Emergency regulations issued to make safe a batch of faulty in-service fuel pumps have affected operations with a range of Boeing types, reducing payload or range on marginal routes and increasing operating costs on others.
The US Federal Aviation Administration emergency airworthiness directive (AD) sets strict conditions on the use of centre-wing fuel tank pumps to avoid arcing that "could result in fire/explosion in the centre fuel tank" of 747s, 757s, and Next Generation 737s.
The FAA's AD was prompted by carriers that reported fuel-pump failure in their centre-wing tanks. Pilots of one of the airlines that detected the fault, UK-based EasyJet, reported low fuel pressure, so the airline returned the affected pumps to manufacturer Hydro-Aire of Burbank, California.
Investigations revealed a manufacturing fault that resulted in chafing between the stator lead wire bundle when it came into contact with the rotor, according to the FAA. Airlines can replace all centre-wing tank fuel pumps if they have the specified part numbers or maintain specific minimum fuel quantities in the tanks to ensure that there is enough fuel to prevent "dry running" of the pumps and that electrical arcing from a faulty pump does not occur.
Payload/range can be affected by the requirement to carry a significant amount of unusable fuel. EasyJet, which flies 737-700s, says the only route on which it could be payload-limited is Liverpool, UK, to Malaga, Spain. Industry has been alert to tank ignition risks since the 1996 Trans World Airlines 747 in-flight centre fuel tank explosion.
Source: Flight International
