TOP
Topic Author
Posts: 250
Joined: Wed May 10, 2000 5:22 am

Why Do Tire Burst At Too High Speed?

Fri Nov 24, 2000 5:21 am

A short question, why do tire burst at too high speed?
(>204 kts for a 744 on ground)

Thanks,
Stephan
 
Guest

RE: Why Do Tire Burst At Too High Speed?

Fri Nov 24, 2000 6:18 am

The stress on the tires is much more at a high speed!
Iain
 
prebennorholm
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RE: Why Do Tire Burst At Too High Speed?

Fri Nov 24, 2000 9:40 am

TOP wrote:
-------------------------------
A short question, why do tire burst at too high speed?
(>204 kts for a 744 on ground)
Thanks,
Stephan
-------------------------------
200 kts is a lot faster than any F1 car has ever made. The centrifugal forces are immense, and so is the friction heat buildup. A 744 at MTOW is 500+ times heavier than a F1 racecar. Or ten times heavier than an 18-wheeler truck.
Any car tyre also has a max load and max speed, but those figures are calculated for continuous driving. A 744 would never roll for many miles at 200 kts, or the tyres would melt or bust into fire.
Wheels on airliners are a weak thing which must be treated with the outmost respect.
Best regards, Preben Norholm
Always keep your number of landings equal to your number of take-offs
 
AA737-823
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RE: Why Do Tire Burst At Too High Speed?

Fri Nov 24, 2000 2:51 pm

The reason tires burst at high speeds is somewhat easy to explain.

By the way, why do you Brits call them "Tyres?" They're TIRES!!!!

Okay, past the language barrier

A tire has a flat spot on the bottom, from the weight resting on it. As it rolls (picture this in your mind) the rubber that is flat then moves up and becomes round again. Consequently, the part that was round is now touching the ground and is flat. This is the normal flexing of a tire. But, the problem is that this flexing creates heat. The faster the tire is spinning on the ground, the more it is flexing, the more heat it is creating.

Hot air takes up more space than cold air. When the air inside a tire gets too hot, it becomes "bigger" and causes the tire to explode. That is why a tire on your car is guaranteed to a certain speed- mine are guaranteed to 130 miles per hour, without exploding. It works the same for an airplane. Boeing knows that airplane tires on a 747 can go X speed safely, and they blow up at Y speed. So they tell you- don't go faster than 200 so you don't lose a tire.

Now, a side note, plane tires are not filled with air, they are filled with nitrogen, I believe. The gas is less flammable, so in case they do blow out, there won't be a huge ball of fire. The gas also handles heat better.

That is why tires blow up when you go too fast- they get hot!
 
L-188
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RE: Why Do Tire Burst At Too High Speed?

Fri Nov 24, 2000 5:19 pm

It is a combination of heat build up in the tire, the heat weakens the tire. Acceleration and centrifical(spl??) forces acting on the tire.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
prebennorholm
Posts: 6430
Joined: Tue Mar 21, 2000 6:25 am

RE: Tire/tyre

Sat Nov 25, 2000 12:02 am

Hey folks, I was first to write "tYre", and I'm not British. I'm Danish - proud to be Danish!
I often wondered why half of the people couldn't spell "tyre" correctly. Finally I got the explanation. Certainly my English teacher would have put a fat red mark under each "tire" I wrote.
Best regards, Preben Norholm
Always keep your number of landings equal to your number of take-offs
 
Guest

RE: Why Do Tire Burst At Too High Speed?

Sat Nov 25, 2000 1:44 am

What everyone else has described about heat and the expansion of air is true.... nitrogen is used because it is super stable and non-flammable. The tires also have a safety thermal fuse plug built into the wheel assembly so that when the wheel reaches the max temperature the fuse bursts and allows the air to escape so that the tire doesn't explode.
 
Guest

RE: Why Do Tire Burst At Too High Speed?

Sat Nov 25, 2000 9:10 am

One anamoly or incident of excessive speed will not, probably, by itself, cause a tire (or TYRE) to burst.

It is the CONTINUOUS incidents of excessive speeds which cause abnormal wear and bursting. Keep in mind that the speed does not have to be overly excessive. (The max ground roll speed for the 9 is 195kts in our FOM--off the top of my head).

Here is an example. Friend of mine now works for Marconi as an aeronautical engineer--in the area of PHM--prognostic health management (yes, it's an aerospece term!) and fault detection. Over a beer, he told me an interesting case he worked on as a consultant. A few years back a well-known African airline was reviewing its operating history and found that its annual tire (or TYRE) costs for its 737s were almost a million dollars over the projected budget, and the bean counters rightly found that to be unacceptable. My friend was called in to research and they collected data from a wide range of parameters. In cross checking their operating data, they found, in short order, that the rotation speed regularly exceeded Boeing's recommendation by a mere 4 knots! Someone had, by oversight, published the wrong information in the airline's FOM. This overspeed was adding large sums of money onto the airline's operating costs.

The problem was, evidently, quickly corrected.
 
TOP
Topic Author
Posts: 250
Joined: Wed May 10, 2000 5:22 am

Thank You!

Sun Nov 26, 2000 6:24 pm

Thank you,
Stephan

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