The fuel jettison system allows the aircraft to dump fuel quickly in order to reduce its weight to a safe landing weight in the event of an emergency after takeoff.
The APU is a small engine located in the tail of the aircraft that provides electrical power and bleed air, primarily for starting the main engines and for air conditioning when the engines are not running.
V1 is the critical decision speed during takeoff. At or below V1, the pilot can safely abort the takeoff and bring the aircraft to a stop on the remaining runway. Above V1, the pilot is committed to continuing the takeoff.
The pressurization system ensures that the cabin remains at a comfortable pressure level for passengers and crew when the aircraft is flying at high altitudes where the outside air pressure is too low to breathe comfortably.
