It is around 08.00 lt (local time) in the morning, of this day in aviation history in 2007, at Bethel (Alaska, USA) when the pilot of a Cessna 208B Grand Caravan performs the preflight inspection of his aircraft. It is still dark on the clear and cold morning in(Visual Meteorological Conditions. During the inspection, a layer of frost was discovered on the aircraft. The pilot was able to use a broom to remove the frost from the wings and the tail of the aircraft, as the frost had not bonded to the fuselage. The critical surfaces were described by the pilot as clean, no de-icing fluid was used.
The aircraft wreck in daylight conditions (© ADSP)
At 08.54, the aircraft took off from Runway 36 at Bethel, with the pilot and a ground support employee of the airline onboard the aircraft. The weather at the time of the departure (recorded at 08.53 lt) was as follows;
Wind - 330º at 10 knots
Temperature - -24ºC Dewpoint - -28ºC
Clouds - None
Visibility - 10 miles
Altimeter - 29.71 inHg / 1005 mbar
As the aircraft climbed out, with the flaps in the take-off configuration of 20 degrees, the aircraft accelerated to a speed of 100 knots while climbing at ~500 ft/min, at which point the flaps were selected to 10 degrees. A short while later, as the aircraft accelerated through 110 knots, the flaps were selected up. As the flaps moved through the 5 degrees position the aircraft started to roll to the right, to the pilot it appeared as if they had flown into a vortex of an unknown origin. The pilot countered the roll with a left aileron input and lowered the flaps again to the 20 degrees position. The pilot confirmed the engine was operating normally as the right roll increased and the pilot observed the aircraft descending to the ground.
He immediately selected full flaps, however, this was too late and at 08.56 lt the aircraft hit the snow-covered ground, throwing the pilot out of the aircraft (receiving minor injuries), while the passenger sustained serious injuries during the impact.
The aircraft wreck in daylight conditions (© ADSP)
The NTSB (National Transportation Safety Board) was alerted and launched an investigation to establish the cause of the accident. A Federal Aviation Administrator (FAA) inspector was dispatched to the accident scene for an onsite investigation. The pilot and passenger were interviewed by the NTSB, as well as the director of operations of the airline. The FAA inspector examined the airplane and had the following observations;
The righthand wing, torn loose from and folded against the fuselage
All three landing gears destroyed
Belly pod destroyed
The righthand side of the fuselage was torn open
Left wingtip bent upward
All three composite propellor blades were torn off at the propellor hub
The engine power lever and propeller control lever were both in the full forward position
The fuel condition lever was in the "run" position
The aircraft wreck in daylight conditions (© ADSP)
During the investigation, process emphasis was placed on the removal of frost by the pilot in relation to the relevant sections in the Airplane's information manual. The Airplane information manual alerted, amongst others for;
Small amounts of contamination on the wing and tailplane will degrade the airplane's performance
Prohibition to take off if frost, ice or snow may reasonably be expected to adhere to the airplane between the tactile check and takeoff."
On the 17th of November 2009, the NTSB published its investigation report into the accident. This report, which was the source for this blog, can be read by clicking on the .pdf file at the end of this blog.
The NTSB concluded that the probable cause(s) of this accident was: The pilot's failure to adequately remove frost contamination from the airplane, which resulted in a loss of control and subsequent collision with terrain during an emergency landing after takeoff.
The aircraft wreck in daylight conditions (© ADSP)