On June 11, 1999, about 1540 Alaska daylight time, a Short Takeoff and Landing (STOL) equipped Piper PA-18 airplane, N2668P, sustained substantial damage during takeoff at the Goose Bay airstrip, about 10 miles south of Big Lake, Alaska. The airplane was being operated as a visual flight rules (VFR) personal flight under Title 14, CFR Part 91, when the accident occurred. The certificated private pilot, the sole occupant, sustained serious injuries. Visual meteorological conditions prevailed, and no flight plan was filed. The flight was en route to Merrill Field, Anchorage, Alaska. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on June 11, the pilot reported that he departed on runway 07. During the initial climb, about 100 feet above the ground, he said he encountered turbulence and windshear, and the airplane abruptly rolled to the right. He said he responded with abrupt aileron control input to the left, but the airplane did not respond, and indicated the controls felt "mushy, and ineffective." He was unable to regain control of the airplane, and it nosed down and collided with trees bordering the airstrip. He estimated the wind to be easterly, at 15, gusting to 25, knots. The pilot also noted in his NTSB Pilot/Operator Accident Report, that there were no preimpact mechanical anomalies with the airplane. The IIC interviewed another pilot who departed the same runway about 15 minutes prior to the accident airplane. This pilot reported moderate low level turbulence on initial climb. When he returned about 45 minutes later (about 30 minutes after the accident flight), he said the level of turbulence had increased, and he was forced to use full aileron control deflection during the approach and landing. An FAA airworthiness inspector went to the accident site the day of the accident and inspected the airplane. He reported to the NTSB IIC that all the flight controls were attached to their appropriate controls, and appeared functional. He discovered no evidence of any preimpact mechanical anomaly. The airplane sustained substantial damage to the propeller and left wing.