On December 12, 2015, about 1200 eastern standard time, a DeHavilland Tiger Moth DH-82A, N9410, was substantially damaged during a forced landing after takeoff from Old Orchard Airpark (2NK9), Modena, New York. The pilot and a passenger were not injured. Visual meteorological conditions prevailed and no flight plan had been filed for the personal flight that was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. The pilot reported that he conducted a pre-takeoff engine run, which included an operational check of the magnetos with no anomalies noted. The airplane subsequently experienced a 200-rpm reduction in engine power during the initial climb after takeoff from runway 18. The pilot attempted to return to the runway; however, the airplane was not able to maintain altitude and struck tress about 1/4-mile from the airport. The airplane was manufactured in 1940 and equipped with a DeHavilland Gipsy Major 1C, 145-horsepower engine Postaccident examination of the airplane by a Federal Aviation Administration inspector revealed that the airplane sustained substantial damage to both wings, the empennage, and the fuselage. When the inspector rotated the engine crankshaft, continuity was observed to the accessory section and compression was attained on all cylinders with exception of the forward (No. 1) cylinder, which produced "little to no compression." Due to the engine's disposition, the inspector was unable to check the ignition system for proper operation. No further examination of the engine was performed. The pilot further reported that subsequent teardown of the engine revealed that the No. 1 cylinder exhaust value was stuck in the open position. In addition, disassembly of the left magneto revealed that the "breaker spring" was fractured. The pilot stated that the loss of compression to one of the four engine cylinders alone would have resulted in a forced landing; however, he believed that the combination of the loss of compression on the No. 1 cylinder and the failure of the left magneto resulted in the loss of engine power that the airplane experienced during the accident flight.