weight would increase massively.
Joined: Mar 2007
Posts: 79
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From: FL410
Mr.Brown and other other guys !
Really sorry for incorrect writing . I was thinking of oxygen at the time of writting and that's why i wrote oxygen instead of air . really sorry , The airline name is Caspian and is a real safe one because the only airline that never had an accident though it has high number of flights and its planes are always in flight .
again sorry....
Really sorry for incorrect writing . I was thinking of oxygen at the time of writting and that's why i wrote oxygen instead of air . really sorry , The airline name is Caspian and is a real safe one because the only airline that never had an accident though it has high number of flights and its planes are always in flight .
again sorry....
Joined: Dec 2006
Posts: 14
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From: Scotland
Tyres inflated with air and subject to excessive heating due to braking action can experience a chemical reaction releasing volatile gases. In the presence of oxygen this can cause an explosion. AWN's require that tyres on aircraft over 5700kg with retractable landing gear should be inflated with a suitable inert gas with oxygen levels no greater than 5% by volume.....Such as nitrogen 
