Accident Sequence
About 20 minutes before the accident, the pilot informed the air traffic controller of an engine problem requiring shutdown. The aircraft had just leveled at 23,000 feet. The controller advised the pilot of proximity to Jackson, Tennessee, and cleared a descent to 7,000 feet. Approximately 10 minutes later, the pilot reported being at 8,000 feet and requested radar vectors for an instrument landing system approach to runway 2 at McKellar-Sipes Regional Airport. The pilot stated the left engine was shut down.
About 5 minutes later, the pilot reported a propeller runaway. Roughly 1 minute afterward, the pilot indicated visual conditions and requested radar vectors direct to the airport. About 2 minutes after that, the pilot reported a cloud layer below and that the localizer frequency for runway 2 was set. The pilot was then instructed to contact the McKellar Airport control tower and acknowledged. No further transmissions were received.
Examination Findings
Examination of the left engine at the accident site revealed the propeller control was disconnected at the attachment point of the propeller control extension bracket to the propeller governor. The propeller control cable had pulled loose from a swaged point on the control rod and was also separated further aft due to overstress. The control rod housing was securely attached to the engine, and the control rod was securely attached to the extension bracket. The propeller governor control arm, disconnected from the cable and rod, was found spring-loaded to the high RPM position.
The NTSB Materials Laboratory examined the fractured left propeller bracket assembly. The fracture occurred at the outermost eyehole where a bolt passes through the bracket and the governor arm. The fracture surface showed small amounts of dirt, grease, and minor corrosion. Features included flat areas on multiple planes separated by ratchet marks, consistent with fatigue crack propagation. The fatigue crack originated from multiple origins on opposite sides of the bracket and covered approximately 85 percent of the fracture surfaces. The cracks propagated inward from the outer edges. The remaining 15 percent exhibited features of overstress separation. Microfissures near the middle of each fatigue region suggested high-stress propagation. The separation point between the left propeller control flexible cable and the rigid rod was examined; the cable and swaged part were in good condition without fractures or damage.
Pilot Information
Pilot logbook records indicated the pilot completed a simulator training course for the accident model airplane about 9 days before the accident and had approximately 13 flight hours in the Piper PA-31-T2. The Piper PA-31-T2 Pilot Operating Handbook, Section 3, Emergency Procedures, did not contain a procedure for loss of propeller control. It did contain a procedure for "Over speeding Propeller," stating that if propeller speed exceeded 1,976 rpm, the power lever of the affected engine should be placed to idle, the propeller feathered, the condition lever moved to stop, and engine shutdown procedures completed.