On August 18, 2005, about 1920 eastern daylight time, a Piper PA-23-250, N40504, was substantially damaged during a forced landing, after takeoff from Smoketown Airport (S37), Smoketown, Pennsylvania. The certified flight instructor and certificated private pilot student were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local instructional flight, conducted under 14 CFR Part 91. According to the student, after arriving at 1800 he preflighted the airplane. All control surfaces were "free and clear" and all airframe components were intact and working properly. No water or contaminants were revealed when the fuel system was sumped, and all fuel tanks were full. At approximately 1830 after the instructor arrived they discussed the flight lesson, boarded the airplane, and started the engines. No anomalies were noted with the electric boost pumps, all the engine instruments indicated normal pressures, the magnetos were checked, and both propellers cycled normally. According to the flight instructor, the airplane departed from runway 28, which was 2,400 feet long. As the airplane climbed, he felt a sudden power surge and yaw as they were passing over the approximate location of the departure end of the runway; however, he was unable to identify which engine was malfunctioning. After verifying that the mixture controls, propeller controls, and throttle controls were "full forward", he took control of the airplane from the student. He then retracted the landing gear in an attempt to lessen the aerodynamic drag, and continue the climb, but observed the airspeed decaying towards the minimum controllable airspeed. He subsequently elected to perform a forced landing to a cornfield. During the landing, the airplane's wings, fuselage, and right propeller were damaged. The flight instructor held an airline transport pilot certificate with multiple ratings including airplane multi-engine-land. He reported a total flight time of 2,386 flight hours, with 632 hours in multi-engine airplanes and 207.6 hours in the Piper Aztec. His last FAA second-class medical certificate was issued on May 19, 2005. The student held a private pilot certificate with ratings for airplane single and multi-engine land. He reported a total flight time of 592.4 hours, with 373.5 hours in multi-engine airplanes and 167.4 hours in the Piper Aztec. His last FAA third-class medical certificate was issued on January 10, 2005. The airplane was manufactured in 1973. The airplane's most recent annual inspection was completed on October 1, 2004. At the time of the inspection, the airplane had accrued 11,121.7 total hours of operation. A postaccident examination of the airplane by a Federal Aviation Administration inspector revealed no evidence of mechanical failure or malfunction.