On July 20, 2003, about 1245 Alaska daylight time, a tundra tire-equipped Maule M-4 airplane, N40344, sustained substantial damage when it collided with trees during a forced landing following takeoff from the Dahl Creek Airport, about 1.5 miles northwest of Kobuk, Alaska. The airplane was being operated as a visual flight rules (VFR) cross-country personal flight under Title 14, CFR Part 91, when the accident occurred. The airplane was operated by the pilot. The private certificated pilot, the sole occupant, received minor injuries. Visual meteorological conditions prevailed. The planned destination was Fairbanks, Alaska. No flight plan was filed, nor was one required. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on July 22, the pilot reported that after liftoff from runway 26 at Dahl Creek, the engine power began to decrease slowly. He said the engine did not have any roughness or unusual sounds, but the rpm decreased to about 2,200 and the airplane began to lose altitude. About 200 feet above the ground, the pilot said he began to turn to the north in an effort to return to the runway, but the airspeed was decreasing. The airplane collided with numerous trees and sustained damage to the wings, lift struts, elevator, and the right main landing gear. Runway 26 at Dahl Creek has a gravel surface that is 4,780 feet long and 75 feet wide. The pilot said the sky condition was clear, the wind was from the southwest about 10 knots, and the temperature was about 70 degrees F. In the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1) submitted by the pilot, the pilot indicated that prior to the accident flight, he fueled the airplane with 14 gallons of fuel from a 55 gallon drum that he has stored at his cabin. He conducted a preflight of the airplane, which included draining the airplane's fuel sumps, and found no water in the sumps. On October 9, in a telephone conversation with the NTSB IIC, the pilot reported that following the accident, he examined the fuel from the airplane. He said he discovered that the fuel he placed in the airplane before departure was diesel fuel. He reported that his storage drum was mislabeled.