A321xlr
#21
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Joined APC: Aug 2018
Posts: 330
Speaking of ULCCs looks like F9 might be getting the 321XLR
https://www.reuters.com/article/us-f...-idUSKCN1TE2QJ
https://www.reuters.com/article/us-f...-idUSKCN1TE2QJ
#22
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Joined APC: Dec 2006
Position: 737 FO
Posts: 2,370
Anyone ever experimented with brake temps on low vs med?
I've always wondered if in a heavy 321, autobrakes medium might yield a lower brake temperature because the brake application is so much shorter? When you have a high approach speed in a heavy 321, autobrakes low seems to make for such a long application of brakes, I've always wondered if a shorted, harder application might be better. I don't know. I only use medium on short runways for passenger comfort, but a heavy 321 can sure cook the brakes.
Also, brake fans on the 320NEO are awesome and badly missing on the 321
I've always wondered if in a heavy 321, autobrakes medium might yield a lower brake temperature because the brake application is so much shorter? When you have a high approach speed in a heavy 321, autobrakes low seems to make for such a long application of brakes, I've always wondered if a shorted, harder application might be better. I don't know. I only use medium on short runways for passenger comfort, but a heavy 321 can sure cook the brakes.
Also, brake fans on the 320NEO are awesome and badly missing on the 321
#23
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And of course, you can not use auto brakes, let the max reverse thrust slow you down, then apply brakes manually later. But again, I asked a specific question about low vs medium auto brakes
#24
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Im thinking thats part of the mid cabin lav on 321
#25
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#26
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No I'm not. I'm asking a specific question. Obviously if I'm trying to preserve brake temps, I'm going to use max reverse thrust and land full flaps.
And of course, you can not use auto brakes, let the max reverse thrust slow you down, then apply brakes manually later. But again, I asked a specific question about low vs medium auto brakes
And of course, you can not use auto brakes, let the max reverse thrust slow you down, then apply brakes manually later. But again, I asked a specific question about low vs medium auto brakes
Brake temperature is a function of how much energy the brakes have to absorb. The longer time you spend decelerating the more time the thrust reversers and drag devices have to slow you down via other means. As they are all more effective at higher airspeeds, the energy removed is greatest in the higher speed regime. Thus if you use a lower brake application you are allowing more energy to be dissipated by those devices rather than having to be absorbed by the brakes not only by a longer time for them to work at a higher speed but a longer period of time for them to work overall. Note that the thrust reversers are selectable, but all else being equal the other drag devices still work and still reduce their most energy at higher airspeeds.
Think of it in terms of a max brake landing vs landing on a really long runway where you don't need to use the brakes. The latter is going to have a much lower brake temperature. Heavy vs light brake application is on the same curve when there are other things slowing you down as well.
Note that this is different than taxiing. When you taxi the amount of energy dissipated is constant so the difference between riding the brakes and pulses is that with a pulse there is a period where the brakes are relaxed and are better able to cool.
#28
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#29
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#30
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You apparently are ignoring it, or you aren't really thinking about it as the brakes aren't operating without relation to the other factors.
Brake temperature is a function of how much energy the brakes have to absorb. The longer time you spend decelerating the more time the thrust reversers and drag devices have to slow you down via other means. As they are all more effective at higher airspeeds, the energy removed is greatest in the higher speed regime. Thus if you use a lower brake application you are allowing more energy to be dissipated by those devices rather than having to be absorbed by the brakes not only by a longer time for them to work at a higher speed but a longer period of time for them to work overall. Note that the thrust reversers are selectable, but all else being equal the other drag devices still work and still reduce their most energy at higher airspeeds.
Think of it in terms of a max brake landing vs landing on a really long runway where you don't need to use the brakes. The latter is going to have a much lower brake temperature. Heavy vs light brake application is on the same curve when there are other things slowing you down as well.
Note that this is different than taxiing. When you taxi the amount of energy dissipated is constant so the difference between riding the brakes and pulses is that with a pulse there is a period where the brakes are relaxed and are better able to cool.
Brake temperature is a function of how much energy the brakes have to absorb. The longer time you spend decelerating the more time the thrust reversers and drag devices have to slow you down via other means. As they are all more effective at higher airspeeds, the energy removed is greatest in the higher speed regime. Thus if you use a lower brake application you are allowing more energy to be dissipated by those devices rather than having to be absorbed by the brakes not only by a longer time for them to work at a higher speed but a longer period of time for them to work overall. Note that the thrust reversers are selectable, but all else being equal the other drag devices still work and still reduce their most energy at higher airspeeds.
Think of it in terms of a max brake landing vs landing on a really long runway where you don't need to use the brakes. The latter is going to have a much lower brake temperature. Heavy vs light brake application is on the same curve when there are other things slowing you down as well.
Note that this is different than taxiing. When you taxi the amount of energy dissipated is constant so the difference between riding the brakes and pulses is that with a pulse there is a period where the brakes are relaxed and are better able to cool.
Allright. Thanks for the response. I see what you are saying. So then would you agree that the best way to preserve brake temps would be to land with auto brakes off, use max reverse thrust and allow the aircraft to decelerate for a bit before applying the brakes manually?