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Brake Cooling With Steam  
User currently offlineHAWK21M From , joined Dec 1969, posts, RR:
Posted (7 years 5 months 2 weeks 7 hours ago) and read 3537 times:


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I've noticed this a lot of Russian Carriers.In case of Hot brakes,use of steam/water is a normal practice.
Wouldn't the Brakes/Wheel be exposed to shock treatment in this case & crack.

regds
MEL

24 replies: All unread, jump to last
 
User currently offlineBAe146QT From , joined Dec 1969, posts, RR:
Reply 1, posted (7 years 5 months 2 weeks 6 hours ago) and read 3531 times:

Not sure about cracking, but water + hot (metal) brake disk = warping because of uneven cooling.

The comment on the picture leads me to infer that this was NOT normal practice or something that was done by design. It was probably a case of "warped disks would be better than a fire". And if they warped or cracked then I guess they would have to replace them.

Perhaps they are carbon silicide or ceramic? I don't have any figures but I expect they are more resistant to warpage.


User currently offline411A From , joined Dec 1969, posts, RR:
Reply 2, posted (7 years 5 months 1 week 6 days 22 hours ago) and read 3444 times:

Standard procedure on the Lockheed TriStar if the airplane is landed with flaps/slats retracted, due to a flap/slat malfunction, water is used to cool the tires, and brakes....carefully.
Works as advertised, and in this way, it is possible to prevent wheel fuse plugs from melting.


User currently offlineTheJoe From , joined Dec 1969, posts, RR:
Reply 3, posted (7 years 5 months 1 week 6 days 16 hours ago) and read 3393 times:

Mmmm, third wheel from the left looks a little average. Almost no tread left. The one on the far right isn't so healthy as well! I'd say they would be U/S, it certainly are by our standards! Makes me wonder how good the brakes are... Possibly the reason for the overheat?

User currently offlineMD11Engineer From , joined Dec 1969, posts, RR:
Reply 4, posted (7 years 5 months 1 week 6 days 15 hours ago) and read 3373 times:

If water is being used, then NOT as astream, but as a fine fog to prevent shock cooling and damage to the brakes.

Jan


User currently offlineHAWK21M From , joined Dec 1969, posts, RR:
Reply 5, posted (7 years 5 months 1 week 6 days 15 hours ago) and read 3370 times:

On the Boeings.Isn't spraying of water on the Brakes/wheels when hot Not permitted.
regds
MEL


User currently offlineArrow From , joined Dec 1969, posts, RR:
Reply 6, posted (7 years 5 months 1 week 6 days 7 hours ago) and read 3309 times:
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I thought the preferred cooling method was high-capacity fans blowing air over the bogies. Gives you a much more even cooling effect, although it probably takes longer. But I guess that would be problematic if it looked like a fire was imminent

User currently offlineBAe146QT From , joined Dec 1969, posts, RR:
Reply 7, posted (7 years 5 months 1 week 6 days 5 hours ago) and read 3288 times:

Quoting Arrow:
But I guess that would be problematic if it looked like a fire was imminent

Agreed. The way I read it - and 411A's post confirms it even though he's talking about a different bird - is that it's certainly an abnormal procedure. Not something that would be done as a matter of course and might have negative side-effects that require corrective action afterward.

I'm obviously not a mech, but I would expect that at the very least, it would require an inspection of sorts.


User currently offlineTheJoe From , joined Dec 1969, posts, RR:
Reply 8, posted (7 years 5 months 1 week 5 days 17 hours ago) and read 3238 times:

Read the discription on the photo... It says that the brakes became overheated and the fire-fighters hosed them down with water. Obviously not a normal procedure.

Probably due to poor maintenance.

Quoting TheJoe (Reply 3):
Mmmm, third wheel from the left looks a little average. Almost no tread left. The one on the far right isn't so healthy as well! I'd say they would be U/S, it certainly are by our standards! Makes me wonder how good the brakes are... Possibly the reason for the overheat?


User currently offlineL-188 From , joined Dec 1969, posts, RR:
Reply 9, posted (7 years 5 months 1 week 5 days 17 hours ago) and read 3237 times:

Quoting TheJoe (Reply 3):
Mmmm, third wheel from the left looks a little average. Almost no tread left. The one on the far right isn't so healthy as well! I'd say they would be U/S, it certainly

Got to be careful with that one. There was a lot of heartburn up here when the russians started flying into Anchorage. A lot of the FAA guys where tagging the russians for bad tires, but according to russian standards they where perfectly fine.

Quoting HAWK21M (Reply 5):
On the Boeings.Isn't spraying of water on the Brakes/wheels when hot Not permitted.

All Boeing? I ask because a lot of the newer ones have carbon fiber vs. steel.

Quoting TheJoe (Reply 8):
It says that the brakes became overheated and the fire-fighters hosed them down with water

Where that firefighter is might not be the smartest place if a blowout plug melts.


User currently offlineMD11Engineer From , joined Dec 1969, posts, RR:
Reply 10, posted (7 years 5 months 1 week 5 days 17 hours ago) and read 3234 times:

Quoting L-188 (Reply 9):
Quoting TheJoe (Reply 3):
Mmmm, third wheel from the left looks a little average. Almost no tread left. The one on the far right isn't so healthy as well! I'd say they would be U/S, it certainly

Got to be careful with that one. There was a lot of heartburn up here when the russians started flying into Anchorage. A lot of the FAA guys where tagging the russians for bad tires, but according to russian standards they where perfectly fine.

Most western airlines rethread their tyres, so the maxiimum wear is just to show the second thread reinforcement layer.
Russian airlines (as far as I have seen them) use their tyres totally up and scrap them.

Jan


User currently offlineTheJoe From , joined Dec 1969, posts, RR:
Reply 11, posted (7 years 5 months 1 week 5 days 16 hours ago) and read 3228 times:

Quoting MD11Engineer (Reply 10):
Most western airlines rethread their tyres, so the maxiimum wear is just to show the second thread reinforcement layer.
Russian airlines (as far as I have seen them) use their tyres totally up and scrap them.

That's a very good point. We had an An-124 come in to work and we noticed that as well. As you can imagine we don't have to much to do with Russian airlines over here! Thanks for the info.


User currently offlineBallpeeen From , joined Dec 1969, posts, RR:
Reply 12, posted (7 years 5 months 1 week 5 days 12 hours ago) and read 3194 times:

Quoting TheJoe (Reply 8):
Probably due to poor maintenance.

The brake overheated due to poor mx? Not poor piloting or adverse runway conditions? Why does everyone hate mechanics so much?

As to the tire, most operators I'm familiar with allow for revenue dispatch and return with a certain amount of cord showing through. Applying that standard here, I would change that tire if it was RON, but during a turn, I would have to let it go.


User currently offlineBAe146QT From , joined Dec 1969, posts, RR:
Reply 13, posted (7 years 5 months 1 week 5 days 10 hours ago) and read 3182 times:

Quoting Ballpeen:
The brake overheated due to poor mx? Not poor piloting or adverse runway conditions?

I think you've got a good point.

The photo description (which TheJoe asked us to look at in reply 8) states that the aircraft was landing on a 2000m runway.

The rollout for an IL76T is between 800 to 1000m depending on weight.

I'm not really sure how to word this so please don't be too harsh on me, but I reckon that it is not unreasonable to say that in certain conditions, (missing the TDZ, tailwind, floating, contaminated runway, off-runway obstruction or terrain) it would possible for that 2000 metres to be a little... tight.

I'll leave it to someone who is ATP qualified to provide a factual view, but I think that from a simple photo it's not really fair to bash MX - Russian or not.


User currently offlineHAWK21M From , joined Dec 1969, posts, RR:
Reply 14, posted (7 years 5 months 1 week 5 days 9 hours ago) and read 3170 times:

Quoting TheJoe (Reply 8):
It says that the brakes became overheated and the fire-fighters hosed them down with water. Obviously not a normal procedure

Irrespective.One should not use Water as a cooling medium on Overheated brakes & also avoiid approaching them until cooled,especially from sides.

Quoting L-188 (Reply 9):
All Boeing? I ask because a lot of the newer ones have carbon fiber vs. steel

All Boeing.But those that are Overheated brakes.

regds
MEL


User currently offlineBAe146QT From , joined Dec 1969, posts, RR:
Reply 15, posted (7 years 5 months 1 week 5 days 5 hours ago) and read 3143 times:

Quoting HAWK21M (Reply 14):
Irrespective.One should not use Water as a cooling medium on Overheated brakes & also avoiid approaching them until cooled,especially from sides.

But surely destroying a brake disk - or even an entire hub assembly - is better than a hull loss through fire?


User currently offlineTheJoe From , joined Dec 1969, posts, RR:
Reply 16, posted (7 years 5 months 1 week 4 days 16 hours ago) and read 3096 times:

Quoting Ballpeeen (Reply 12):
The brake overheated due to poor mx? Not poor piloting or adverse runway conditions? Why does everyone hate mechanics so much?

Well, I was just saying that judging by the condition of the other tyres. By the way, I am a mechanic so no, I do not hate myself! Big grin

Quoting Ballpeeen (Reply 12):
As to the tire, most operators I'm familiar with allow for revenue dispatch and return with a certain amount of cord showing through. Applying that standard here, I would change that tire if it was RON, but during a turn, I would have to let it go.

Well that comes down to the individual operator / manufacturer limits. Yes, I would let it go in that condition as well. Just a suggestion. I've seen aircraft taxi back in after high-energy stops and we haven't had to hose the brakes down with water! In the situation we are talking about you're right, it could have been the pilots, it could have been poor conditions, it could have been the design, it could be through poor manufacturing techniques or it could be through poor maintenance and worn parts! I guess we'll never know...


User currently offlineHAWK21M From , joined Dec 1969, posts, RR:
Reply 17, posted (7 years 5 months 1 week 4 days 15 hours ago) and read 3092 times:

Quoting TheJoe (Reply 16):
I've seen aircraft taxi back in after high-energy stops and we haven't had to hose the brakes down with water



Quoting BAe146QT (Reply 15):
But surely destroying a brake disk - or even an entire hub assembly - is better than a hull loss through fire

I was referring to the Dangers posed by Water Spray.This could be an Exception case,But at BOM I've seen This being done on Russian Aircraft very frequently.

regds
MEL


User currently offlineScooter01 From , joined Dec 1969, posts, RR:
Reply 18, posted (7 years 5 months 1 week 4 days 1 hour ago) and read 3035 times:
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Quoting MD11Engineer (Reply 10):
Russian airlines (as far as I have seen them) use their tyres totally up and scrap them.

Not just their airliners....
Big version: Width: 1024 Height: 1536 File size: 1106kb

Found this MiG-23 in Riga, guess why it was left there to rot.



But one thing I've learned about brakes (in car racing) is that if you keep on moving during the cool-down period, the discs have a lesser chance of warping since the heat from the pads will be distributed more evenly.

Scooter


User currently offlineL-188 From , joined Dec 1969, posts, RR:
Reply 19, posted (7 years 5 months 1 week 3 days 19 hours ago) and read 3008 times:

Quoting Scooter01 (Reply 18):
Found this MiG-23 in Riga, guess why it was left there to rot.

Actually I think that is a serviceable tire for the russians.

I remember once seeing a similar condition tire. It was on a RAF Jaguar during arctic thunder. Those low pressure tires on the nosewheel are not designed for paved conditions.


User currently offlineHAWK21M From , joined Dec 1969, posts, RR:
Reply 20, posted (7 years 5 months 1 week 2 days 22 hours ago) and read 2959 times:

Quoting Scooter01 (Reply 18):
Found this MiG-23 in Riga, guess why it was left there to rot.

Possibility that since it was a stored Aircraft,the tires could have been replaced with worn out ones while the existing ones reused on a servicable jet of the same type.

Lots of corrosion on the Hardware though.For How long was this Aircraft not flying.

regds
MEL


User currently offlineScooter01 From , joined Dec 1969, posts, RR:
Reply 21, posted (7 years 5 months 1 week 2 days 12 hours ago) and read 2929 times:
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Quoting HAWK21M (Reply 20):
For How long was this Aircraft not flying.

The pic was taken on July 12, 2004. Russia completed it's military withdrawal in 1994 so this gives you a timeframe.

BTW, I found the notes I wrote while visiting the aircraft collection at Skulte, and from a plaque in front of the plane it says this is a MiG 25 RBS, built in '72. RBS means it is a reconnaissance-bomber and they were used in the Baltic area.

Sorry about giving the wrong description in the earlier pic.

Hope this helps

Scooter

[Edited 2007-02-18 11:54:21]

User currently offlineHAWK21M From , joined Dec 1969, posts, RR:
Reply 22, posted (7 years 5 months 1 week 1 day 20 hours ago) and read 2872 times:

Quoting Scooter01 (Reply 21):
The pic was taken on July 12, 2004. Russia completed it's military withdrawal in 1994 so this gives you a timeframe

That Explains the Corrosion & Tire Condition.
regds
MEL


User currently offlineGrunf From , joined Dec 1969, posts, RR:
Reply 23, posted (7 years 5 months 1 week 1 day 15 hours ago) and read 2854 times:

Quoting Scooter01 (Reply 18):

But one thing I've learned about brakes (in car racing) is that if you keep on moving during the cool-down period, the discs have a lesser chance of warping since the heat from the pads will be distributed more evenly.

You do a cooldown lap to let discs cool down evenly. When not braking, pads aren't heating up the discs. Pads have small thermal capacity and will heat up only when braking. It's the disc itself that acts as energy storage that is to be dissipated as fast as possible. Most race cars have cooling scoops that let air enter the disc hub. Driving around (as opposed to standing still) "scoops" the air into the brakes, thus making them cool down more quickly.

Hosing hot steel brakes with water will almost always warp them. It doesn't always make them unusable but vibrations from warped disc warrants an replacement. Don't know how carbon or ceramic discs behave though.


On topic:
Racing trucks usually us watercooled brakes (by evenly spraying water when braking), so I guess it's possible to do this even for a airplane brakes but weight penalty probably isn't worth it.


User currently offlineScooter01 From , joined Dec 1969, posts, RR:
Reply 24, posted (7 years 5 months 1 week 1 day 2 hours ago) and read 2811 times:
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Quoting Grunf (Reply 23):
You do a cooldown lap to let discs cool down evenly. When not braking, pads aren't heating up the discs. Pads have small thermal capacity and will heat up only when braking.

I probably did not express my self correctly earlier, what I meant was moving/pushing the car a 3rd or less of a wheel-revolution back and forth in the pits after a race or a lapping session, not to let it sit and cool off stationary. This is particulary useful for those people who use their personal roadcars on lapping sessions.
Racecars in the Formula Ford/Formula V size or smaller usually don't use vented discs to have as little as possble of unsprung weight.
The heat stored in the pads and calipers is enough to create havoc in solid discs if the wheel-assembly is not moved around as mentioned earlier.

Scooter


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