Accident Details
The pilot reported conducting three off-airport soft field landings in a field, landing in a southerly direction. After the third landing, he turned the aircraft around and initiated a takeoff to the north, citing tall trees on the south end of the strip as the reason. During the takeoff climb, the pilot encountered wind shear, which caused the airspeed to drop from 50 knots to 30 knots. The airplane subsequently struck a tree, descended, and impacted terrain.
Weather Information
The pilot noted that the wind was calm on the ground at the accident site. However, the nearest Meteorological Aerodrome Report (METAR), from an aerodrome located approximately three miles northeast of the site, indicated that around the time of the accident the wind was from 210° at 13 knots. The METAR also showed that the prevailing wind throughout the day was southerly.
Pilot Report
The pilot stated that there were no pre-accident mechanical malfunctions or failures with the airplane that would have precluded normal operation.
Handbook Reference
According to the Pilot's Handbook of Aeronautical Knowledge, in the section on Takeoff Performance, the effect of wind on takeoff distance is significant. A headwind that is 10 percent of the takeoff airspeed reduces takeoff distance by approximately 19 percent, while a tailwind that is 10 percent of the takeoff airspeed increases takeoff distance by about 21 percent.