NTSB Identification: LAX03FA074.
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Accident occurred Friday, January 24, 2003 in Rancho Cucamong, CA
Probable Cause Approval Date: 09/14/2007
Aircraft: Beech 95, registration: N2733Y
Injuries: 1 Fatal.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
While in cruise flight, a portion of a propeller blade separated from the right engine. The resulting vibration partially separated the engine from its airframe mounts, and the uncontrollable airplane rolled inverted and dived into a private residence. The house was severely damaged, the airplane was destroyed. The separated propeller was overhauled about 3 years and 5 operational hours prior to the accident flight. The separated 2.5-foot-long span of the failed blade was found about 1 mile from the main wreckage. The blade was examined by the NTSB's Metallurgical Laboratory, which found that the blade failed as a result of fatigue cracking initiated by corrosion pitting in the pilot tube bore. A fatigue crack had initiated at two corrosion pit sites in the bore, which had been painted over without the corrosion being dressed out during the overhaul. Also, many additional corrosion pits were located circumferentially in line with the origin area. The blade's bore was also contaminated with glass beads. All of these conditions found during the examination were contrary to the procedural steps in the manufacturer's overhaul instructions, and established that the blade was reassembled with an incomplete and improper overhaul. The FAA inspector assigned to oversee the overhaul company said he did not observe any repair station deficiencies during his surveillance inspections. A Safety Board inspection following the accident disclosed that the repair station's personnel were not following prescribed manufacturer overhaul procedures, did not have the required chemicals for blade treatment, and did not possess required procedure manuals. Additional inspections of other propellers overhauled by the company revealed that propellers overhauled as early as 1997, when the company commenced business, showed evidence of corrosion in the pilot bores, and were unairworthy.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The fracture and separation of a propeller blade during cruise flight due to fatigue and corrosion pits in the blade pilot bore, and an improper overhaul of the separated propeller by repair station personnel. Factors contributing to the accident were the FAA's inadequate surveillance of the repair station, and the repair station's inadequate procedures. Full narrative available
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