United Airlines Flight 826 was severely buffeted by turbulence that killed one woman and injured more than 100 others aboard, but the plane's so-called black box shows it actually dropped much less than thought.
Initial estimates were that the giant Boeing 747 plummeted 1,000 feet Sunday in the incident over the Pacific Ocean between Tokyo and Hawaii.But the National Transportation Safety Board said Tuesday the abrupt change in altitude was more like 100 feet. However, the agency confirmed that the box recorded severe shaking by the plane as it went through the unstable air.
The board received the digital flight data recorder - the "black box," which is really bright orange - from the plane at about midnight Monday night and analyzed the contents Tuesday. The recorder keeps track of 17 types of data.
According to a statement released by the safety board, about 1 hour and 31 minutes into the flight, while cruising at 31,000 feet altitude, the plane was suddenly struck with an upward force of 1.8 times the force of gravity and a sideways push of about one-tenth the force of gravity.
At the same moment a burst of wind from behind accelerated the plane from 385 mph to 403 mph.
Six seconds later the plane plunged with a downward force about 80 percent of gravity, with the passengers subjected to approximate weightlessness for about one-half second. During this period the plane rolled 17 degrees right wing down.
The data indicate that altitude changes were less than 100 feet, the board reported.
Meanwhile, United Airlines refused to turn over to Japanese investigators a list of passengers who were aboard the airliner.
Interviews with passengers are critical to the investigation of the incident.
Passengers say the plane's seat-belt sign was not lit at the time the turbulence struck; the airlines says it was on.
Makoto Kitazawa, a member of a Transport Ministry committee investigating the incident, said Wednesday a complaint had been made to the U.S. Embassy in Tokyo to press United Airlines to release the list.
United spokesman Hideki Isayama said the airline was following company policy in not turning over the list to Japan's Transport Ministry.