A robot submarine, normally on duty fixing ocean telephone cables, yesterday dove more than a mile deep in the Atlantic to grab with stubby metal arms the cockpit voice recorder that may help determine whether Air-India Flight 182 was bombed.
The unmanned submarine, in repeated dives, is still searching for the other "black box" recorder that read altitude, speed, heading and engine speed aboard the Boeing 747.
The voice recorder recovered from about 6,600 feet under water at 8 a.m. local time yesterday was said to be in good condition, and it is hoped that cockpit alarms, conversations and other noises such as engine pitch may reveal what was happening aboard the jet during its last moments of flight on June 23. The plane crashed without emitting a distress signal, and 329 persons were killed.
It was the first time such a voice recorder was plucked from so great a depth, said H.S. Khola, India's director of aviation safety. To retrieve the recorder, the robot sub went deeper than the diving depth for which it was designed.
Other submersibles, such as those owned by the U.S. Navy, are designed to retrieve objects at depths of more than 10,000 feet. The United States reportedly recovered parts of a Soviet submarine from a depth of 16,000 feet in the 1970s, only to lose them again.
The voice recorder and the data recorder -- known as "black boxes" but actually colored orange -- will be returned to India for examination. There is some worry that little information was recorded in either device, since they are located in the tail of the aircraft and are connected by wires to the cockpit and power supplies. A sudden explosion could have severed the wiring before the recorders could tell much other than that the incident was sudden.
Because of weather, sea currents, and sometimes confusing signals put out by sonar "pingers" such as the one broadcasting from the data recorder, the recovery "is no simple job," according to Frank Busby, of Busby Associates in Arlington, a specialist in such underwater operations.
The robot that retrieved the recorder is called a Scarab, and is built by a U.S. company and run for AT&T by Cable and Wireless company of London, Busby said. It was taken to about 100 miles southwest of the Irish coast on a French ship, the Leon Thevenin.
Scarab took three passes yesterday before it could locate and retrieve the voice recorder. If poor weather or currents intervene, the flight data recorder, which sat next to the voice recorder in flight, may not be recovered. Such conditions prevented a submersible from retrieving the recorders in the case of Korean Air Lines Flight 007, Busby said.
When in action, the 5,000-pound, 11-foot-long Scarab is dropped overboard and pulled downward into the sea by two or more of six propellers that are set at different angles to maneuver the vehicle. Cables attached to the top of the Scarab carry signals from two television cameras and two three-foot robot arms.
The machine listens with sonar ears for the ping of the black box amid background noise and possible false signals that bounce off hills on the sea floor.
To start the search, microphones were first lowered to listen to the pinging beacon without getting an exact location. Then, side-looking radar viewed the ocean bottom to search for dark outlines of what might be plane wreckage.
With the area of search thus narrowed, the Scarab dove in. It descended more than 5,000 feet before getting a good fix on the recorder at 2 a.m. local time. At that point, it motored toward the box, watching through its cameras until it found the box on a "smallish" piece of wreckage on the bottom at about 6,600 feet.
The craft edged over and reached down and collected the box, which is about the size of a safe deposit box.
There is now no evidence, despite much speculation, that the plane was blown up by a terrorist bomb. But that is one theory investigators are working on.
The retrieval of the voice recorder was the culmination of two weeks of searching.
Since the batteries in the recorders last about a month, searchers have two more weeks before the last box stops transmitting.