On July 14, 2009, about 1010 mountain daylight time, a Cessna U206G, N71BS, collided with trees just after taking off from a remote airstrip near, Yellow Pine, Idaho. The private pilot received minor injuries; his instructor pilot received serious injuries, and the airplane, which was owned by the private pilot, sustained substantial damage. The Title 14 Code of Federal Regulations, Part 91 Flight Review evaluation flight, was being conducted in visual meteorological conditions. The flight initially departed Hailey, Idaho, at 0750, and had landed at three other back-county airstrips prior to the accident. No flight plan had been filed. According to the private pilot, who was acting as pilot-in-command (PIC), the purpose of the flight was for him to receive a signoff for a biennial flight review. Prior to landing at the strip where the accident took place, he and his instructor landed at three other "back-county" airstrips. Then as they flew near Yellow Pine, the instructor suggested to the PIC that they land at the Simonds Airstrip. Although the PIC had not planned to go into the 800 to 900 foot-long airstrip, had not been in there before, and had not familiarized himself with it prior to the flight, he elected to make the landing anyway. He said that he made that decision because one of the other airstrips he already landed at that day was about the same length. The landing, which the PIC described as "routine," was made on the sloping rough surface of the runway, with the airplane coming to a stop near its uphill end. The two occupants then spent about four minutes discussing the landing and the upcoming takeoff and departure. The PIC then turned back onto the runway, adding power during the turn, and headed downhill for the takeoff. According to the PIC, everything seemed normal until just after the airplane became airborne. At that point the amount of aft pressure he needed to apply to the control yoke to get the airplane to climb seemed to increase substantially. Then, no more than two seconds after passing the end of the runway, at about 50 feet above ground level (AGL), the airplane began to impact the tops of a group of dead standing pines, each of which had diameters of between six to ten inches. Soon thereafter the airplane descended rapidly into the terrain. During a post-accident phone interview, the pilot said that the temperature at the time of the accident was between 50 and 60 degrees Fahrenheit, and the field elevation was 5,243 feet mean sea level (MSL). These ambient conditions resulted in a density altitude of about 6,300 feet (based upon 55 degrees). When asked if he had done any performance calculations prior to either the landing or takeoff, he stated that he had not. When asked if he had checked his airplane's Outside Air Temperature (OAT) gauge prior to the takeoff, he said that he had not. During the same interview, the pilot said that he had landed at many of the back-country airstrips in the area over a period of many years, but would not have gone into this one except for the fact that the instructor suggested it. During further discussions the PIC said that from the time he added power for the takeoff, until the plane started impacting the trees, he did not detect anything unusual about the engine, and that there had not been any missing, coughing sputtering, or rpm changes. A post-accident inspection of the engine found fuel in the fuel pump, fuel distribution valve, and the fuel injector lines. Spark was produced at all spark leads by both of the magnetos. There was no evidence of engine anomalies or malfunctions that would have affected the performance of the airplane. A post-accident inspection of the airframe found two issues of interest. The first was that the elevator trim had been set at the five degrees tab up (airplane nose down) position. The second was that although the flap position lever in the cockpit was in the 20 degrees extended position, the flap position jackscrew was determined to be extended 4.6 inches, which equates to a flap position of 25 degrees. According to Cessna Aircraft Company, both of these conditions may have contributed to the need for the pilot to apply more backpressure on the yoke just after liftoff than he had expected. In further discussions with Cessna Aircraft Company it was determined that the discrepancy between the cockpit flap position indicator and the flap jackscrew was most likely from either 30 years of wear in the system since the airplane was manufactured in 1979, or as a result of adjustments made when the Supplemental Type Certificate (STC) which added the Short Takeoff and Landing (STOL) kit onto the airplane was performed. In the pilot report that he submitted to the NTSB, the PIC stated, "For my airplane, this runway leaves too little margin for the unexpected." In addition, he stated that, "…it would have been helpful if the departure end trees were removed or shortened."