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On October 6, 2005, about 0540 central daylight time, a Cessna 208B, Canadian registration C-FEXS, operated by Morning Star Air Express as cargo flight 8060, was destroyed when it impacted the ground about 5 minutes after takeoff from the Winnipeg International Airport (CYWG), Winnipeg, Manitoba, Canada. The certificated airline transport pilot was killed.
According to FDR data, the airplane climbed to a cruising altitude of 9,840 feet after takeoff. About 1906, an air traffic controller informed the flight crew that moderate icing in the clouds was forecasted. The pilots responded that they were above the clouds and were not experiencing any icing conditions. Review of the airplane’s CVR revealed that about 5 minutes later, the pilots discussed amongst themselves that they were experiencing “severe icing” conditions. About 1914, ATC again asked the pilots about icing conditions and they responded that they were experiencing “light icing.” About 1920, as the airplane neared the airport, ATC cleared the flight to descend to 5,900 feet then to 4,900 feet to begin the approach for landing. About 1925, the airplane leveled off at 4,920 feet at an airspeed of about 118 knots. The CVR recorded the crew reading the descent checklist about the time that the FDR indicated that the airplane began to pitch up (from -0.1º to +7.3º) as the airspeed began to decrease.10 About 1926, at an airspeed of about 102 knots, the airplane experienced a decrease in vertical acceleration and a slight decrease in airplane pitch angle consistent with significant flow separation over the wings and the initiation of an aerodynamic stall.11 Shortly thereafter, the autopilot disengaged, and the airplane descended toward the ground with bank angle excursions of + 40º and reached a maximum airspeed of about 226 knots just before ground impact. Preliminary calculations using FDR data indicate that the angle of attack (AOA)12 was about 9º at the time of the initial upset. Additionally, the sound of the stall warning horn was not heard on the CVR until after the disconnect of the autopilot and onset of the roll excursion. Accident History Cessna 208 During the past 15 years, 12 in-flight icing-related fatal accidents in Cessna 208 airplanes have occurred, resulting in 33 fatalities. Nine non-fatal, in-flight icing-related accidents and incidents also occurred during the same period. This accident/incident history, along with the recent information from the Winnipeg and Moscow accidents, has prompted the Safety Board to investigate systemic problems with the airplane’s design and operation in icing conditions. Use Of AutoPilot Specifically, the decrease in airspeed and increase in pitch attitude preceding the upset were gradual, and the changing control inputs required to maintain altitude were masked by the pilots’ use of the autopilot. Therefore, the National Transportation Safety Board recommends that the Federal Aviation Administration: Require all operators of Cessna 208 series airplanes to maintain a minimum operating airspeed of 120 knots during flight in icing conditions, even if a descent is required to do so. (A-06-01) Urgent
Prohibit all operators of Cessna 208 series airplanes from conducting flight into any icing conditions determined to be more than light icing. (A-06-02) Urgent
Require all operators of Cessna 208 series airplanes to disengage the autopilot and fly the airplane manually when operating in icing conditions. (A-06-03) Urgent
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