How does autobrake work? An autobrake is a type of automatic wheel-based hydraulic brake system for advanced airplanes. The autobrake is normally enabled during takeoff 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 - Wikipedia



How does the aircraft "know" when is time to activate the autobrake
systems on a rejected takeoff and landing?
Does it apply full brake to all the aircraft's wheels?
Is it really used by commercial jets?
Not all commercial jets have autobrakes, and the ones that do usually have a company policy dictating when it will be used.

The criteria for activating the brakes are different depending on the manufacturer and model of aircraft, but are typically some combination of:


System must be armed
A certain takeoff power setting must be set by the throttles
A certain airspeed must be obtained
Thrust levers must be pulled back to idle
Aircraft must still be on the ground


Usually for a rejected takeoff it does use max braking, however the autobrake usually has different settings for landing along the lines of "light/medium/max" braking.  Each setting will use a different amount of runway for landing, much like lightly pressing on the brake pedal in your car versus jamming it to the floor.