Nitrogen Tyre Inflation
Thread Starter
Join Date: Apr 2007
Location: Sitting in a hotel waiting to go to work.
Age: 44
Posts: 19
Likes: 0
Received 0 Likes
on
0 Posts
Nitrogen Tyre Inflation
Hi, I have recently just started flying an aircraft with Nitrogen inflated tyres. Can anyone shed any light on the reason for using Nitrogen instead of compressed air for inflation?
Thought police antagonist
Join Date: Jul 2003
Location: Where I always have been...firmly in the real world
Posts: 1,371
Received 112 Likes
on
79 Posts
The use of nitrogen is primarily to reduce the risk of fire in an overheated tyre as it's an inert gas. Air contains oxygen and will therefore burn if the conditions for combustion occur.
Join Date: Sep 2001
Location: @Work
Age: 60
Posts: 39
Likes: 0
Received 0 Likes
on
0 Posts
It is like Krystal says, Primarily to decrease risk of fire because it is an inert gas. Maybe slightly better from a corrosion point of view. But I think that filling your average car with Nitrogen is a bit over the top. Another way to squeeze out a buck or two from the customer
Two main reasons 'dry nitrogen' is used instead of straight compressed air, firstly it doesn't conduct heat as well as air and secondly it has no water vapour in it.
Both an advantage when the brakes get really hot and the heat starts to conduct into the wheel/tyre assembly.
The heat soak takes longer and the lack of water vapour ensures that steam is not generated in the hot wheel causing a much increased pressure.
Peak brake temps in a an airliner after a high speed rejected take off can exceed 900degC.
Concerning filling your car tyres with nitrogen, pretty much a waste of money IMO, what's already in there is 78.8% nitrogen anyway and very few car drivers will ever have peak brake temps much over a couple of hundred degrees if that.
Last time I had the tryes replaced on my car the tyre tech asked,
'Dya want nitrogen in 'em mate?"
I said,
"No thanks, I already run an 80% nitrogen mix"
"Oh" says he and wanders off.
Regards,
BH.
Both an advantage when the brakes get really hot and the heat starts to conduct into the wheel/tyre assembly.
The heat soak takes longer and the lack of water vapour ensures that steam is not generated in the hot wheel causing a much increased pressure.
Peak brake temps in a an airliner after a high speed rejected take off can exceed 900degC.
Concerning filling your car tyres with nitrogen, pretty much a waste of money IMO, what's already in there is 78.8% nitrogen anyway and very few car drivers will ever have peak brake temps much over a couple of hundred degrees if that.
Last time I had the tryes replaced on my car the tyre tech asked,
'Dya want nitrogen in 'em mate?"
I said,
"No thanks, I already run an 80% nitrogen mix"
"Oh" says he and wanders off.
Regards,
BH.
Last edited by Bullethead; 8th Mar 2009 at 06:58.
Join Date: Jun 1997
Location: auckland, new zealand
Posts: 224
Likes: 0
Received 0 Likes
on
0 Posts
This is from an article I read a while ago (source unknown). It agrees with what I was taught as a boy, but I can claim no better authority than that.
"Nitrogen is used for a few reasons, first it is a inert gas. This means that it is a stable gas and non oxidizing. These things that are important for safety. As a non oxidizing gas, it is a fire retardant, and prevents corrizion of the rims. Second it that is has no water vapor. Water vapor can freeze at high altitudes making ice in the tire, or even worse, when landing, and the heat buildup, can cause steam which will result in a tire blow out. (Water when turned into steam, will expand over 1000x its original volume).
Third, is the ease of storage and cost. Nitrogen gas is relatively cheap compared to other inert gases, and can be stored in a metal tank for long periods of time with out any negative effects. This is the main reason N is used, even though there are many other types of inert gases.
Another reason, is that N maintains a more constant pressure 3 to 4 x longer because of the lack of oxygen and water vapor found in "shop air". ."
"Nitrogen is used for a few reasons, first it is a inert gas. This means that it is a stable gas and non oxidizing. These things that are important for safety. As a non oxidizing gas, it is a fire retardant, and prevents corrizion of the rims. Second it that is has no water vapor. Water vapor can freeze at high altitudes making ice in the tire, or even worse, when landing, and the heat buildup, can cause steam which will result in a tire blow out. (Water when turned into steam, will expand over 1000x its original volume).
Third, is the ease of storage and cost. Nitrogen gas is relatively cheap compared to other inert gases, and can be stored in a metal tank for long periods of time with out any negative effects. This is the main reason N is used, even though there are many other types of inert gases.
Another reason, is that N maintains a more constant pressure 3 to 4 x longer because of the lack of oxygen and water vapor found in "shop air". ."
Join Date: Jun 2005
Location: 20000 leagues under the sea
Posts: 147
Likes: 0
Received 0 Likes
on
0 Posts
I think the main purpose is to remove moisture, the AMM sates:
If nitrogen is not available, Source of Clean Dry Air, maximum moisture content that isequivalent to an atmospheric dew point of -208 F (-298 C).
but being an inert gas is valid in my point of view.
If nitrogen is not available, Source of Clean Dry Air, maximum moisture content that isequivalent to an atmospheric dew point of -208 F (-298 C).
but being an inert gas is valid in my point of view.
Guest
Posts: n/a
I recall being told many years ago when I learned to fly that it was also because nitrogen expanded less at altitude. Never really thought about it 'til now...and can't remember my physics from school. Was I being fed a line by an engineer with a sense of humour?
Join Date: Aug 2008
Location: Exmoor
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
One other reason for Nitrogen.
We were taught in the early 1960's (by the Royal Air Force) that during inflation pressure release of the tyre (tire) prior to disassembly of the wheel (Split or detachable rim) even if the schrader valve core had been removed, the rapid reduction in pressure could cause any moisture in the air within the tyre to freeze in the aperture of the valve causing a blockage that could lead to the false impression that the tyre was fully deflated with obvious danger of accident if the rim securing devices were released while pressure still was trapped.
From memory tyre pressures on the Handley Page 'Victor' main gear were in the region of 250 psi (around 16 bar?)
and the English Electric 'Lightning' mains 400-450 psi (30 bar?)
Always inflated for the first time in the workshop in a safety cage.
Exmek
We were taught in the early 1960's (by the Royal Air Force) that during inflation pressure release of the tyre (tire) prior to disassembly of the wheel (Split or detachable rim) even if the schrader valve core had been removed, the rapid reduction in pressure could cause any moisture in the air within the tyre to freeze in the aperture of the valve causing a blockage that could lead to the false impression that the tyre was fully deflated with obvious danger of accident if the rim securing devices were released while pressure still was trapped.
From memory tyre pressures on the Handley Page 'Victor' main gear were in the region of 250 psi (around 16 bar?)
and the English Electric 'Lightning' mains 400-450 psi (30 bar?)
Always inflated for the first time in the workshop in a safety cage.
Exmek
Join Date: Nov 2006
Location: SoCalif
Posts: 896
Likes: 0
Received 0 Likes
on
0 Posts
FAA Requires it in Part 121
and probably in Part 25 ops.
It was about 1987 that a Mexicana 727-200 arrived at Mexico City airport with squawk of dragging brake. Departing Capt took the plane without delay, had his wife aboard and kid on his lap to depart for KLAX and Disneyland. It was a full 178 SOB, at gross.
Brake was still dragging, so he powered back to help tug move the plane. MEX is 7400' elevation, with warm to hot temps. Normal initial climbout in 727-2 there is 500'/min until cleaned up, after rotating upon reaching the red lights at the last 1,000' of 13,000.
Pilot had retracted gear right after takeoff, of course. There was a catastrophic explosion before they reached cruise.
Cause was initially thought to be a bomb. Reportedly this was the Capt wife first flight since surviving a bomb in a 727 as FA some years prior.
NTSB determined that oxygen in the tire combined with volatile gases released from the very hot rubber made an explosive mixture, and only needed a spark.
--------
A similar fate befell a DC-8 on hajj in that same year.
-------
Yes, 100% nitrogen is better than air in even your car tires. Its larger molecules won't leak out as easily, so I'm told.
It was about 1987 that a Mexicana 727-200 arrived at Mexico City airport with squawk of dragging brake. Departing Capt took the plane without delay, had his wife aboard and kid on his lap to depart for KLAX and Disneyland. It was a full 178 SOB, at gross.
Brake was still dragging, so he powered back to help tug move the plane. MEX is 7400' elevation, with warm to hot temps. Normal initial climbout in 727-2 there is 500'/min until cleaned up, after rotating upon reaching the red lights at the last 1,000' of 13,000.
Pilot had retracted gear right after takeoff, of course. There was a catastrophic explosion before they reached cruise.
Cause was initially thought to be a bomb. Reportedly this was the Capt wife first flight since surviving a bomb in a 727 as FA some years prior.
NTSB determined that oxygen in the tire combined with volatile gases released from the very hot rubber made an explosive mixture, and only needed a spark.
--------
A similar fate befell a DC-8 on hajj in that same year.
-------
Yes, 100% nitrogen is better than air in even your car tires. Its larger molecules won't leak out as easily, so I'm told.
Join Date: Jan 2008
Location: France
Age: 59
Posts: 19
Likes: 0
Received 0 Likes
on
0 Posts
Nitrogen in Tyres
There are several reasons why nitrogen is used, most of which have already been mentioned in other posts
- It is 'dry' therefore expands less with changes in temperature - so as tyre heats up during taxi or during an RTO the change in tyre pressure is lower. This can also be important if operating to/from airfield with very different ambients temps.
- It's inert, so if after an RTO the fuse plugs in the wheels melt to release the pressure before the wheel explodes you are not releasing any oxygen onto already red hot brakes
- The nitrogen molecule is bigger than oxygen and hence the tyre will hold it's pressure better/longer thus reducing maintenance
- Nitrogen also does not attack/degrade the membrane on the inside of the rubber tyre - the rubber is porous and the membrane makes it airtight.
Using nitrogen in car tyres is a good thing - it means you can increase cold inflation pressures and still get the same optimum hot inflation pressures. It means that the car will use less fuel on short journeys when tyres are cold as the higher inflation pressure reduces rolling resistance and for those with sports cars it means the car will handle better until the tyres warm up. The smae can be acheived with 'dry' air if you can get it.
- It is 'dry' therefore expands less with changes in temperature - so as tyre heats up during taxi or during an RTO the change in tyre pressure is lower. This can also be important if operating to/from airfield with very different ambients temps.
- It's inert, so if after an RTO the fuse plugs in the wheels melt to release the pressure before the wheel explodes you are not releasing any oxygen onto already red hot brakes
- The nitrogen molecule is bigger than oxygen and hence the tyre will hold it's pressure better/longer thus reducing maintenance
- Nitrogen also does not attack/degrade the membrane on the inside of the rubber tyre - the rubber is porous and the membrane makes it airtight.
Using nitrogen in car tyres is a good thing - it means you can increase cold inflation pressures and still get the same optimum hot inflation pressures. It means that the car will use less fuel on short journeys when tyres are cold as the higher inflation pressure reduces rolling resistance and for those with sports cars it means the car will handle better until the tyres warm up. The smae can be acheived with 'dry' air if you can get it.
Join Date: Dec 2001
Location: Richmond Texas
Posts: 305
Likes: 0
Received 0 Likes
on
0 Posts
A couple of minor points...
Nitrogen molecules should be smaller than oxygen, MW=28 vs 32.
There ain't no such a thing as -298 C.
How do they get it so dry? It probably comes from air and unmixing the water vapour should be an expensive process.
After an excellent landing you can use the airplane again.
Nitrogen molecules should be smaller than oxygen, MW=28 vs 32.
There ain't no such a thing as -298 C.
How do they get it so dry? It probably comes from air and unmixing the water vapour should be an expensive process.
After an excellent landing you can use the airplane again.
Join Date: Nov 2006
Location: SoCalif
Posts: 896
Likes: 0
Received 0 Likes
on
0 Posts
I'm pretty sure I read it in Aviation Week & Space Technology, IGh. Mexicana started using nitrogen in the tires after that.
Did you find anything on the Hajj DC-8? It was possibly a Canadian carrier, and IIRC, they had either low tire or dragging brake, and no nitrogen available at the airport, so used air.
GB
Did you find anything on the Hajj DC-8? It was possibly a Canadian carrier, and IIRC, they had either low tire or dragging brake, and no nitrogen available at the airport, so used air.
GB
Join Date: Nov 2006
Location: SoCalif
Posts: 896
Likes: 0
Received 0 Likes
on
0 Posts
from wiki:
Flight 940 was operating its scheduled flight route Mexico City-Puerto Vallarta-Mazatlán-Los Angeles operated by Mexicana Airlines (Compañia Mexicana de Aviación).
On March 31, 1986, the flight departed from Mexico City utilizing a Boeing 727-264 registered as XA-MEM.
Shortly into the morning flight an over-heated tire, a part of the main landing gear unit, exploded within the gear bay. It exploded because it was filled with compressed air, rather than inert nitrogen. The explosion damaged the aircraft's hydraulic and electrical systems and caused a fire. Although the crew reported the problem and declared an emergency, the aircraft crashed near Maravatio, northwest of Mexico City.
The crash killed all 167 passengers and crew and remains the deadliest airline disaster in Mexican history and is the world's worst air disaster involving the Boeing 727.
GB
On March 31, 1986, the flight departed from Mexico City utilizing a Boeing 727-264 registered as XA-MEM.
Shortly into the morning flight an over-heated tire, a part of the main landing gear unit, exploded within the gear bay. It exploded because it was filled with compressed air, rather than inert nitrogen. The explosion damaged the aircraft's hydraulic and electrical systems and caused a fire. Although the crew reported the problem and declared an emergency, the aircraft crashed near Maravatio, northwest of Mexico City.
The crash killed all 167 passengers and crew and remains the deadliest airline disaster in Mexican history and is the world's worst air disaster involving the Boeing 727.
GB
The CAA (GR16) also require with effect from 1 April 1988, all braked wheels of retractable landing gear units on aeroplanes above 5700 kgs will be required to have tyres inflated with Nitrogen, or other suitable inert gas, and maintained such as to limit the Oxygen content of the compressed gases to not greater than 5% by volume.
http://www.caa.co.uk/docs/33/CAP747.PDF
http://www.caa.co.uk/docs/33/CAP747.PDF