The crew of the Colgan Air Q400 that crashed outside Buffalo on February 12 observed “significant” ice accretion on the aircraft’s windows and wings before the eventual upset that killed all 49 on board and one person on the ground, according to the NTSB’s lead investigator for the accident, Steven Chealander.
The flight data recorder indicates that the airplane’s autopilot did not disengage until the stick shaker activated, and airmets for the Buffalo area indicated no worse than moderate icing. In fact, according to Chealander, only 27 minutes after the accident another Colgan Q400 flew to Buffalo from Newark on virtually the same flight path.
Operating as Continental Connection Flight 3407 from Newark, N.J., to Buffalo Niagara International Airport, the 74-seat turbo- prop carried 45 passengers and four on-duty crewmembers when, around 10:20 p.m., after the airplane descended to about 2,300 feet, ATC lost contact with the pilots. FDR data shows that the Q400 pitched up at an angle of 31 degrees, then down to 45 degrees, followed by a 46-degree roll to the left, then a 105-degree roll to the right. The airplane fell the last 800 feet in five seconds before crashing virtually flat onto a single house in the suburban town of Clarence Center, N.Y., killing one of the residents. Two other residents escaped with minor injuries.
Chealander said that the National Weather Service issued a sigmet for turbulence that night in the Buffalo area and that a pirep indicated severe icing over Dunkirk, N.Y., some 50 miles southwest of Buffalo.
Along with a recommendation that pilots activate leading-edge de-icing boots as soon as they encounter icing, a Dec. 18, 2008 safety alert issued by the NTSB said they should “turn off or limit the use of the autopilot in order to better ‘feel’ changes in the handling qualities of the airplane.” Chealander, however, wouldn’t characterize the pilots’ failure to disengage the autopilot as necessarily improper. In fact, only when the airplane encounters “severe” icing must the flight crew disengage the autopilot, according to the Bombardier Q400 aircraft flight manual.
The flight’s captain, Marvin Renslow, had flown more than 3,379 hours in his career, but only 110 hours on the Q400. First Officer Rebecca Shaw had accumulated 2,244 hours, 774 hours of which she flew on the Q400 for Colgan.
Chealander said the NTSB will send questionnaires to “every pilot who flew that night” to try to find conditions that could have led to such a violent upset. That, he said, would take several weeks, and the investigation, in total, could last up to a year.