The Boeing 737 has a history of rudder system-related anomalies, including numerous instances of jamming. A number of accidents and incidents were the result of the airplanes unexpected movement of their rudders. During the course of the four and a half year investigation of the crash of USAir Flight 427 near Aliquippa, Pennsylvania, killing 132 people, the NTSB discovered that the PCUs dual servo valve could jam as well as deflect the rudder in the opposite direction of the pilots input, due to thermal shock, caused when cold PCUs are injected with hot hydraulic fluid. This finally solved...

On July 26, 2002, about 0537 eastern daylight time, Federal Express flight 1478, a Boeing 727-232F, on its way from Memphis International Airport to Tallahassee Regional airport, struck trees on short final approach and crashed short of runway 9 at the Tallahassee Regional Airport, Florida. The flight was operating as a scheduled cargo flight from Memphis, to Tallahassee. The captain, first officer, and flight engineer were seriously injured, and the airplane was destroyed by impact and resulting fire. Night visual meteorological conditions prevailed for the flight, which operated on an...