Easy's first A319
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The 319's definately DO have brake fans. I've personally only had to use them twice so far. Hot brakes are really no problem, even with 25 min turnarounds. By the time you get taxying for the next departure they've cooled well below 250 degrees.
And EZY normally land the 737 with autobrakes on, normally 2, no matter what length the runway, but as there are no brake temp guages, as Man Flex says ' Ignorance is bliss'.
Last edited by kriskross; 18th Nov 2003 at 05:07.
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KTT's
I'm only a simpleton, and not an Airbus driver, but:
I'm confused. How does putting the gear down early before landing reduce the brake temperature? I'm assuming that the temperature rose due to braking and taxi-ing after landing, and would continue to rise if locked away in the belly.
You then said that "high temp's did not effect the takeoff performance, only when you could put the gear up. Delaying gear retraction would cool the brakes."
Delaying the gear retraction will surely cool the brakes, (I had to do it on a quick turn-round from a short runway in B767), but it will also effect the takeoff performance calculation if the gear is left dangling longer than expected.
Moving on quickly to the 'tongue in cheek phase'; I heard, many years ago from an old sage, that he had flown with a miss-guided youth who believed that fast taxing, and via all the puddles, would cool the tyres and brakes. While this might be true for racing cars and bikes, when on dry tyres, it sure ain't true for lumbering non earth bound machines.
tara.
I'm only a simpleton, and not an Airbus driver, but:
I'm confused. How does putting the gear down early before landing reduce the brake temperature? I'm assuming that the temperature rose due to braking and taxi-ing after landing, and would continue to rise if locked away in the belly.
You then said that "high temp's did not effect the takeoff performance, only when you could put the gear up. Delaying gear retraction would cool the brakes."
Delaying the gear retraction will surely cool the brakes, (I had to do it on a quick turn-round from a short runway in B767), but it will also effect the takeoff performance calculation if the gear is left dangling longer than expected.
Moving on quickly to the 'tongue in cheek phase'; I heard, many years ago from an old sage, that he had flown with a miss-guided youth who believed that fast taxing, and via all the puddles, would cool the tyres and brakes. While this might be true for racing cars and bikes, when on dry tyres, it sure ain't true for lumbering non earth bound machines.
tara.
RAt 5,
putting the gear down early before landing is like using almighty brakes fans! The chill factor of a 200mph wind is great for reducing the brake temps - after all thats exactly what brake fans do, albeit at a slower speed!!
Like early starts/late finishes, its all about culmulative fatigue or in this case temperature. If you have just done a sector, quick turnround and off again the brakes will 'store' a lot of heat in them - they may be, say, 180C when the gear is retracted as opposed to, say, 80C after the first take off of the day. If you then go on to do another 3 sectors with 20 min turnrounds the brake temps will increase more and more and the store of heat could get to the magic 300C. Used to be a problem going from Skiathos to thessaloniki - and that was after an hours turnround.
Agreed, take-off performance will be limited if gear is left down after takeoff, quite significantly I recall, somewhere in the order of 7 tonnes. but at the weights we fly around at it could still be possible.
A chap did a study once, in parallel with Airbus, and its such a complicated subject. very involved with considerations of OAT, speed brakes applied, what temp were brakes before application determining how much of a skim was taken off the carbon fibre discs etc etc etc. The upshot was to get as much heat into the brakes as quickly as possible and do so in one contimuous application (carbon fibre brakes, NOT steel) and so NOT to use autobrake!
Take cover!!!!
putting the gear down early before landing is like using almighty brakes fans! The chill factor of a 200mph wind is great for reducing the brake temps - after all thats exactly what brake fans do, albeit at a slower speed!!
Like early starts/late finishes, its all about culmulative fatigue or in this case temperature. If you have just done a sector, quick turnround and off again the brakes will 'store' a lot of heat in them - they may be, say, 180C when the gear is retracted as opposed to, say, 80C after the first take off of the day. If you then go on to do another 3 sectors with 20 min turnrounds the brake temps will increase more and more and the store of heat could get to the magic 300C. Used to be a problem going from Skiathos to thessaloniki - and that was after an hours turnround.
Agreed, take-off performance will be limited if gear is left down after takeoff, quite significantly I recall, somewhere in the order of 7 tonnes. but at the weights we fly around at it could still be possible.
A chap did a study once, in parallel with Airbus, and its such a complicated subject. very involved with considerations of OAT, speed brakes applied, what temp were brakes before application determining how much of a skim was taken off the carbon fibre discs etc etc etc. The upshot was to get as much heat into the brakes as quickly as possible and do so in one contimuous application (carbon fibre brakes, NOT steel) and so NOT to use autobrake!
Take cover!!!!
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Carbon Brakes
The use of Autobrake results in a constant deceleration rate during the landing roll which is achieved by modulating the brake pressure within a single application. A single application means reduced brake wear. It is also a means of brake temperature optimisation. To increase carbon brake life brakes should be operated either cold or hot but not at intermediate warm temperatures. Brake wear is highest at temperatures between 80 and 250 degrees centigrade (indicated).
P.S. If the brake fans are running then the limiting temperature of 300 degrees is equivalent to 150 degrees indicated (not 250!).
P.S. If the brake fans are running then the limiting temperature of 300 degrees is equivalent to 150 degrees indicated (not 250!).
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Norman Stanley Fletcher,
I know I'm referring to a quite old post now, but please, could you clarify one point:
Should that read:
" ... when the alpha (aoa) of the aircraft increases above Alpha Prot ......." ?
Also, except from the FCOM, could you specified on which bases you was able to conclude on this specific accident …
Thanks
I know I'm referring to a quite old post now, but please, could you clarify one point:
It becomes active when the alpha (aoa) of the aircraft decays below Alpha Prot (the angle of attack when the sidestick starts to control alpha directly) and before the stall aoa known as Alpha Max
" ... when the alpha (aoa) of the aircraft increases above Alpha Prot ......." ?
Also, except from the FCOM, could you specified on which bases you was able to conclude on this specific accident …
Thanks
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Hi Conf iture
I said "It becomes active when the alpha (aoa) of the aircraft decays below Alpha Prot (the angle of attack when the sidestick starts to control alpha directly) and before the stall aoa known as Alpha Max"
On the PFD, the speed tape shows speed which decays with high alpha. Also alongside the speed tape is a 'tiger's tail' which shows the area between V Alpha prot and V Alpha max (note they are given in terms of speed and not alpha). Therefore from the pilot's point of view these 2 features are displayed not in terms of numerical value of alpha (although that is clearly what they are related to) but in terms of a higher and lower speed. Therefore when I used the expression above it would have been more correct to talk in terms of decays towards V Alpha Prot and V Alpha max to avoid confusion. As you will be aware an Airbus pilot has no readout of alpha directly but of speed only. The limits are displayed to pilot in terms of speed and not alpha.
Regarding the accident, Airbus have published a number of specific reports on this accident and I believe that what I stated is an accurate view of the Airbus 'view' of what took place. It is certainly the widely-taught view within Airbus operators and I have seen no evidence to suggest that it is not correct.
I hope that helps.
I said "It becomes active when the alpha (aoa) of the aircraft decays below Alpha Prot (the angle of attack when the sidestick starts to control alpha directly) and before the stall aoa known as Alpha Max"
On the PFD, the speed tape shows speed which decays with high alpha. Also alongside the speed tape is a 'tiger's tail' which shows the area between V Alpha prot and V Alpha max (note they are given in terms of speed and not alpha). Therefore from the pilot's point of view these 2 features are displayed not in terms of numerical value of alpha (although that is clearly what they are related to) but in terms of a higher and lower speed. Therefore when I used the expression above it would have been more correct to talk in terms of decays towards V Alpha Prot and V Alpha max to avoid confusion. As you will be aware an Airbus pilot has no readout of alpha directly but of speed only. The limits are displayed to pilot in terms of speed and not alpha.
Regarding the accident, Airbus have published a number of specific reports on this accident and I believe that what I stated is an accurate view of the Airbus 'view' of what took place. It is certainly the widely-taught view within Airbus operators and I have seen no evidence to suggest that it is not correct.
I hope that helps.
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Thank you Norman for your reply,
but I'd like to suggest some reading on Habsheim, something a little different from the usual view
http://www.caac.cc/atcdata/html/1391.html
but I'd like to suggest some reading on Habsheim, something a little different from the usual view
http://www.caac.cc/atcdata/html/1391.html
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Hi there
A very interesting view - but not one that I can have any real confidence in. I am intrigued by the website - an oriental one which seems to have an interest in 'conspiracy theories'.
I am forced to admit that I cannot say categorically that the accusations of changed data recorders, misfunctioning radalts, changed software and so forth do not have some truth in them. Therefore I cannot dismiss completely this particular conspiracy theory. I would go as far as to say that the accusations may have some significant truth in them. Frankly it would come as no surprise to me to find that Airbus (as Boeing have done under similar circumstances) have misreperesented things to ensure the pilots get the blame instead of them.
What I can say, however, is that there is a totally rational practical expalanation for why the engines did not spool up and why 'alpha floor' failed to kick in. My natural desire is to want to believe the conspiracy theory - my head says the pilot blew it! The simple fact is that since that time a vast amount more has been done in pilot training to prevent a repetition of Habsheim - and sure enough it has not been repeated! It is my hope that this would not happen again simply because there is such a wider understanding of the safety protections built into Airbus fly-by-wire aircraft (including their limitations). I know that when I went through the course, great emphasis was placed on understanding the protections and I am sure this is directly attributable to this unfortunate accident.
A very interesting view - but not one that I can have any real confidence in. I am intrigued by the website - an oriental one which seems to have an interest in 'conspiracy theories'.
I am forced to admit that I cannot say categorically that the accusations of changed data recorders, misfunctioning radalts, changed software and so forth do not have some truth in them. Therefore I cannot dismiss completely this particular conspiracy theory. I would go as far as to say that the accusations may have some significant truth in them. Frankly it would come as no surprise to me to find that Airbus (as Boeing have done under similar circumstances) have misreperesented things to ensure the pilots get the blame instead of them.
What I can say, however, is that there is a totally rational practical expalanation for why the engines did not spool up and why 'alpha floor' failed to kick in. My natural desire is to want to believe the conspiracy theory - my head says the pilot blew it! The simple fact is that since that time a vast amount more has been done in pilot training to prevent a repetition of Habsheim - and sure enough it has not been repeated! It is my hope that this would not happen again simply because there is such a wider understanding of the safety protections built into Airbus fly-by-wire aircraft (including their limitations). I know that when I went through the course, great emphasis was placed on understanding the protections and I am sure this is directly attributable to this unfortunate accident.
Last edited by Norman Stanley Fletcher; 23rd Mar 2005 at 09:29.
