Accident Overview
On July 11, 2018, at approximately 1920 eastern daylight time, an experimental, amateur-built Glasair SH2 (registration N352GL) was substantially damaged during a forced landing near Passadumkeag, Maine. The commercial pilot, who was the sole occupant, was not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal operation.
Flight and Engine Failure
The pilot performed a preflight inspection, noting 19 gallons of fuel on board, and reported no anomalies before takeoff. After climbing to 1,200 ft mean sea level, the pilot observed normal engine parameters. About 10 miles southwest of the departure airport, the engine began to run rough and lost partial power. The pilot checked the engine gauges, found no irregularities, and attempted to restore power by turning on the fuel boost pump, but the attempt was unsuccessful. Within approximately 30 seconds of the initial power loss, the engine lost total power, and the propeller stopped turning.
Forced Landing and Damage
The pilot executed a forced landing to a bog. During the landing, the airplane came to rest inverted, and the empennage separated from the fuselage. The aircraft sustained substantial damage.
Engine Examination
Post-accident examination of the engine revealed that the No. 4 connecting rod exhibited thermal discoloration and impact damage. The No. 4 connecting rod journal was fractured, with thermal discoloration and rotational scoring. The crankshaft was fractured at the forward section of the No. 4 connecting rod journal. Examination using a scanning electron microscope found three primary fatigue initiation sites on the journal surface, with possible smaller initiation sites in the same area. Mechanical defects such as gouges and streaks were present at the crack initiation sites, but it could not be determined whether the mechanical damage existed before the fracture or occurred after the final fracture. The fracture surface exhibited fatigue striations consistent with high-cycle fatigue crack propagation, and the final overstress fracture showed dimple rupture features. The Nos. 1 and 2 main bearing journals showed no anomalies; the No. 3 main bearing journal had rotational scoring and wear; the No. 4 main bearing journal had minor wear but no anomalies. All crankshaft oil passages were clear of debris.
Previous Maintenance History
According to the engine maintenance log, on March 25, 2013, at a tachometer time of 324.4 hours, the engine experienced a propeller strike during a landing incident. The log entry noted that the crankshaft flange dialed 0.001 or less, and referenced FAA Advisory Circular AC 39-7D and AD 2004-10-14, stating that the inspection was not mandatory for an experimental, non-type-certificated engine. The entry concluded: "Although recommended, I have elected not to have the inspection performed and accept all future responsibility related to non-compliance of the airworthiness directive."