What happened
While cruising at 23,000 feet, the pilot of a Piper PA-31-T2 notified air traffic control of an engine issue and indicated a need to shut down the engine. Following instructions from the controller, the aircraft descended toward Jackson, Tennessee. During the descent, the pilot confirmed that the left engine had been shut down and requested vectors for an ILS approach to runway 2 at McKellar-Sipes Regional Airport.
Approximately five minutes after the engine shutdown was confirmed, the pilot reported a propeller runaway. The pilot subsequently requested vectors for a direct approach to the airport under visual conditions. After reporting that a cloud layer was present beneath the aircraft and confirming the localizer frequency, the pilot was instructed to contact the McKellar Airport control tower. No further communication was established following this instruction.
Findings
Post-accident investigation of the left engine revealed that the propeller control had become disconnected where the control extension bracket meets the propeller governor. The propeller control cable had also detached from a swaged point on the control rod and suffered further separation due to overstress. The propeller governor control arm was found in a spring-loaded, high-RPM position.
Analysis of the fractured left propeller bracket assembly by the NTSB Materials Laboratory identified a fatigue crack that originated from multiple points on opposite sides of the bracket. This fatigue crack covered roughly 85% of the fracture surface, with the remaining 15% showing evidence of overstress separation. The investigation also noted that the pilot's training records indicated approximately 13 flight hours in the Piper PA-31-T2 and recent simulator training. While the pilot operating handbook included procedures for an overspeeding propeller, it lacked specific instructions for a total loss of propeller control.