What happened
On August 23, 2016, a private VFR flight involving a Fairchild 24R46A (registration HB-ERO) experienced a sudden engine failure during the cruise phase. The aircraft, operated by the Verein Fairchild Club, had departed from Lommis (LSZT) for a local sightseeing flight with two occupants.
While cruising at approximately 3,000 feet near Ermatingen, the pilot noted the engine RPM at roughly 2,000 and observed oil temperatures slightly above normal levels. Suddenly, the engine began to sputter, followed by a loud bang and an immediate seizure. The pilot quickly identified a suitable landing site and executed an emergency touchdown in an uncultivated field near Oberhöhnwilen. The landing resulted in no injuries to the two occupants and caused no damage to third-party property.
The investigation
Investigators from SUST examined the wreckage and the engine, a 200 HP Ranger 6-440-C5. The inspection revealed significant internal damage, including a destroyed first cylinder, a broken crankshaft, and a bent camshaft. The crankcase was also ruptured.
Metallographic analysis of the crankshaft components identified fatigue fractures that had been developing at various points on a crankcase web of the rear cylinder. The investigation focused on whether this defect could have been detected during previous maintenance, specifically noting the engine's last major overhaul in 2005.