Accident Overview
According to a friend of the pilot, the pilot was taking the airplane to have an annual inspection completed. The friend assisted the pilot before departure and watched as the airplane departed. He did not notice any anomalies during the takeoff or climbout.
Witness Observation
A witness in the vicinity heard the airplane approaching at very low altitude. He saw it approximately 200 feet over his house, descending toward trees. The right propeller was not turning, and the right engine was not running. The left engine sounded as if it was at full power. The airplane pitched up to avoid a power line, rolled to the right, and descended below the tree line. A plume of smoke and an explosion followed.
Examination Findings
Examination of the right propeller assembly revealed evidence of significant frontal impact. The blades were bent but lacked rotational scoring, indicating they were likely not rotating at impact. One preload plate impact mark showed the blades at an approximate 23-degree angle, whereas feathered blades are about 86 degrees. Due to fire and impact damage to the right engine and related systems, the reason for the loss of power could not be determined.
The airframe and left engine showed no mechanical malfunctions or failures that would have precluded normal operation.
Maintenance Records
A review of the airplane maintenance logbooks revealed that the annual inspection was 12 days overdue. According to Lycoming Service Instruction No. 1009AS, the recommended time between engine overhauls is 1,200 hours or 12 years, whichever occurs first. The right engine had accumulated 1,435 hours since major overhaul, and neither engine had been overhauled within the preceding 12 years.
Propeller Feathering Procedures
Although the propeller manufacturer recommends feathering before engine rpm drops below 1,000 rpm, the latest revision of the pilot operating handbook (POH) did not specify this in the feathering procedure for engine failure. It is likely that the pilot did not feather the right propeller before the engine reached the critical 1,000 rpm, which prevented the propeller from engaging in the feathered position.
Probable Cause
The official probable cause states: "The pilot’s failure to maintain airplane control following loss of power in the right engine for reasons that could not be determined because of fire and impact damage. Contributing to the accident was the pilot’s delayed feathering of the right propeller following the loss of engine power and the lack of specific emergency procedures in the pilot operating handbook indicating the need to feather the propellers before engine rpm falls below 1,000 rpm."