United 811's near-disaster marks the first time that a 747 jumbo jetliner has flown with two engines out on the same wing, Boeing Aircraft said Friday.
"The pilots did a terrific job," Boeing spokesman Jack Gamble said. "United has to be very proud of them."
Though National Transportation Safety Board investigators haven't determined the exact cause of flight 811's mishap near Hawaii _ nine people were sucked out of the plane _ suspicion is centered on a cargo hatch located below and behind the cockpit on the plane's right side.
There are indications the hatch wasn't closed or malfunctioned and the door set off a chain reaction that ripped off the hatch and a 10 foot by 40 foot chunk of the plane's fuselage.
Debris then spewed from the hatch area and was ingested by the plane's right-wing engines, No. 3 and No. 4. The pilots were forced to turn them off.
"Fortunately, the plane was at 20,000 feet and had good airspeed," Avmark Inc. aircraft expert Stephen Rehrmann said. "That gave the pilots time to cope with the emergency."
Following procedures learned in simulators at United's Flight Training Center in Denver, chief pilot Dave Cronin and his co-pilot compensated for loss of the two right-wing engines by boosting power on the left-wing engines. The pilots dropped the wing a bit and added left rudder, said Rehrmann, a licensed four-engine pilot.
Together, the three corrective actions enabled flight 811's pilots to make a careful turn and gingerly descend to a near-perfect landing at Honolulu International Airport.
The huge gash in the plane's side probably made the plane wobble and weave across the sky, Rehrmann said. "To the best of my knowledge," Boeing's Gamble said, "this is the first time that a 747 has been flown with only two engines (functioning) on the same wing."
He said, "747s are designed to fly on two engines but in a pinch can fly on one."
He also said the plane involved in flight 811's mishap was the 89th built by the Seattle, Wash., aircraft company.
"Though it came off our assembly line in November 1970, the plane hasn't been overly used and has no history of incidents," Gamble said.
Air Transport Association spokesman Bill Jackman said former pilots in his organization are full of admiration for flight 811's pilots.
"It was a very impressive piece of flying," Jackman said. "Keeping that airplane level must have been a hell of a problem."
Former FAA Administrator T. Allan McArtor said flight 811's accident shows the ruggedness of modern passenger aircraft. The 747 and other airliners can remain in the air if their primary flight structures remain intact, he said.
But he added, "It's always a feat of airmanship for a crew to get a damaged plane down safety."