Safety Checks of Wiring on Jets Are Urged

The National Transportation Safety Board on Wednesday recommended sweeping efforts to improve electrical wiring on airliners--particularly older ones--to avoid a catastrophic explosion like the one that destroyed TWA Flight 800.

The action came as the board formally concluded its investigation of the 1996 disaster, finding--as expected--that a short circuit in the plane’s nearly 200 miles of wiring probably led to a fuel tank explosion that tore the aircraft apart about 13,800 feet above the Atlantic Ocean. All 230 people aboard the New York-to-Paris flight perished.

The Federal Aviation Administration said it would implement the recommendations from the safety board, an independent watchdog agency. Every type of aircraft in commercial service would be affected, but the ultimate cost of the recommendations would depend on specific repairs yet to be determined.

Bernard S. Loeb, director of the NTSB’s office of aviation safety, said the likelihood that many aging aircraft have wiring problems does not automatically render them unsafe to fly.

“We are not saying that these planes are unsafe,” Loeb told the board. “What we are saying is that there are problems that need to be addressed.”

The FAA said it already has launched an intensive research program to improve the safety of wiring. In a shift, the agency also has embraced an earlier NTSB recommendation that airlines eventually be required to pump nitrogen into fuel tanks to render volatile vapors incapable of sudden ignition.

“We think they are appropriate,” Tom McSweeny, the FAA’s associate administrator, said of the newest recommendations. “We will be moving forward on them. We are already working on many of the issues.”

The safety board left no doubt that it is especially concerned about the condition of electrical wiring on older aircraft. The average age of commercial airliners in the United States is 16 years, but many are much older than that. The TWA Flight 800 plane--a Boeing 747--was about 25 years old.

After the crash, NTSB and FAA officials examined dozens of aircraft and found numerous examples of cracked insulation on wires and of wiring contaminated by lint, toilet fluids and other debris.

“I would like to think that this will change the system as far as aging aircraft” are concerned, said NTSB Chairman Jim Hall. “This is the most significant thing that could come out of this tragedy.”

At the conclusion of a two-day public hearing, the board issued four new recommendations on wiring and fuel tank safety. Each contained several parts.

The board called on the FAA to review the design of wiring on all aircraft approved to carry passengers in United States, to ensure that wiring for critical safety systems is adequately separated from other wires.

The intent is to prevent such problems as a power surge from being passed on to these critical systems. In the case of Flight 800, board investigators believe that a high-voltage current somehow found its way into low-voltage wires connected to a fuel-measuring device in the plane’s center tank.

The NTSB also called for new regulations to improve maintenance of wiring and to require precise reporting of any work done on them. Investigators found that normally meticulous aircraft maintenance procedures do not seem to apply to wiring. Some electrical repairs are not fully documented, and some go unreported.

And more advanced circuit breakers should be developed and installed on planes, the board said. The FAA already is working on such a project.

With regard to fuel tanks, the safety board called for design changes to eliminate the buildup of a compound called silver sulfide.

Board investigators believe that deposits of the substance--which have been found on fuel measuring equipment--may have prompted a spark that ignited an already volatile mixture of air and fuel in Flight 800’s center tank.

The board also called for an examination of fuel tank designs to eliminate potential ignition hazards.

Fuel-tank explosions are extremely rare, and the airline industry recently issued a study that concluded that tanks and fuel systems used on commercial jets are very safe.

But Hall said “it doesn’t give me any warm and fuzzies” to learn that the wiring on many older planes may be chafed, cracked or contaminated. He suggested that perhaps passengers should be told the age of the aircraft they are about to board.

Elizabeth Erickson, who heads the FAA office that approves aircraft for flight, said age should not be a safety factor if an airplane is properly maintained. “What we are going after is to make sure that the same safety level that is designed into an aircraft is maintained over time,” Erickson said.

The FAA has tackled aging-aircraft problems successfully in the past, Erickson said. For example, when part of the metal skin of an Aloha Airlines Boeing 737 sheared off during flight in 1988, the agency launched a program to upgrade deteriorating airplane structures. There have been no other such accidents since then, she said.

In the aftermath of Flight 800, a similar program is being followed for wiring and internal systems. The FAA has acquired and is dismantling six retired jetliners to study the condition of wiring and other internal systems.

In another safety area related to Flight 800, the FAA said it is making progress on devising a system to render volatile vapors in fuel tanks virtually incapable of sudden ignition. This can be done by pumping nitrogen into the tanks--a method already employed by the U.S. Air Force.

The FAA previously had been skeptical of requiring airlines to adopt a similar practice, but the agency now says that recent technical innovations make the added precautions feasible and cost-effective.

It is estimated that center fuel tanks on commercial aircraft are capable of ignition--if a spark were introduced--about 30% of the time. With the addition of nitrogen, that risk could be reduced to 2%.

Addressing dozens of family members of victims, NTSB member John Goglia said improved safety would be the legacy of the tragedy. His voice breaking, he recalled his visits to the Long Island hangar where the wreckage of the plane was painstakingly reassembled after being raised from the ocean floor.

“We will have failed in our efforts if we do not put that airplane to good use,” he said.