Older airplanes pressed into service longer than expected737 inspections raise questions about how long aging aircraft can be trustedMay 11, 1998Web posted at: 1:24 p.m. EST (1824 GMT) From CNN Correspondent Alan Duke (CNN) -- Commercial jetliners built decades ago are lasting longer than expected. With good maintenance and occasional overhauls, airlines have found they can keep aging aircraft flying and capital costs down -- an important factor in a competitive business. It's also an especially important factor for some discount airlines that count on hand-me-down planes as the backbone of their service. But when a plane is rebuilt, not everything is replaced. What is done varies airline to airline, with the Federal Aviation Administration setting only minimum standards.
After an aging Boeing 737 lost part of its front fuselage during a flight over Hawaii ten years ago, the FAA increased inspections for structural corrosion and fatigue. And after the TWA Flight 800 crash in July 1996, President Clinton created a commission to look into aviation safety. The commission's report last year raised a red flag about non-structural parts of aging commercial jets. It said little is known about the effects of age on fuel and hydraulic lines, pumps, sensors and electrical wiring. "The Commission is concerned that existing procedures, directives, quality assurance and inspections may not be sufficient to prevent safety related problems caused by the corrosive and deteriorating effects of non-structural components of commercial aircraft as they age," the report said. This month engineers learned an important lesson about what age does to electrical wires running through fuel tanks in Boeing 737s: They discovered a dangerous situation that one engineer called "a recipe for disaster."
Designers thought the coating on copper wiring would never need replacing, but last week they found that in some planes, wires have been rubbed raw. In one plane, fuel was leaking onto the exposed wires. "It could cause a fire or explosion in the wing fuel tank," said Tom McSweeny, the FAA's director of aircraft certification, "neither which we would like to see." Investigators suspect the fiery crash of TWA 800 may have been sparked by worn wiring in the Boeing 747, although no conclusion has been made. The presidential commission predicted within two years, U.S. airplanes will be flying 2,500 planes beyond their original design lifespan. But airline officials insist they are safe as new, if properly overhauled and maintained. Questions raised by the TWA 800 crash and recent revelations made about wiring inside the fuel tanks of some aging jets have the FAA and airlines, however, rethinking how older aircraft are maintained. 
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