Date: 03 Nov 98 02:05:38 From: JF Mezei <email@example.com> References: 1 2 Followups: 1 2 3 4
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STeveC01e wrote: > I'm not able to answer your specific question, but regarding the > circumstances, I suppose if the Flight 111 had a electrical fire in a major > bus, then once the Fuel Dump was initiated, then the crew would NOT be able > to stop it IF they lost all power. There have been other comments that on the MD11, the pilots would enter the amount of fuel to keep and everything else is done automatically. There have been comments about valves shutting off automatically. Other comments about pumps used to throw the fuel out, while others mentioned it was done by gravity. It seems to me that fuel dump is used for emergencies. Right? And in emergencies, power is something which is realistically lost, right? Are the various valves designed to mechanically shut off when power is lost? I went through the FA 25.1001 and found that for turbine engines: (f) For turbine engine powered airplanes, means must be provided to prevent jettisoning the fuel in the tanks used for takeoff and landing below the level allowing climb from sea level to 10,000 feet and thereafter allowing 45 minutes cruise at a speed for maximum range. However, if there is an auxiliary control independent of the main jettisoning control, the system may be designed to jettison the remaining fuel by means of the auxiliary jettisoning control. Question: Since dumping of fuel is used for an emergency which requires the plane to land ASAP, (are there other uses?), why would the FAA want the fuel dumping system to retain enough fuel to climb and fly for 45 minutes? Is this to allow for a missed approach? Do missed approaches really take that long, do planes really climb back to 10k feet? Is the dumping of fuel something which is done in circumstances which are not actual emergencies and which require the plane to abide by congested airport queing and waiting (thus requirememt to stay in air 45 minutes) or is fuel dump done only in circumstances requiring immediate landing and thus declaring emergency which gives the plane immediate access to the runway of its choice? Question: If it allows for an auxiliary system which dumps all of the fuel, and such system has no requierement for a minimum reserve (5 minutes flight?), what's the point of the first fuel jettison system? Or is such system used only for maintenance purposes and not to be used by pilots? Question: Why does the FAA not mention a need to reduce to a bare minimum is the amount of fuel so that if the landing doesn't go too well (UA 232 comes to mind), the resulting fire will be as small as possible? Seems to me that 45 minutes worth of fuel is a lot.