The National Transportation Safety Board explains that the majority of aviation accidents are due to human error, but twenty-three percent of these accidents are attributed to some sort of weather condition (Kulsea, 2002). There are a number of weather conditions that can affect aircraft at all stages of flight.
Summer storms bring rain, wind, thunder, lightning, fog, and hail as well as severe storm conditions such as tornadoes. On the ground, these conditions can affect visibility and control of the aircraft. In the air, aircraft can be exposed to varying degrees turbulence due to wind shear. On both the ground and in the air, aircraft lightning strikes can be very damaging. (Kulsea, 2002; Vickers et al., 2001).
Winter weather brings icy conditions that can make runways treacherous during take-off and landing, decreased visibility due to falling snow, and increased build-up of ice on the aircraft. Icing is the term used for the build-up of ice on the aircraft and can occur while the aircraft is on the ground and while in the air. Larger aircraft are most vulnerable to ice build-up while on the ground or during take-off and landing, whereas smaller aircraft can be vulnerable to ice build-up during flight due to the tendency to fly at “altitudes where temperatures and clouds are most favorable for ice formation” (Kulsea, 2002, p. 3). Ice increases the weight of the plane as well as changing the shape of the wing.
This will affect the aircrafts lift, drag, speed, and fuel consumption. The risk of stalling is increased significantly. The ice can also build up in the engine, which can cause mechanical and control issues. (Kulsea, 2002; Vickers et al., 2001).
Borrell (2009) described a devastating fatal accident of Continental Express flight 3407 that crashed into a house in five miles short of the Buffalo, NY runway where it was expected to land on February 12, 2009. The pilot of this Bombardier Dash 8 Q400 aircraft had turned on the vessel’s de-icing equipment, “pneumatic de-icing boots that inflate and deflate to break off the crust that [formed] on the wing’s leading edge during flight.”
The pilot had also commented on the build up of ice on the windshield and the wings. Borrell (2009) consulted an expert from the NASA Glenn Research Center who explained how ice changed the shape of the “lift-producing parts of the airplane: the wings and the tail.” The ice made the normally smooth surfaces very rough. The roughness changed the aerodynamics of the wing such that there was more drag and less lift. When the angle of the wing changed in relation to the airstream due to the roughness of the surface and because of the decreased lift, the aircraft experienced an aerodynamic stall. When this situation occurs, the pilot would normally bring the nose of the aircraft down to reengage the wing with the airflow.
Reported Causes of the Accident
The National Transportation Safety Board (2010) detailed report on this fatal crash point to the ice build-up on the wing as a contributing factor in this accident, however, the report explains that the pilot’s use of the auto-pilot and negligence in monitoring the flight instruments were the actual cause. The report was most specific in pointing out that:
Explicit cues associated with the impending stick shaker onset, including the decreasing margin between indicated airspeed and the low-speed cue, the airspeed trend vector pointing downward into the low-speed cue, the changing color of the numbers on the airplane’s indicated airspeed display, and the airplane’s excessive nose-up pitch attitude, were presented on the flight instruments with adequate time for the pilots to initiate corrective action, but neither pilot responded to the presence of these cues. (National Transportation Safety Board., 2010, p. 151).
Role of Weather in the Accident
Weather, specifically the build up of ice, was a major contributing factor to this aviation accident, but as was pointed out by the National Transportation Safety Board (2010), sufficient technology and expertise existed that made this fatality completely avoidable.