On takeoff, after gear retraction, does the tire temperature?
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On takeoff, after gear retraction, does the tire temperature?
HI
I have seen this on a book, asking how will the tire temperature change once after gear retraction on take off... the answer is that tire temp will increase
However I cannot find any resources on the internet to prove this is correct...
Can anyone tell me is it correct or wrong?
Thanks!!!
I have seen this on a book, asking how will the tire temperature change once after gear retraction on take off... the answer is that tire temp will increase
However I cannot find any resources on the internet to prove this is correct...
Can anyone tell me is it correct or wrong?
Thanks!!!
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In my experience with the 747-100/200 (which have brake temp gauges), the brake temperatures will initially increase due to the lack of airflow in the wheelwells after the gear doors close, then decrease slowly over time.
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If we understand, by 'tire temperature' the mean temperature of the whole tire, the answer is that it gets cooler after takeoff. It will cool faster in a non-retracted position, exposed to the airstream, but will cool anyway, also retracted into a closed well (if at a slower pace...).
But if we understand by 'tire temperature' that of the external layers of the track, the answer is that those external layers, initially colder because 'air cooled', will heat up once the tire is inside the well, as the (uncooled) inner layers of the tire will be hotter and will heat up the now uncooled outer layers by conduction, until thermal equilibrium is reached...
But if we understand by 'tire temperature' that of the external layers of the track, the answer is that those external layers, initially colder because 'air cooled', will heat up once the tire is inside the well, as the (uncooled) inner layers of the tire will be hotter and will heat up the now uncooled outer layers by conduction, until thermal equilibrium is reached...
Last edited by XXXavier; 24th Jul 2013 at 12:14.
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Depends on brake usage during taxiing and on the turnaround time between flights. A short taxi will not change the tyre temps too much. A long taxi and extensive use of brakes will let the temperatures go up further when the gears are in the wheel bays, because they slowly take over the heat of the brakes. Sometimes pilots let the gear a bit longer down after takeoff to let the brakes cool in the airflow, otherwise a (false) wheel well fire might get triggered by the fire loops after a few minutes in the air. I've only seen A-320's doing this, but I'm sure other types can do the same. We've had an A300 taxiing to the runway on a hot day, and just short of lining up, the brakes ovht warning light came on. This is a no go, so the aircraft had to taxi back to stand, which made the problem worse. Only solution was to put up fans near the gear to get the cooling time down to 1 hour.
Last edited by Piper19; 24th Jul 2013 at 12:59.
Rubbish, all they had to do was wait 15 mins or so at the holding point ( or somewhere convenient to ATC ) for the temps to drop below 300 deg THEN depart...they should not have left the gate with hot brakes in the first place..
1/Professional Airline Pilots don't leave the gear down after takeoff for cooling, if the brakes were too hot to takeoff then DON'T TAKE OFF. What would happen if they suffered an Engine failure in such a situation?? They would have to retract the gear for performance and this would be an issue.....see note 2 below
2/ the Airbus doesn't have fire detection in the wheel well ( unlike Boeing ) therefore the 300 deg limit is there so you don't retract hot brakes into the wheels well and thus risk a fire......( a fire you wouldn't know about !!
)
1/Professional Airline Pilots don't leave the gear down after takeoff for cooling, if the brakes were too hot to takeoff then DON'T TAKE OFF. What would happen if they suffered an Engine failure in such a situation?? They would have to retract the gear for performance and this would be an issue.....see note 2 below
2/ the Airbus doesn't have fire detection in the wheel well ( unlike Boeing ) therefore the 300 deg limit is there so you don't retract hot brakes into the wheels well and thus risk a fire......( a fire you wouldn't know about !!
)
Last edited by nitpicker330; 24th Jul 2013 at 13:12.
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Which we also knew as mx guys, nitpicker330! But the pilots were not that reluctant to go, so we could not do any more than delay the flight and wait for them to cool. Caused us some problems afterwards, because the bosses would like to know why the aircraft returned to stand, and was again ready to fly after an hour without doing any mx...
And I've seen several times an A320 letting the gear down till they are at about 3000ft. Pilots told me this is for cooling the gear, what should it be for according to you then?
And I've seen several times an A320 letting the gear down till they are at about 3000ft. Pilots told me this is for cooling the gear, what should it be for according to you then?
Last edited by Piper19; 24th Jul 2013 at 13:13.
Well I hope they re-read their Airbus FCOM manuals which state the following limitation in the A330 ( I'm sure the A 320 is the same )
Edit---I've just checked and the A320 has the same limitation.
Maximum brake temperature for takeoff. . . . . . . . . . . . . . . . . . . . . . 300 C
They most likely haven't calculated performance based on gear down as well, so god help them if they suffer an Engine Failure......
Edit---I've just checked and the A320 has the same limitation.
Maximum brake temperature for takeoff. . . . . . . . . . . . . . . . . . . . . . 300 C
They most likely haven't calculated performance based on gear down as well, so god help them if they suffer an Engine Failure......
Last edited by nitpicker330; 24th Jul 2013 at 13:24.
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Given that the main wheels have a brake application on retraction and are removed from the cooling airstream I think it's clear that there will be an initial temperature rise. This has been the case on every large aircraft type I've flown or taught.
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@Nitpicker330:
I think Piper19 was telling that the crew took off with brakes below the maximum temperature of 300°, but that there is a possibility to get a BRAKES HOT warning after TO because the brake temperature can rise due to the closed compartment of the gear.
Not all A320 have brake fans to cool the brakes.
Let's say that you take-off with a brake temperature of 290° and you have a short flight. When you land it could be that the temperature is still around 290° and you have to land on a short runway with MLW and OAT is around 40°C.
No brake fan available for cooling. Good luck in trying to cool the brakes before the next flight.
Delaying retraction or an early gear extension can reduce the time you have to wait on the ground. Brake fans can be very useful, if installed, because with certain conditions it's very difficult to cool the brakes on an A320 if you don't have them.
Just saying that with the right conditions and no brake fans, the brakes can use some help to cool down. I've been in this situation before.
About having an engine failure with the gear extended, ofcourse you'll need to retract the gear as soon as possible.
But with an engine failure at V1, initially your gear will be extended as well.
And with an engine failure after V1 you will already have gained more altitude on the initial climb with 2 engines and gear down compared to an engine failure at V1
I think Piper19 was telling that the crew took off with brakes below the maximum temperature of 300°, but that there is a possibility to get a BRAKES HOT warning after TO because the brake temperature can rise due to the closed compartment of the gear.
Not all A320 have brake fans to cool the brakes.
Let's say that you take-off with a brake temperature of 290° and you have a short flight. When you land it could be that the temperature is still around 290° and you have to land on a short runway with MLW and OAT is around 40°C.
No brake fan available for cooling. Good luck in trying to cool the brakes before the next flight.
Delaying retraction or an early gear extension can reduce the time you have to wait on the ground. Brake fans can be very useful, if installed, because with certain conditions it's very difficult to cool the brakes on an A320 if you don't have them.
Just saying that with the right conditions and no brake fans, the brakes can use some help to cool down. I've been in this situation before.
About having an engine failure with the gear extended, ofcourse you'll need to retract the gear as soon as possible.
But with an engine failure at V1, initially your gear will be extended as well.
And with an engine failure after V1 you will already have gained more altitude on the initial climb with 2 engines and gear down compared to an engine failure at V1
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Gear down for cooling!
Several years ago I had the pleasure of doing a gear-down ferry on a 747 classic. Out of interest we monitored the brake temps and it took approx 10 minutes for the brakes to cool from top of green and low amber bands to reach middle of the green band!
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John Smith
Sorry bt I think Airbus does agree with Nitpicker.
The procedure you mention is a procedure for when you get the brakes hot indication. This is, as the title says and ABNORMAL situation, not a "pilotīs discretion" situation, and is triggered by a "Brakes Hot" indicated condition, not a "supposed" one.
Also, the procedure then goes to say "if performance permits". So it is also considering the case of an engine failure. In that case, performance does not permit, therefore gear will be retracted.
But still, my main point is you are describing an ABNORMAL procedure triggered by a specific advisory, while some people here are talking about a "pilot does as he feels like" situation.
Cheers.
Sorry bt I think Airbus does agree with Nitpicker.
The procedure you mention is a procedure for when you get the brakes hot indication. This is, as the title says and ABNORMAL situation, not a "pilotīs discretion" situation, and is triggered by a "Brakes Hot" indicated condition, not a "supposed" one.
Also, the procedure then goes to say "if performance permits". So it is also considering the case of an engine failure. In that case, performance does not permit, therefore gear will be retracted.
But still, my main point is you are describing an ABNORMAL procedure triggered by a specific advisory, while some people here are talking about a "pilot does as he feels like" situation.
Cheers.
And I've seen several times an A320 letting the gear down till they are at about 3000ft. Pilots told me this is for cooling the gear, what should it be for according to you then?
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Another consideration.
If one is at or around a limiting brake temperature for takeoff, one can consider employing the FT technique (presuming AEO) of delaying gear up selection for a period to accelerate cooling.
If one is at or around a limiting brake temperature for takeoff, one can consider employing the FT technique (presuming AEO) of delaying gear up selection for a period to accelerate cooling.
Simple:---
1/300c at the holding point? then don't go.
2/ hot brakes indication in flight, put the gear down.
In other words follow your FCOM and ECAM.
Don't takeoff with 300c and then leave the gear down especially without taking gear down into performance calculations.
It's simple really, don't leave the gate with more than 250c and this will never be an issue.
The six P's
Prior planning prevents piss poor performance.....
We come across this issue all the time in CX as we don't have brake fans and we need to PLAN ahead.....
1/300c at the holding point? then don't go.
2/ hot brakes indication in flight, put the gear down.
In other words follow your FCOM and ECAM.
Don't takeoff with 300c and then leave the gear down especially without taking gear down into performance calculations.
It's simple really, don't leave the gate with more than 250c and this will never be an issue.
The six P's
Prior planning prevents piss poor performance.....
We come across this issue all the time in CX as we don't have brake fans and we need to PLAN ahead.....
Last edited by nitpicker330; 24th Jul 2013 at 23:27.
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hot brakes
on buses 330/340 if brakes seem excessive hot after +45' on ground i.e. ambient <+30 and esp with wind. recycle the resets and temps will almost allways settle.
hope this helps some one
hope this helps some one
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On the 727 tire temperature could be very critical. There were two airframe losses due to hot tire temperature, one a Mexican airlines whose name I have forgotten and a Braniff airliner. With both cases it was a hot day takeoff, preceded by a extended taxi time.
In the case of the Mexican airline's 727, the tire/s exploded and caused the associated wing to depart the aircraft and everyone on board were killed. With the Braniff aircraft, the tire exploded, but the wing, even though severely damaged, stayed attached and the crew managed to land the aircraft. The airframe was written off and parted out.
Back in the 727 days, there was no gear temperature gauges, however, we did have taxi charts that were used to make sure we were under critical temperature for departure. Now it was very seldom that I was ever faced with having to consult these charts, as one did have to land with heavy braking, followed by a long taxi distance, a short ground stop (under 30 minutes) followed by another long taxi to the departure runway. All of this on a hot day. Therefore, unless one had all of the conditions above, tire temperature was not a factor.
The easiest way to check, was just before engine start, was to physical touch the tires and brakes with your bare hand, yeah I know real scientific, if cool to the touch, you were good to go. If they were too hot to put your hand, you consulted the charts, figured out the required cooling time, then waited until that time was up. The few times this happened to me, I or one of the other pilots would recheck the tires and brakes, usually whoever was playing FE that day.
So tire temperature was not something that you took casually on hot days with long taxi distances, after a landing and a short ground stop.
Oh, one procedure we used when faced with the conditions that could cause overly hot tires, was not to use the brakes as much as possible while taxing in , but to use the reverses to slow the aircraft while taxing. That helped and not to use the parking brakes after you stopped on the ramp, as soon as the wheels were chocked, release the parking brake.
In the case of the Mexican airline's 727, the tire/s exploded and caused the associated wing to depart the aircraft and everyone on board were killed. With the Braniff aircraft, the tire exploded, but the wing, even though severely damaged, stayed attached and the crew managed to land the aircraft. The airframe was written off and parted out.
Back in the 727 days, there was no gear temperature gauges, however, we did have taxi charts that were used to make sure we were under critical temperature for departure. Now it was very seldom that I was ever faced with having to consult these charts, as one did have to land with heavy braking, followed by a long taxi distance, a short ground stop (under 30 minutes) followed by another long taxi to the departure runway. All of this on a hot day. Therefore, unless one had all of the conditions above, tire temperature was not a factor.
The easiest way to check, was just before engine start, was to physical touch the tires and brakes with your bare hand, yeah I know real scientific, if cool to the touch, you were good to go. If they were too hot to put your hand, you consulted the charts, figured out the required cooling time, then waited until that time was up. The few times this happened to me, I or one of the other pilots would recheck the tires and brakes, usually whoever was playing FE that day.
So tire temperature was not something that you took casually on hot days with long taxi distances, after a landing and a short ground stop.
Oh, one procedure we used when faced with the conditions that could cause overly hot tires, was not to use the brakes as much as possible while taxing in , but to use the reverses to slow the aircraft while taxing. That helped and not to use the parking brakes after you stopped on the ramp, as soon as the wheels were chocked, release the parking brake.
Last edited by con-pilot; 26th Jul 2013 at 17:30.
