A fuel jettison system is required for transport category and general aviation aircraft if the maximum takeoff weight exceeds the maximum landing weight. The maximum takeoff and landing weights are design specifications and may be found in the Aircraft Type Certificate data sheets.
A fuel jettison system must be able to jettison enough fuel within 10 minutes for general aviation, or 15 minutes for transport category aircraft, to meet the requirements of the specifications and Federal Air Regulations. It must be operable under the conditions encountered during all operations of the aircraft.
Design requirements are that fuel jettisoning must be stopped with a minimum of fuel for 45 minutes of cruise at maximum continuous power for reciprocating engines. Turbine powered aircraft require enough fuel for takeoff and landing and 45 minutes cruising time.
The fuel jettisoning system is usually divided into two separate, independent systems, one for each wing, so that lateral stability can be maintained by jettisoning fuel from the "heavy" wing if it is necessary to do so. Normally, if an unbalanced fuel load exists, fuel will be used from the "heavy" wing by supplying fuel to engines on the opposite wing. The system consists of lines, valves, dump chutes and chute operating mechanisms. Each wing contains either a fixed or an extendable dump chute depending upon system design. In either case the fuel must discharge clear of the airplane.