On March 21, 2003, about 1630 Alaska standard time, an Aero Commander 100 airplane, N4123X, sustained substantial damage when it collided with trees during a forced landing after takeoff from the Bradley Sky-Ranch Airport, North Pole, Alaska. The airplane was being operated as a visual flight rules (VFR) instructional flight under Title 14, CFR Part 91, when the accident occurred. The first pilot, seated in the right seat, a certificated flight instructor, and the second pilot, seated in the left seat, a student pilot, were not injured. The airplane was owned by the second pilot. Visual meteorological conditions prevailed, and no flight plan was filed. The local area flight originated at the Bradley Sky-Ranch Airport, about 1615. During a telephone conversation with the National Transportation Safety Board investigator-in-charge on March 25, the instructor pilot reported that he was providing flight instruction to the student pilot. The instructor pilot reported that after takeoff from runway 15, about 100 feet above the runway, the airplane's engine began to run rough and lose power. He said that emergency engine procedures did not restore engine power. The airplane collided with a stand of trees at the departure end of the airport, and sustained substantial damage to the wings, fuselage, and empennage. Prior to reporting the accident on March 25, the instructor and student pilot disassembled the airplane, transported it to a vacant lot on the airport, and covered it with a tarp. On March 28, a Federal Aviation Administration (FAA) airworthiness inspector, Fairbanks Flight Standards District Office, traveled to the Bradley Sky-Ranch Airport to inspect the accident airplane. The inspector reported finding no preaccident mechanical anomalies with the airplane. The FAA inspector added that during the inspection he spoke with the student pilot involved in the accident. The student pilot reported to the FAA inspector that prior to the accident takeoff, just after starting the airplane's engine, the instructor pilot leaned the fuel mixture and applied full carburetor heat during the 15 to 20 minute engine warm-up time. He said that after the engine was warm, they taxied to the departure end of runway 15, and started their takeoff roll, with the mixture control and carburetor heat in the same position. He reported that just after takeoff the engine began to run rough, and lose power. He said that the instructor pilot then took control of the airplane, pushed in the carburetor heat control (off), and all engine power was lost. The airplane collided with a stand of trees at the departure end of the airport. The student pilot reported that immediately following the accident, both pilots noticed that the mixture control was still in the lean position.