USAir Flight 427 was a scheduled flight from Chicago's O'Hare International Airport to Pittsburgh, Pennsylvania, with a final destination of West Palm Beach, Florida. The flight crashed on 8 September 1994, killing everyone on board.
The Boeing 737-3B7 flying the route, registered N513AU, was approaching runway 28R of Pittsburgh International Airport, located in Findlay Township, Pennsylvania. The airport then was the fortress hub for USAir.
Captain Peter Germano and First Officer Charles B. "Chuck" Emmett III piloted the aircraft. At about 6,000 feet (1,830 m) and 6 miles (10 km) from the runway, the aircraft experienced a sudden loss of control and slammed into the ground in a nearly vertical nose down position in Hopewell Township, Beaver County near Aliquippa, Pennsylvania, killing all 127 passengers and 5 crew members.
Flight 427 has the third highest death toll of any aviation accident involving a Boeing 737-300 after the crash of Flash Airlines Flight 604.
After the longest investigation in aviation history—more than four and a half years—the concluding statement said:
The National Transportation Safety Board determines that the probable cause of the USAir flight 427 accident was a loss of control of the airplane resulting from the movement of the rudder surface to its blowdown limit. The rudder surface most likely deflected in a direction opposite to that commanded by the pilots as a result of a jam of the main rudder power control unit servo valve secondary slide to the servo valve housing offset from its neutral position and overtravel of the primary slide.
The NTSB concluded that similar rudder problems caused the previously mysterious 3 March 1991 crash of United Airlines Flight 585, and the 9 June 1996 incident involving Eastwind Airlines Flight 517, both of which were Boeing 737s. As a result of the investigation, pilots were warned of and trained how to deal with insufficient aileron authority at an airspeed at or less than 190 knots (218 mph, 354 km/h), formerly the usual approach speed for a B737. Four additional channels of information—pilot rudder pedal commands—were incorporated into flight data recorders, while Boeing redesigned the rudder system on 737s and retrofitted existing craft until the affected systems could be replaced. The United States Congress also required airlines to deal more sensitively with the families of crash victims.
427 is no longer a valid flight number on US Airways.
Flight 427 was the second fatal crash within six months at the company (the other being USAir Flight 1016 at Charlotte-Douglas Airport in July, 1994). Some feel these crashes contributed to the financial crisis USAir was experiencing at the time.
The crash killed noted neuroethologist Walter Heiligenberg (born 1938).