Closer inspections suggested for jetliners' inner workings Witnesses list problems that may give clue to loss of Flight 800

December 12, 1997|By Suzanne Wooton | Suzanne Wooton,SUN STAFF

With the specific cause of the explosion of TWA Flight 800 likely to remain a mystery, investigators said yesterday that more rigorous inspections of the internal systems of aging aircraft may help to prevent similar tragedies.

As the weeklong hearing in Baltimore by the National Transportation Safety Board wound toward today's close, investigators suggested that inspections of the internal workings of aging jets should be mandated, as are examinations of their structural frames.

"We do not know what caused the TWA 800 tragedy," NTSB Chairman James E. Hall reiterated yesterday. "One of the factors that has been widely reported and considered is the age of the aircraft."

Built in 1971, the Boeing 747-100 used for Flight 800 was one of the earliest models of the 747 jumbo jet. It was one of 211 still in use when it crashed off Long Island in July 1996, killing all 230 people aboard.

Industry officials testified yesterday that there is no specific life limit on the Boeing 747, provided it receives proper maintenance. As the jets age, they receive more intense -- and more costly -- inspections, industry officials said.

A 20-year-old aircraft has typically experienced 20,000 takeoffs and landings and 60,000 flying hours. The plane used on the Paris-bound Flight 800 showed no evidence of fatigue cracking when it was inspected after 13,000 takeoffs and landings and again after 16,000. At the time of the crash, it was due for its next inspection.

Standards date from '80s

Airframe inspection standards were established by the Federal Aviation Administration in the early 1980s and stepped up after 1988, when a large part of fuselage ripped off an Aloha Airlines Boeing 737 in midflight.

At that time, the FAA did not extend the mandatory inspection requirements to internal areas, such as the fuel measuring, electrical or hydraulic systems, which are far less visible and often difficult to evaluate.

But the FAA said yesterday it would make recommendations next June to incorporate system checks into the overall inspection process. Industry experts cautioned about the dangers of damaging the wiring during the inspection itself.

"One problem with inspection is every time you disturb that bundle, you can do damage," George A. Slenski, lead engineer for electronic materials at Wright Laboratory in Dayton, Ohio, was quoted by the Associated Press as saying. "In the process of inspection, you can do more damage."

While no specific cause has emerged after the 17-month investigation, witnesses this week ticked off several problems, including frayed wiring, that may provide a clue to the TWA 800 explosion.

In light of the information presented this week about possible systems flaws, Hall indicated yesterday that there appeared to be a need to inspect aircraft systems as well as structures.

Earlier this week, an NTSB investigator, Robert Swaim, suggested that damaged wires and corrosion of a fuel measuring rod could have helped to cause Flight 800's nearly empty and highly volatile center fuel tank to explode.

Cutting maintenance?

Yesterday, Swaim questioned whether airlines were cutting back maintenance to save money. "There's feeling among pilots and mechanics that with deregulation and competition, airlines are cutting back on maintenance," he said.

But Robert Vannoy, Boeing's 747 fleet support chief, denied that was the case, saying older 747s are subjected to a scheduled maintenance check one day every month, a weeklong inspection every year and a monthlong heavy maintenance overhaul every five years.

Wiring on the 747 has not been a continuing problem area, nor has there been any reported incident of arcing, or a sudden electrical surge, both Boeing and TWA said.

Pub Date: 12/12/97

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