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| Sailvi767
2025-07-01T12:39:00 permalink Post: 11914246 |
On the 767, 757 and A330 anytime you are in single generator operations the aircraft is load shedding. The 787 with a totally different electrical system might function differently.
Subjects: APU Fuel (All) Fuel Pumps Generators/Alternators Hydraulic Failure (All) Hydraulic Pumps |
| Sailvi767
2025-07-01T13:23:00 permalink Post: 11914271 |
Sorry, you missed the point I was trying to make. \xa7 25.903(b) does say that the fuel system
must
be able to operate
in an isolated, two-sided mode (for a twin engined jet), such that nothing on one side, such as bad fuel, will adversely affect the other engine. Of course, during Takeoff, both sides drawing fuel from a Centre Tank containing a lot of contaminants (e.g. Fuel Bug matter, water) is a scenario that could bring down the plane. We are all aware of that. But the point I was trying to make is that although \xa7 25.903(b) requires "at least one configuration" that separates both systems entirely (such as Left engine drawing from Left Main Tank, and Right from Right) which
can
be configured, the Rule doesn't appear to make that compulsory for Takeoff.
A lot of other posters here have stated that according to FCOM instructions, the normal, accepted 787 Takeoff configuration is "Both sides draw from centre" if the Centre tanks have enough fuel in them. I think (maybe wrongly) that this (prior few posts) is the first time this exact point has been raised. I hope I'm correct there. If not, my humble apologies. The great thing about this forum and sadly, this tragic accident, is that it's drawing a few previously little-known worms out of the woodwork. \x93Fuel from the center tank is transferred to the inner tanks to keep the inner tanks near full. The FCMC automatically controls the flow from the center to the inner tanks by operating the inner tank inlet valves. The center tank pumps run continuously when there is fuel in the center tank and provide fuel to the fueling manifold. When the inner tanks are full, the inner tank inlet valves are commanded closed until the inner tank fuel is burned down to approximately 4400 lbs below full. At that point, the inner tank inlet valves reopen to allow the inner tanks to fill, and repeat. \x93 Subjects: Centre Tank FCOM |