On August 12, 2001, approximately 1442 Pacific daylight time, a Republic RC-3, N6755K, recently purchased and being flown by an airline transport rated pilot, was substantially damaged during an in flight collision with objects during the landing flare following a loss of power and forced landing, near Chimacum, Washington. The pilot was uninjured. Visual meteorological conditions prevailed and no flight plan had been filed. The flight, which was personal, was operated under 14 CFR 91, and originated from Orcas Island, Washington, approximately 1415. The pilot reported that he conducted a pre-takeoff run-up including magneto and ignition checks, which were satisfactory (the aircraft's total ignition system consisted of an automotive type coil ignition and a magneto for redundancy). He then departed Orcas Island, Washington, destined for Aurora, Oregon and experienced no engine problems until just passing slightly southwest of Chimacum, Washington. He reported that at that time the engine began to run rough. He selected the "mag" position and determined the magneto was not operating. He then selected the "ignition" position and determined that although the coil ignition was operating, the engine was running rough. The roughness increased until the engine finally quit. The area he was traversing consisted of a channel with shallow water (low tide) and tree stumps/deadheads. He identified a dairy pasture with cattle at the east end and executed a 180-degree right turn to land to the west over flying the cattle. As he entered into the turn he noted a 1,000-foot/minute rate of descent, which was greater than he had anticipated. The landing gear had been extended and as the aircraft was maneuvered onto a short final the right main landing gear struck a cow. The aircraft yawed into a left skid, contacted the ground and skidded through a barbwire fence. The pilot reported that the owner of the field he landed in had operated his Cessna 177 in and out of this same field and that "...it's the only decent place to land within 5 miles radius...." Post crash examination by the pilot, an airframe and power plant mechanic, revealed evidence of arcing due to a direct ground of the coil lead within the coil ignition, as reported to an inspector assigned to the Federal Aviation Administration's Renton Flight Standards District Office (refer to attached Inspector's Report). A check of the ignition coil system by the owner and FAA inspector determined that the coil ignition was unable to produce a spark at any spark plug. After the owner and FAA inspector repaired the coil ignition system, the engine was cranked via the starter. During this evolution, the coil ignition system produced sparks at the respective spark plugs but the magneto, installed on the engine right accessory pad, failed to produce any sparks. Further examination and bench testing of the magneto by the FAA inspector confirmed the magneto had grounded internally (refer to attached Inspector's Report).