User:Whoop whoop pull up/Japan Airlines Flight 46E

Japan Airlines Flight 46E
Accident
Date	31 March 1993
Summary	Inflight engine separation in severe turbulence
Site	Anchorage, Alaska
Aircraft
Aircraft type	Boeing 747-121
Operator	Evergreen International Airlines
IATA flight No.	JL46E
ICAO flight No.	JAL46E
Call sign	JAPAN AIR 46 ECHO
Registration	N473EV
Flight origin	Narita International Airport, Narita, Chiba, Japan
Stopover	Anchorage International Airport, Anchorage, Alaska
Destination	O'Hare International Airport, Chicago, Illinois
Occupants	5
Passengers	2
Crew	3
Fatalities	0
Injuries	0
Survivors	5 (all)

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Japan Airlines Flight 46E was a scheduled cargo flight from Narita International Airport near Tokyo to O'Hare International Airport in Chicago, with a stopover at Anchorage International Airport in Anchorage, Alaska. On 31 March 1993, the wet-leased Evergreen International Airlines Boeing 747-100 operating the flight suffered an inflight separation of its #2 (left inboard) engine in severe turbulence shortly after takeoff from Anchorage, but was able to return to the airport and make a safe emergency landing without injuries to the five occupants or persons on the ground.^[1]

Accident

Flight 46E, with three flight crew and two company employees flying as passengers onboard, was originally scheduled to depart Anchorage at 1125 Alaska Standard Time, but was delayed by an indication of a malfunction in the #2 engine, which was traced to a faulty indicator system.^[1]^[a] At the time that the flight was recleared to taxi at 1221, SIGMET India 3 was current, warning, in part, of severe turbulence associated with mountain waves in an area south of Anchorage; the SIGMET had been intended to cover Anchorage as well, but one of the sets of coordinate points defining the corners of the area covered by the SIGMET had inadvertently been omitted during transcription.^[1]^[b]

Another Evergreen-operated 747 cargo flight, Japan Airlines Flight 42E, took off shortly before Flight 46E on the same departure route. During its climbout, Flight 42E experienced severe turbulence, large variations in airspeed, and areas of powerful downdrafts at altitudes between 2,000 and 4,500 feet, followed by moderate turbulence up to 8,500 feet; this information was passed along to the crew of Flight 46E.^[1]

Flight 46E took off from runway 6R at approximately 1230, and began to encounter moderate turbulence passing an altitude of 1,500 feet. While climbing out of 2,000 feet in a left turn to the SID heading of 330 degrees, the flight experienced violent turbulence which caused severe pitch and roll oscillations, a 75-knot variation in airspeed (between a high of 245 knots indicated airspeed [KIAS] and a low of 170 KIAS, starting from an initial airspeed of 183 KIAS), and a "huge" yaw, "at which time the No. 2 throttle slammed to its aft stop, the No. 2 reverser indicator showed thrust reverser deployment, and the No. 2 engine electrical bus failed."^[1] Ground witnesses observed the #2 engine separate from the aircraft at this point,^[2] as did the pilots of a pair of F-15 Eagle fighter jets flying in the area, who radioed the air traffic control tower at Elmendorf Air Force Base to report that a large object had fallen from a 747 departing Anchorage; the Elmendorf AFB tower controllers then telephoned their counterparts at the Anchorage International Airport tower with this information.^[1]^[c] The separated engine and pieces of pylon and wing structure fell to earth within urban Anchorage, causing considerable damage to several houses and automobiles, but no injuries or fatalities on the ground.^[1]^[2]

Aboard Flight 46E, the crew performed the emergency-checklist items for an engine failure, the first officer declared an emergency to the Anchorage tower, and the flight engineer began dumping fuel to lighten the aircraft. The captain, flying the aircraft, was able to maintain control by selecting maximum power on the #1 engine together with full to near-full right flight-control inputs.^[1] The two F-15 pilots who had observed the #2 engine fall from Flight 46E approached the 747 and reported that the #2 engine was missing, as was the leading edge of the left wing between the #1 and #2 engine positions, and that the trailing-edge flaps on the left wing had suffered damage; this information was relayed to the crew of Flight 46E.^[1] The captain flew a large left-hand turn to return for a landing on runway 6R (during which he continued to experience some difficulty in controlling the aircraft), and Flight 46E made a safe, though severely overweight,^[d] emergency landing at 1245.^[1]

Investigation

The National Transportation Safety Board (NTSB)'s Anchorage field office was notified of the accident while Flight 46E was still airborne, and investigators were on scene at the airport soon after the emergency landing.^[1] Inspection of the aircraft and the separated engine and other debris revealed no evidence of a mechanical failure of the engine prior to its separation from the aircraft. The engine pylon was found broken into four pieces by multiple fractures; most of the fractures exhibited characteristics of having been caused by overstress, but two areas of fatigue cracking were found, one of which (in the forward portion of the engine firewall^[e]) was continuous with the adjacent overstress fractures and showed signs of the latter having originated from it.^[1]^[f]^[g] The NTSB determined that the forward portion of the pylon failed first, under leftward lateral forces, and that the engine then rotated to the left under the influence of these same forces, bending the aft portion of the pylon until it, too, fractured, allowing the engine to separate completely from the wing; the engine then departed the aircraft in an upwards and leftwards direction, tearing away the wing's leading edge between the #1 and #2 engine positions as it did so.^[1]

At the time of the Flight 46E accident, two earlier accidents involving in-flight engine separations on 747s were under active investigation in other countries (the fatal crashes of China Airlines Flight 358 in December 1991 and El Al Flight 1862 in October 1992). In those accidents, a fatigue failure in the fuse pins holding the pylon to the wing allowed the engine to separate from the aircraft, and there was initial concern that this had happened with Flight 46E as well.^[3] However, all but one of the fuse pins from Flight 46E's #2 engine pylon were recovered intact (although two of the pins were deformed by excessive force, as was one of the fuse pins from the #1 pylon), and the single exception exhibited characteristics of a pure overstress failure, with no signs of prior fatigue cracking; as a result, the NTSB deemed the Flight 46E accident to be unrelated to the China Airlines and El Al accidents.^[1]^[4]

Notes

^ This discrepancy was determined to be unrelated to the later separation of the #2 engine.
^ This error was noticed and rectified at 1342, about an hour after the accident.
^ The F-15 pilots could not contact the Anchorage tower or Flight 46E directly, as their radio equipment was built to operate in the UHF band used by military aviation, and was not compatible with the VHF radios used by the civilian controllers and aircrews.
^ Flight 46E was approximately 100,000 pounds above the 747-100's normal maximum landing weight of 585,000 pounds when it landed back on runway 6R; as a result, the brakes on the left side of the aircraft heated up enough during the landing roll to necessitate special precautions to protect ground personnel from a possible wheel explosion.
^ The firewall is a horizontal inconel plate which, in addition to carrying part of the structural loads borne by the engine pylon, serves to help contain an engine fire, if one should occur, and prevent it from propagating upwards toward the primary wing structure and the wing fuel tanks.
^ The other fatigue crack was not connected to any of the overstress fractures and was in an area (the web of the horizontal pylon midspar near its extreme aft end) that is not critical for carrying loads in the same direction as those which caused the separation of Flight 46E's #2 engine.
^ The firewall and midspar are different sections of the same physical horizontal beam.