zfw
As an instructor of many years, I can clearly state that agents are taught that the reason for having a ZFW is to ensure that
a/The structure on the wing roots is not compromised/stressed beyond its capability if ZFW was at maximum permitted
b/At any stage of a flight, the captain uses the ZFW to determine diversion data in case of landing at unscheduled airports, usually just into flight. (ZFW plus fuel remaining = est landing weight.
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There have been two instances whereby an aircraft has run out of fuel en route and still glided safely into land.
(Alidair Viscount-Exeter,, Air Transat-Azores.
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Any employer using despatchers as runners for the summer season or periodically should not let them lose onto a/c until they have proven training records of understanding _theory of flight-ZFW/TOW/RLW/Loadsheet principals and 6 point check of any document handed to them to give to crew.
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There is no legislation as to training capabilities in law yet but any good crew member may ask to see training records of any despatcher who appears to be unknowledgeable about the loadsheet/loading instructions.
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Who knows..It could just stop a potential incident if more challenges were made to the ground services handling agent about competency of the staff let loose to visit the flight deck!!