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Max Q
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Tire temperature?

Sun Jan 21, 2018 5:26 am

Lots of aircraft have brake temperature and
tire pressure sensing with readouts in the
cockpit on some types


Does any type have tire temperature
sensing and readout ?
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Francoflier
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Re: Tire temperature?

Sun Jan 21, 2018 9:33 am

Not that I know of.
There is no use for it. Tyres are designed to withstand and be effective under a wide range of temperatures, more than enough for even intensive usage. The only thing that would heat them up (or rather the gas inside them) enough to cause issues are the brakes, and even then, they are protected from blowing by the fuse plugs.
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Flow2706
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Re: Tire temperature?

Sun Jan 21, 2018 12:39 pm

Brake Temperature Indications are used in many aircraft types, but I don't know of any aircraft that has a tyre temperature indication. On the A320 takeoff is only authorized if the brake temperature is less than 300C. The objective of the limitation is to avoid a fire in the gear bay - if there was an unrecognized hydraulic leak in the gear bay and the hydraulic fluid drips onto the hot brakes there would be a risk of ignition if the temperature is above 300C (and unlike other types, f.e. 737 the A320 is not equipped with a wheel well fire warning)...
 
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fr8mech
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Re: Tire temperature?

Sun Jan 21, 2018 3:27 pm

Flow2706 wrote:
Brake Temperature Indications are used in many aircraft types, but I don't know of any aircraft that has a tyre temperature indication. On the A320 takeoff is only authorized if the brake temperature is less than 300C. The objective of the limitation is to avoid a fire in the gear bay - if there was an unrecognized hydraulic leak in the gear bay and the hydraulic fluid drips onto the hot brakes there would be a risk of ignition if the temperature is above 300C (and unlike other types, f.e. 737 the A320 is not equipped with a wheel well fire warning)...


I’m not so sure of that. As I recall, the flashpoint of Skydrol is somewhere around 320F with the fire point just above that.

I was always taught that the brake temp limitations for takeoff are in case of a rejected takeoff. A hot brake can not absorb as much energy, and sufficiently dissipate the heat generated, as a cold brake. An already hot brake asked to handle an RTO will probably fail.
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longhauler
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Re: Tire temperature?

Sun Jan 21, 2018 4:54 pm

fr8mech wrote:
I was always taught that the brake temp limitations for takeoff are in case of a rejected takeoff. A hot brake can not absorb as much energy, and sufficiently dissipate the heat generated, as a cold brake. An already hot brake asked to handle an RTO will probably fail.

That was true for the old steel brakes.

Carbon brakes become much more efffective when very hot. The 300C limit for take-off wasn't for the reject but for bringing hot materials into a tight space with vulnerable systems close by. In fact, if a brake warning is sounded after take-off (it is inhibited during the part of the take-off run) then SOP with both engines running is to leave the landing gear extended until the brakes cool.

A reject, or heavy use landing will see temps rise to over 600C. The brakes are still very effective ... but you don't want anyone near your landing gear with temps like that.
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Balerit
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Re: Tire temperature?

Sun Jan 21, 2018 4:57 pm

fr8mech wrote:
Flow2706 wrote:
Brake Temperature Indications are used in many aircraft types, but I don't know of any aircraft that has a tyre temperature indication. On the A320 takeoff is only authorized if the brake temperature is less than 300C. The objective of the limitation is to avoid a fire in the gear bay - if there was an unrecognized hydraulic leak in the gear bay and the hydraulic fluid drips onto the hot brakes there would be a risk of ignition if the temperature is above 300C (and unlike other types, f.e. 737 the A320 is not equipped with a wheel well fire warning)...


I’m not so sure of that. As I recall, the flashpoint of Skydrol is somewhere around 320F with the fire point just above that.

I was always taught that the brake temp limitations for takeoff are in case of a rejected takeoff. A hot brake can not absorb as much energy, and sufficiently dissipate the heat generated, as a cold brake. An already hot brake asked to handle an RTO will probably fail.


An overheated brake can also cause a tyre explosion inside the wheel well, just have a look at the A340 RTO test.

https://www.youtube.com/watch?v=lUMuOyMTQ8Y

https://www.youtube.com/watch?v=aPELUntJjPo
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zeke
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Re: Tire temperature?

Sun Jan 21, 2018 5:17 pm

They are fuse plugs which you find on all airliners these days. They are doing exactly as they are supposed to do.
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Flow2706
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Re: Tire temperature?

Sun Jan 21, 2018 8:10 pm

fr8mech wrote:

I’m not so sure of that. As I recall, the flashpoint of Skydrol is somewhere around 320F with the fire point just above that.

I was always taught that the brake temp limitations for takeoff are in case of a rejected takeoff. A hot brake can not absorb as much energy, and sufficiently dissipate the heat generated, as a cold brake. An already hot brake asked to handle an RTO will probably fail.

Check FCTM-NP Taxi/Brake Temperature. In this section it is mentioned that the reason for the 300C limitation is to avoid ignition in case of an hydraulic leak...
 
Apprentice
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Re: Tire temperature?

Mon Jan 22, 2018 10:49 am

zeke wrote:
They are fuse plugs which you find on all airliners these days. They are doing exactly as they are supposed to do.


Hi:
You are right, normally there are 3 fuses, located each at 120º from the others. Depends on tire’s manufacturer, they are located on outside or inside part. Beside avoid a blow-out of the tire, venting N2 pressure ( and lefting the tire fully deflated) to atmophere, they also indicated that tire temp rise above certain limits.
When fuses blow, mechanic should change the wheel and in dependence of number of fuse blow, he also should replace the brake, writting the reason i.e. numbers of fuses melted, and made an special check to wheel’s axis for possible overtemp damages. In the shop, in dependence of this information, tire and brake will be check more or less deep, or even, considered completely inop and discarded. If wheel axis was damaged for overtemp event, has to be also replaced and most probably You will be AOG for a litle while.

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Apprentice
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Re: Tire temperature?

Mon Jan 22, 2018 11:04 am

Fr8mec, hi. I was also said that brake temp high will, in first order, limit the quantity of energy that brake can absorb in subsequents braking or, more important, on a rejected TO, even to make it disfuntionally. For that reason, short turnarounds are limited until brake temp indicate some value.And during TO / Landing trainings, a/c will return after several landings to ramp, to wait for brake’s temp to recover, or even, after TO, Landing Gears will be not retracted for a while, waiting for temp to drop.

I remember old days, steel brakes, on trainings, brakes temp lowered with water betwen Landing and TO

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“An4; IL18; IL6; Tu5; D10; MD11; MD83; B32; B34: B37; B744; B748; B752; B763; B772; B773; B77W; A320; A332; A333; A342; A343.
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benbeny
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Re: Tire temperature?

Mon Jan 22, 2018 2:35 pm

When we have fuse plugs, why do we need to bother with tire temp sensor? Less part to fail, less cost for new planes, less line to connect.

Besides, gas expansion rate when heated is well known. We can therefore predict the gas temperature just by observing the pressure, therefore we can safely use fuse plugs. It's simpler, cost-effective, and has same effect as tire temperature sensors.

For tire pressure sensors, that might be interesting proposition. But I don't see much benefits in it either.
 
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CALTECH
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Re: Tire temperature?

Mon Jan 22, 2018 5:03 pm

longhauler wrote:
fr8mech wrote:
I was always taught that the brake temp limitations for takeoff are in case of a rejected takeoff. A hot brake can not absorb as much energy, and sufficiently dissipate the heat generated, as a cold brake. An already hot brake asked to handle an RTO will probably fail.

That was true for the old steel brakes.

Carbon brakes become much more efffective when very hot. The 300C limit for take-off wasn't for the reject but for bringing hot materials into a tight space with vulnerable systems close by. In fact, if a brake warning is sounded after take-off (it is inhibited during the part of the take-off run) then SOP with both engines running is to leave the landing gear extended until the brakes cool.

A reject, or heavy use landing will see temps rise to over 600C. The brakes are still very effective ... but you don't want anyone near your landing gear with temps like that.


More like both reasons are correct....

https://www.iata.org/whatwedo/ops-infra ... Airbus.pdf

" Taxi Out
For safety reasons, Airbus does not recommend any procedure that would systematically and intentionally increase brake temperature before takeoff. The aircraft may not be able to sustain the certified maximum brake energy in some cases of high-energy rejected takeoff with hot brakes (e.g. with worn brakes, without the use of reversers...). Certification does not include this type of situation judged not highly probable. However, if the aircraft does not have brake fans, repeated short flight legs and short turnaround times (as described in Figure 4), may result in a taxi out with hot brakes. This is acceptable only if the BRAKE HOT warning does not come on before takeoff. In all cases, do not start a taxi out with the BRAKE HOT warning on."

" Airbus designs its aircraft so that the brake fans are necessary for short turnarounds. This avoids the extra weight of oversized brakes. Brake cooling fans also help to control brake temperature and therefore increase brake life bringing the brake temperature in the areas where the wear is minimum. "

"FCTM is clear: The FCOM limits brake temperature to 300 Deg C. before takeoff is started. This limit ensures that, in the case of hydraulic fluid leakage, any hydraulic fluid, that may come into contact with the brake units, will not be ignited in the wheelwell.
This limit does not ensure that, in the case of a high energy rejected takeoff, the maximum brake energy limitation will be respected."
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