Accident Overview
The accident airplane, a six-passenger multiengine aircraft, arrived at the departure airport with a malfunctioning landing gear system. Due to a lack of maintenance personnel, the pilot decided to conduct the flight with the landing gear extended. The airplane departed with seven occupants aboard, at a weight near its certified gross weight.
Witness Observations
Witnesses reported seeing the airplane flying at an altitude of about 200 to 300 feet above the ground. They noted that the engines were "sputtering and backfiring." The airplane then made a left turn toward the airport, descended, and eventually came to rest in a wooded area located approximately 2 miles southeast of the airport.
Engine Examination
Post-accident examination of the right engine revealed that the propeller was not feathered. The number 5 cylinder head was found fractured about 3/4 inch from the bottom of the upper portion of the head. A fatigue fracture had initiated in the root radius of the cylinder head thread that engaged with the top thread on the cylinder barrel. Indentations and displaced material on the upper and lower flanks of the cylinder head threads matched the locations of protruding material observed on the cylinder barrel threads. The protruding material was located on the flank/crown radius of the threads and was consistent with the folding over of a burr into the thread, originating during the manufacturing process.
The number 5 cylinder assembly consisted of a new cylinder head that had been installed on a remanufactured barrel. The right engine had been remanufactured in 2001 and had accumulated about 140 total hours of operation since that time.
Regulatory Context
According to 14 CFR Part 91.7, "No person may operate a civil aircraft unless it is in an airworthy condition. The pilot in command of a civil aircraft is responsible for determining whether that aircraft is in condition for safe flight. The pilot in command shall discontinue the flight when unairworthy mechanical, electrical, or structural conditions occur." Additionally, 14 CFR Part 91.107 requires that each person on board a U.S.-registered civil aircraft must occupy an approved seat or berth with a safety belt during movement on the surface, takeoff, and landing. The Airplane Flying Handbook (FAA-H-8083-3), Transition to a Multiengine Airplanes, notes that when one engine fails on a multiengine airplane, performance is not halved but is reduced by approximately 80 percent.