An autobrake is a type of automatic wheel-based

hydraulic brake A hydraulic brake is an arrangement of braking mechanism which uses brake fluid, typically containing glycol ethers or diethylene glycol, to transfer pressure from the controlling mechanism to the braking mechanism. History During 1904, Frederick ...

system for advanced

airplanes An airplane or aeroplane (informally plane) is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurations. The broad spectr ...

. The autobrake is normally enabled during

takeoff Takeoff is the phase of flight in which an aerospace vehicle leaves the ground and becomes airborne. For aircraft traveling vertically, this is known as liftoff. For aircraft that take off horizontally, this usually involves starting with a ...

and landing procedures, when the aircraft's longitudinal deceleration system can be handled by the automated systems of the aircraft itself in order to keep the pilot free to perform other tasks.

Landing

While landing, the autobrake can help to free up the pilot to allow monitoring other systems (such as the execution of the

landing flare The landing flare, also referred to as the round out, is a maneuver or stage during the landing of an aircraft. The flare follows the final approach phase and precedes the touchdown and roll-out phases of landing. In the flare, the nose of ...

). There are usually several settings for the rate of deceleration. The selection of these settings are normally undertaken on the aircraft instrument panel before landing. Aircraft have multiple autobrake settings, with higher settings providing more aggressive braking forces. These are set based on factors such as runway length or desired exit point from the runway. When the landing feature of the autobrake is engaged, the aircraft automatically engages pressurized wheel braking upon touchdown to the landing surface. During the roll out, application of the brake pedals transfers control back to the pilot. One of the main advantages of engaging the autobrake as opposed to manually pressing on brake pedals is the uniform deceleration mechanism of the autobrake. The aircraft automatically decelerates at the selected level regardless of other factors, such as aircraft drag and other deceleration methods such as deployment of

thrust reversers Thrust reversal, also called reverse thrust, is the temporary diversion of an aircraft engine's thrust for it to act against the forward travel of the aircraft, providing deceleration. Thrust reverser systems are featured on many jet aircraft to ...

or spoilers.

Rejected takeoff

While taking off, the aircraft's autobrake can be set to the rejected takeoff mode, commonly indicated on an aircraft instrument panel as RTO. In case of the Airbus A300-600 and A320 family models, "MAX" mode is set. In RTO setting, the aircraft monitors certain variables, depending on the autobrake model. Most autobrakes engage RTO braking if the pilot returns the throttle to the "idle" position, or if reverse thrust is engaged. Other autobrake systems may monitor critical flight controls for failures.

References

{{Aircraft components Aircraft undercarriage Aircraft controls