Incident Summary
A certified flight instructor (CFI) reported that during a training flight, the aircraft was at 6,000 feet mean sea level (msl) when they began practicing an engine failure procedure. Upon shutting off fuel using the right fuel selector valve, a propeller blade separated from the right engine. An unknown part penetrated the windshield. The CFI stated that the right engine "came almost completely apart and off in a matter of two seconds." The right engine became canted and hung downward, and the aircraft could not maintain altitude. The CFI maintained sufficient airspeed for control during the descent but chose to perform a forced landing in a field due to the loss of altitude. The airplane struck the side of a creek during the forced landing and came to rest upright in approximately three feet of water in the creek.
Investigation Findings
The Hartzell two-bladed propeller hub and other components from the propeller assembly were sent to the National Transportation Safety Board's (NTSB) Materials Laboratory for examination. The hub from the right engine was a left-hand rotating propeller (counterclockwise when viewed from the rear). Inspection revealed that the hub was fractured around the socket for blade #1 (designated by serial number location) through both the forward and aft halves of the hub. The fracture surface exhibited features consistent with fatigue crack progression generally propagating away from the grease fitting hole. The entire fatigue region measured approximately 3.1 inches in length, extending from the grease fitting hole to near the forward centerline of the blade socket.
Service Bulletin
On September 17, 2007, Hartzell Propeller Inc. issued Alert Service Bulletin "HC-1SB-61-297, Propeller Hub Inspection." The bulletin noted that there had been a recent blade separation event originating from the lubrication hole located on the shoulder of the hub blade socket in a left-hand rotating propeller. The bulletin introduced an initial and repetitive eddy current inspection of the area around the lubrication holes on left-hand rotating propellers installed on certain aircraft models.