Fire in the Sky

Many an airline passenger has tensed uneasily as lightning streaked the sky and the eerie blue glow of static electricity outlined the wing tips and propellers. Yet airmen have considered static electricity aloft relatively harmless. Now and then, lightning may blow out radio equipment or burn small holes in aircraft skin sections, but there are no recorded cases of major damage. Discharge of static electricity, named St. Elmo's fire by mariners of the Middle Ages, who thought the phenomenon a good omen from their patron saint, is considered no danger at all. When a plane flies through stormy air, static electricity may build up a force of 300,000 volts, discharging from the craft in a flickering blue halo.

Last week aircraft experts were prepared to release a report telling of a "million-to-one shot" where scientists think St. Elmo's fire proved fatal. The plane: a Trans World Airlines Super Constellation that took off into a stormy Italian sky last June 26 from Milan, bound for New York, and crashed twelve minutes later, killing all of the nine crew members and 59 passengers aboard.

At the start of the eleven-month investigation, crash detectives from the Italian and U.S. governments,TWA, and Lockheed Aircraft, builder of the plane, had precious few clues to go on. "It was a mess," said one of the experts. "All we could tell at first was that the right wing had come off in midair.'' All servicing and takeoff procedures were normal; the pilot had reported no trouble by radio. At the wooded crash site, technicians gathered the twisted fragments and sorted them into the plane's component parts. Metallurgical tests showed that the fuel tanks had been subjected to terrific pressure inside and had exploded. Studying fragments from the baggage compartment by microscope, the experts ruled out sabotage by bomb. Further investigation showed that neither the engines nor the plane's internal wiring system had caused the explosion. Eventually, the scientists eliminated all known possibilities save one: St. Elmo's fire.

From the belly tank, empty at the time of explosion, to the trailing edge of the right wing ran a small vent through which fuel could drain in case dangerous pressure built up in the tank. The investigators believe that a lingering bit of St. Elmo's fire, instead of discharging normally from the special tassles on the plane, somehow found its way into the pressure vent and touched off the gas fumes. The fire raced back to the tank, blowing a hole in the right fuselage and exploding a wing tank that in turn blew off the right wing.

Lockheed confirmed the theory by building an experimental wing at its Burbank, Calif. plant and duplicating the explosion conditions. The cure was as simple as the cause of the crash had been tough to pin down: Lockheed installed a flame-arrester screen on the vent pipe openings of all its planes, thus hopefully eliminating another opportunity for St. Elmo's fire to turn from a good omen to tragedy.

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