Airbus Auto Brake system
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If you used MAX auto brakes on a A330 with a fairly heavy load the brakes will get so hot the thermal fuses in the wheels go.
The aircraft that I saw this happen on did NOT have inbuilt cooling fans but I am informed that if the brake temp goes thru 470 Deg cooling fans or not you are up for wheel changes....
The aircraft that I saw this happen on did NOT have inbuilt cooling fans but I am informed that if the brake temp goes thru 470 Deg cooling fans or not you are up for wheel changes....
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Hey there Bolty,
Stop scaring the you know what out of everyone!
The fuse plugs should not melt earlier than 800 degrees C (1472 degrees F). That being the limit in the maintenance manual.
They MAY melt earlier, but hey, some times you catch a break.
As to use of auto brake MAX, there is no reason to say that setting will cause an overheat if you are heavy. I've never seen an overheat when auto was used, but I have seen a few when a pilot stomped the pedals.
In any event, the Airbus brakes have always stunk and they do funny things if you just look at them the wrong way, so what does it matter?
PB
Stop scaring the you know what out of everyone!
The fuse plugs should not melt earlier than 800 degrees C (1472 degrees F). That being the limit in the maintenance manual.
They MAY melt earlier, but hey, some times you catch a break.
As to use of auto brake MAX, there is no reason to say that setting will cause an overheat if you are heavy. I've never seen an overheat when auto was used, but I have seen a few when a pilot stomped the pedals.
In any event, the Airbus brakes have always stunk and they do funny things if you just look at them the wrong way, so what does it matter?
PB
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Hey Plastic
I was relaying what I have seen.
I agree with what the manual states. I was not trying to scare anyone as the thermal plugs wait for quite a while before letting go, the tech crew will probably be doing their duty free shopping at the time the heat soak from the un cooled brake does the damage.
I have also seen an RTO with 300 pax on board at 80 odd knots and temps reached 420. No drama
If there are some A330 pilots out there whom are willing to give the MAX setting a go, I will gladly be proven wrong.
I was relaying what I have seen.
I agree with what the manual states. I was not trying to scare anyone as the thermal plugs wait for quite a while before letting go, the tech crew will probably be doing their duty free shopping at the time the heat soak from the un cooled brake does the damage.
I have also seen an RTO with 300 pax on board at 80 odd knots and temps reached 420. No drama
If there are some A330 pilots out there whom are willing to give the MAX setting a go, I will gladly be proven wrong.
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Airbus Max auotobrake.
I was in an A300-600 that landed with max once by mistake,( no mention of the autobrake in the immediate reland check list- now changed)
Certainly dramatic made the first turn off,crew faces nearly as red as the discs, we had to wait for a couple of hours before we could change the tyres.
Certainly dramatic made the first turn off,crew faces nearly as red as the discs, we had to wait for a couple of hours before we could change the tyres.
Only half a speed-brake
Unlike Boeing, the Airbus MAX selection is the equivalent of full manual braking, it is alos the setting used for RTOs. Hence the use for landing is definitely a big no-no.
AutoBrake Max not to be used for landing as the manufacturer says don't do it.
DragonAir used it once on an A320 in an emergency landing after problem with electronic flight controls. The aircraft departed the runway after landing, crossed the grass and ended up on the parallel taxiway.
I been in two A330s that landed with AutoBrake Max accidently selected (by the copilot pushing the wrong button to select EGPWS display during descent - this happened after descent chex were completed which included Low or Med Auto Brake selection and cross-check).
These landings were normal for the first three seconds then got very sporty indeed! Lots of very subdued passengers and very red faces upfront.
Absolutely NO problem with brakes, tyres or brake temperatures due to normal landing weights being way below the very high weights and energy required for MTOW certification requirements of the braking system.
When we received our first A340-600 I noted that the AutoBrake system selector was changed from the previous standard pushbutton system.
DragonAir used it once on an A320 in an emergency landing after problem with electronic flight controls. The aircraft departed the runway after landing, crossed the grass and ended up on the parallel taxiway.
I been in two A330s that landed with AutoBrake Max accidently selected (by the copilot pushing the wrong button to select EGPWS display during descent - this happened after descent chex were completed which included Low or Med Auto Brake selection and cross-check).
These landings were normal for the first three seconds then got very sporty indeed! Lots of very subdued passengers and very red faces upfront.
Absolutely NO problem with brakes, tyres or brake temperatures due to normal landing weights being way below the very high weights and energy required for MTOW certification requirements of the braking system.
When we received our first A340-600 I noted that the AutoBrake system selector was changed from the previous standard pushbutton system.
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I have no tale to tell but I would think that if you land with a wrong autobrake setting, you very soon find out and can remedy the situation by shortly depressing the pedals. Since your feet are going rapidly in the same direction anyway 
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To add to Plastic bugs claims...
The thermal fuses in my companies fleet of A330 is set to melt when the hottest part of the rim reaches 205 Deg C as stated by the manual.....
I am not sure what plastic thinks aircraft wheels and tyres are made of to think they can stand 800 Deg C
Most ally alloys will deform at that temp and I am sure the tyres would burn.
And I have no idea what kind bearing grease to use in such high temperature applications.
The thermal fuses in my companies fleet of A330 is set to melt when the hottest part of the rim reaches 205 Deg C as stated by the manual.....
I am not sure what plastic thinks aircraft wheels and tyres are made of to think they can stand 800 Deg C
Most ally alloys will deform at that temp and I am sure the tyres would burn.
And I have no idea what kind bearing grease to use in such high temperature applications.
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Bolty,
Um, we ARE talking about INDICATED temps, right?
Bus brakes REGULARLY exceed 300 C with no problems.
600 C is met as well with no sweat. That's indicated from the core of the brake and is our prime (actually only) indicator (aside from flames or deflated tires).
800 C is the AMM special inspection limit if you haven't melted a fuse plug. That leads me to believe that exceeding 700 but not 800 would be OK for flight provided the fuse plug hasn't melted.
This ain't from someone I know, it's in the book.
PB
Um, we ARE talking about INDICATED temps, right?
Bus brakes REGULARLY exceed 300 C with no problems.
600 C is met as well with no sweat. That's indicated from the core of the brake and is our prime (actually only) indicator (aside from flames or deflated tires).
800 C is the AMM special inspection limit if you haven't melted a fuse plug. That leads me to believe that exceeding 700 but not 800 would be OK for flight provided the fuse plug hasn't melted.
This ain't from someone I know, it's in the book.
PB
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Plastis Bug
The surface temp of carbon brake discs may reach all manner of temperatures eg 800 DEG C but the overall brake temp is never allowed to reach such temperatures without various other fail safes kicking in.
Eg thermal fuses and over pressure valves relieving the tyre pressure before a critical pressure is reached.
please give a cut n paste from your "manual" to show the limits you describe.
As Ivan aromer described a similar incident I had seen, you should take note. I was not scaring anyone just relaying my experiences
Some aircraft have a crap braking systems that rely heavily on ground support equipment to keep them cool for a quick turn around!
All rudeness deleted and was unwarranted. Apologies Bolty
The fuse plugs should not melt earlier than 800 degrees C (1472 degrees F). That being the limit in the maintenance manual
The surface temp of carbon brake discs may reach all manner of temperatures eg 800 DEG C but the overall brake temp is never allowed to reach such temperatures without various other fail safes kicking in.
Eg thermal fuses and over pressure valves relieving the tyre pressure before a critical pressure is reached.
please give a cut n paste from your "manual" to show the limits you describe.
I was in an A300-600 that landed with max once by mistake,( no mention of the autobrake in the immediate reland check list- now changed)
Certainly dramatic made the first turn off, crew faces nearly as red as the discs, we had to wait for a couple of hours before we could change the tyres
Certainly dramatic made the first turn off, crew faces nearly as red as the discs, we had to wait for a couple of hours before we could change the tyres
Some aircraft have a crap braking systems that rely heavily on ground support equipment to keep them cool for a quick turn around!
All rudeness deleted and was unwarranted. Apologies Bolty
Last edited by Bolty McBolt; 1st Oct 2006 at 02:58.
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Somebody owes me a beer, preferably Australian.
For reference, please see:
TASK 05-51-16-200-801
Inspection After Brake Overheat
Specifically:
1. Reason for the Job
This inspection is necessary after a crew report of:
- a brake temperature of more than 800 deg. C,
- wheel fuse plug(s) melt.
Now, somebody out there may have a system of measuring the temps at the wheel rim, if so, fine. I am not aware of any such system, but I have been proved wrong in the past. Always a good day to learn something new. Until I see otherwise, the only temperature reference I can consider is the one installed on the airplane that measures the temperature at the core of the brake pack.
As to being relegated to the spotters corner, well, aren't we ALL spotters? I mean, just what got us into this cockamamie business in the first place if it wasn't watching airplanes? Now we actually get PAID to hang around airports and look at airplanes all day! What a deal!
Happy Contrails Folks!
PB
For reference, please see:
TASK 05-51-16-200-801
Inspection After Brake Overheat
Specifically:
1. Reason for the Job
This inspection is necessary after a crew report of:
- a brake temperature of more than 800 deg. C,
- wheel fuse plug(s) melt.
Now, somebody out there may have a system of measuring the temps at the wheel rim, if so, fine. I am not aware of any such system, but I have been proved wrong in the past. Always a good day to learn something new. Until I see otherwise, the only temperature reference I can consider is the one installed on the airplane that measures the temperature at the core of the brake pack.
As to being relegated to the spotters corner, well, aren't we ALL spotters? I mean, just what got us into this cockamamie business in the first place if it wasn't watching airplanes? Now we actually get PAID to hang around airports and look at airplanes all day! What a deal!
Happy Contrails Folks!
PB
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Can anyone enlighten me?
For the A330
Is there more than one fuse plug on a wheel?
How/where is "brake temperature" measured, and is it the mean temperature of the pads, or just at a certain spot?
If fuse plugs let go at a certain temperature, is it correct to say that generally, for the A330, this equals a pre defined amount of absorbed enery by the brakes, regardless of landing speed or weight?
Stan
Is there more than one fuse plug on a wheel?
How/where is "brake temperature" measured, and is it the mean temperature of the pads, or just at a certain spot?
If fuse plugs let go at a certain temperature, is it correct to say that generally, for the A330, this equals a pre defined amount of absorbed enery by the brakes, regardless of landing speed or weight?
Stan
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Ok I am back on the rails.. Apologies for my previous post.
Back to the debate
My point about brake temps revolves around some basic metallurgy 101
Almost all aluminium and magnesium alloys used in aviation construction have a melting point at 650 Degree C.(+/- 50 Deg C) and an annealing temp at around 400 Degree C.
Lets assume these alloys structural strength/integrity is not compromised up to 350 Deg C
If you wish to check my figures use the link below
www.matweb.com/search/SearchSubcat.asp?st=sc&catid=352#nfm
A330 wheels are made of these alloys and therefore could not operate in temperatures above 350 Deg C
The A330 has a “eutectic” fuse in each wheel that will melt at 205 Deg C and to use the words out of the manual “ the fuse will melt when the hottest part of the rim reaches 205 Deg C”
The A330 wheel also has an over pressure relief valve in case pressures get to high.
The inner side of the rim/wheel has a stainless steel heat sheild fitted to prevent the working brake temperatures radiating into the wheel and tyre.
The brake temp is measured by an thermocouple probe that is positioned in the core of the brake to give indication of the working temp.
The manual ref given by plastic bug is a special inspection ie Something has gone wrong.
To explain my earlier post about tyres deflating from hard applications of brakes. The brake assy on the A330 is so large that when the "heat pack" (carbon discs and rotors) gets to a certain temp there is insufficient conductivity to wick the heat away before it soaks into the wheel assy thru the heat sheild to the rim to prevent the 205 deg C being felt at the fuse..
From my experience if you have an indicated brake temp at 800 Degs and the eutectic fuse will have melted and I am certainly not going anywhere near a wheel or brake that is that hot and still has the nitrogen in the tyre
Back to the debate
My point about brake temps revolves around some basic metallurgy 101
Almost all aluminium and magnesium alloys used in aviation construction have a melting point at 650 Degree C.(+/- 50 Deg C) and an annealing temp at around 400 Degree C.
Lets assume these alloys structural strength/integrity is not compromised up to 350 Deg C
If you wish to check my figures use the link below
www.matweb.com/search/SearchSubcat.asp?st=sc&catid=352#nfm
A330 wheels are made of these alloys and therefore could not operate in temperatures above 350 Deg C
The A330 has a “eutectic” fuse in each wheel that will melt at 205 Deg C and to use the words out of the manual “ the fuse will melt when the hottest part of the rim reaches 205 Deg C”
The A330 wheel also has an over pressure relief valve in case pressures get to high.
The inner side of the rim/wheel has a stainless steel heat sheild fitted to prevent the working brake temperatures radiating into the wheel and tyre.
The brake temp is measured by an thermocouple probe that is positioned in the core of the brake to give indication of the working temp.
The manual ref given by plastic bug is a special inspection ie Something has gone wrong.
To explain my earlier post about tyres deflating from hard applications of brakes. The brake assy on the A330 is so large that when the "heat pack" (carbon discs and rotors) gets to a certain temp there is insufficient conductivity to wick the heat away before it soaks into the wheel assy thru the heat sheild to the rim to prevent the 205 deg C being felt at the fuse..
From my experience if you have an indicated brake temp at 800 Degs and the eutectic fuse will have melted and I am certainly not going anywhere near a wheel or brake that is that hot and still has the nitrogen in the tyre
Last edited by Bolty McBolt; 4th Oct 2006 at 04:17.
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Ho Kay..
Lets take a break from the physics debate for a bit and get back to the original question, which was: "Why can't you use auto brake MAX for landing" or something like that.
All other parameters being met, auto brake lo and med engage upon main wheel weight on wheels. MAX engages when all of those parameters are met PLUS NOSE GEAR weight on wheels.
So you are the greatest Pilot in the world, you decide to do a snappy arrival, you select auto brake MAX. You touch down flawlessly, noone feels the mains touch down, the SMOOTHEST landing(s) in recorded history. You demonstrate your superior airmanship by stretching aerodynamic braking until you can no longer hold the nose off..
TOUCHDOWN! The brakes apply FULLY, the Grandmother in 39C loses her teeth to the back of the head of the unfortunate sot in 29C, you actually make the taxiway behind you and every other unsecured item in the airplane is now embedded in the cockpit door like something out of "Carrie".
Thank God for that armor plated door!
So the question should not be: "Can you use auto brake MAX?", but "Should you...?"
Naturally, if you are someone who routinely plants the nose gear on landing, this wouldn't really apply, but that would be another topic, wouldn't it?
PB
Lets take a break from the physics debate for a bit and get back to the original question, which was: "Why can't you use auto brake MAX for landing" or something like that.
All other parameters being met, auto brake lo and med engage upon main wheel weight on wheels. MAX engages when all of those parameters are met PLUS NOSE GEAR weight on wheels.
So you are the greatest Pilot in the world, you decide to do a snappy arrival, you select auto brake MAX. You touch down flawlessly, noone feels the mains touch down, the SMOOTHEST landing(s) in recorded history. You demonstrate your superior airmanship by stretching aerodynamic braking until you can no longer hold the nose off..
TOUCHDOWN! The brakes apply FULLY, the Grandmother in 39C loses her teeth to the back of the head of the unfortunate sot in 29C, you actually make the taxiway behind you and every other unsecured item in the airplane is now embedded in the cockpit door like something out of "Carrie".
Thank God for that armor plated door!
So the question should not be: "Can you use auto brake MAX?", but "Should you...?"
Naturally, if you are someone who routinely plants the nose gear on landing, this wouldn't really apply, but that would be another topic, wouldn't it?
PB
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To explain my earlier post about tyres deflating from hard applications of brakes. The brake assy on the A330 is so large that when the "heat pack" (carbon discs and rotors) gets to a certain temp (above 490) there is insufficient conductivity in a confined space to wick the heat away before it soaks into the wheel assy thru the heat sheild to the rim to prevent the 205 deg C being felt at the fuse..without external cooling applied.
My notes state when MAX brakes selected they come on without delay(FCOM states with nose squat made) , no mention of nose gear squat switch where as the LO and MED setting have a delay built in to give an artificial feel (not sure why??)
My notes state when MAX brakes selected they come on without delay(FCOM states with nose squat made) , no mention of nose gear squat switch where as the LO and MED setting have a delay built in to give an artificial feel (not sure why??)
Last edited by Bolty McBolt; 6th Oct 2006 at 03:53. Reason: found ref in FCOM
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Bolty,
The "feel" for the Lo and Med settings are to stop the A/B system instantly trying to attain x.x m/s/s decell, but rather give it a smooth transition.
I recall (but can't find a reference) a WoW nose wheel requirement for MAX to occur, but can't find a reference. Certainly when I saw it in the sim last there is a delay until the nose wheel is down.
Off topic, <since you seem to know a bit about it> are you sure they use Mg and Al alloys in the region of the wheels/brakes? I could see Ti/Co/Ni alloys, (or maybe Mn at a stretch) but Mg and Al just doesn't add up to me. Happy to be told otherwise, but what little I do know about high alloy metallurgy makes it difficult to grasp your statement.
The "feel" for the Lo and Med settings are to stop the A/B system instantly trying to attain x.x m/s/s decell, but rather give it a smooth transition.
I recall (but can't find a reference) a WoW nose wheel requirement for MAX to occur, but can't find a reference. Certainly when I saw it in the sim last there is a delay until the nose wheel is down.
Off topic, <since you seem to know a bit about it> are you sure they use Mg and Al alloys in the region of the wheels/brakes? I could see Ti/Co/Ni alloys, (or maybe Mn at a stretch) but Mg and Al just doesn't add up to me. Happy to be told otherwise, but what little I do know about high alloy metallurgy makes it difficult to grasp your statement.