Autobrakes 
The auto brake system provides automatic braking at pre-selected deceleration rates for landing after touchdown. Various deceleration rates can be selected; however, the maximum autobrakes deceleration rate is less than that produced by full manual braking.
The system operates only when the normal/reserve brake system is functioning. Antiskid system protection is provided during auto brake operation.
The AUTO BRAKES light illuminates and the EICAS advisory message AUTOBRAKES displays if the auto brake system is disarmed or inoperative.
Autobrakes Selector
The autobrakes system is armed by selecting a deceleration rate. Latching of the Autobrakes Selector indicates the system is armed and operative. During autobrakes operation the deceleration selection can be changed by rotating the selector without disarming the system.
Landing
Five levels of deceleration can be selected for landing. However, on dry runways, the maximum auto brake deceleration rate in the landing mode is less than that produced by full pedal braking.
Autobrakes Activation
After landing and if the autobrakes are armed, auto brake application begins when:
- both Thrust Levers are retarded to idle, and
- main gear Truck un-tilt and
- the wheels have spun up
Auto brake application occurs slightly after main gear touchdown. When the above conditions are met, hydraulic pressure is metered to the brakes, establishing an initial low-level pressure and deceleration is limited until the pitch angle is less than one degree (as measured by the Inertial Reference System). As the airplane de-rotates through the one degree reference attitude, brake pressure increases and deceleration increases to the selected level. The deceleration level can be changed (without disarming the system) by rotating the selector.
To maintain the selected airplane deceleration rate, auto brake pressure is reduced as other controls, such as Thrust Reversers and spoilers (Speedbrakes), contribute to total deceleration. The system provides braking to a complete stop or until it is disarmed.
Autobrakes - Disarm
The system disarms immediately, the AUTO BRAKES light illuminates and the EICAS advisory message AUTOBRAKES displays if any of the following occur:
- pedal braking applied
- either Thrust Lever advanced after landing
- Speedbrake Lever is moved towards the DOWN detent after the speedbrakes have deployed on the ground
- DISARM or OFF position selected on the AUTO BRAKES selector
- auto brake fault
- normal antiskid system fault
When the auto brake system disarms after landing, the auto brakes selector automatically moves to the DISARM position, the AUTO BRAKES light illuminates, and power is removed from the auto brake system. Rotating the Autobrakes Selector to OFF removes power from the system and extinguishes the light.
Rejected Takeoff (RTO)
As installed
Selecting RTO prior to takeoff arms the auto brake system. The RTO mode can be selected only on the ground. The RTO auto brake setting commands maximum braking pressure if:
- the airplane is on the ground,
- groundspeed is above 85 knots and
- both thrust levers are retarded to idle
Maximum braking is obtained in this mode. If an RTO is initiated below 85 knots, the RTO auto brake function does not operate.
When the auto brake system disarms following a rejected takeoff above 85 kt, the auto brakes selector remains in the RTO position and the Autobrakes INOP light illuminates. After takeoff, the AUTO BRAKES selector automatically moves to OFF.During a rejected takeoff above 85 kt, the same conditions which disarm the landing mode also disarm the RTO mode.
