To make things simple from the Boeing 757 AMM For the 1,2,3,4 or MAX AUTO positions, the system uses the average of the speed signal from the main wheels for spin up logic and the airplane IRS speed data for deceleration control. The system compares the airplane speed with the selected level of braking to generate a pressure command to the control servo valve. The valve provides the commanded pressure via the normal antiskid valves to the brakes.
Autobrake deceleration level inputs
The autobrake system automatically applies brake pressure selected by the pilot:
Autobrake Selector Switch / Brake Pressure / Decel Level
(PSI) (ft/sec/sec)
1 1500 / 4.5
2 1750 / 5.0
3 2000 / 6.3
4 2400 / 8.5
Max Auto 3000 / 11.0
RTO 3000 Max system pressure applied
Last edited by We Fix Them; 25th Oct 2009 at 07:34.