Deep Grab

By Janice Castro

For more than two weeks, searchers from India, Canada, Ireland, the U.S., Britain and France had combed some 5 sq. mi. of ocean 110 miles southwest of Cork, Ireland, hoping to discover why Air-India Flight 182 had plunged into the North Atlantic on June 23, killing all 329 passengers and crew aboard. The clues were thought to be contained in two small bright orange metal boxes, commonly called "black boxes." One records the voices of the plane's crew; the other collects data about flight conditions. Both boxes are located behind a ceiling panel just forward of the Boeing 747's tail. Although the boxes are designed to survive fires, crashes and immersion in salt water, the problem facing searchers was immense: Flight 182's recorders were in the plane's wreckage more than a mile below the ocean surface, deeper than any human diver can go.

Air-India brought the most advanced undersea technology to the search by chartering the Leon Thevenin, a French cable-laying ship, and a remote-controlled underwater drone operated by a British company. Known as Scarab 1 (for submersible craft assisting repair and burial), the diving machine was built by Ametek Inc. in 1976 to install and repair transoceanic telephone cables. The Scarab 1 is 11 ft. long, weighs approximately 2 1/2 tons and is equipped with sophisticated sonar, as well as television cameras with zoom lenses and high-intensity lights that illuminate the ocean floor. A team of eight engineers from London, working four to a shift, controlled the submersible from aboard the cable ship by firing electric and hydraulic thrusters to maneuver the craft, which was attached to a 10,000-ft. umbilical cord. Scarab 1's cameras and mechanical arms were also operated electronically as the engineers tracked its progress on TV screens.

The tiny craft probed a corridor 10 miles long by 1 mile wide for several days, gradually narrowing the search area as it scanned the bottom for wreckage. On Friday, the Scarab 1 first detected the distinctive electronic pinging signals emitted by flight recorders but could not fix their location. Then, at 2 a.m. last Tuesday, the engineers hit the jackpot: on their video screens they saw the downed plane's voice recorder on the ocean floor, 6,700 ft. below. Maneuvering the sub closer by firing small bursts from its thrusters, they gingerly extended one of Scarab's mechanical arms so that it carefully picked up the black box. The submersible was then slowly hoisted aboard the Leon Thevenin, clutching its prize.

Next day, after searching for only two hours, Scarab 1 located the data recorder about a quarter of a mile from the spot where the first box had been found. Engineers at the site expressed surprise that the craft had been able to operate so well at a depth from which only a handful of successful recoveries have ever been made. The Scarab, which is designed to dive to 6,000 ft., had never before worked so far below the ocean surface.

The recorders were flown to Bombay, where electronics experts were expected to take several days to analyze the data. The voice recorder should have preserved every sound in the cockpit during the last 30 minutes of flight, from the voices of the crew to possible instrument noises, like alarms. The flight-data recorder should show precise measurements of altitude, engine speed, heading and other flight conditions from takeoff to the impact of the crash.

The suddenness with which Flight 182 disappeared from radar screens at Ireland's Shannon Airport only six minutes after the crew reported that all was well suggested to many that a catastrophic explosion had taken place, possibly of a bomb planted by Sikh terrorists. But with only 2% of the wreckage recovered by week's end, it was too early to ascribe the crash to any one cause. Analysts on the scene said that it was also possible that the world's worst aircraft disaster at sea might have been caused by an electrical failure that cut off all power. If this was the case, then the flight recorders may not tell the whole story, since they depend on the aircraft's power systems. --By Janice Castro. Reported by Mary Cronin/London

With reporting by Reported by Mary Cronin/London