Northwest Airlines Flight 6231
The crash of Northwest Airlines flight 6231 took place on 1 December 1974 in the vicinity of Stony Point in Harriman State Park ( New York State ). The aircraft was chartered to a football team in Buffalo (New York) record. The accident happened before landing in Buffalo, the three crew members on board were killed.
The cause of the accident was a stall ( stall ) and a rapid descent. This happened because the pilots responded incorrectly on an unreliable airspeed indicator. This in turn was caused by the pilots forgot before starting, turn on the Pitot heating and the tube iced in flight.
The accident
The flight should include in Buffalo, New York, the Baltimore Colts ( now Indianapolis Colts ) after the departure of their actual aircraft was prevented by a snowstorm in Detroit.
The replacement aircraft, a Boeing 727-251 with the air vehicle registration N274US started at 19:14 Clock from John F. Kennedy International Airport for the flight to Buffalo. When the plane reached 16,000 feet ( 4876 m), sounded the warning signals for high speed flight, which was ten seconds later replaced by a stick shaker.
The aircraft then climbed further to 24,800 feet ( 7315 m), where it went into a tailspin and lost altitude. A maximum acceleration of 5 g had a on the plane. At 19:26 clock struck the aircraft in a slightly positive slope, with the right wing face down on the ground. The aircraft lost in 83 seconds 24,000 feet in height, which (230 km / h) corresponds to a rate of descent of 17,350 feet / minute.
The accident was traced until the day after the accident. Police described the crash site as densely forested wetland, and access was complicated by wind and sleet.
The crew
Since it was a ferry flight, were only three crew members, but no passengers on board. Captain John B. Lagario worked for eight years for Northwest Airlines, First Officer Walter A. Zadra and the second officer James F. Cox Jr. were both working for Northwest for six years.
The cause of the accident
The national air accident investigation agency, the National Transportation Safety Board ( NTSB ), led the investigation of this accident and published the final report on August 13, 1975. Were also involved, the Federal Aviation Administration (FAA), Northwest Airlines, Boeing, unions Air Line Pilots Association and International Association of Machinists and Aerospace Workers and the engine manufacturer Pratt & Whitney.
The authorities found that the pitot tubes, which measure the airspeed ( indicated airspeed ), were clogged by ice and the pilot therefore had false speed information. The pilots assumed that they were flying too fast, and pulled the engine high to rapidly reduce speed. In fact, the aircraft was traveling at a normal speed, so the speed following a pull was too low. At high angles of attack was a stall, and the aircraft went into a tailspin.
From the accident report from the NTSB:
The accident was caused by the fact that the crew control of the aircraft lost because they did not recognize the high angle of attack, stall at low speed and spin. The stall was caused by the incorrect response of the pilots on the unreliable airspeed indication. In turn, this happened because the pitot tubes iced during the flight.
Examination of the cockpit voice recording ( cockpit voice recorder, CVR) revealed that the pilot held the shaking of the stick for a sign of approaching the speed of sound ( engl. "mach buffet" ). In fact, warns the "stick shaker " in front of a stall and then before too low airspeed.
Due to the fact that the pilots were misled by an unreliable speed indication and did not perform the necessary procedures, this accident has similarity with the crash of Air France flight 447 in June 2009.