On April 6, 1993, the McDonnell-Douglas MD-11 operating the service was cruising above the Pacific Ocean at Mach 0.84 when a crew member accidentally deployed the slats near the Aleutian Islands. The plane then encountered severe oscillations[2] and made an emergency landing at Shemya Air Force Base in Shemya, Semichi Islands, Alaska.[3]
Of the 255 passengers and crew, 60 were hospitalized; two ultimately died.[4] Of the cockpit crew, five received no injuries and three received serious injuries. Of the flight attendants, eight received no injuries and four received serious injuries. Of the surviving passengers, 84 received no injuries, 96 received minor injuries, and 53 received serious injuries.[4] By April 24, 1993 all but three of the surviving passengers were discharged from the hospital.[5]
Investigation
The National Transportation Safety Board report found that the handle used to actuate the leading edge flaps/slats was poorly designed, and the captain likely moved this handle unintentionally while performing an unrelated task. This unexpected slats deployment caused the nose to pitch up. The pilot returned the handle to the correct position and, in an effort to correct the plane's pitch, pushed the control column forward with enough force to trigger the autopilot to disengage, thus causing an abrupt nose-down elevator movement. The plane continued to oscillate between nose up and nose down pitch due to the pilot's overcorrection of the elevator inputs until they were able to stabilize the plane's attitude. The violent pitching movement caused injuries to the occupants. At the time of the accident, passengers were either not wearing seatbelts or had them loose, or were standing in the aisle, exacerbating the number and extent of injuries.
Other contributing factors included the lack of pilot training in high altitude upset recovery, the light control force characteristics at cruising altitude, and the influence of the stall warning system engaging and disengaging during the oscillations on the pilot's control inputs.[4]
Aftermath
The airframe was repaired and continued to operate for China Eastern until March 2005, when it was converted as a cargo freighter for China Cargo Airlines. In July 2010, it was redesignated as N951AR, later served for US-based Sky Lease Cargo, and was eventually scrapped in November 2016.[citation needed]