NTSB Factual Report

On August 16, 2015, about 1955 eastern daylight time, a Beech V35 airplane, N2059W, experienced a propeller and engine over speed while in cruise flight near Mount Vernon, Ohio. The pilot and passenger were not injured. The propeller separated from the propeller flange inflight and no damage was sustained to the airplane. The airplane was registered to the Bennett Ramsey Group and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which operated on an instrument flight rules flight plan. The flight originated from the Rowan County Airport (KRUQ), Salisbury, North Carolina, at 1800 and was en route to the Ann Arbor Municipal Airport (KARB), Ann Arbor, Michigan.

According to the pilot, while in cruise flight at 8,000 feet mean sea level, he heard a sudden high pitched whine from the engine. He saw that the engine tachometer read about 3,500 rpm. Unable to bring the engine rpm within limits, the pilot declared an emergency and headed towards the Knox County Airport (4I3). While on final approach to the airport, the pilot heard a "pop" and oil covered the windscreen. The pilot landed on the runway and discovered that the propeller was missing from the airplane.

A postaccident examination of the engine found metal particles in the propeller governor. The propeller governor was removed from the airplane and sent to the manufacturer for an examination. An x-ray revealed that the flyweight was loose from its position and a bench-test of the governor would not be possible. Under the auspices of the Federal Aviation Administration, the governor was disassembled and examined. The hole for the flyweight retaining pin on the flyweight carrier was excessively worn and was not be able to properly secure the retaining pin. With the flyweight loose, the proper loading on the propeller governor pilot valve could not be maintained and the engine and propeller speed would then be commanded between 130-150%. A hardness test of the installed carrier did not meet factory specification and did not appear to be case hardened. Internal components were different than the factory original and it is likely that the governor had been overhauled at least once after it had left the manufacturer in 1966. Woodward did not have any record of a deficient batch of flyweight carriers not meeting hardness requirements and the history of the installed carrier flyweight is not known. Based on records provided by the owner, an engine logbook entry dated October 4, 1999, documented that an overhauled propeller governor was installed on the airplane. No further log book entries pertaining to the propeller governor were found in the provided records. Based off the information provided, it could not be determined if the incorrect part was installed in the propeller governor during the overhaul or at a time subsequent to the overhaul.

NTSB Probable Cause

The loosening of the flyweight due to the installation of an improperly hardened flyweight carrier, which resulted in the overspeed of the propeller and engine and the subsequent in-flight separation of the propeller.