On March 31, 1993, the No. 2 engine and engine pylon separated from Japan Airlines, Inc. flight 46E, a Boeing 747-121, which had been wet-leased from Evergreen International Airlines, Inc., shortly after departure from Anchorage International Airport, Anchorage, Alaska. The accident occurred about 1234 Alaska Standard Tim

9. The turbulence-induced G-loads recorded on the recorders of flights 46E and 42E can be combined and time-phased such as to cause the ultimate lateral strength of the Boeing 747 engine pylon structure to be exceeded.

13. There was no specific requirement to perform inspections in the area of the forward firewall web of the pylon where the crack was found, however, to date, inspections of other Boeing 747s have found no additional evidence of cracking in this area.

The Safety Board finds that the accident involving flight 46E further amplifies the need for a better understanding of mountain-induced meteorological phenomena and their effects on aircraft. Therefore, the Safety Board reiterates Safety Recommendation A-92-58, which addresses that need. Additionally, the Safety Board believes that the FAA should develop and implement a meteorological program to observe, document, and analyze potential meteorological aircraft hazards in the area of Anchorage, Alaska, with a focus on the approach and departure paths of the Anchorage International Airport. Further, the Safety Board believes that the National Weather Service (NWS) should use the WSR-88D system at ANC to document mountain-generated wind fields in the Anchorage area. The WSR-88D system should also be used by the NWS develop in greater detail low altitude turbulence forecasts.

4. Consider the necessity and feasibility of requiring the modification of the aircraft departure routes at Anchorage International Airport during periods of moderate or severe turbulence to minimize the potential of aircraft encountering mountain-induced low- level turbulence.

5. The meteorological factors that produced the turbulence occur frequently in the Anchorage area. However, the production of significant turbulence and accompanying vortices due to the interaction of wind with mountains is common in all mountainous areas.

The pilots of the F-15s informed the Elmendorf tower that the B-747 had lost the No. 2 engine, all of the leading edge devices between the No. 1 and No. 2 engines and that the trailing edge flaps were damaged.

7. The flight crew's actions were not a factor in the accident.

Some topics in this essay:
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