FAA Places Operating Limits on Boeing 737 Center Wing Tank Fuel Pumps

WASHINGTON - The Federal Aviation Administration (FAA) has
prohibited U.S. operators of 737 aircraft from running center wing
tank fuel pumps unless the quantity of fuel exceeds a certain
minimum level.

The airworthiness directive (AD) is one of many FAA initiatives to
enhance fuel tank safety, including a proposed rule that would
require airplane manufacturers and operators to change how
airplane fuel tanks are designed, maintained and operated. The
FAA has also issued or proposed nearly 40 airworthiness
directives (ADs) on fuel tank safety.

This action is intended to prevent the ignition of fuel vapors inside
the center wing fuel tank. The FAA has determined that it is
necessary to turn off fuel pumps when the tank is depleted of
fuel; extended dry operation can result in overheating and
excessive wear of the pump bearings. This in turn has the
potential to create an ignition source that could cause a fuel tank
explosion.

The AD, effective immediately, calls for the following limitations,
which will be placed in 737 flight manuals:
ˇFor ground operations, center tank fuel pump switches must not
be positioned to "ON" when the fuel quantity is below 1,000
pounds.
ˇFuel pump switches must be positioned to "OFF" when both low
pressure lights illuminate.
ˇFuel pumps must not be "ON" unless personnel are available in
the flight deck to monitor low pressure lights.

The AD effects 1,501 U.S.-registered 737s at an estimated cost
of $60 per aircraft.