USAir Flight 427

USAir Flight 427 was a scheduled flight from Chicago's O'Hare International Airport to Pittsburgh International Airport, with a final destination of West Palm Beach, Florida. The flight crashed on Thursday, September 8, 1994, killing all 132 on board. The Boeing 737-3B7 flying the route, registered N513AU, and previously registered as N382AU, was approaching runway 28R of Pittsburgh International Airport, located in Findlay Township, Allegheny County, Pennsylvania, which was at the time the largest hub for the airline.

Crash

The sister aircraft of N513AU, a USAir (rebranded and repainted as US Airways) Boeing 737-3B7, registration N527AU.

Captain Peter Germano, 45, was hired by USAir in February 1981. First officer Charles B. "Chuck" Emmett III, 38, was hired in February 1987 by Piedmont Airlines. Both the captain and first officer were regarded as excellent pilots. They were both very experienced, with approximately 12,000 flight hours and 9,119 flight hours respectively. Flight attendants Stanley Canty and April Slater were hired in 1989 by Piedmont Airlines. Flight attendant Sarah Slocum-Hamley was hired in October 1988 by USAir. Piedmont merged with USAir in 1989.

During its arrival into Pittsburgh, Flight 427 was sequenced behind Delta Airlines Flight 1083, a Boeing 727-200. At no time was Flight 427 closer than 4.1 miles to Delta 1083, according to radar data.^[1] During the approach, Flight 427 encountered wake turbulence from Delta 1083; the FAA, however, determined "the wake vortex encounter alone would not have caused the continued heading change that occurred after 1903:00."^[2] At 7:02:57 p.m., there were three sudden thumps, clicking sounds, and a louder thump, and then the 737 began to bank and roll to the left. The aircraft stalled and rolled upside down. Germano exclaimed "Hold on" numerous times, while Emmett said "Oh shit" frequently. Germano exclaimed, "What the hell is this?" As air traffic control noticed Flight 427 descending without permission, Germano keyed the mic and stated, "Four-twenty-seven, emergency!" The aircraft then rolled back upright, but after a few seconds on its side, the aircraft continued to roll while pitched nose-down at the ground. Emmett shouted "What the hell!" and the air traffic controller heard this. In an 80-degree nose-down position, banked 60 degrees left and traveling at 300 mph (480 km/h), the 737 slammed into the ground and exploded at 7:03:25 p.m. in Hopewell Township, Beaver County,^[3] near Aliquippa. All 127 passengers and five crew members were killed. The plane just barely missed the Green Garden shopping plaza and the Aliquippa exit of the Beaver Valley Expressway (I-376, then PA-60), which was crowded with commuter traffic. The 737 crashed onto a private gravel driveway and hillside on Pettita Lane in an area protected against trespassing. A memorial has been placed at the site of impact.

At the time of the crash, Flight 427 was the second-deadliest accident involving a Boeing 737; as of 2012, it was the sixth deadliest. It was also the seventh-deadliest aviation disaster in the history of the United States; as of 2012, it ranked ninth. The accident marked USAir's fifth crash in the period from 1989 to 1994.^[4]

After the crash, USAir had difficulty determining Flight 427's passenger list, facing confusion regarding five or six passengers. Several employees of the U.S. Department of Energy had tickets to take later flights, but used them to fly on Flight 427. One young child was not ticketed.^[4] As a result of the severity of the crash impact, the bodies of the passengers and crew were severely fragmented, leading investigators to declare the site a biohazard.

Investigation

After one of the longest accident investigations in aviation history — lasting 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.^[5]

The exact mechanism of the failure involved the servo valve, which remains dormant and cold for much of the flight at high altitude, seizing after being injected with hot hydraulic fluid that has been in continuous action throughout the plane. This specific condition occurred in fewer than 1% of the lab tests, but perfectly explained all of the successive rudder malfunctions that caused Flight 427 to crash.

The National Transportation Safety Board concluded that similar rudder problems had caused the previously mysterious March 3, 1991 crash of United Airlines Flight 585 and the June 9, 1996 incident involving Eastwind Airlines Flight 517, both 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 (352 km/h), formerly the usual approach speed for a Boeing 737. 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.^[6]

427 is no longer a valid flight number in the US Airways system.

Flight 427 was the second fatal USAir crash in just over two months, the other being Flight 1016 at Charlotte-Douglas Airport in July 1994. The crashes contributed to the financial crisis USAir was experiencing at the time.^[7]

Among the victims of the crash was noted neuroethologist Walter Heiligenberg.^[8]

See also

• Boeing 737 rudder issues
• United Airlines Flight 585
• Eastwind Airlines Flight 517
• American Airlines Flight 1
• Northwest Airlines Flight 85

References

External links

• www.airliners.net - picture of N513AU painted in USAir's brown, orange, and red livery
• NTSB Accident Investigation Docket (Archive)
• AVweb article
• AVweb supplement
• Accident description at the Aviation Safety Network
• 28 Seconds Four-part article from the Saint Petersburg Times
• Boeing 737 Rudder Design Defect
• "Remembering Flight 427." Pittsburgh Tribune-Review. (Archive)
• Pre-Crash accident photos from Airliners.net
• Schaarsmith, Amy McConnell. "Mourners remember at 15th anniversary." Pittsburgh Post-Gazette. September 9, 2009.
• Memorial location

Books

• Bill Adair, The Mystery of Flight 427: Inside a Crash Investigation, ISBN 1-58834-005-8
• Gerry Byrne, Flight 427: Anatomy of an Air Disaster, ISBN 0-387-95256-X