Incident Details
On December 10, 2009, at approximately 1205 eastern standard time, a Beech 58, registration N391MC, operated by Air Lexington Inc., sustained minor damage during a landing at Blue Grass Airport (LEX) in Lexington, Kentucky. The airline transport pilot and the commercial pilot on board were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight, which originated from LEX around 1030. The flight was conducted under 14 Code of Federal Regulations Part 91 as a personal flight.
Pilot Actions
According to the pilots, the commercial pilot was practicing instrument approaches while the airline transport pilot served as a safety pilot. During a go-around, the commercial pilot retracted the landing gear and observed the corresponding cockpit indication for gear retraction. However, the LEX Approach controller informed the pilots that the nose landing gear appeared to be in the extended position. The pilots then selected the landing gear to the extended position and noted the corresponding cockpit indication. During a subsequent landing on runway 22, after touchdown, the nose landing gear collapsed, and the airplane slid to a stop on the runway.
Damage and Examination
Examination by a Federal Aviation Administration (FAA) airworthiness inspector revealed damage to the nose gear area and both propellers. The right side of the nose landing gear aft drag brace had separated. The nose landing gear indicating system and linkage remained intact and undamaged. The separated component was sent to the NTSB Materials Laboratory in Washington, DC.
The FAA inspector forwarded photographs of the damage to a representative of the aircraft manufacturer. The representative observed that a plug used to contain linseed oil within the drag brace appeared to be missing, and the component tubing was absent of linseed oil, which was required per Hawker Beechcraft Specification 455. The aircraft was manufactured in 1976; the component was redesigned in 1977 as a forged part, eliminating the need for the plug and linseed oil. The manufacturer's field condition reports contained no record of similar failures to the same model nose landing gear aft drag brace.
Examination by an NTSB metallurgist determined that the fracture origin exhibited features consistent with overstress and that crack arrest marks along the fracture extension were consistent with an overstress failure over time. The fracture initiated from a different area than that of the missing plug. The investigation could not positively determine if the plug departed before or after the component failure.
Maintenance History
Review of the maintenance manual indicated that the nose gear was an "on condition" inspection item. The FAA inspector noted that the fracture was in an area that would not be easily visible or detected during an annual or 100-hour inspection. The aircraft was maintained under an FAA-approved inspection program (AAIP). The most recent AAIP inspection was completed on November 9, 2009. The aircraft had accumulated 20.2 hours of operation since that inspection and had 10,437.3 total hours of operation at the time of the incident.