Boeing 747 operators are assessing the possible effects on their long-range schedules of a US Federal Aviation Administration emergency airworthiness directive which effectively cuts usable fuel.
European airlines say that they are not planning extra fuel stops, but transpacific operators, including Cathay Pacific and Northwest Airlines, say they are planning for contingency stops in Anchorage on some US-Asia Pacific services.
The FAA says that its directive, which concerns faulty fuel pumps, is not related to investigation of the 1996 Trans World Airlines 747-100 accident near Long Island, New York, in which the centre-wing fuel tank exploded.
The organisation reports that a 747 operator has had to remove seven override/jettison fuel tank pumps from the centre-wing tanks because the bearings were prematurely worn, leading to an axial shift of the steel paddle wheel and allowing it to contact the pump end plates. This has caused pump circuit breakers to trip. The FAA says that this may constitute an ignition risk.
The directive requires that the fuel pumps are switched off before tanks are empty, and bans the use of the horizontal-stabiliser fuel tanks in 747-400s.
Source: Flight International
