ᴇɴɢɪɴᴇ ʀɪᴘᴘᴇᴅ ᴏғғ ʙᴏᴇɪɴɢ 𝟽𝟺𝟽 – ᴊᴀᴘᴀɴ ᴀɪʀʟɪɴᴇs 𝟺𝟼ᴇ
On March 31, 1993, Japan Airlines Flight 46E , a Boeing 747 cargo plane , took off at 12:30 PM from Ted Stevens Anchorage International Airport bound for Chicago-O’Hare International Airport.. Before taking off, the crew of another Evergreen 747 had reported severe turbulence at an altitude of 2,500 feet (about 850 meters).
Despite the warning, Japan Airlines Flight 46E was unable to avoid the turbulence, which became very strong at an altitude of 2000 feet (about 650 meters).
Shortly after, the flight crew declared the emergency procedure because they had lost the number 2 engine. Immediately afterwards, the flight commander made a wide left turn to land again at the airport. Using maximum power in the number 1 engine, the aircraft managed to land without major incident at 12:45 PM (15 minutes after takeoff).
The National Transportation Safety Board determines that the probable cause of this accident was the lateral separation of the No. 2 engine pylon due to an encounter with severe or possibly extreme turbulence that resulted in dynamic multi-axis lateral loadings that exceeded the ultimate lateral load-carrying capability of the pylon, which was already reduced by the presence of the fatigue crack near the forward end of the pylon’s forward firewall web.
As a result of its investigation of this accident, the National Transportation Safety Board made seven recommendations to the Federal Aviation Administration, including the inspection of B-747 engine pylons, the potential meteorological hazards to aircraft, an increase in the lateral load capability of engine pylon structures, and the modification of the aircraft departure routes at Anchorage International Airport during periods of moderate or severe turbulence.
The Safety Board recommended that the National Weather Service use the WSR-88D Doppler weather radar system at Anchorage, Alaska, to document mountain-generated wind fields in the Anchorage area and to develop detailed low altitude turbulence forecasts.
Additionally, the Safety Board reiterated to the Federal Aviation Administration Safety Recommendation A-92-58, which urged the development of a meteorological aircraft hazard program to include other airports in or near mountainous terrain.