NTSB Factual Report

On August 1, 2005, about 1730 Pacific daylight time, a privately owned and operated Malechek, Q-200, N870BM, experienced the in-flight separation of the outer portion of one propeller blade during cruise flight. The pilot received directions to the nearest airport from a Federal Aviation Administration (FAA) air traffic controller (ATC). During the forced landing, the experimental airplane collided with objects while on final approach to runway 14 at the Delano Municipal Airport, Delano, California. Visual meteorological conditions prevailed at the time, and no flight plan had been filed. The airplane was destroyed. The private pilot was seriously injured, and the passenger sustained minor injuries. The flight was performed under the provisions of 14 CFR Part 91. The personal flight originated from Modesto, California, about 1630.

The pilot reported to the National Transportation Safety Board investigator that, while en route to his intended Ramona, California, destination, and cruising at 9,500 feet mean sea level, he had suddenly experienced a severe vibration and believed one propeller had separated from the engine. Thereafter, he shutoff the airplane's engine. Ground-based witnesses reported that the airplane approached the Delano Municipal Airport from the north, and it was heading straight for the runway. The pilot made a forced landing and the airplane touched down short of the runway. It collided with a pole and a chain link fence, broke apart, and came to rest upside down approximately 1,000 feet prior to reaching the approach end of the runway. There was no fire.

According to the pilot, 1/2 of the blade's span had broken off. A local FAA certificated airframe and powerplant mechanic recovered some of the airplane's propeller blade. The mechanic noted that the 2-bladed Aymar-DeMuth 60 X 72 wood propeller (S/N 04371) had experienced a separation at the glue joints. The propeller delaminated.

In the pilot's completed "Aircraft Accident Report," he indicated his procedures for torquing the propeller blade's attachment bolts. The owner reported that rather than torquing the bolts to the recommended 15-foot-pound value, he torqued the bolts to 18-foot-pounds, according to a placard on the propeller.

The FAA coordinator reported observing evidence of a hair-line crack emanating from one of the propeller's attachment bolt holes. The FAA coordinator reported to the Safety Board investigator that the attachment bolt torquing sequence was not specified by the manufacturer.

NTSB Probable Cause

the in-flight delamination and separation of a propeller blade for undetermined reasons.