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Old 06-16-2019, 06:24 AM
  #21  
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Speaking of ULCCs looks like F9 might be getting the 321XLR

https://www.reuters.com/article/us-f...-idUSKCN1TE2QJ
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Old 06-16-2019, 07:08 AM
  #22  
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Originally Posted by Aero1900 View Post
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
You are completely ignoring that brakes aren't the only things slowing the airplane.
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Old 06-16-2019, 08:06 AM
  #23  
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Originally Posted by Baradium View Post
You are completely ignoring that brakes aren't the only things slowing the airplane.
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
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Old 06-16-2019, 08:07 AM
  #24  
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Originally Posted by full of luv View Post
For some reason on long narrowbody flts seems like the fa’s are always in aisle and using bathroom more of a timing exercise. On wb they seem to be able to get through faster plus additional bathrooms to use. May just be a perception.
Im thinking thats part of the mid cabin lav on 321
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Old 06-16-2019, 08:13 AM
  #25  
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Originally Posted by 4runner View Post
You guys sound like flight instructors and LCC dweebs that are in their rooms at a LC hotel, playing flight sim and posting on web forums, while the cool kids are chasing girls at the bar.
You mad you didn't get invited to the LAN party?
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Old 06-16-2019, 08:15 AM
  #26  
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Originally Posted by Aero1900 View Post
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
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.
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Old 06-16-2019, 08:19 AM
  #27  
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AB selection is typically a deceleration rate and not a brake 'application' level.
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Old 06-16-2019, 08:24 AM
  #28  
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Originally Posted by BobZ View Post
AB selection is typically a deceleration rate and not a brake 'application' level.
If you're responding to me, it does have a direct effect on the amount of force applied to the brakes with all else being equal as the aircraft works towards that level.
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Old 06-16-2019, 08:44 AM
  #29  
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Originally Posted by Baradium View Post
If you're responding to me, it does have a direct effect on the amount of force applied to the brakes with all else being equal as the aircraft works towards that level.
Wasnt specifically....just an observation on generally what is goin on.
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Old 06-16-2019, 08:51 AM
  #30  
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Originally Posted by Baradium View Post
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.

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?
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