cobra27
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Some Questions About Tires?

Thu Oct 18, 2007 7:14 am

How much do they cost? The 747 Michelin tire I think is around 4500 $?
How many landings do they last an average? 150?
Do they blowout regulary? Are they changed frequently? How do they fill them with nitrogen

Tanks
 
fr8mech
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RE: Some Questions About Tires?

Thu Oct 18, 2007 8:22 am

Quoting Cobra27 (Thread starter):
Do they blowout regulary?

No.

Quoting Cobra27 (Thread starter):
Are they changed frequently?

No. They are changed on condition.

Quoting Cobra27 (Thread starter):
How do they fill them with nitrogen

Much like your car or bike tire; through a fill valve in the wheel.
When seconds count...the police are minutes away.
 
b78710
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RE: Some Questions About Tires?

Thu Oct 18, 2007 8:50 am

Quoting Cobra27 (Thread starter):

they get changed when they get worn down to the core braid basically!

unless you find any individual deep cuts in the tyre that expose the braid, that will also warrant a wheel change!
 
Tristarsteve
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RE: Some Questions About Tires?

Thu Oct 18, 2007 9:21 am

Quoting Cobra27 (Thread starter):
How many landings do they last an average? 150?

I would say around 500 landings, about every 4 months for a short haul aircraft.
With modern radial ply tyres, about 99pc are changed because they are worn out, They are extremly resistant to cuts and other damage.
Older cross ply tyres are more susceptible to punctures but only a little, maybe 97pc are changed due worn out.

I have worked on the line on A320 since 1988, and have NEVER changed a tyre for damage.

When I worked on B737-400 with cross plies, I changed about one a year for a puncture (4 flights a day).
 
KELPkid
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RE: Some Questions About Tires?

Thu Oct 18, 2007 1:37 pm

Quoting B78710 (Reply 2):
they get changed when they get worn down to the core braid basically!

unless you find any individual deep cuts in the tyre that expose the braid, that will also warrant a wheel change!

Flat spots (in GA aircraft, at least  Wink ) can be caused by an over anxious pilot on the brakes, or even landing with the brakes engaged, and lead to premature tire replacement.
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
A10WARTHOG
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RE: Some Questions About Tires?

Thu Oct 18, 2007 2:19 pm

ERJ-145 we had to change them when there was less the 2/32 in of tread left or due to tire damage. Normally I think they last about 45 days for a main tire.
 
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Scooter01
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RE: Some Questions About Tires?

Thu Oct 18, 2007 5:30 pm

Sometimes I guess they just park them instead of changing the tires  duck 

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Scooter01
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roseflyer
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RE: Some Questions About Tires?

Thu Oct 18, 2007 5:51 pm

Most tires are not actually new on an airplane unlike cars. Tires can be retreaded many times. You get new tires out of the factory, but after that unless there is a problem with the tire, it will be reused.

Quoting TristarSteve (Reply 3):
When I worked on B737-400 with cross plies, I changed about one a year for a puncture (4 flights a day).

Finally the 737 will be moving to radial tires within the next year or so. It's been a long time in development to switch them, but hopefully it will help.
If you have never designed an airplane part before, let the real designers do the work!
 
474218
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RE: Some Questions About Tires?

Thu Oct 18, 2007 6:46 pm

Quoting Fr8Mech (Reply 1):
Much like your car or bike tire; through a fill valve in the wheel.

Its called a Schader Valve. The are also used on the landing gear for air charges.
 
A10WARTHOG
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RE: Some Questions About Tires?

Thu Oct 18, 2007 7:28 pm

Quoting 474218 (Reply 8):
Its called a Schader Valve. The are also used on the landing gear for air charges.

I have only see schader valves on struts and hyd. accumulators. All the valve stems on the tires I have serviced from a ERJ-145 to a 747 are just like a valve stem on a car or truck tire.
 
KELPkid
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RE: Some Questions About Tires?

Thu Oct 18, 2007 7:38 pm

Quoting 474218 (Reply 8):
Its called a Schader Valve. The are also used on the landing gear for air charges.

I remember one time, when stranded at a remote airfield (due to a nose strut that had deflated on the ramp overnight) in New Mexico, trying to inflate the nose strut in a Cessna 172 with a nitrogen bottle (note: I'm not a mechanic  Wink ). Well, I ended up getting sprayed with pink, oily-smelling goo  Sad So I ran into town from the airport, and got ahold of the plane's mechanic (via payphone) back at the home base who told me "Have someone hold the tail down next time, you idiot!"  Embarrassment BTW, it's just a standard Schrader valve on top of the nose strut...
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474218
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RE: Some Questions About Tires?

Thu Oct 18, 2007 8:44 pm

Quoting A10WARTHOG (Reply 9):
All the valve stems on the tires I have serviced from a ERJ-145 to a 747 are just like a valve stem on a car or truck tire.

The valve stem used on car and truck wheels is a Schrader Valve, just like the one used on aircraft tries and landing gear struts. While the aircraft my hold a little more pressure than the ones on your car, they share the same basic design. I use aircraft Schrader Valve caps (the yellow ones) on my car.
 
b78710
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RE: Some Questions About Tires?

Thu Oct 18, 2007 9:09 pm

Quoting 474218 (Reply 11):

i've always known a scraeder valve to be the type used to charge accumulators!

wind on the fitting and air line, open the valve, charge to required pressure, close the valve and remove the adaptor and hose!

always release the pressure before removing the hose though  Wink i know someone who learnt that the hard way
 
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Scooter01
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RE: Some Questions About Tires?

Thu Oct 18, 2007 9:58 pm

Quoting 474218 (Reply 8):
Its called a Schrader Valve. The are also used on the landing gear for air charges.

You can also see them integrated in the Boston-valve for inflated water-sport articles, like a Le Tube for instance, for easier filling at a gas-station.....

Scooter01
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fr8mech
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RE: Some Questions About Tires?

Fri Oct 19, 2007 2:39 am

The tire servicing valve is not a Schraeder valve, it is a valve with a removable core. In order to service the tire, you just apply the service chuck with enough pressure to unseat the core.

A Schraeder valve has a 3/4" jam nut on it which allows the user to open or close the valve as required to service.

The inflation valve may be based on a design by Schraeder, but is not what is commonly called a Schraeder valve, at least not in my 20 years in maintenance.

Some B747 aircraft I've been exposed to had larger diameter valve stems, but functioned the same.

But the caps are interchangeable.

I know, anal, but this industry is getting tough enough without us losing our language and terminology.
When seconds count...the police are minutes away.
 
bok269
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RE: Some Questions About Tires?

Fri Oct 19, 2007 3:08 am

QUick question: what is the typical PSI of an aircraft tire?
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tdscanuck
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RE: Some Questions About Tires?

Fri Oct 19, 2007 4:42 am

Quoting Cobra27 (Thread starter):
How much do they cost? The 747 Michelin tire I think is around 4500 $?

When the did the 777 RTO test they ruined all 12 tires and I think they said it cost about $250000...that works out to about $20000/tire.

Quoting Bok269 (Reply 15):
QUick question: what is the typical PSI of an aircraft tire?

A 737 is anywhere from 120 to 205 psi (cold), depending on conditions.

Tom.
 
b78710
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RE: Some Questions About Tires?

Fri Oct 19, 2007 9:51 am

Quoting Bok269 (Reply 15):
QUick question: what is the typical PSI of an aircraft tire?

744 main gear 200-205 psi nose wheels 175-180 IIRC
 
roseflyer
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RE: Some Questions About Tires?

Fri Oct 19, 2007 12:14 pm

Quoting Tdscanuck (Reply 16):
When the did the 777 RTO test they ruined all 12 tires and I think they said it cost about $250000...that works out to about $20000/tire.

Did that cost include new wheels and brakes? Everything caught fire in the test.

Interesting fact:
On all Boeing planes like the 737 and 777, the landing gear is the second most expensive part on the airplane that comes from a supplier.
If you have never designed an airplane part before, let the real designers do the work!
 
AirframeAS
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RE: Some Questions About Tires?

Fri Oct 19, 2007 12:24 pm

Quoting RoseFlyer (Reply 7):
Tires can be retreaded many times.

Ah ah! Hold on sec on that....thats not necessarly true. Certain aircraft tires can only be retreaded a certain amount of times. It all depends on the tire manufacturer and the aircraft type.
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Tristarsteve
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RE: Some Questions About Tires?

Fri Oct 19, 2007 12:51 pm

Quoting AirframeAS (Reply 19):
Ah ah! Hold on sec on that....thats not necessarly true. Certain aircraft tires can only be retreaded a certain amount of times. It all depends on the tire manufacturer and the aircraft type.

Yes allowable retreads on airline tyres are from 0 to about 10 times before the tyre is scrapped.
 
b78710
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RE: Some Questions About Tires?

Fri Oct 19, 2007 1:15 pm

Quoting TristarSteve (Reply 20):

does the tread depth change each time? or will the tenth tread be as deep as the first?

not been in the game long, but all the wheels ive changed, i think the new ones have always been brand new, certainly had that "new" look to them anyway, you know you get those little strands of rubberon the surface?
 
Tristarsteve
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RE: Some Questions About Tires?

Fri Oct 19, 2007 9:56 pm

Quoting B78710 (Reply 21):
does the tread depth change each time? or will the tenth tread be as deep as the first?

No it is the same.

Quoting B78710 (Reply 21):
i think the new ones have always been brand new, certainly had that "new" look to them anyway, you know you get those little strands of rubberon the surface?

Retreaded tyres look brand new. We are not talking about regrooved tyres here. The whole cap is new. The only way to tell if a tyre is retreaded is to look at the sidewall. You can see the original tyre, and the retread, and the join. Sometimes the retread is a different manufacturer from the original.
By the way the shelf life of a retreaded tyre is 10 years from date of original tyre manufacture. Might not seem significant but on a line station we sometimes send tyres back because they are time expired!!
 
tdscanuck
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RE: Some Questions About Tires?

Fri Oct 19, 2007 10:34 pm

Quoting RoseFlyer (Reply 18):
Quoting Tdscanuck (Reply 16):
When the did the 777 RTO test they ruined all 12 tires and I think they said it cost about $250000...that works out to about $20000/tire.

Did that cost include new wheels and brakes? Everything caught fire in the test.

That's a darn good question and I don't know the answer. They certainly would have had to replace the brakes and at least overhaul the wheels (plus, obviously, new tires).

Tom.
 
AirframeAS
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RE: Some Questions About Tires?

Fri Oct 19, 2007 11:58 pm

Quoting TristarSteve (Reply 22):
The only way to tell if a tyre is retreaded is to look at the sidewall. You can see the original tyre, and the retread, and the join.

It also indicates, for example, the tire has been retread 5 times after the manufacturer retreaded it.
A Safe Flight Begins With Quality Maintenance On The Ground.
 
jetstar
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RE: Some Questions About Tires?

Sat Oct 20, 2007 12:53 am

On the Lockheed JetStar, tire pressures were 205 psi, cold, mains and nose and dry nitrogen was used to inflate the tires. This pressure was to high to use an air chuck, we had a combination air gauge and valve unit, first I hand tightened the air valve end on the valve stem, then used a wrench and tightened the valve end down, then I screwed in the valve stem which opened the valve core and showed the tire pressure. If air was needed there was a fitting on the gauge line that I attached the nitrogen line to, then making sure the nitrogen regulator was turned totally off, I would open the main valve on the bottle, then using the nitrogen regulator I would add nitrogen to the tire until we got the desired tire pressure.

I spent my aviation career in corporate aviation and the use of recapped tires was almost nonexistent, I only knew of one flight department that used recapped tires. Corporate flight departments, basically the rich kids on the block would always buy new tires and just discard the run out tires.

On the JetStar, Lockheed stated in an official JetStar maintenance publication called an OMR (Operators Maintenance Report) that recapped tires were not approved. Recapped tires are somewhat larger than new tires and in most corporate jets, tire clearance in the wheel wells was very tight and there was a risk of a tire hanging up in the wheel well and this is why Lockheed did not approve recapped tires. I know of a Beech Baron that had recapped tires and this problem caused the landing gear to bind up and prevented the landing gear from extending and they had to land gear up.

Tire life was almost totally dependant on the pilots, normally we would get about 150 to 180 landings on a main tires, but if they were heavy on the brakes this shortened the life. We were allowed to run them down to the first layer of cord called a barrier cord was totally exposed, but to the uninformed like the CEO of the company this looked bad so almost all corporations would change the tire as soon as the first sign of cord was seen and that was when I changed the tire unless there was a cut in the tire into the cord.

The worst abuse was when they used maximum braking in the rain and the tire hit a small puddle of water, before the anti skid could release the brake pressure, the tire would start to lock up and start to hydroplane, then when the tire hit just the wet pavement the locked up tire would drag along the runway until the anti skid released the pressure. This would shave down the bottom edge and sometimes so badly that I would have to change the tire.

I always told our pilots in wet conditions to use all the runway that our taxes paid for, but of course they felt that the brakes were there for them to use to make the first turnoff so our tire and brake costs were high. And also they didn’t have to the change tires and brakes, that was my job and they considered it job security for me.

I knew of one Jetstar operator whose Chief Pilot ordered the pilots to always let the airplane roll out to the end of the runway and to use minimal brakes and thrust reverse, they averaged over 250 landings on their main tires and over 1200 landings on the brakes where we would get between 500 to 700 landings.
 
474218
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RE: Some Questions About Tires?

Sat Oct 20, 2007 1:09 am

Quoting TristarSteve (Reply 22):
Retreaded tyres look brand new. We are not talking about regrooved tyres here. The whole cap is new. The only way to tell if a tyre is retreaded is to look at the sidewall. You can see the original tyre, and the retread, and the join. Sometimes the retread is a different manufacturer from the original.

The number of times the tire will be stamped on the side with the Letter R and a number, such as R12.
 
AirframeAS
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RE: Some Questions About Tires?

Sat Oct 20, 2007 1:30 am

Quoting 474218 (Reply 26):
The number of times the tire will be stamped on the side with the Letter R and a number, such as R12.

Yeah, thats what I said....

Quoting AirframeAS (Reply 24):
It also indicates, for example, the tire has been retread 5 times after the manufacturer retreaded it.
A Safe Flight Begins With Quality Maintenance On The Ground.
 
lrdc9
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RE: Some Questions About Tires?

Sat Oct 20, 2007 2:05 am

Quoting Jetstar (Reply 25):
dry nitrogen was used to inflate the tires.

Why do they use nitrogen for a/c tires?
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2H4
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RE: Some Questions About Tires?

Sat Oct 20, 2007 2:44 am

Quoting Bok269 (Reply 15):
QUick question: what is the typical PSI of an aircraft tire?

The nose tire on an F-16 takes 300psi.

Quoting Lrdc9 (Reply 28):
Why do they use nitrogen for a/c tires?

Here you go

2H4

Intentionally Left Blank
 
tdscanuck
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RE: Some Questions About Tires?

Sat Oct 20, 2007 2:48 am

Quoting Lrdc9 (Reply 28):

Why do they use nitrogen for a/c tires?

It helps prevent oxidation on the inside of the tire, but the biggest reason is flammability. A tire can get very hot while taxiing, so hot that the rubber will off-gas volatile compounds. If you combine these with hot oxygen inside the tire you can end up with an explosive mixture above it's autoignition temperature and...boom. Supposedly, this used to happen from time to time on heavily loaded 707-era jets.

From a purely practical point of view, you need to have high pressure nitrogen around for servicing the shock struts anyway, so it's convenient to use the same gas for tires too.

Tom.
 
cobra27
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RE: Some Questions About Tires?

Sat Oct 20, 2007 7:39 am

Some where on the web is the PDF from Michelin with some ingo about their aviation tires
 
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HAWK21M
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RE: Some Questions About Tires?

Sat Oct 20, 2007 8:04 am

B752 150psi Nose Wheel & 180-186psi Mainwheel approx depending on Wheel Temperature.

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
ha763
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RE: Some Questions About Tires?

Sat Oct 20, 2007 8:44 am

Quoting Cobra27 (Thread starter):
How much do they cost? The 747 Michelin tire I think is around 4500 $?

I just had to clear a 747 tire assembly through Customs today. The invoice value was over $15,000. A little over $1400 for the tire (foreign made) and a little over $11,000 for the hub (USA made). Maintenance also brought over a used tire assembly to ship back and showed an invoice value around $10,800.
 
b78710
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RE: Some Questions About Tires?

Sat Oct 20, 2007 8:58 am

Quoting TristarSteve (Reply 22):

ahhh ok, i assumed it was just the actual tread was recut

will have to look out for that! thanks!
 
nema
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RE: Some Questions About Tires?

Sat Oct 20, 2007 1:40 pm

Quoting Cobra27 (Thread starter):
Do they blowout regulary?

Ive always wondered this, it has been a thought over time that ive had especially where there are only two tyres per strut like on the 737 or A319 as opposed to the four tyres per strut on a 767 for example. Get a puncture on the latter and youve got three left on that strut, seems better than just one doesnt it?
There isnt really a dark side to the moon, as a matter of fact its all dark!
 
jetstar
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RE: Some Questions About Tires?

Sat Oct 20, 2007 4:06 pm

Quoting NEMA (Reply 35):
Ive always wondered this, it has been a thought over time that ive had especially where there are only two tyres per strut like on the 737 or A319 as opposed to the four tyres per strut on a 767 for example. Get a puncture on the latter and youve got three left on that strut, seems better than just one doesnt it?

For certification purposes, any airplane that has a 2 wheel main landing gear, each tire must be able to support the aircraft at the maximum weight in case the other tire fails during takeoff or landing. Also the landing gear assembly must support the weight of the aircraft on that one tire during takeoff and landing.
 
MD11Engineer
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RE: Some Questions About Tires?

Sat Oct 20, 2007 4:56 pm

Quoting B78710 (Reply 34):
Quoting TristarSteve (Reply 22):

ahhh ok, i assumed it was just the actual tread was recut

will have to look out for that! thanks!

On recapping the tire will be ground down on a kind of lathe to just below the thread reenfocement fabric layers. Then a new cap with grooves will be vulcanised on.


BTW, the tyre valves are being made by Schrader as well.

Jan
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VAAengineer
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RE: Some Questions About Tires?

Sun Oct 21, 2007 2:48 am

VS 747 wheel is 15000USD
VS A346 wheel is 30000USD
God's Gift To Aviation
 
2H4
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RE: Some Questions About Tires?

Sun Oct 21, 2007 2:55 am

Quoting VAAengineer (Reply 38):
VS 747 wheel is 15000USD
VS A346 wheel is 30000USD

Do any technical factors account for the large price difference, or is it simply a matter of Airbus charging more for essentially the same thing?

2H4

Intentionally Left Blank
 
tdscanuck
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RE: Some Questions About Tires?

Sun Oct 21, 2007 3:59 am

Quoting 2H4 (Reply 39):
Quoting VAAengineer (Reply 38):
VS 747 wheel is 15000USD
VS A346 wheel is 30000USD

Do any technical factors account for the large price difference, or is it simply a matter of Airbus charging more for essentially the same thing?

I would guess that economies of scale enter in there...there are a whole lot more 747 tires in the world than A346 tires.

Tom.
 
2H4
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RE: Some Questions About Tires?

Sun Oct 21, 2007 4:30 am

Quoting Tdscanuck (Reply 40):
I would guess that economies of scale enter in there...there are a whole lot more 747 tires in the world than A346 tires.

If that's the case, I wonder why Airbus was unable to utilize a more standardized wheel...I wonder what might be specialized and/or unique about the A346 wheels...

2H4

Intentionally Left Blank
 
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jetmech
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RE: Some Questions About Tires?

Sun Oct 21, 2007 4:38 am

Quoting Tdscanuck (Reply 40):
I would guess that economies of scale enter in there...there are a whole lot more 747 tires in the world than A346 tires.



Quoting 2H4 (Reply 41):
If that's the case, I wonder why Airbus was unable to utilize a more standardized wheel...I wonder what might be specialized and/or unique about the A346 wheels...

It may also be the fact that an A330 / A340 main wheel assembly is physically much larger that a 747 wheel assembly.

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
WingedMigrator
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RE: Some Questions About Tires?

Sun Oct 21, 2007 5:30 am

Quoting Tdscanuck (Reply 40):
I would guess that economies of scale enter in there...there are a whole lot more 747 tires in the world than A346 tires.

And every time a 747 is scrapped, another 16 wheel rims arrive on the market? Even $15K sounds like more than the scrap value of the aluminum.

Another possible factor: the A346 wheels are significantly more highly loaded than the 744 wheels. (roughly 32 metric tons vs. 25 metric tons)
 
Lemurs
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RE: Some Questions About Tires?

Sun Oct 21, 2007 7:12 am

Quoting WingedMigrator (Reply 43):
Another possible factor: the A346 wheels are significantly more highly loaded than the 744 wheels. (roughly 32 metric tons vs. 25 metric tons)

I was thinking the same thing...the engineering and tolerances on the A346 wheels are probably tighter than the 747 due to their different operational demands. It's a non-trivial thing to create those things and make them safe after all...the MTOW RTO video for the A346 prototype proves that out!
There are 10 kinds of people in the world; those who understand binary, and those that don't.
 
b78710
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RE: Some Questions About Tires?

Sun Oct 21, 2007 1:09 pm

Quoting Lemurs (Reply 44):

alos quite a bit bigger!
 
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readytotaxi
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RE: Some Questions About Tires?

Sun Oct 21, 2007 5:11 pm

Quoting KELPkid (Reply 4):

Gosh, does a modern aircraft allow you to land with the parking brake on ???
you don't get a second chance to make a first impression!
 
Tristarsteve
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RE: Some Questions About Tires?

Sun Oct 21, 2007 5:55 pm

Quoting NEMA (Reply 35):
Quoting Cobra27 (Thread starter):
Do they blowout regulary?

Ive always wondered this, it has been a thought over time that ive had especially where there are only two tyres per strut like on the 737 or A319 as opposed to the four tyres per strut on a 767 for example. Get a puncture on the latter and youve got three left on that strut, seems better than just one doesnt it?



Quoting Jetstar (Reply 36):
For certification purposes, any airplane that has a 2 wheel main landing gear, each tire must be able to support the aircraft at the maximum weight in case the other tire fails during takeoff or landing. Also the landing gear assembly must support the weight of the aircraft on that one tire during takeoff and landing.

The worst tyre failure I have experienced was on a GF L1011 taking off from BAH for LHR about 1980. It was about 0100 and one of the fwd main wheels failed, the other wheel on the same axle also failed under the stress and the aircraft stopped at the end of the runway on its brake units. Pieces of the failed wheel rims punctured the wing but luckily there was no fire. It took us nearly five hours to get the aircraft off the single runway, which meant that about eight B747s diverted that night. About a year later the TSO for wheels was changed to make them much stronger so the second wheel would survive such an incident today.
 
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HAWK21M
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RE: Some Questions About Tires?

Sun Oct 21, 2007 8:37 pm

Quoting Readytotaxi (Reply 46):
Gosh, does a modern aircraft allow you to land with the parking brake on

No.Locked wheel protection prevents it.

I found Aquaplaning to cause a lot of damage to Tires especially in the rainy season out here,

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
KELPkid
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RE: Some Questions About Tires?

Mon Oct 22, 2007 3:19 am

Quoting Readytotaxi (Reply 46):
Gosh, does a modern aircraft allow you to land with the parking brake on ???

I hear some Embraer pilots have managed to do just this...  Wink
Celebrating the birth of KELPkidJR on August 5, 2009 :-)

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