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What Are Aircraft Tires Inflated With?  
User currently offlineCAP2008 From United States of America, joined May 2007, 255 posts, RR: 2
Posted (6 years 8 months 2 weeks 6 days 10 hours ago) and read 9766 times:

After watching the episode of Mythbusters where they were dealing with the weight of air, and replacing air with helium in certain objects to reduce weight, I wonder would inflating aircraft tires with helium, especially in a 747 or a 380 gain any significant weight advantage? I know that nitrogen is used to inflate tires in some race cars and now increasingly in passenger cars, because it does not expand or contract with temperature like air does, but what about helium?


The mother of the last KC-135 pilot has yet to be born.
21 replies: All unread, jump to last
 
User currently offlineAvt007 From Canada, joined Jul 2000, 2132 posts, RR: 5
Reply 1, posted (6 years 8 months 2 weeks 6 days 10 hours ago) and read 9766 times:

Nitrogen is used in aircraft. The tire pressure does change with temperature, because it isn't a pure nitrogen atmosphere inside the tire, it is mixed with the air that was in there before inflation was started. The difference hot to cold is only a few pounds, but noticeable.

User currently offlinePilotNTrng From United States of America, joined Dec 2003, 897 posts, RR: 3
Reply 2, posted (6 years 8 months 2 weeks 6 days 10 hours ago) and read 9766 times:

It is Nitrogen, I certainly am not a rocket scientist and I hated chemistry, but I can recall from my ramp rat days lookin at the tires, they called for nitrogen.


Booooo Lois, Yaaaa Beer!!!
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9661 posts, RR: 52
Reply 3, posted (6 years 8 months 2 weeks 6 days 10 hours ago) and read 9761 times:



Quoting CAP2008 (Thread starter):
I know that nitrogen is used to inflate tires in some race cars and now increasingly in passenger cars, because it does not expand or contract with temperature like air does, but what about helium?

Nitrogen is used because it does not contain water vapor. Air with a very low humidity will expand and contrat the same with temperature as nitrogen does. However, nitrogen is easier to use since it guarantes that no water will condense within the tire, which can have a significant effect on the pressure in the tire. Nitrogen does expand and contract though depending on temperature. The equation PV=nRT pretty much always works as long as there isn't a phase change ie. water condensing. You don't want water in the tire.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 4, posted (6 years 8 months 2 weeks 6 days 10 hours ago) and read 9750 times:



Quoting RoseFlyer (Reply 3):
You don't want water in the tire.

True, and to the OP, here's a perfect example of why...

http://aviation-safety.net/database/record.php?id=19860331-1


User currently offlineKELPkid From United States of America, joined Nov 2005, 6398 posts, RR: 3
Reply 5, posted (6 years 8 months 2 weeks 6 days 8 hours ago) and read 9692 times:

Nitrogen is also used because of its fire retarding properties...a fire will not burn in pure nitrogen  Smile


Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineTristarSteve From Sweden, joined Nov 2005, 4015 posts, RR: 34
Reply 6, posted (6 years 8 months 2 weeks 6 days 1 hour ago) and read 9612 times:



Quoting Avt007 (Reply 1):
The difference hot to cold is only a few pounds, but noticeable.

It can be a lot more than a few lbs, a tyre that is 180psi cold can be over 210psi after a braked landing. That is why we try and measure the tyre pressures as long as possible after landing.
I work in one of the colder airports on our companies network. We are forever inflating tyres that seemed to be correct at the last nightstop down in the Med, but are now too low when the OAT is below zero.
Last week I had a write up on a B777 that they had Tyre Pressure EICAS message in the cruise. On checking on the ground the pressures were OK, but at the lower end of the range. Sitting in the nose gear bay for 11 hours at M45deg , the pressure had dropped below the warning level. I inflated them to the top of the range and the message didn't reoccur.


User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 7, posted (6 years 8 months 2 weeks 5 days 20 hours ago) and read 9527 times:

Nitrogen is is used mainly since it is an Inert gas.
Air can be used too for inflation,but to a certain percentage & only for a small period of time.
regds
MEL



Think of the brighter side!
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 8, posted (6 years 8 months 2 weeks 5 days 19 hours ago) and read 9508 times:



Quoting CAP2008 (Thread starter):
After watching the episode of Mythbusters where they were dealing with the weight of air, and replacing air with helium in certain objects to reduce weight, I wonder would inflating aircraft tires with helium, especially in a 747 or a 380 gain any significant weight advantage?

The weight difference would be very small (on the order of ten kilograms per tire). However, you'd have an issue with greatly increased diffusion through the tire, so you'd have to be pressuring it back up more often, and I suspect helium costs a lot more than nitrogen.

Tom.


User currently offlineAvt007 From Canada, joined Jul 2000, 2132 posts, RR: 5
Reply 9, posted (6 years 8 months 2 weeks 5 days 18 hours ago) and read 9490 times:



Quoting TristarSteve (Reply 6):


Quoting Avt007 (Reply 1):
The difference hot to cold is only a few pounds, but noticeable.

It can be a lot more than a few lbs,

In my experience, maybe 5% would be the most I saw, changing a nominal 101 psi tire to 106, sitting on the gate.


User currently offlineIFixPlanes From Germany, joined Feb 2005, 239 posts, RR: 0
Reply 10, posted (6 years 8 months 2 weeks 5 days 17 hours ago) and read 9443 times:



Quoting HAWK21M (Reply 7):
... Air can be used too for inflation,but to a certain percentage & only for a small period of time. ...

AD 87-08-09 says:

Quote:
...
a. On braked wheels, install only tires that have been inflated with dry nitrogen or other gases shown to be inert such that the gas mixture does not exceed 5 percent oxygen by volume.

b. Tires on braked wheels may be serviced with air at remote locations where dry nitrogen is not available, provided that:

i. the oxygen content does not exceed 5 percent by volume; or

ii. within the next 15 hours time-in-service, the tire must be purged of air and inflated with dry nitrogen so that the oxygen does not exceed 5 percent by volume.

...




never tell an engineer he is wrong ;-)
User currently offlineCAP2008 From United States of America, joined May 2007, 255 posts, RR: 2
Reply 11, posted (6 years 8 months 2 weeks 5 days 1 hour ago) and read 9252 times:

Thanks for your responses guys.


The mother of the last KC-135 pilot has yet to be born.
User currently offlineKELPkid From United States of America, joined Nov 2005, 6398 posts, RR: 3
Reply 12, posted (6 years 8 months 2 weeks 4 days 14 hours ago) and read 9146 times:

Also, I forgot: yet another reason that pure nitrogen is used is to keep the rubber compounds in the tire from degrading prematurely...Oxygen is the primary culprit in weather checking on rubber  Wink


Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineEssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 13, posted (6 years 8 months 2 weeks 4 days 8 hours ago) and read 9094 times:



Quoting KELPkid (Reply 5):
Nitrogen is also used because of its fire retarding properties...a fire will not burn in pure nitrogen

Many pure gasses other than N are inert as well...


User currently offlineKELPkid From United States of America, joined Nov 2005, 6398 posts, RR: 3
Reply 14, posted (6 years 8 months 2 weeks 4 days 8 hours ago) and read 9087 times:



Quoting EssentialPowr (Reply 13):
Many pure gasses other than N are inert as well...

However, Nitrogen is the cheapest since it comprises 80% of the Earth's atmosphere.



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineRwessel From United States of America, joined Jan 2007, 2353 posts, RR: 2
Reply 15, posted (6 years 8 months 2 weeks 4 days 8 hours ago) and read 9075 times:
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Quoting EssentialPowr (Reply 13):
Many pure gasses other than N are inert as well...



Quoting KELPkid (Reply 14):
However, Nitrogen is the cheapest since it comprises 80% of the Earth's atmosphere.

Not only are almost all the other fairly non-reactive gasses* more expensive than N2, they're mostly all heavier as well.


*Gas at the required temperatures and pressures


User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 16, posted (6 years 8 months 2 weeks 4 days 4 hours ago) and read 9054 times:



Quoting KELPkid (Reply 14):

Quoting EssentialPowr (Reply 13):
Many pure gasses other than N are inert as well...

However, Nitrogen is the cheapest since it comprises 80% of the Earth's atmosphere.

This is Aviation.Weight is an Issue too.

regds
MEL



Think of the brighter side!
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 17, posted (6 years 8 months 2 weeks 3 days 18 hours ago) and read 9015 times:



Quoting HAWK21M (Reply 16):
Quoting KELPkid (Reply 14):

Quoting EssentialPowr (Reply 13):
Many pure gasses other than N are inert as well...

However, Nitrogen is the cheapest since it comprises 80% of the Earth's atmosphere.

This is Aviation.Weight is an Issue too.

True, but weight is an issue only to the extent that it goes to cost. If your choice is cheaper and heavier or more expensive and lighter, they'll go with cheaper. The trick is that you have to roll *all* the costs, not just acquisition, into your "cheap" and "expensive" calculations.

Tom.


User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 18, posted (6 years 8 months 2 weeks 3 days 17 hours ago) and read 9001 times:



Quoting Tdscanuck (Reply 17):
If your choice is cheaper and heavier or more expensive and lighter, they'll go with cheaper.

Which other gases than N2 are you referring to?
regds
MEL



Think of the brighter side!
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 19, posted (6 years 8 months 2 weeks 3 days 17 hours ago) and read 8992 times:



Quoting HAWK21M (Reply 18):
Quoting Tdscanuck (Reply 17):
If your choice is cheaper and heavier or more expensive and lighter, they'll go with cheaper.

Which other gases than N2 are you referring to?

I think this started back when helium was suggested. It's inert, like N2 (at the temperatures we're talking about), but lighter. But I suspect the weight improvement isn't enough to tolerate the other expense increases.

Tom.


User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 20, posted (6 years 8 months 2 weeks 3 days 5 hours ago) and read 8901 times:



Quoting Tdscanuck (Reply 19):
I think this started back when helium was suggested. It's inert, like N2 (at the temperatures we're talking about), but lighter. But I suspect the weight improvement isn't enough to tolerate the other expense increases

No,What I meant is....Which other Inert gas has been used in service practically apart from N2?
Im referring to non experimental basis.
regds
MEL



Think of the brighter side!
User currently offlineThrottleHold From South Africa, joined Jul 2006, 657 posts, RR: 1
Reply 21, posted (6 years 8 months 1 week 6 days 21 hours ago) and read 8715 times:



Quoting CAP2008 (Thread starter):
What Are Aircraft Tires Inflated With?

Management's ego.


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