Originally Posted by
Chesty Morgan
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.
Apparently you are not familiar with the concepts behind your first statement, but are only trying to justify a practice that is not supported anywhere that I have seen.
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