AUTOBRAKE TECHNICAL INFORMATION
Autobrake Selector / Max Pressure at Brakes (PSI) / Deceleration Rate (ft/sec2)
1 / 1250 PSI / 4 ft/sec2
2 / 1500 PSI / 5 ft/sec2
3 / 2000 PSI / 7.2 ft/sec2
Max / 3000 PSI / 12 ft/sec2 below 80 kts
Max / 3000 PSI / 14 ft/sec2 above 80 kts
RTO / Full Pressure / uncontrolled rate
There is an "on ramp" period where autobrake pressure is applied over a period of time. Approximately 750psi is applied in 1.75 sec, then the pressures above are reached in another 1.25sec for autobrakes 1, 2, or 3 and approx. 1.0 sec for autobrake MAX.
Using high autobrake settings with idle reverse is particularly hard on the brakes as they will be working for the given deceleration rate without the assistance of full reverse thrust. This could lead to the rate not being achieved when the pressure is applied for the selected rate, especially on more slippery runway conditions.
To cancel the autobrake on the landing roll with toe brakes you must apply a brake pressure in excess of 800psi (less than that required for autobrake 1).