A 320 Braking Technique
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A 320 Braking Technique
Sometimes the brake temperatures go up considerably in A320 when using Manual Braking even when other conditions are ideal, like correct approach speeds and landing in headwinds and no brake binding. Any ideas on how to prevent this?
Last edited by Boyington; 9th May 2015 at 11:09.
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A 320 Braking Technique
Autobrake sets a given deceleration so using full reverse will put less energy into the braking system resulting in lower temperatures. Manual braking puts no energy into the brakes so if the runway is long enough and a quick turn is required think about that. Presumably your company has an SOP regarding brake fans
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I prefer to use max reverse and not touch the brakes until 60kts or so, runway permitting. Brakes end up well under 150C even on hot days. It bears mentioning that our 320s don't have brake fans. Our 321s and about half of our 319s do.
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Amadis of Gaul I prefer to use max reverse and not touch the brakes until 60kts or so, runway permitting. Brakes end up well under 150C even on hot days. It bears mentioning that our 320s don't have brake fans. Our 321s and about half of our 319s do.
Allmost all airfields I operate to have max idle reverse unless for safety reasons.
I found that idle reverse and manuel brakes gives the best result. I wait quite long in the rollout before applying then brakes and the gradually apply the brakes for pax comfort, but in the end quite hard braking and then all the way to very low speed (also helps minimum runway occupancy time). That way the brakes have been on for only a short time and you avoid several applications, that gives mere wear and heat. Also when the aircraft is coming up to taxi speed the APU is now running, so you can do single engine taxi saving fuel and brakes. Glance at the brake temps and use the coolest on the way in to get even temp.
I found that idle reverse and manuel brakes gives the best result. I wait quite long in the rollout before applying then brakes and the gradually apply the brakes for pax comfort, but in the end quite hard braking and then all the way to very low speed (also helps minimum runway occupancy time). That way the brakes have been on for only a short time and you avoid several applications, that gives mere wear and heat. Also when the aircraft is coming up to taxi speed the APU is now running, so you can do single engine taxi saving fuel and brakes. Glance at the brake temps and use the coolest on the way in to get even temp.
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At our company it deemed cheaper to leave reverse idle and one brake application regardless or resulting temperature. except landing distances where temp will likely exceed 500c where brake oxidation occurs.
also brake fans should be delayed as much as posible to allow brake assembly temps to even out.
also brake fans should be delayed as much as posible to allow brake assembly temps to even out.
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There's a good presentation by Airbus on this topic somewhere in the Internet - try googling 'Airbus braking recommendations".
The bottom line is:
- Brake temperature is NOT a problem in terms of brake wear. In fact the hotter they get, the less they wear down. This is true till approx 500 deg, where oxidation comes into play. Further increase in temp increases the wear dramatically. So as long as you keep them below ~500 degs, you're fine and no special tehniques are necessary. What kills the brakes is the number of applications. Try to keep it as low as necessary.
Personally, I prefer to use autobrake most of the time and don't care about the temperature too much. Usual combination is LO BRK+IDLE REV, or MED BRK+MAX REV. I am not a big fan of delaying brake application like other posters advocate.
The only time Brake temp is really an issue, is when turnaround time is short. But then, if the company wants me to tanker fuel onto a short runway with signicant tailwind, like they did today - I have no problem delaying the next takeoff until the brakes are below 300 degs...
The bottom line is:
- Brake temperature is NOT a problem in terms of brake wear. In fact the hotter they get, the less they wear down. This is true till approx 500 deg, where oxidation comes into play. Further increase in temp increases the wear dramatically. So as long as you keep them below ~500 degs, you're fine and no special tehniques are necessary. What kills the brakes is the number of applications. Try to keep it as low as necessary.
Personally, I prefer to use autobrake most of the time and don't care about the temperature too much. Usual combination is LO BRK+IDLE REV, or MED BRK+MAX REV. I am not a big fan of delaying brake application like other posters advocate.
The only time Brake temp is really an issue, is when turnaround time is short. But then, if the company wants me to tanker fuel onto a short runway with signicant tailwind, like they did today - I have no problem delaying the next takeoff until the brakes are below 300 degs...
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Personally, I prefer to use autobrake most of the time and don't care about the temperature too much. Usual combination is LO BRK+IDLE REV, or MED BRK+MAX REV. I am not a big fan of delaying brake application like other posters advocate.
When we had some old 320s without Brake Fans, or they are MEL'd out, I get really ****ed off with crews who hand me over an aircraft with 500C+ brakes. 1+hr to cool for takeoff. As above, those are the days to use Max Rev, Manual Brakes and keep you feet off the brakes as late as you can... you can be on stand at <150C easily.
Not saying it should be done everyday...
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Airbus GOPs (Green Operating Procedures) recommend Flaps 3/autobrake low/idle reverse as the most cost and fuel effective method. Next step would be Flaps FULL, then Autobrake MED and lastly full reverse.
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@NOD - We have no brake fans on our Buses and our standard turnaround time is 30 minutes. We often operate to short-ish runways and tanker fuel quite a lot. Still, brake temp is hardly ever an issue and I have yet to see 500deg on handover...
While I agree delayed braking is a useful tool in some situations, I think it
shouldn't be an SOP. I see a lot of people using it on daily basis, to keep the brakes as cool as possible - there's no operational benefit of doing so...
AFAIK, the tempeature band of 100-250 deg, which is targeted by these techniques, is in fact the most detrimental for brake wear...
The following video is quite informative...
https://www.youtube.com/watch?v=SG4Aw5BujEU
While I agree delayed braking is a useful tool in some situations, I think it
shouldn't be an SOP. I see a lot of people using it on daily basis, to keep the brakes as cool as possible - there's no operational benefit of doing so...
AFAIK, the tempeature band of 100-250 deg, which is targeted by these techniques, is in fact the most detrimental for brake wear...
The following video is quite informative...
https://www.youtube.com/watch?v=SG4Aw5BujEU
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C*
We are in agreement... the 500C takes some doing, but MLW, Flap 3 and idle reverse + early turn off some people managed it.. leading to a delayed departure.
It just takes some thought as to what to do one the day - not "one size fits all"
We are in agreement... the 500C takes some doing, but MLW, Flap 3 and idle reverse + early turn off some people managed it.. leading to a delayed departure.
It just takes some thought as to what to do one the day - not "one size fits all"
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Seen that vid before and been told the same over 2 decades, however it seems to be ignored by the A/C makers! My memory 320 SOP with fans is fans on when double band over temp ind. (circa 110 degrees), same when I was on 146 yrs ago, fans off below 100. Neither had the fans left to after parking.??
Anyone know?
Recently told that is due to tyre wear when hot??
Seen that vid before and been told the same over 2 decades, however it seems to be ignored by the A/C makers! My memory 320 SOP with fans is fans on when double band over temp ind. (circa 110 degrees), same when I was on 146 yrs ago, fans off below 100. Neither had the fans left to after parking.??
Anyone know?
Recently told that is due to tyre wear when hot??
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The OP asked how to keep brake temperatures down when the approach and landing is normal. The obvious answer is to transfer less energy to brakes by using more reverse and less braking. The rest of the discussion is about how to decrease brake wear and saving on engine maintenance costs. Carbon brakes wear by the number of applications rather than high brake temperatures. Brake wear increases till it reaches a peak temperature and then it rapidly decreases. Airbus document on braking mentions three brake manufacturers BF Goodrich, Messier-Bugatti and Honeywell. They have different peak temperatures. In case of Goodrich it is 80C, Messier-Bugatti it is APPX. 160C and Honeywell 200C. Beyond these brake wear decreases. However as the graph shows the brake wear reaches nearly the same value at about 315C and after that only Goodrich keeps dropping linearly but in case of the other two the brake wear starts to increase. So unless you have Goodrich brakes fitted the least wear would occur around 350C. Depending on the LDA you can achieve these temperatures by using idle reverse and low or medium brake. Auto brake results in single application. Idle reverse saves maintenance costs but finally whether you have brake fans or not and turn around time will govern your decision to use this technique. According to brake manufacturers ideally brake fan should be switched on after 5mts. for thermal equalisation but airbus recommends to put them on when the green arc appears. So take your pick.
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This link is pretty good and shows a wear/temp graph which answers my questions.
Just scroll through to T/O & LNG.
http://www.scribd.com/doc/44837750/A...dations#scribd
Just scroll through to T/O & LNG.
http://www.scribd.com/doc/44837750/A...dations#scribd
There are at least two separate issues to consider here.
Minimising brake wear over the life of the brakes, to do this follow your SOPs which will no doubt be guided by the information in the video above.
The other issue is simply keeping the brake temps within FCOM limitations for takeoff.
While these two considerations will ideally be managed together, if you are simply trying to bring down the brake temperatures so that you remain within takeoff limitations once taxi has commenced, simply keeping your speed lower will help. I'll try to explain why.
Looking back to the kinetic energy formula: Kinetic energy of KE = 1/2 MV(squared), V is the only variable that can be controlled, short of offloading pax, fuel or freight. Having said that, it has a disproportionately advantageous effect on reducing the the brake energy demand and hence keeping the temps below TO limits. For the mathematicians, brake energy required is proportional square of taxi speed. So if you halve the average taxi speed then you input a quarter of the brake energy.
Whilst this specifically runs contrary to minimising brake wear as such, there are some circumstances where it is hard to avoid and this will get you airborne without exceeding any limitations.
Minimising brake wear over the life of the brakes, to do this follow your SOPs which will no doubt be guided by the information in the video above.
The other issue is simply keeping the brake temps within FCOM limitations for takeoff.
While these two considerations will ideally be managed together, if you are simply trying to bring down the brake temperatures so that you remain within takeoff limitations once taxi has commenced, simply keeping your speed lower will help. I'll try to explain why.
Looking back to the kinetic energy formula: Kinetic energy of KE = 1/2 MV(squared), V is the only variable that can be controlled, short of offloading pax, fuel or freight. Having said that, it has a disproportionately advantageous effect on reducing the the brake energy demand and hence keeping the temps below TO limits. For the mathematicians, brake energy required is proportional square of taxi speed. So if you halve the average taxi speed then you input a quarter of the brake energy.
Whilst this specifically runs contrary to minimising brake wear as such, there are some circumstances where it is hard to avoid and this will get you airborne without exceeding any limitations.
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Originally Posted by Skyjob
Safety reason: avoiding hot brakes for next departure
