A report yesterday on the search for a cargo door that blew off a United Airlines plane flying near Hawaii last year incorrectly identified the type of jetliner involved. It was a Boeing 747. (Published 8/2/90)

HONOLULU, JULY 31 -- A three-mile-long field of sunken debris probably contains the missing door from United Flight 811, a Navy salvage expert said today.

Navy officials have been hunting a cargo door that blew off a Boeing 727 in February 1989 at 22,000 feet near Hawaii. Nine people were swept to their deaths when the resulting suction peeled back part of the business class cabin, but the airplane managed to land safely.

The National Transportation Safety Board (NTSB) blamed the accident on the cargo door's locking mechanism but officials still want to examine the door. The search has cost $150,000 so far and has involved a deep-sea Navy sonar device called Orion that is towed close to the bottom.

Bob Whaley, project engineer with the Naval Sea Systems Command, said the largest and most promising object found so far extends roughly 10 or 11 feet from an otherwise flat and featureless ocean floor more than 14,000 feet deep. He said the search ship marked the spot with an underwater acoustic device so it can be relocated.

"What the debris is, we're not sure," Whaley said. "It doesn't look like geology. It's not rocks or anything like that. It's a relatively fresh debris field, and man-made."

He said the sonar images were not detailed enough to identify individual objects, such as an airline seat, but said the location of the debris coincides exactly with radar tracks of objects that fell from the plane. A supersensitive Navy radar was precise enough in its tracking to enable searchers to confine the hunt to a 24-square-mile area.

The large piece is among 40 sonar contacts found over the past six days, said Whaley, who supervised the search aboard the fleet ocean tug Narragansett.

"If it isn't, then it can't be very far," he said. "I'd say it's a very good chance, running better than 50 percent, that this is the debris field from the plane."

Whaley said the Orion system located the field on the first day of searching last Wednesday, then picked up stronger contacts as the ship crossed over the target area.

Whaley said the sponsors of the search, the NTSB and the Federal Aviation Administration, would be informed of the discovery and then would decide whether to sponsor a salvage mission.

The search was hampered by heavy current, which limited the ship to south-to-north passes over the target area, he said. The ship covered only about 20 percent of the target area, but Whaley said he has a high degree of confidence that the debris is from the plane.

"It's nothing, just blank bottom, then all of a sudden we find debris and then we don't find anything," he said.