What happened
The captain reported that the airplane was cruising at 5,000 feet mean sea level with the propeller RPM at 100 percent and all other engine indications appearing normal. During the flight, the crew experienced a sudden and immediate loss of power on the number two engine. Following the failure, the flightcrew declared an emergency and successfully transitioned to a visual approach, landing at Grand Forks without further incident.
The investigation
Post-flight examination of the aircraft identified eleven impact marks located on the right side of the fuselage, two of which had penetrated the fuselage skin. An inspection of the engine revealed evidence of an overload failure and penetration of the gearbox.
Investigators found fatigue fractures in the rim of the second stage compressor impeller. These fractures originated from a heat-affected, rubbed area on the impeller blades. A matching rubbed area was discovered on the impeller shroud, where aluminum material had become fused to the titanium impeller. No material defects were identified during the examination.