On a jumbo, Fuel Jettison Non-Normal is normally carried out as Capt Fathom indicates but may also be carried out, if desired, as contained in several other checklists eg. Two-Engines Inoperative. Fuel Jettison is typically used shortly after takeoff when some form of problem (engine/ gear/ flap) makes further flight impractical. Can also be used at any time when the aircraft is above max landing weight and a prompt landing is required yet sufficient time is available or the severity of the problem does not require an immediate landing overweight.
Emergency - eg. uncontrolled fire, land overweight and ask questions later.
Vee1-rotate, 747 has two jettison valves, one on each wing. Jettison valves come off a common manifold pressurised by a total of six jettison pumps - two each in main tanks 2 and 3 and two in the centre wing tank. Jettison transfer valves also exist between main tanks 1 and 4 and their respective inboard mains (2 and 3) allowing fuel to be jettisoned from all four main tanks and the CWT simultaneously. Jettison rate with all six pumps on is about 2500 kg/min. CWT jettison pumps are also used as the normal supply pumps for fuel from the CWT to the fuel system.
Last edited by DirectAnywhere; 14th Aug 2005 at 22:40.