Brake Temperature
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Originally Posted by alexban
Milt, Boeing says that in case of hot brakes,for ex high speed RTo, use of parking brakes should be avoided.What would be the reason for this,in your oppinion?
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Don't we still need someone to tell us what it is that may cause the brake pads to move away from the disks when, parked against the chocks, we let the brakes off? Same for a car's brakes. Could it be the relaxation of the O ring seals (usually square) slightly retracting their pistons?
Once did a max brake stop with a heavy on Boscombe Down's wetted runway from a speed calculated to cause the brake units to reach maximum designed energy absorption. Antiskids were Maxarets. An exciting ride!
A couple of tyres blew at low speed and much smoke as we ground to a stop. Disks were thick copper plated with hard chrome. Disassembled brake units looked terrible but they passed the test. Don't recall the final disk temperature nor whether the brake units were reuseable.
Once did a max brake stop with a heavy on Boscombe Down's wetted runway from a speed calculated to cause the brake units to reach maximum designed energy absorption. Antiskids were Maxarets. An exciting ride!
A couple of tyres blew at low speed and much smoke as we ground to a stop. Disks were thick copper plated with hard chrome. Disassembled brake units looked terrible but they passed the test. Don't recall the final disk temperature nor whether the brake units were reuseable.
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mark,I don't know about racing cars,but brakes on the 737 are nothing like brakes on my car.There is small chance of getting a 'hot spot' cause the brake pad is actually a brake disk,not like a car brake pad.
milt,there are some springs on brake assembly,which could probably move away the brake pad.First time I'll see the mechs changing a tyre I'll go take a closer look at the brake...I have the designs but I can't get a clue from them..
milt,there are some springs on brake assembly,which could probably move away the brake pad.First time I'll see the mechs changing a tyre I'll go take a closer look at the brake...I have the designs but I can't get a clue from them..
Last edited by alexban; 8th Jul 2006 at 15:20.
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B737 AMM:
"Each main wheel is provided with a brake unit bolted to a flange on the axle. The brakes are multiple disc type, with stationary carrier and divided lining discs, and segmented rotating brake discs. Each brake is provided with pistons which actuate the brakes when hydraulic pressure is applied. The brakes are also provided with combination return springs and automatic adjusters. The automatic adjusters compensate for brake wear."
and A320:(d)
Do not set the parking brake ON when "BRAKES HOT" warning is shown on the upper ECAM DU.
12 twists per inch is right, it's a bit of a hangover from the old days of brake siezures. Some airlines release them on blocks and some dont.
"Each main wheel is provided with a brake unit bolted to a flange on the axle. The brakes are multiple disc type, with stationary carrier and divided lining discs, and segmented rotating brake discs. Each brake is provided with pistons which actuate the brakes when hydraulic pressure is applied. The brakes are also provided with combination return springs and automatic adjusters. The automatic adjusters compensate for brake wear."
and A320:(d)
Do not set the parking brake ON when "BRAKES HOT" warning is shown on the upper ECAM DU.
12 twists per inch is right, it's a bit of a hangover from the old days of brake siezures. Some airlines release them on blocks and some dont.
Another aspect to consider, perhaps the most important, is the heat flow and heat soak into the tyres. Tyres probably suffer more from overheat than the brake packs.
This was one of the reasons in the recommendation in the BAe146 / Avro RJ for brakes off; it also was a major part of the ‘brakes’ limitation on early aircraft for the number of short sectors within a given time.
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This was one of the reasons in the recommendation in the BAe146 / Avro RJ for brakes off; it also was a major part of the ‘brakes’ limitation on early aircraft for the number of short sectors within a given time.
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Originally Posted by alexban
mark,I don't know about racing cars,but brakes on the 737 are nothing like brakes on my car.There is small chance of getting a 'hot spot' cause the brake pad is actually a brake disk,not like a car brake pad.
milt,there are some springs on brake assembly,which could probably move away the brake pad.First time I'll see the mechs changing a tyre I'll go take a closer look at the brake...I have the designs but I can't get a clue from them..
milt,there are some springs on brake assembly,which could probably move away the brake pad.First time I'll see the mechs changing a tyre I'll go take a closer look at the brake...I have the designs but I can't get a clue from them..
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Does this help shon7?
"Increasingly, people in industry and academia are exploring the benefits of of fuzzy logic and its related technologies. Fuzzy logic can be used for situations in which conventional logic technologies are not effective, such as systems and devices that cannot be precisely described by mathematical models, those that have significant uncertainties or contradictory conditions, and linguistically controlled devices or systems. As Lotfi Zadeh once stated, fuzzy logic is not going to replace conventional logic (computers) or methodologies, rather it will supplement them in circumstances where conventional approaches fail to solve a problem effectively.
"In recent years, there has been a growing interest in fuzzy logic, both in industry and academia. Current applications include modeling, evaluation, optimization, decision making, control, diagnosis and information. In particular, fuzzy logic is best suited for control-systems fields. For instance, fuzzy logic has been applied in areas such as breakdown prediction of nuclear reactors in Europe, earthquake forecasting in China, and subway control in Japan.
"One prominent application of fuzzy logic is in the anti-lock braking system found in many modern automobiles. The control rules that describe an anti-lock braking system may consist of parameters such as the car's speed, the brake pressure, the brake temperature, the interval between applications of the brakes and the angle of the car's lateral motion to its forward motion. The range of values of these parameters are all continuous, open to interpretation by a design engineer. One such rule in an anti-lock braking system could be:
IF brake temperature is 'warm' AND speed is 'not very fast,' then brake pressure is 'slightly decreased.'
"The temperature might have a range of states such as cold, cool, warm and hot; the range of these linguistic terms can be precisely determined by defining membership functions by an expert. "There are many consumer products that use fuzzy logic in their operation. There are also many fuzzy logic chips (processors) that are built to do special tasks without using conventional computers. The outlook for fuzzy logic is therefore very promising."
"Increasingly, people in industry and academia are exploring the benefits of of fuzzy logic and its related technologies. Fuzzy logic can be used for situations in which conventional logic technologies are not effective, such as systems and devices that cannot be precisely described by mathematical models, those that have significant uncertainties or contradictory conditions, and linguistically controlled devices or systems. As Lotfi Zadeh once stated, fuzzy logic is not going to replace conventional logic (computers) or methodologies, rather it will supplement them in circumstances where conventional approaches fail to solve a problem effectively.
"In recent years, there has been a growing interest in fuzzy logic, both in industry and academia. Current applications include modeling, evaluation, optimization, decision making, control, diagnosis and information. In particular, fuzzy logic is best suited for control-systems fields. For instance, fuzzy logic has been applied in areas such as breakdown prediction of nuclear reactors in Europe, earthquake forecasting in China, and subway control in Japan.
"One prominent application of fuzzy logic is in the anti-lock braking system found in many modern automobiles. The control rules that describe an anti-lock braking system may consist of parameters such as the car's speed, the brake pressure, the brake temperature, the interval between applications of the brakes and the angle of the car's lateral motion to its forward motion. The range of values of these parameters are all continuous, open to interpretation by a design engineer. One such rule in an anti-lock braking system could be:
IF brake temperature is 'warm' AND speed is 'not very fast,' then brake pressure is 'slightly decreased.'
"The temperature might have a range of states such as cold, cool, warm and hot; the range of these linguistic terms can be precisely determined by defining membership functions by an expert. "There are many consumer products that use fuzzy logic in their operation. There are also many fuzzy logic chips (processors) that are built to do special tasks without using conventional computers. The outlook for fuzzy logic is therefore very promising."
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Brake cooling
I thought there was a much-earlier thread on brake cooling and release/not-release, but I couldn't find it because the search facilities of this latest generation of [PPRUNE's] vBulletin software had defeated me and I couldn't make the search or advanced search functions search more than one keyword.
I might have typed in several keywords but it searched as keyword1 OR keyword2 OR keyword3 etc. This potentially returned thousands of posts but since there is a limit of 500 posts in the search response, many were not actually listed. The results were often not much use.
No longer – the earlier brake cooling thread is thread=10891
For other searchers who have been struggling, let me share with you the results of umpteen trawls through arcane geek forums to find out how to search this bulletin board with more than one keyword. It's probably something that everyone else knows but here it is:
RIGHT WAY
brakes+cooling+release
ERRATIC WAY
brakes +cooling +release
WRONG WAY
brakes AND cooling AND release
I thought there was a much-earlier thread on brake cooling and release/not-release, but I couldn't find it because the search facilities of this latest generation of [PPRUNE's] vBulletin software had defeated me and I couldn't make the search or advanced search functions search more than one keyword.
I might have typed in several keywords but it searched as keyword1 OR keyword2 OR keyword3 etc. This potentially returned thousands of posts but since there is a limit of 500 posts in the search response, many were not actually listed. The results were often not much use.
No longer – the earlier brake cooling thread is thread=10891
For other searchers who have been struggling, let me share with you the results of umpteen trawls through arcane geek forums to find out how to search this bulletin board with more than one keyword. It's probably something that everyone else knows but here it is:
RIGHT WAY
brakes+cooling+release
ERRATIC WAY
brakes +cooling +release
WRONG WAY
brakes AND cooling AND release
