It was about 08.00 on a cold and clear morning when the pilot of a Cessna 208B Grand Caravan performed its preflight activities at Bethel Airport (Alaska, USA). Frost was found on the fuselage, wings and tailplane, which was removed with a broom, resulting in a clean wing and tailplane. There was no de-icing and/or anti-icing fluid applied.
The aircraft wreckage (Source: Aviation-Safety.net © NTSB)
It was still dark as the pilot completed the flight preparations, the weather at the time was as follows;
Wind - 330º at 10 knots
Clouds - Clear
Temperature - -24ºC
Dewpoint - -28ºC
Visibility - 10 miles
Altimeter - 29.71 inHg / 1006 hPa
Once all preparations were completed, the Pratt & Whitney Canada PT6A-114A was started for the VFR flight to Hooper Bay Airport (Alaska, USA). Besides the pilot, two passengers were on board the aircraft for the short flight (244 km / 132 nm).
The aircraft wreckage (Source: Aviation-Safety.net © NTSB)
At approximately 08,54 lt (local time) the take-off was initiated from runway 36, with the flaps in the 20-degree position. Once airborne, at a speed of 110 knots, with a vertical speed of ~500 ft/min, the flaps were retracted from the take-off position to the 5-degree position. The aircraft then rolled to the right, like flying into a vortex. The pilot applied left aileron and lowered the flaps to the 20-degree position. This did not improve the attitude of the aircraft and the roll to the right increased. With the engine operating normally the pilot noticed the aircraft was descending toward the ground. To arrest the descent, the pilot lowered the flaps to the full down position. Moments later the aircraft collided with the ground. The pilot received minor injuries. The passenger, a ground support employee of the operator, received serious injuries. Damage to the aircraft was extensive, the right wing was torn loose from the fuselage and folded aft against the fuselage. The landing gear and belly cargo pod were destroyed. The fuselage was torn open along the right side, and the left wing was bent upward at the tip. The engine propeller blades are fibreglass composite, and all three of the blades were sheared off at the base of each blade, just outboard from the propeller hub.
The aircraft wreckage (Source: Aviation-Safety.net © NTSB) The accident was investigated by the NTSB (National Transportation Safety Board) with the assistance of the FAA (Federal Aviation Administration). Both agencies interviewed the pilot, and the engine was sent to the manufacturer for analysis. Normal wear and tear was found with no signs of a condition that would have prevented normal operation of the engine. The airplane's information manual contains several pages of limitations and warnings about departing with even small amounts of frost, ice, snow, or slush on the airplane, as it adversely affects the airplane's flight characteristics. A visual or tactile inspection of the wings and horizontal stabilizer is mandated by the manufacturer to ensure they are free of ice or frost if the outside air temperature is below 10 degrees C, (50 degrees F),
The aircraft wreckage (Source: Aviation-Safety.net © NTSB)
The NTSB determined the probable cause(s) of this accident to be: 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 NTSB report, which served as the source for this blog, is available for the reader's reference by clicking on the .pdf file below;