Changing auto brake setting during roll out
Gender Faculty Specialist
I did it yesterday. 3 would have required a large backtrack due to WIP at one of the exits and max would have meant stopping too soon. So I went from max to 3. It worked, we kept the advantage of auto brakes and if you hadn't guessed by now I am still alive.
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I was a passenger in a FR 738 some time back when the crew inadvertently selected what I believe to be RTO during the landing roll out. The sudden decelaration was enough to propel me into the seatback in front, I sustained a minor injury to my right hand while trying to save myself. Very unpleasant and no explanation from the flightdeck. Senior Cabin Crew was in the flightdeck during disembarkation asking WTF was going on..
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So you think using MAX right after landing, and later reducing to 3, was better for the aircraft than using 3 and then increasing brake pressure after your speed had decreased??
By your logic in the second line, aren't you now implying manual braking is not how the plane is designed to be used and bad for the airplane? I'm sure you managed fine and are still alive. Personally I'd still prefer to keep my attention outside and hand and feet in standard positions instead of going for knobs/buttons during rollout. To each their own.
Gender Faculty Specialist
The use of autobrake reduces brake wear and minimises brake temperatures whilst still achieving what you want to achieve. Brakes are obviously designed to be used without autobrake or brake pedals wouldn’t be fitted and whilst manual braking is not necessarily bad for the aeroplane it is, categorically, not as efficient as using autobrakes.
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The use of autobrake reduces brake wear and minimises brake temperatures whilst still achieving what you want to achieve. Brakes are obviously designed to be used without autobrake or brake pedals wouldn’t be fitted and whilst manual braking is not necessarily bad for the aeroplane it is, categorically, not as efficient as using autobrakes.
First, using MAX autobrakes when they are not needed will NOT minimize brake temperature or brake wear. To minimize temperature, you use as little braking as possible while the airplane is at high speed. As others have pointed out, in your case you should have started with Autobrakes 3, then increased pressure after the airplane had slowed down.
Second, the practice of changing the Autobrake setting during the landing roll is not supported in any Boeing document that I have seen, and was actively discouraged - effectively prohibited - at my airline. Trying to move a switch, that is unnecessary and which may not remain in the newly selected position, during the landing roll is a major distraction at best and a dangerous risk if the switch solenoid happens to release or fail during the attempt. Use of the brake pedals to manually modulate brake pressure is the proper way to override the Autobrakes setting.
From the Boeing 747-400 Flight Crew Training Manual:
Use an appropriate autobrake setting or manually apply wheel brakes smoothly with steadily increasing pedal pressure as required for runway condition and runway length available. Maintain deceleration rate with constant or increasing brake pressure as required until stopped or desired taxi speed is reached.
. . .
For normal landing conditions, autobrakes 2 or 3 optimizes brake wear, passenger comfort, and stopping performance.
. . .
To minimize brake temperature build-up, use the following landing techniques:
. . .
use an autobrake setting, consistent with reported runway conditions, that will result in the use of all available runway length. A stopping distance safety margin should be used in accordance with airline policy. Although the autobrakes initially increase brake temperature, the brake contribution is minimized after reverser deployment
. . .
For normal landing conditions, autobrakes 2 or 3 optimizes brake wear, passenger comfort, and stopping performance.
. . .
To minimize brake temperature build-up, use the following landing techniques:
. . .
use an autobrake setting, consistent with reported runway conditions, that will result in the use of all available runway length. A stopping distance safety margin should be used in accordance with airline policy. Although the autobrakes initially increase brake temperature, the brake contribution is minimized after reverser deployment
Gender Faculty Specialist
Well my dear MAX was the minimum needed to ensure we made the exit. But thanks for your input on a flight you have no knowledge of.
And, FYI, autobrake will minimise brake wear when compared to manual braking. A concept I assume you are aware of.
And, FYI, autobrake will minimise brake wear when compared to manual braking. A concept I assume you are aware of.
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B737 bulletin CEX-5 certainly hints at not changing the autobtake setting during the landing roll as the RTO mode CAN be inadvertently activated (a service bulletin provides a fix to the RTO logic that allows this).
Still not quite sure why you would prefer fiddling with knobs when your focus could be outside, all limbs on the necessary controls and ready to react to anything non-standard. Again, to each their own.
Pretty sure in the near future, we'll have pilots who have no idea what it feels like to slow a plane down with manual braking.
Pretty sure in the near future, we'll have pilots who have no idea what it feels like to slow a plane down with manual braking.
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This discussion is such BS. The airplane has the ability to change AB setting during roll out. No, it is not described in the FCOM. Neither is the use of the lights!! Airmanship comes into play!! When transitioning from AB to manual braking often times you have to increase pressure on the pedals beyond the braking pressure being applied by the AB system giving an uncomfortable jolt in braking when transitioning!! I find it much more comfortable to apply brake pressure just before the point where the AB system kicks off and then asking the PM to select AB off, this gives a much smoother transition to manual braking!! I have on occasion asked the PM to increase the brake setting to a higher setting to make an exit. Again this is usually a smoother transition than applying manual brake.!!
the notion that you could inadvertently select RTO is absolute nonsense!! The RTO mode won’t arm unless speed is less than 60kts and then will only engage with speed above 90kts! How is this going to happen during landing!!
Yes, I have spent the first half of my career flying airplanes without AB and I do now how to brake without AB. However, the system is there, use it! And NO, I don’t change it myself!! I simply ask the PM to change it “set autobrake off” while looking outside!! DUH!!
And yes, I have used AB max as well! granted, probably 3 or for times, but flying a heavy 900 sometimes that’s what needed! Shortest runways I fly to are ABZ and AMS rwy22 under stormy conditions. AB 3 won’t be enough with the 15% increase( it is there for a reason!). Simple PA to the PAX, ” due to WX conditions/ short runway we will be landing on today we will use a higher braking setting, please make sure that your seatbelts are securely fastened, please don’t be alarmed, it is normal under the circumstances to guarantee maximum safety”, done!!!!
some of the comments I read here, really, are you that insecure about your flying skills that you have to constantly propagate about manual skills versus using the automatics the manufacturer build into the airplane?
the notion that you could inadvertently select RTO is absolute nonsense!! The RTO mode won’t arm unless speed is less than 60kts and then will only engage with speed above 90kts! How is this going to happen during landing!!
Yes, I have spent the first half of my career flying airplanes without AB and I do now how to brake without AB. However, the system is there, use it! And NO, I don’t change it myself!! I simply ask the PM to change it “set autobrake off” while looking outside!! DUH!!
And yes, I have used AB max as well! granted, probably 3 or for times, but flying a heavy 900 sometimes that’s what needed! Shortest runways I fly to are ABZ and AMS rwy22 under stormy conditions. AB 3 won’t be enough with the 15% increase( it is there for a reason!). Simple PA to the PAX, ” due to WX conditions/ short runway we will be landing on today we will use a higher braking setting, please make sure that your seatbelts are securely fastened, please don’t be alarmed, it is normal under the circumstances to guarantee maximum safety”, done!!!!
some of the comments I read here, really, are you that insecure about your flying skills that you have to constantly propagate about manual skills versus using the automatics the manufacturer build into the airplane?
Last edited by flyburg; 6th Nov 2018 at 10:50.
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Refreshing my SOPs during this pandemic I found something of interest that caught my eye, and couldn’t find a reference for. In the landing section of my A320 SOPs it says:
I already knew we weren’t supposed to switch selection during landing roll; but not “Note”, not “Caution”, “Warning”. And well, it is specifically prohibited. Yes, I know FCOMs are tailored.
Warning implies “risk of personal injury or loss of life”... Any inputs on this?
Regards
Originally Posted by Company’s A320 FCOM
WARNING: Never change the A/BRK selection during roll out.
Warning implies “risk of personal injury or loss of life”... Any inputs on this?
Regards
Only half a speed-brake
Inadvertent MAX selection through action slip or worse. Just a guess.
IIRC the original FCOM wording of MAX changed not so long ago from use for landing is not recommended to simply imply that MAX is not a landing setting at all.
IIRC the original FCOM wording of MAX changed not so long ago from use for landing is not recommended to simply imply that MAX is not a landing setting at all.
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Airbus FCOM is silent about selection change during roll out. On new MSNs it is simply not possible to select MAX for landing. So Airbus has ended the discussion.
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This is an old thread, but I still found it disturbing that the subject even came up for discussion. Unnecessarily twiddling knobs or pushing buttons during the landing roll seems a distinctively unprofessional during a critical phase of flight.
If you don't like what the automatics are doing, disconnect and revert to manual.
If you don't like what the automatics are doing, disconnect and revert to manual.
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Macdo: I concur with your opinion (and I apply that myself). I just found it curious that it’s labeled as a warning. Then again, I think FD’s right on the money.
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I have yet to fly a plane with auto brakes so no first hand experience, but all this talk gives me the feel of watching when someone's flying by twiddling the heading and VS knobs like an Etch-a-sketch and making a harder job for themselves, than simply using the yoke.