What happened
During the takeoff phase, an aircraft failed to gain sufficient altitude following liftoff. While the pilot had received a weather briefing indicating favorable conditions, the aircraft encountered difficulties immediately after departing runway 21. The pilot noted that the plane had ceased climbing and requested updated wind information from the tower. In an attempt to avoid approaching trees, the pilot maneuvered the aircraft toward a clearing; however, the left wing struck a tree, causing the aircraft to descend into the ground.
At the time of the accident, the aircraft's gross weight was 6,000 pounds, and the density altitude was calculated at 9,481 feet. Although the pilot reported no mechanical issues with the engines or airframe, performance charts for the aircraft type indicated that the plane should have maintained a positive rate of climb of approximately 1,100 feet per minute under the recorded atmospheric conditions.
Findings
Investigation of the airport's wind recording system revealed significant fluctuations in wind speed and direction during the departure. While the initial wind reported was 300 degrees at 10 knots, subsequent data samples showed a rapid shift. Specifically, the sensor at the departure end of the runway recorded a 10-knot increase in wind speed, while the approach end sensor recorded a shift from a headwind to a tailwind of 10 knots.
Analysis of these meteorological conditions suggests that the aircraft encountered wind shear caused by developing convection over the runway. This increasing tailwind event significantly degraded the takeoff and climb performance of the aircraft.