Slats

On April 6, 1993, a China Eastern Airlines McDonnell Douglas MD-11, flight 583, on its way from Beijing, China, to Los Angeles, California, had an inadvertent deployment of the leading edge wing slats while in cruise flight, not far from Shemya, Alaska. The autopilot disconnected, and the captain was manually controlling the airplane when it progressed through several violent pitch oscillations and lost 5,000 feet of altitude. Two passengers were fatally injured, and 149 passengers and 7 crewmembers received various injuries. The airplane did not receive external structural damage, but the passenger cabin was substantially damaged. The National Transportation Safety Board determined that the probable cause of this accident was the inadequate design of the flap/slat actuation handle by the Douglas Aircraft Company that allowed the handle to be easily and inadvertently dislodged from the UP/RET position, thereby causing extension of the leading edge slats during cruise flight.

The data presented in this report were obtained by North American Aviation, Inc., from an investigation conducted in the Southern California Cooperative Wind Tunnel. Tests were made over a range of Mach numbers from 0.300 to 0.883 to determine the aerodynamic characteristics of a semispan model of a 35 degree swept-back wing equipped with a leading-edge slat and to gain additional knowledge of the aerodynamic loads and automatic operation of the slat. Lift, drag, and pitching-moment characteristics of a model wing in the presence of a fuselage were measured as well as pressures acting on the slat in the retracted and the full-open positions. The pressure data were analyzed to ascertain the opening characteristics of the slat for two possible circular-arc slat tracks which could be used for automatic operation of the slat.

An investigation of the two-dimensional aerodynamic characteristics of an NACA 64A010 airfoil with a slat has been conducted in the Mach number range from 0.25 to 0.85, with a corresponding Reynolds number range from 3.4 million to 8.1 million. Two families of slat positions were investigated, one with the slat leading edge extended forward along the airfoil chord line, and the other with the slat extended forward and displaced below the chord line.