What happened
While cruising at 9,000 feet, the pilot of the Cessna experienced an engine malfunction characterized by a drop in oil pressure, oil temperature, and manifold pressure. The pilot attempted to reach the nearest airport by maintaining a descent rate between 500 and 800 feet per minute. However, unable to reach the airport, the pilot selected a field for an emergency landing. After clearing surrounding trees, the pilot deployed flaps to reduce airspeed. Due to the muddy condition of the field, the pilot utilized the emergency gear extension to ensure the landing gear was lowered, aiming to prevent the aircraft from sliding into nearby trees. The aircraft touched down and slid approximately 25 feet before coming to a stop. The aircraft sustained substantial damage to the fuselage and the left wing, though the pilot was not injured.
The investigation
A teardown of the engine revealed holes in the crankcase near the number four cylinder, indicating that the engine had suffered both mechanical and thermal damage due to oil starvation. Investigators also identified a hole in the turbine wheel shroud within the hot section of the right turbocharger. This specific turbocharger lacked a data plate, model number, or serial number, though it was identified by part number 466304-0003. While the oil inlet and outlet fittings appeared intact with no signs of leakage, an inspection of the turbocharger revealed that the turbine wheel shroud had fragmented due to a fatigue failure. Contact signatures from the shroud were found on the back surface of the shaft and wheel assembly. Maintenance records indicated that both the left and right turbochargers were installed on June 21, 1988. While the left turbocharger's data plate matched these records, the lack of a serial number on the right turbocharger prevented verification of its installation date, though no subsequent replacement records were found.