The Colgan Air 3407 accident
An understanding of the factors that lead to aircraft accidents can enable the aviation industry to develop policies and procedures to avoid these catastrophes. On February 12, 2009, a Colgan Air, Inc., Bombardier DHC-8-400, N200WQ, operating as Continental Connection flight 3407, crashed into a residence in Clarence Center, New York. All persons on board (2 pilots, 2 flight attendants, and 45 passengers) and one individual on the ground were killed, and the aircraft was destroyed by the impact forces and a postcrash fire (National Transport Safety Board [NTSB], 81). According to NTSB’s report, the accident was caused by the captain’s inappropriate responses to the activation of the stick shaker that resulted in an irrecoverable aerodynamic stall.
The flight data recorder (FDR) of the Colgan Air 3407, recorded the activation and propeller deice equipment when the plane was climbing to its assigned cruising altitude of 1600 feet. Since the sky had a lot of ice, the captain would have turned the ref speed switch to the increase position; however, he did not (NTSB 81). Normally, the turning of the ref speeds switch from off to increase position increases the position of the low-speed cue on pilots IAS displays by about 15 knots and lowers the angle of attack (AOA) reference for stick shaker activation.
At 2150:42, the first officer received a signal from the Buffalo Niagara International Airport (BUF ATIS) and entered the planned landing information including the airplane’s landing weight and intended runway into the Aircraft Communications Addressing and Reporting System (ACARS) for transmittal. Despite the icing conditions, she did not enter the keywords “icing” or ‘eice” when sending the information (NTSB 81). As a result, at 2153:00, ACARS returned incorrect AeroDAta landing performance showing a Vref of 118knots and a Vga of 114 knots (NTSB 81). These speeds were inappropriate for an airplane cruising in icing conditions. Despite the inaccurate data, the airplane responded to the control inputs until the wing stalled.
At 2216:27, the stick shaker was activated, which occurred at an AOA of about 8 degrees, a load factor of 1 G, and an airspeed of 131 knots (NTSB 81). Since the ref speeds had been selected for icing conditions, the stall warning occurred at an airspeed of 15 knots higher than expected for a Q400 when there is no ice accretion. In a normal condition, stick shakers usually provide pilots with a warning of between 5 and 7 knots of an imminent stall (NTSB 82). Therefore, the pilots had a 20-22 knot warning of a potential stall.
The flight data recorder indicated that the autopilot disconnected automatically after the stick shaker activated. In response, the captain applied a 37-pound pull force to the control column, which resulted in an airplane-nose-up elevator deflection and increased power (NTSB 82). As a result, the AOA increased to 13 degrees, the pitch attitude moved to 18 degrees, the load factor changed from 1.0 to 1.4 Gs, and the airspeed slowed to 125 knots. Consequently, there was an increase in the airspeed at which a stall would occur (NTSB 82). These inputs made the airflow over the wing to separate because the AOA was exceeded, which resulted in an aerodynamic stall that made the left wing to roll down up to an angle of 45 degrees.
Following the erroneous reaction by the captain, the airplane experienced several roll oscillations during the aerodynamic stall. The roll angle shifted to 105 degrees right wing down when the captain applied a 41-pound pull force to the control column. Later on, he applied a 90-pound pull force that made the roll angle to shift to 35 degrees left wing and 100 degrees right wing down (NTSB 82). The final wing angle at the time of the crash was 25 degrees for the right wing and the airplane was pitched at 25 degrees airplane nose down.
According to the NTSB, the airplane experienced minimal performance degradation due to the ice accretion and could have been safely operated at normal flight conditions without the risk of stalling (83). Consequently, NTSB notes that the minimal flight degradation due to the ice accumulation did not affect the captain’s ability to control the airplane, rather, it was his inappropriate control inputs in response to stick shaker that caused the accident (83). In this regard, if Colgan Air had ensured that all its pilots were competent to fly their airplanes, this catastrophe would have been avoided.
If an analysis of the Colgan Air 3407 accident is based on the normal accident theory (NAT), it can be concluded that it was due to the pilots’ incompetence. According to NAT, accidents are avoidable if employees are trained, mindful, and have enough knowledge of operating their tools (Shrivastava, et al. 1360). Since the Colgan Air 3407 crash was due to inappropriate inputs by the captain in response to stick shaker, the accident would have been avoided if he inputted the correct ones. In the high-reliability theory (HRT), accidents are unavoidable and are naturally occurring events (Shrivastava, et al. 1361). From this perspective, the air crash would still have occurred even if the pilots were competent to make proper decisions. In this regard, NAT would advocate for better training of pilots and increased supervision by Colgan Air on its employees, while HRT would recommend for increased counseling and customer care to the victims of the accident since the company cannot prevent the occurrence of catastrophes.
National Transport Safety Board [NTSB]. “Loss of Control on Approach Colgan Air, Inc. Operating as Continental Connection Flight 3407 Bombardier DHC-8-400, N200WQ Clarence Center, New York February 12, 2009.” Accident Report NTSB/AAR-10/01 PB2010-910401, 2 February 2010, p. 1-299. Available from https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR1001.pdf.
Shrivastava, Samir, et al. “Normal Accident Theory Versus High Reliability Theory: A Resolution And Call for an Open Systems View of Accidents.” Human Relations Journal, vol. 62, no. 9, 2009, pp. 1357-90.