On October 21, 2002, about 1645 mountain standard time, a Piper PA-28-161, N4332W, collided with a tree during a precautionary landing at an abandoned airstrip near Queen Creek, Arizona. Falcon Executive Aviation was operating the airplane under the provisions of 14 CFR Part 91. The certified flight instructor (CFI) and student pilot were not injured; the airplane sustained substantial damage. The local flight originated from Falcon Field Airport, Mesa, Arizona, about 1500. Visual meteorological conditions prevailed, and a flight plan had not been filed. During a telephone conversation with a National Transportation Safety Board investigator, the operator stated that the purpose of the flight was for the student pilot to practice emergency landing procedures. The area in which the instructional flight was being conducted was near an abandoned United States Army airstrip, where it was common for flight instructors to take their students in an effort to practice emergency procedures. The standard protocol for executing simulated emergency procedures in that area was to terminate the procedure at 500 feet above ground level (agl), which the flight school approved as a safe practice. The operator further stated that while the airplane was configured to simulate a loss of engine power, the student pilot maneuvered the airplane to line up with the airstrip and completed the emergency checklist items. Upon reaching 500 feet agl, the CFI directed the student to perform a go-around in an effort to regain altitude and continue the training flight. The student manipulated the throttle to a full power setting, but the engine failed to respond to the control input. The CFI took command of the airplane and opted to execute a forced landing at the abandoned airstrip below. While performing the landing, the CFI could not maneuver the airplane clear of terrain, and the airplane impacted trees located on the left side of the runway. The airplane incurred damage to the landing gear and wings. The Federal Aviation Administration (FAA) inspector stated that the CFI reported to him that during the attempted landing he overshot the intended landing surface, and opted to maneuver the airplane in a turn back to the airstrip. While the CFI was maneuvering the airplane in a left turn, the airplane's left wing collided with a tree. The CFI added that the propeller was turning at the time of the impact. The FAA inspector stated that he examined the airplane wreckage; at which time he noted that the carburetor heat control was in the "on" position, and the propeller blades were twisted and bent forward at the tips. He preformed an engine examination several days after the accident occurred. During the examination he conducted an engine run and noted no anomalies or failures that would have precluded the engine from operating normally. After completing the investigation, he opined that when terminating the forced landing, the student pilot forgot to turn the carburetor heat to the off position, hindering the engine from producing full power. He further thought that the CFI did not correctly identify the problem. A routine aviation weather report (METAR) for Williams Gateway Airport, Phoenix, Arizona, (located about 7 nautical miles in a north westerly direction) was issued several minutes after the accident. It reported a temperature of 29 degrees Celsius and an altimeter setting of 29.80 InHg. Based upon the atmospheric conditions provided by the METAR, a Safety Board computer program calculated the density altitude to be 3,687 feet mean sea level (msl); the approximate altitude of the wreckage was 1,550 feet msl.