Accident Details
On November 1, 2018, about 1630 Alaska daylight time, a Piper PA-12 airplane, registration N3227M, sustained substantial damage during a forced landing following a total loss of engine power. The accident occurred about 8 miles northwest of Willow Airport (PAUO) near Willow, Alaska. The aircraft was registered to and operated by the pilot under 14 Code of Federal Regulations Part 91 as a visual flight rules flight. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight had departed a private airstrip located about 1 mile east of the accident location at about 1629.
According to the pilot, during the initial climb, the engine popped three times "like a backfire" and then lost all power. He switched from the left fuel tank to the right fuel tank and applied carburetor heat, but the engine failed to respond. During the subsequent forced landing into trees, the airplane sustained substantial damage to the wings and fuselage. The commercial pilot sustained serious injuries.
A friend of the pilot, who was an airframe and powerplant mechanic, stated that this was the first flight following engine maintenance. He and the pilot had been troubleshooting for excessive magneto drops and a cold cylinder, and they had just reinstalled the fine wire spark plugs after cleaning them.
Post-Accident Examination
The National Transportation Safety Board (NTSB) investigator-in-charge, along with another NTSB investigator, conducted a post-accident examination of the airplane after recovery. The spark plugs and rocker arm covers were removed from the engine. All spark plugs exhibited normal operational signatures with no defects or anomalies. Manual rotation of the crankshaft yielded thumb compression and suction on all four cylinders, and continuity was established throughout the engine and valvetrain.
The wiring from the ignition switch to the magnetos was frayed and separated. It could not be determined whether the separation occurred before the accident or as a result of the accident. Both magnetos were removed and tested at Alaskan Aircraft Engines in Anchorage, Alaska. Both magnetos produced spark at all terminals as designed. Neither distributor was fractured, but the impulse coupler inside the left magneto was fractured; however, that did not preclude the magneto from sparking.
The ignition harness was removed and sent to Continental Motors for testing. The ignition switch was connected to a magneto synchronizer box (Model E50). The key was rotated through the OFF, L, R, and BOTH positions, with normal function observed.