Cooling brakes with water as a normal procedure

[JammedStab]

Was just reading an article about brakes and the fellow writing it said "the
procedure that JAL (Japan Air Lines) routinely used for cooling the brakes of their 727s, DC8s and 747s with water. This caused immense steam clouds."

The article is a bit dated. Is this something that is still done. Have never heard of it or seen it done.

[Centaurus]

Saw it done at Kai Tak on a 707 about thirty years ago. Steam was most impressive.

[1jz]

Better choice is using the cool air from air conditioning van. Lesser chances of temperature shocks.

[Tech_Log]

Never seen it done here in the UK. The airbus has brake fans which is a good invention.

I'd have thought it to be a pretty bad idea due to the steam (and risk of it burning you!), heat shock on the materials and the fact tyres would be hot as well. Obviously depends on how cold the water is but still I wouldn't really do it.

[latetonite]

Where on the tarmac can you find those air-conditioning van's?

[Skyjob]

You can always argue that brake cooling is not required...

Heard that too many times in my career on the flight deck. I guess if superiors and/or trainers promulgate that message enough it MUST be true, right?

[1jz]

We have the ac vans for cooling during the turn around, I don't know what's with the fields you operate at. Bad luck if you don't have em around.

[latetonite]

To 1ej: I have been working a bit all over the world. Must have been unlucky to never have seen any of the air-conditioning van's. Where are you flying?

[Skyjob]

Maybe he means aircraft brake cooling fans?
Option to gave them fitted...

[underfire]

Jammed,

I dont think that happens any longer, and would be surprised if that was even allowed back in the day.

If one looks at the properties of steel, heating and rapid quenching creates a hardening (brittle) surface that one would not want on a brake surface..

If this was in efect today, with a ceramic disk, it is likely to fragment...

[1jz]

@ latetonite, sir may be i fly small turbo prop atr thats why we use it mostly to avoid keeping our engine running.. i fly in southasia and we also utilize it at sharjah etc.. n i m not talking about brake cooling fans like airbus has em. besides the fact that our brakes normally cool within the turnaround time but at times this technique had also been used.. n here we are disscussing if its practical to cool brakes with blown air or water etc. if they (ac vans) were not around over the parking stands then i wouldnt have said it.

[latetonite]

I see now. You cool the brakes with the air from the A/C cart.
'Tarmac' mode versus 'hotel mode'.

[chimbu warrior]

Prior to the opening of the current international terminal in Brisbane, the distance from the old terminal o the runway (particularly the RW19 threshold, about 8 km) was such that brake temperatures could become an issue.

A solution to this was to taxi through a low spot on the taxiway (L as I recall) where water lay to provide brake cooling. The advantage was that because the wheels and discs were turning as they went through this water, there was no tendency to warp discs.

[tdracer]

When Boeing is doing high-speed taxi tests (i.e. prior to first flight of a new model) they pull off and cool the brakes with fans (not sure if there is active "a/c" style cooling - it's always been well in the distance when I watched). Never heard of them using water to cool the brakes.

Most of the current production Boeing aircraft use carbon/carbon brakes (weight savings and longer life compared to steel) - I've not heard that carbon brakes have issues with rapid cooling. I'm unaware of ceramic brakes being certified for commercial aircraft use.

[ksjc]

Carbon brakes absorb water which can freeze at altitude causing locked wheels and blown tires during landing. Never spray water onto carbon brakes.

One report: http://www.skybrary.aero/bookshelf/books/1359.pdf

[DaveReidUK]

The airbus has brake fans which is a good invention.Integral brake cooling fans were of course around long before Airbus came on the scene.

[JammedStab]

Carbon brakes absorb water which can freeze at altitude causing locked wheels and blown tires during landing. Never spray water onto carbon brakes.

One report: http://www.skybrary.aero/bookshelf/books/1359.pdf

Thanks, I have heard of this happening on an ATR. The-72 has carbon brakes.

From the ATR-72 manual: "SPECIAL CASE
If contaminant layer is significant enough to possibly accumulate in the
brake area during ground operation, brake disks may join due to icing
during the flight, leading to possible tire damage at subsequent landing.
The following special procedure should be applied during taxi before and
as close as possible to take off.
Set 18% Torque on each engine and keep taxi speed down to a "man
pace" during 30 seconds using normal brakes with minimum use of nose
wheel steering to ensure a symmetrical warming up of the brakes."

[Don_Apron]

Seen brakes cooled with water in the old Eastern block countries on occasion. Never liked the idea myself, shock cooling and all the rest of it.

The best way to not to have the brakes heat up in the first instance, apart from excessive braking during the landing run. On a long taxi, IIMO was to shut down the 2 outer engines after a cooling period. It is the constant use of the brakes after landing, when the aircraft is light that caused a lot of the trouble.

The big airports in KSA you had to be careful as there were long taxis.

[bcgallacher]

Cooling brakes with water is not an acceptable practice - it can cause distortion and cracking of wheels as well as damage to brakes. Boeing with regard to brake cooling on 747s states that a fine mist of water may be used for cooling but not hoses or as I have seen ,buckets of water being thrown over brakes - this causes thermal shock. AC trucks can provide ambient air for brake cooling but usually there is only one provided so it is time consuming.The best I have seen was at the old Bangkok airport -Don Maung - where individual fans driven by small Honda motors could be positioned at each wheel to suck air through the brake units - very effective. The were brought by the handling company on a trailer but as there were only 8 units they had to be swapped around on a 16 wheel 747. Used them a couple of times when Flight Mech on heavy 747s and was impressed. Never seen such equipment anywhere else.

[Rubber Dog]

I had also heard in the past that the high temps could split the water into hydrogen and oxygen. A dangerous situation. However having just looked it up, I see that that only starts to occur at 2200 deg C. Don't think I will be getting my brakes that hot!

[rudderrudderrat]

Hi Rubber Dog,
A dangerous situation.
No, not really.
The energy released by burning Hydrogen in the Oxygen released will exactly balance the energy absorbed during the splitting.
Hence no exothermic reaction.

[Rubber Dog]

Thanks RR, my chemistry is 28 years lapsed :)

[grounded27]

It is a bad practice but I have in the past grabbed a case of liter bottles to make an on time turn happen, was always careful to slowly douche the shroud only (never direct contact with the brake). It works, this was ACMI ops, many years ago. The other option is to take off and leave the gear extended until the temps turn green. I only convinced a crew to do this once, back when the day of common sense was actually an option.

[nitpicker330]

Common sense of just ignorant dumb???

I'd say the latter!! ( for the Airbus anyway )

Yes go on, let's put hot brakes into a wheel well without a Fire detection system and pray it's all good!!

Or let's leave the gear down after T/O to cool those hot brakes ( Against Airbus and Boeing normal SOP's ) all good stuff until the Engine fails at V2 and you need to retract hot gear because you didn't do the takeoff data based on gear down.....
Which you can't anyway unless using Brakes deactivated data.

Airbus put 300c in their limitations for a reason.

Plan ahead your brake cooling requirements ( use reverse, use brake fans etc ) in your transits and follow Airbus SOP's and Limitations :ok:

[nitpicker330]

Airbus FCOM quote

BRAKE TEMPERATURE

The FCOM limits brake temperature to 300 °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. Thermal oxidation increases at high temperatures. Therefore, if the brakes absorb too much heat, carbon oxidation will increase. This is the reason why the brakes should not be used repeatedly at temperatures above 500 °C during normal operation. In addition, after heavy braking, the use of brake fans can increase oxidation of the brake surface hot spots, if the brakes are not thermally equalized

[rudderrudderrat]

Hi nitpicker330,
Common sense of just ignorant dumb???
For aircraft without brake cooling fans nor brake temperature gauges, but with wheel well Fire Detectors fitted, leaving the gear down after take off was an approved method of cooling the brakes (e.g. B707).
I'd say the latter!! ( for the Airbus anyway )
That's probably because they have (a) brake temp gauges and (b) cooling fans fitted to help (a) raise awareness and (b) reduce minimum turn round times.

[kinteafrokunta]

Or let's leave the gear down after T/O to cool those hot brakes ( Against Airbus and Boeing normal SOP's ) all good stuff until the Engine fails at V2 and you need to retract hot gear because you didn't do the takeoff data based on gear down.....
Which you can't anyway unless using Brakes deactivated data.



The other option is to take off and leave the gear extended until the temps turn green. I only convinced a crew to do this once, back when the day of common sense was actually an option.

Well and good einsteins...what about your dispatch and takeoff performance? If you need to do an RTO,..................:ugh::=

[nitpicker330]

I'm on your side.

300c Max for RTO and Fire avoidance :ok:

Although having said that the Airbus FCTM does say that "the limit does not ensure that, in the case of a high energy rejected takeoff, the maximum brake energy limitation will be respected"

As per my post above. :ok:

[nitpicker330]

Not all operators have fans, we don't.

And I did say Airbus for a reason.

[Agaricus bisporus]

Don't you suppose that if a water douche was an appropriate method of cooling brakes the manufacturers would have fitted such a system or recommended its use? Dumping cold water onto hot metal is a great way to cause unnecessary and often harmful stress and crystalline changes in the metal and as many car drivers know dunking red hot disks in water is likely to result in said disks warping. Rotating the disks as you drench them is unlikely to make the situation much more acceptable outside a lab or manufacturing process where it is properly planned and controlled.

This daft idea has no place in aviation.

[Don_Apron]

I'm with grounded on this.

In 1st generation turbojet powered aircraft, you did not know how hot your tyres and therefore brakes to a certain extent, would be after a long taxi to t/o in high ambient temperatures at MTOW. If there was any doubt we used to leave the gear down, sometimes for up to 20 mins. Terrain permitting in a lot of cases of course. 250 kts of rushing air is as good as any fan that I know of. Yes we had wheel well fire detectors, but they don't detect a burning bogie being retracted into a wheel well.

Yes you could say it was guesswork but common sense did prevail in most cases.

[nitpicker330]

If your wheel well fire detectors didn't detect a fire in a bogie after the wheels retract and the doors closed then I'd get them checked!!

Anyway that was history.

This is 2013.

[latetonite]

Kynteafrocunta. I am with you on this one. Wanted to say the same thing.

I had a wheel fire on an A300 one day during take off. Locked brake. Tower informed me during TO. Took off, left the gear down, circuit at CDG and overweight landing. Besides the 4 wheels and a brake, they had to change the whole boogey.

[Don_Apron]

Nitpicker330.

"If your wheel well fire detectors didn't detect a fire in a bogie after the wheels retract and the doors closed then I'd get them checked!!"

You said that, not me.

This is indeed 2013. Very observant of you.

Concorde PCG was at the turn of this century.

The DC 8 crash at Jeddah, KSA, early 1990's

The 2 accidents above were caused by tyres, hot or disintegrating. Would suggest you take a read of the report, on the DC8. It should be compusery reading for all aircrew. Wheels and tyres and their condition are capable of killing everyone on board as CFIT.

You may just learn something by studying a bit of history as regards to aircraft accidents. History does have a history of repeating itself.

Did they teach you anything about wheels and tyres on your 330 conversion? No I bet they didn't. The latest AB is uncrash-able I believe.

[Uplinker]

I've been told by the airport fire crews that pouring water onto hot brakes could make them explode because of thermal shock.

I will take their word for it. I certainly wouldn't want to be standing anywhere near a hot brake that was being doused.

[NSEU]

The best I have seen was at the old Bangkok airport -Don Maung - where individual fans driven by small Honda motors could be positioned at each wheel to suck air through the brake units - very effective.

Our airline has them in Sydney, too. We don't seem to use them all that often, nowadays - Perhaps because of carbon brakes and intelligent autobrake selections. It's funny that you should mention Bangkok. Thai Airways seemed to be the biggest user when we used to have the maintenance contract for Thai. Short turnaround times or leadfoots? :)

[Desert185]

+1 on fans, not water. Boeing's 747-100SR (short range), which JAL used domestically had, air ducts to the brakes for "quick turns".

If a fairly short leg was flown after a turn was done (and knowing brake temps were good for takeoff), we would lower the gear early for the landing instead of leaving gear down after takeoff. You could watch the temps go down well into the green for the upcoming landing, precluding cumulative brake temp increase during the landing rollout and taxi in, even when near max landing weight.

[tdracer]

Many years ago I was on a 767 flight test where they were doing max performance brake testing. We'd touch down (hard) and they'd apply max braking (no reverse thrust allowed). It was pretty amazing how fast such a big airplane could stop. We wouldn't be stationary long - less than a minute - and immediately takeoff again using the remaining runway (Moses Lake has a long runway - although in retrospect, between the already hot brakes and the remaining runway, it could have been interesting if we'd needed to RTO :uhoh:).

After takeoff, they'd leave the gear down to cool the brakes. After maybe 15 minutes they'd get word from instrumentation that the brakes were cool enough and we'd do it again. We did several hours of flight testing without ever retracting the gear - even leaving them down on the return to Boeing Field when we were done.

[nitpicker330]

Don_Apron

I think you misunderstand what I've been badly trying to say!!

All I've said is
1/ In an Airbus with no wheel well fire detection system don't takeoff with temps above 300c,
2/ Don't leave the gear down after takeoff to cool the brakes ( you shouldn't have taken off in the first place ) in a NORMAL situation without first using appropriate performance adjustments to your data ( if you can )

All of those accidents you mention above are out of the blue emergency situations completely different to what I've been talking about in normal line ops following Airbus limitations and SOP's.

You mentioned you had a wheel well fire detection system that wouldn't detect a burning bogie after gear retraction. All I'm saying is that you should get it checked because that is exactly what it's designed to monitor...if not fire/heat then what are the dual fire detector loops designed to detect in the wheel well? You mean Boeing didn't design it to detect any kind of fire inside the bay????:D

If the Tower report a brake fire after takeoff on my A330 of course I'm going to leave the gear down as an emergency situation now exists. I would select TOGA to ensure terrain clearance etc and later land ASAP...

That situation is different to deliberately departing with hot brakes.


Don't take out of context what I've said ok...

[grounded27]

Please read my response before posting a reply. Understand the difference between a brake assy and the shroud that is simply there to dissipate heat. Learn from your piers to understand common practice on the aircraft that operated before your Scarebus ways. I speak of history (lil bit of grey area) AND ALSO PAST COMMON PRACTICE. Eat this up as you wish, I amongst many others are living to tell this story.

[Don_Apron]

nitpicker330

"being retracted" I meant in transition. That process begins when the gear lever is moved to the up position.

I should qualify I was referring to cargo ops, which normally inured higher weights.

We did not have brake heat sensors, like they do now..

Yes we carried out a fire warning check which included the WW fire detection system, as required by the checklist.

Tyre incidents are still happening too frequently.

We never trusted the Ground/base engineers completely as their a:mad:s would not be strapped to the aircraft.

From which direction would you approach suspected hot tyres or brakes?? Serious question, as they can even kill you on the ground.

Hope that helps.

[nitpicker330]

1/ as a cockpit crew I wouldn't ever approach hot brakes, especially ones that had melted fuse plugs and deflated tyres..........not my job:ouch:

2/ I'm told that if the brake assembly explodes it usually does to the side, therefore approaching from directly in front or behind is best if you have a suicidal tendency...:D

3/ you'll see me running away with my pax well away from the brakes, I'll sit back and watch the show from a safe distance....:ok:


p.s no wheel well system fire detection loop will detect a wheel or brake fire during retraction unless it's a damn hot and a big event. I thought that would be obvious!! :eek: when you wrote "after retraction" I thought you meant after the cycle completed and it was all buttoned up....:)

[Natstrackalpha]

A good invention - except the fans blow air over the sensors which give a lower, cooler indication on the flightdeck. so for hot brakes - temp could be a lot higher.

[nitpicker330]

I still say lucky you!!

Better than none, believe me..:{

[Don_Apron]

Nit

Are you one of those Qantas sky Gods? I think you might be. Should have known better to even query such a superior. You need to learn to accommodate other peoples point of view with a little more tolerance. I don't know all the answers and neither do you.

The moment that gear lever is in the up position after liftoff, on the aircraft I am referring, your fate would sealed if you have burning or flailing wheels. Wheel well fire detectors or no ww fire detectors. That was all I was trying to explain.

[nitpicker330]

No not a Qantas sky god as you put it. I'll take it as a compliment though as I have a lot of friends in QF that are top notch operators and I could only hope to keep up to their professional standings.

You seem a bit touchy, what was it that I wrote that was wrong exactly?

How do we differ in our opinions anyway? I actually think if you re read my posts we agree generally.

I answered your "serious question" about how to approach hot brakes, was I wrong?

Now take a chill pill and settle down. :ok:

[bcgallacher]

Nitpicker - be aware it is not the brakes that will explode it is the tires, but it is correct to approach from front or rear as the bits of tire usually go laterally.Frankly it is better to stay a long way away from a smoking landing gear as debris can travel quite a distance and a large chunk of tread can do a great deal of damage. The fusible plugs will usually let go before the tire reaches bursting pressure due to heat but you cannot tell if there is damage to the carcass that might allow it to burst at a lower temp.I worked as a line engineer for 40 years and always treated hot wheels and brakes with the utmost respect - they are capable of killing you.

[Burnie5204]

From which direction would you approach suspected hot tyres or brakes?? Serious question, as they can even kill you on the ground.

Fire crews here say "DONT", let them do it instead.

However, they will approach it at 45 degrees to the direction of the bogey as if it causes the tyres to explode then most rubber will be flung out at 0, 90 and 180 degrees and hub assemblies normally get thrown out at around 90 degrees

[Natstrackalpha]

Nitpicker - be aware it is not the brakes that will explode it is the tires

I was going to say that . . .!

[nitpicker330]

Yes true wheels exploding/brakes exploding. All the same area caused by hot brakes. As I said I won't be going anywhere near hot brakes/wheels, not my job. :ok:

Hadn't heard about the 0 90 and 180 rule. Good to know for Fire fighters...:eek:

[Shawn Coyle]

So if pouring water on hot brakes is a bad thing, does that mean you can't taxi through puddles of water?

[BARKINGMAD]

"However, they will approach it at 45 degrees to the direction of the bogey as if it causes the tyres to explode then most rubber will be flung out at 0, 90 and 180 degrees and hub assemblies normally get thrown out at around 90 degrees"

"Frankly it is better to stay a long way away from a smoking landing gear as debris can travel quite a distance and a large chunk of tread can do a great deal of damage. The fusible plugs will usually let go before the tire reaches bursting pressure due to heat but you cannot tell if there is damage to the carcass that might allow it to burst at a lower temp.I worked as a line engineer for 40 years and always treated hot wheels and brakes with the utmost respect - they are capable of killing you."

"Yes true wheels exploding/brakes exploding. All the same area caused by hot brakes. As I said I won't be going anywhere near hot brakes/wheels, not my job."

SO WHY ARE THE FLIGHTCREWS THESE DAYS SO RELAXED ABOUT THROWING THEIR PAX DOWN THE SLIDES FOR A BIT OF SMOKE AND FIRE WHERE IT IS EXPECTED?

AH WELL YOUR HONOUR, SOMEONE SAID "FIRE!" AND I KNEW LEGALLY I'M COVERED IF I EVACUATE THE PASSENGERS!

PERHAPS A BIT OF THOUGHT AS TO WHAT HAPPENS TO THEM OUT THERE MAY JUST STAY THE HAND BEFORE THEY REALLY GET UNNECESSARILY INJURED?!?!

I now await the incoming fire.........................................:ugh:

[Desert185]

I now await the incoming fire.........................................:ugh:

Not from me. To evac or not depends on the situation.

[Gas Bags]

There is no procedure to use water to cool overheated brakes...the opposite is the case. You should always wait for natural cooling or use cooling fans. Using water on an overheated brake could cause an explosion.

Any one using water has a death wish....Fools and beginners???

[bcgallacher]

Gas Bags -
Boeing had a permitted procedure for spraying water in what they described as a fine mist above the brakes and allowing it to settle on them.What you are supposed to use to produce this 'fine mist' I have no idea. Worst case I witnessed was in Bangkok where local mechanics were pouring water from water cooler containers onto the brakes of our 747 producing large volumes of steam and creaking noises. That was how I found out why we had so many cracked wheels - it did not happen again.

[sb_sfo]

A fire department fog nozzle will do the trick- seen it done about 20 years ago. Weren't many other choices available.

[BARKINGMAD]

Gas Bags, your posting is my understanding also after only 4 decades of professional flying.

What worries me as an old codger is an apparent forgetting of lessons learnt a long time ago in aviation.

I had the same scenario at a regional UK airport last decade, when our NG arrived on the stand with a new brake unit smoking gently on it's first outing into this airport where the runway is not very long.

Fire crew attending were determined to hose it if it looked like it would combust, the off-going captain, a former flight engineer was saying 'no way Hosé', and a real argument developed between the 2 parties.

If this sort of behaviour is symptomatic of the modern aviation "professionals" and their support staff, then it's only a matter of time before the old lessons will have to be re-learned the hard way, and at what cost!

Any engineers/firefighting professionals out there who would like to comment? :suspect:

[bcgallacher]

SB SFO -
Thanks for the info - did not know that such a thing existed - I once had an African fire crew on standby with what was termed a roseate head when I knew a certain captain was operating as he seemed totally incapable of landing the thing without overheating the brakes - fortunately never had to use it.

[Killaroo]

Nitpicker330: I think you misunderstand what I've been badly trying to say!!
HaHa - it's your TONE old boy.
But being Australian you'd never understand.
Free CRM lesson there.

[Killaroo]

Natstrackalpha: A good invention - except the fans blow air over the sensors which give a lower, cooler indication on the flightdeck. so for hot brakes - temp could be a lot higher.

Actually, Airbus give two different values for max temp depending on whether or not you have fans. I'm sure NitWit is just wetting himself to tell us the number (I know it nitty, so get it right).

I learned this trade on aircraft with no brake fans, and no brake temp gauges.
How did we ever survive before wunderkinds like nitty came along to teach us how to fly.
BTW, Did those QF Sky Gods taxi through the puddles? Tsk Tsk. Flying should stop in heavy rain!

[rejeh]

I have read regarding water on hot breams, but those somebody has any information regarding the application of Air Conditione from the external unit directly to hot brakes on the Airbus?, thanks.

[CV880]

To go back to the original question JAL had a water misting system for cooling the brakes at the old Taipei City airport (and maybe other places but TPE was where our staff saw it in action).. It was quite successful and my employer was looking at copying it for our own use as hot brakes and quick turn arounds at the old TPE were quite common.