Event Details


Title:Uncontrolled Descent and Collision with Terrain, USAir Flight 427, Boeing 737-300, N513AU, Near Aliquippa, Pennsylvania, September 8, 1994
Micro summary:This Boeing 737 experienced an in-flight upset and crashed, destroying the airplane.
Event Time:1994-09-08 at 1903:23 EDT
File Name:1994-09-08-US.pdf
Publishing Agency:National Transportation Safety Board (NTSB)
Publishing Country:USA
Report number:NTSB/AAR-99/01
Pages:370
Site of event:Approach to Pittsburgh
Latitude/Longitude:N40°36'14.14", W80°18'36.95"
Departure:Chicago O'Hare International Airport, Chicago, Illinois, USA
Destination:Pittsburgh International Airport (Greater Pittsburgh Airport), Pittsburgh, Pennsylvania, USA
Airplane Type(s):Boeing 737-3B7
Flight Phase:Cruise
Registration(s):N513AU
Operator(s):USAir
Type of flight:Revenue
Occupants:132
Fatalities:132
Serious Injuries:0
Minor/Non-Injured:0
Other Injuries:0
Executive Summary:Executive Summary On September 8, 1994, about 1903:23 eastern daylight time, USAir (now US Airways) flight 427, a Boeing 737-3B7 (737-300), N513AU, crashed while maneuvering to land at Pittsburgh International Airport, Pittsburgh, Pennsylvania. Flight 427 was operating under the provisions of 14 Code of Federal Regulations Part 121 as a scheduled domestic passenger flight from Chicago-O'Hare International Airport, Chicago, Illinois, to Pittsburgh. The flight departed about 1810, with 2 pilots, 3 flight attendants, and 127 passengers on board. The airplane entered an uncontrolled descent and impacted terrain near Aliquippa, Pennsylvania, about 6 miles northwest of the destination airport. All 132 people on board were killed, and the airplane was destroyed by impact forces and fire. Visual meteorological conditions prevailed for the flight, which operated on an instrument flight rules flight plan.

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 safety issues in this report focused on Boeing 737 rudder malfunctions, including rudder reversals; the adequacy of the 737 rudder system design; unusual attitude training for air carrier pilots; and flight data recorder (FDR) parameters.

Safety recommendations concerning these issues were addressed to the Federal Aviation Administration (FAA). Also, as a result of this accident, the Safety Board issued a total of 22 safety recommendations to the FAA on October 18, 1996, and February 20, 1997, regarding operation of the 737 rudder system and unusual attitude recovery procedures. In addition, as a result of this accident and the United Airlines flight 585 accident (involving a 737-291) on March 3, 1991, the Safety Board issued three recommendations (one of which was designated “urgent”) to the FAA on February 22, 1995, regarding the need to increase the number of FDR parameters.
Learning Keywords:Operations - Uncontrolled Flight into Terrain
Operations - Upset in-flight (extreme attitudes, stall, spin)
Consequence - Hull Loss
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In-Flight Icing Encounter And Uncontrolled Collision With Terrain, Comair Flight 3272, Embraer EMB-120RT, N265CA, Monroe, Michigan January 9, 1997
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In-flight upset, United Airlines Flight 585, Boeing 737-291, N999UA, Uncontrolled Collision with Terrain for Undetermined Reasons, 4 Miles South Of Colorado Springs Municipal Airport, Colorado Springs, Colorado, March 3, 1991
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Stall and loss of control on final approach, Atlantic Coast Airlines Inc dba United Express Flight 6291, Jetstream 4101, N304UE, Columbus, Ohio, January 7, 1994
Uncontrolled collision with terrain, Flagship Airlines, Inc., dba American Eagle Flight 3379, BAe Jetstream 3201, N918AE, Morrisville, North Carolina, December 13, 1994
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