lehpron
Posts: 6846
Joined: Tue Jul 10, 2001 3:42 am

### Aircraft Tires

Are they filled with regular air or some cold gas to keep them from heating up when their used?

I've seen pix of bizjets that don't have main bogie doors, so do they burst in the pressure difference when the plane climbs?

When measuring pound-per-square-inch, how much of the tire is used for calculating?
The meaning of life is curiosity; we were put on this planet to explore opportunities.

Klaus
Posts: 20649
Joined: Wed Jul 11, 2001 7:41 am

### RE: Aircraft Tires

Any mechanics correct me where I´m wrong. But since none has answered yet, I´ll try:

Lehpron: Are they filled with regular air or some cold gas to keep them from heating up when their used?

The initial temperature of the gas isn´t relevant as it adapts to the environment´s temperature anyway.

As far as I know, some airlines are using nitrogen to fill their tyres because it has better long-term properties and is also better on temperature changes. (I don´t remember the details very well, here.)
Other than that, conditioned air would be used, as far as I know.

Lehpron: I've seen pix of bizjets that don't have main bogie doors, so do they burst in the pressure difference when the plane climbs?

No. The gear well doors are not airtight. They are only there for aerodynamic purposes.
Even if the plane would fly to outer space, the pressure difference would only be one athmosphere while the normal operating pressure of the tyres is several times that. (I might be wrong here, but I believe even the gear wells of the space shuttle are not pressurized.)

Lehpron: When measuring pound-per-square-inch, how much of the tire is used for calculating?

I´m metric, so I can´t tell for sure...
But the pressure within the tyre is distributed evenly over the entire inner surface. So the pressure would be measured through the valve as it´s done for a car.

Western727
Posts: 1428
Joined: Wed Jan 03, 2007 12:38 pm

### RE: Aircraft Tires

Several airliners don't have "bogie" doors. The Boeing 737, and Embrarer EMB-145 are two that immediatly come to mind.
Jack @ AUS

NKP S2
Posts: 1665
Joined: Mon Dec 20, 1999 3:16 am

### RE: Aircraft Tires

Tires are filled with nitrogen. 17 years in the business from corporate to widebodies, never used anything else but n2. Biggest reason is the lack of moisture as opposed to "shop air".Do not forget that while atmospheric pressure may be lower at altitude ( relative to the tires ), the temperature is much lower. Temperature, whether high or low has large effect on tire pressure. Most tire pressure limits are given fr an average 70F or so day.Whether pneumatic or hydraulics, a given pressure will be constant anywhere within the pressure vessel...be it a tire/wheel assy, 150 feet of hydrauic lines, or pneumatc ducting. You get the idea.

A330
Posts: 688
Joined: Wed May 19, 1999 12:31 am

### RE: Aircraft Tires

Ok,
There is a lot to say about tires, but I will try to write down some more basic things.

First of all, all Aircraft with a MTOMA (Max. T/O Mass Allowed) of more than 5700kg., must have tires filled with Nitrogen. Below this, the use of Air is allowed.
Most tires nowadays are of the tubeless design which have a sealing layer inside.
The tire pressure on Airliners is mostly around 200PSI.
If pressure in a tire gets too high, mostly due to an increase in temperature (rejected T/O, ...), the tires will deflate completely due to so called ''fusible plugs''. These plugs will prevent the tire to burst. The temp. where the plugs will work is mostly around 150deg. Celcius.
Most tires are of a ribbed tire tread pattern, but small planes used on soft fields also use diamond pattern treads!
The tires are measured for strength by their ''ply ratings'', which is an equivalent number about the strenght of the construction ( it used to be the number of layers of cotton between the rubber); the ''tire speed ratings'' which designate the max. speed to operate the tire (ground speed of course).

Remember, if approaching a hot tire, always approach from the front or rear, NEVER from the side, because this is the weakest part of the tire.

A330
Shiek!

Buff
Posts: 1066
Joined: Fri Mar 16, 2007 1:29 pm

### RE: Aircraft Tires

If I'm not mistaken, N2 is also non-flammable. "Air" would aid combustion in the event of a wheel/tire fire.

Best Regards,

Buff

PS I think there is material in the Archive on this subject.

rams777
Posts: 49
Joined: Thu Aug 02, 2001 12:40 am

### Egypt Air

3 Days ago i was on an Egypt Air Boeing747-300 and while the plane was taxing to the runway, the guy sitting next to me was talking on his mobile phone. Do you think the Pilots cared? obviously they knew it was happening but did nothing. This could have cause something to a larger scale.

Notar520AC
Posts: 1517
Joined: Sat Jul 21, 2001 6:53 am

### RE: Aircraft Tires

What does that have to do with tires?
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