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Guest Kritz911

747X Fuel Jettison Question

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Hello Guys and Girls!I have recently been flying the 747X pretty excessively (bought it somewhen early 2008), studied every single Manual I could get into my hands. But there still does remain one question that could not have been answered sufficiently anywhere, neither in the PMDG Manuals, nor in any other manual and tutorial that I have read to this date.When dumping fuel with the Fuel Jettison System on the overhead Panel, you can choose between system A and system B. Now, what exactly is the difference between these two systems, since (as far as I have tested) it's apparently not about a higher pump pressure resulting in more fuel being dumped in less time. Am I right if I am assuming that either one of the systems is a possible backup system, that if for instance system A fails to operate, because of a loss of electricity due to the engine failure (?), system B is still operative?Thanks in advance for your answers, muchly appreciated! :( with kind regards,Chris

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Chris, you are right to assume that Jettison system A and B are the same function. One is just a back-up for the other.The ability to jettison is very important because at gross takeoff weight (GTOW) you may be heavier than maximum landing weight (MLW) (jettison is usually used when the aircraft has to make a landing soon after departure, either by landing at the departure airport or a close-by airport). Landing heavier than MLW may cause structural damage to the airframe and will probably cause an aiframe inspection if the captain reports anything except a very smoothe touch-down.HTH,Cheers, Richard

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Thanks for the confirmation Richard! I've been practicing some abnormal procedures lately and I never got to knew what A and B was all about.Chris

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