himmat01
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Tyre Change In Airplanes?

Sun Jul 17, 2005 2:33 am

The other day, I was with a fellow a.netter, Nimish at BLR. We both were wondering after how many landings are aircraft tyres generally changed? Any aircraft engineers who could provide an answer.

Thanks in advance,

Himmat
An airplane might disappoint any pilot but it'll never surprise a good one.
 
air2gxs
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RE: Tyre Change In Airplanes?

Sun Jul 17, 2005 4:27 am

We don't change tyres, we change tires or more correctly wheel/tire assemblies.

Wheel assymeblies are changed on condition. When the wear reaches the AMM or the operator's limit, it is replaced. There are 3 general limits:
- wear limits
- pressure limits
- damage limits

A worn tire looks just like your car tire whenit gets worn. The tread disappears and the tire gets a real "old" look to it.

If a tire falls below a certain pressure (usually a percentage of the full rated pressure) it must be replaced. If it falls to another threshold (set by the manufacturer) its' mate must be changed.

Tires get damaged, just like anything else exposed to that kind of abuse. We primarlily look for sidewall damage and cord damage. The cord is the layer of steel/rubber that exists under the tread and reinforcing ply. YOu can see the cord if the tread is damaged. Exposed cord does not necesarily mean a replacement. Damaged cord usually does.

Wheel inspections are straight forward. Look for damage and missing tiebolts and/or nuts. Look at the bead area carefully. It's what gets the most stress.
 
OzLAME
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RE: Tyre Change In Airplanes?

Sun Jul 17, 2005 12:52 pm

Quoting Air2gxs (Reply 1):
We don't change tyres, we change tires or more correctly wheel/tire assemblies.

The proper English (i.e. everywhere but the USA) spelling is 'tyre'. Besides, after reading your post I don't think you can lay any claim to being the arbiter of correct spelling.

However, to get back to the thread, someone once told me that the average MLG tyre on a 747 only lasts about a dozen landings. Is this true? It does seem to be a very small number of landings.
Monty Python's Flying Circus has nothing to do with aviation, except perhaps for Management personnel.
 
320tech
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RE: Tyre Change In Airplanes?

Sun Jul 17, 2005 1:37 pm

The proper English (i.e. everywhere but the USA) spelling is 'tyre'.

Canadians also spell it "tire". In my experience, Dash-8 tires last about 350 landings, and A320 tires last maybe 1000 - but less sure about that. Someone who's actually worked line maintenance would have a better idea.

We change tires because of cuts just about as often as we change them for wear. Of course, usually by the time the tire gets cut badly enough to warrant removal, it's already pretty worn.
The primary function of the design engineer is to make things difficult for the manufacturer and impossible for the AME.
 
ArmitageShanks
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RE: Tyre Change In Airplanes?

Sun Jul 17, 2005 2:07 pm

Can you inflate an aircraft tire if it is low like you can a car tire, or do they come pre-filled?
 
242
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RE: Tyre Change In Airplanes?

Sun Jul 17, 2005 3:57 pm

Tires on airliners are changed on condition and don't have a set number of landings they are good for. Tread life depends on many factors, so it's difficult to pinpoint. Just for kicks, a co-worker of mine tracked the nose tire life on MD-88 aircraft, because it seemed we were changing quite a few... and removing that damn spray deflector makes the job take three times as long as it should. The result? 18 days on average.

One dozen landings for a 747 main? Maybe, seems a little short, but sometimes it only takes one botched landing to destroy a tire.

Tire/wheel assemblies do have valve stems, and must be inflated when they are first assembled. Tire pressure is checked daily and dry nitrigen is added when needed.
 
A/c train
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RE: Tyre Change In Airplanes?

Sun Jul 17, 2005 4:00 pm

Yes, you can inflate tyres. You use nitrogen and inflate the wheel to the correct pressure stated by the manufacture. this pressure can commonly be found on the leg of the wheel your inflating.
 
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HAWK21M
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RE: Tyre Change In Airplanes?

Sun Jul 17, 2005 5:22 pm

A2gxs has stated most points.

Quoting ArmitageShanks (Reply 4):
Can you inflate an aircraft tire if it is low like you can a car tire, or do they come pre-filled

Sure,its a part of Scheduled Mx to chk for Tyre pressure & Inflate with Nitrogen.

Quoting Himmat01 (Thread starter):
The other day, I was with a fellow a.netter, Nimish at BLR

Great.Looking fwd to hear what transpired.Good show.

We refer to it as Wheel assys not tyres.As the heavy commercial jets use Tubeless tyres.[Wheel assys are the Tyre & the Hub together].Both havbe their own Part & Serial nos.

Wheel Assy replacement depends on its use & Environment or landing surface it operates from.Taxiing Ability & speed too contribute to wear on the Tyre.

We change our B737 Wheel Assys every 180-200 landings on Average Minimum.The Nose wheels more frequently.

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
air2gxs
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RE: Tyre Change In Airplanes?

Sun Jul 17, 2005 8:00 pm

Quoting OzLAME (Reply 2):
However, to get back to the thread, someone once told me that the average MLG tyre on a 747 only lasts about a dozen landings. Is this true? It does seem to be a very small number of landings.

Just did a quick maintenance history search on one of our B747-200's. It looks like the mains (on this specific aircraft) are coming in at about 4-5 months between changes for wear. Nose tires are about 7-8 months between changes. Don't know how many cycles that works out too, but certainly more than a dozen.
 
UAL Bagsmasher
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Joined: Wed Sep 08, 1999 12:52 pm

RE: Tyre Change In Airplanes?

Sun Jul 17, 2005 9:31 pm

IIRC, on the CRJ-200, a tire up to 5% below minimum inflation pressure may be refilled to its proper inflation pressure. A tire 5%-10% below minimum inflation pressure can be refilled and a log entry must be made. A tire 10%-20% below minimum inflation pressure must be replaced. A tire 20% or more below minimum inflation pressure must be changed, along with its axle mate. The tires come with an inflation pressure range. On the MLG tires for the CRJ-200, the range is 175-183 psi. You would use the 175 psi number for your calculations. The range for the nose tires on our aircraft is 158-165 psi.

As a guesstimate on MLG tire life, I usually see them last an average of around a month or so. I'm not sure on the nose tires.
 
kaddyuk
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RE: Tyre Change In Airplanes?

Mon Jul 18, 2005 1:21 am

Quoting ArmitageShanks (Reply 4):
Can you inflate an aircraft tire if it is low like you can a car tire, or do they come pre-filled?

Yup, we use a inflator gauge just like on a car.

One of the most important things to remember about aircraft tyres is that they must be stored almost deflated. this is incase the tie bolts that hold the rim together shear, the wheel wont blow at 220psi, it will *only* go at 30psi.

You never install an inflated tyre and you never remove an inflated tyre, always deflate before removal and inflate only once installed and secured to the axle.

I think the tyres on a 744 are good for about 1500/2000 landings. depending on all the applicable factors such as speed, weight, surface conditions, braking distance etc etc...
Whoever said "laughter is the best medicine" never had Gonorrhea
 
air2gxs
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RE: Tyre Change In Airplanes?

Mon Jul 18, 2005 2:03 am

Quoting Kaddyuk (Reply 10):
One of the most important things to remember about aircraft tyres is that they must be stored almost deflated. this is incase the tie bolts that hold the rim together shear, the wheel wont blow at 220psi, it will *only* go at 30psi.

That's probably just your operator's procedure. We store, ship and install our tires inflated. Less chance of seperating the bead that way. We do deflate prior to removal in case the tie bolts broke while the wheel was in service.
 
kaddyuk
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RE: Tyre Change In Airplanes?

Mon Jul 18, 2005 2:58 am

They arent stored completly deflated, they have about 30-50 psi in there normally, to prevent any seperation as you mention. and stop tyre slippage.

It might be a difference between the FAA and CAA/EASA requirements i think other EASA operators follow similar procedures...
Whoever said "laughter is the best medicine" never had Gonorrhea
 
AvionicMech
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RE: Tyre Change In Airplanes?

Mon Jul 18, 2005 3:13 am

Here at BY we have all our wheel assemblies delivered at operational pressure. Also the inflation pressure is recorded on the Form 1 so that the pressure can be checked when it is about to be fitted to ensure that it has not lost pressure since it was made serviceable at the overhaul company. If the pressure is then more than 10% below the operating pressure it is rejected.
 
kaddyuk
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RE: Tyre Change In Airplanes?

Mon Jul 18, 2005 4:03 am

Hmmm... okay, i stand corrected. it must be an operator based requirement... :P

LoL!
Whoever said "laughter is the best medicine" never had Gonorrhea
 
MD11Engineer
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RE: Tyre Change In Airplanes?

Mon Jul 18, 2005 5:42 am

The used wheel assys usually go to a wheel and brake shop, where they are dismanteled, the components cleaned and inspected (often the rim, bearings and tie bolts will be subjected to non-destructive testing for cracks etc.). O-rings, tyre and valve core will be replaced. The wghole assembly gets then reassembled with new components and reinflated to the required stoage pressure.
Tyres of small aircraft will usually be replaced directly by the mechanics for a commercial airline it is faster just to change a whole wheel and let the tyre change be done by a specialist shop).

Jan
Je Suis Charlie et je suis Ahmet aussi
 
320tech
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RE: Tyre Change In Airplanes?

Mon Jul 18, 2005 5:48 am

In the air force, we followed strict requirements as to tire pressure for dismounted tires. I believe it was 25%, 20 psi on a Dash-8 tire. On the A320, though, tires are stored at full pressure. I assume this difference is for two reasons:

A320 tires don't hang around long enough to worry about;
the air force is stuck in 1952 and doesn't recognise that technology has changed.

A320 tires can be re-inflated if the tire pressure is found above a certain level - 190 psi, I think (normal pressure 210 - 220). If the pressure is below that, the tire is replaced. If the pressure is below 160 psi, both tires on that axle are replaced.

As far as my wild guess of 1,000 landings for an A320, it's based on an aircraft flying 3,000 to 4,000 hours a year, therefore about 1,200 - 1,500 cycles per year, with tires getting changed about every six to eight months. On this probably conservative estimate, an airline with 100 A320 aircraft will go through 600 to 800 tires a year. So, line maintenance engineers, am I way off?
The primary function of the design engineer is to make things difficult for the manufacturer and impossible for the AME.
 
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HAWK21M
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RE: Tyre Change In Airplanes?

Mon Jul 18, 2005 4:24 pm

Quoting Air2gxs (Reply 11):
That's probably just your operator's procedure. We store, ship and install our tires inflated

Out here Shipping by Air requires Deflation of the Wheel Assys.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
northseatiger
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RE: Tyre Change In Airplanes?

Mon Jul 18, 2005 7:11 pm

On our helicopters (AS332L/L2) the wheels are changed out at 1200 landings, the actual tyre is an "on-condition" item and is replaced as required, this may be after 1199 landings or 10 just depends if the crew have been landing with the brakes on again or not !!. These wheels are split flange type and the tyre used was developed for the Jaguar fighter plane the tyre is removed from the wheel using a jig which once the wheel is split forces it off the flange with a "bang". After 1200 landings the wheels are paint stripped and NDT'D as are the bolts, then re-assembled post painting, presuured checked then sent off for another 1200 landings or until the tyre needs replacing.

Regards NST
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