September 6, 1985
NTSB Number: AAR-87-01
NTIS Number: PB87-910401
At 1521 c.d.t. on September 6, 1985, Midwest Express Airlines, Inc., Flight 105, a McDonnell-Douglas DC-9-14 airplane, crashed into an open field at the edge of a wooded area about 1,680 feet southwest of the departure end of runway 19R shortly after taking off from General Billy Mitchell field, Milwaukee, Wisconsin. The weather was clear with visibility 10 miles. During the initial climb, about 450 feet above ground level (a.g.l.), there was a loud noise and a loss of power associated with an uncontained failure of the 9th to 10th stage high pressure compressor spacer of the right engine. Flight 105 continued to climb to about 700 feet a.g.l. and then rolled to the right until the wings were observed in a near vertical approximately right 90 degree banked turn. During the roll, the airplane entered an accelerated stall, control was lost, and the airplane crashed. The aircraft was destroyed by impact forces and post crash fire. The pilot, the first officer, both flight attendants, and all 27 passengers were fatally injured.
The Safety Board evaluated the performance characteristics of the DC-9-14 airplane following an abrupt loss of power from the right engine in the takeoff phase of flight and found the airplane to be docile, easily controllable, and requiring no unusual pilot skills or strength. Therefore, the Safety Board examined those factors which might have caused the pilots to lose control, including the possibility that fragments of the right engine separated with sufficient energy and trajectory to cause critical damage to the airplane's flight control system; the possibility of control system malfunction(s), which could have rendered the airplane uncontrollable; and the possibility of inappropriate flightcrew response to the emergency.
It was determined that the loss of control was precipitated by improper operation of flight controls, specifically the introduction of incorrect rudder pedal forces about 4 to 5 seconds after the right engine failure, followed by aft control column forces, which allowed the airplane to stall at a high airspeed (accelerated stall). Thus, the Safety Board evaluated flightcrew training of Midwest Express pilots at Republic Airlines, the use and limitations of visual flight simulators used in training, and emergency procedures used by, Midwest Express.
Additionally, the Safety Board evaluated factors, which might have contributed to the right engine failure, including overhaul and inspection practices at AeroThrust Corporation, Federal Aviation Administration (FAA) surveillance at AeroThrust, and FAA and Pratt & Whitney responses to previous removable sleeve spacer failures in JT8D engines.
The National Transportation Safety Board determines that the probable cause of the accident was the flightcrew's improper use of flight controls in response to the catastrophic failure of the right engine during a critical phase of flight, which led to an accelerated stall and loss of control of the airplane. Contributing to the loss of control was a lack of crew coordination in response to the emergency. The right engine failed from the rupture of the 9th to 10th stage removable sleeve spacer in the high pressure compressor because of the spacer's vulnerability to cracks.
During the investigation, the Safety Board issued three recommendations to the FAA related to JT8D removable sleeve compressor spacers. As a result of its investigation, the Safety Board also issued two recommendations on flightcrew training in response to emergencies during the initial climb phase and one recommendation on qualifications for Principal Operations Inspectors. All three recommendations were issued to the FAA.