Accident Overview
On January 16, 2011, at 1500 eastern standard time, a Mitsubishi MU-2B-20, registration N52CD, owned by Hayes Landing, LLC and operated by an individual, experienced a nose landing gear collapse during landing at Lowcountry Regional Airport (RBW) in Walterboro, South Carolina. The pilot and passenger were not injured, and the airplane incurred minor damage. Visual meteorological conditions prevailed, and an instrument flight plan had been filed for the personal flight conducted under Title 14 Code of Federal Regulations Part 91. The flight had departed from Northeast Regional Airport (EDE) in Edenton, North Carolina, earlier that day at about 1330.
Flight Details
The pilot stated that the flight was uneventful. During gear extension on approach to the airport, he heard a “pop” as the nose gear lowered. During the landing roll, the nose gear collapsed, resulting in minor damage to the nose gear doors and the skin behind the nose gear area.
Examination Findings
Maintenance personnel discovered that the attaching bolt for the drag strut of the down lock mechanism assembly had fractured. The bolt had an estimated in-service time of 500 hours with an estimated 290 gear cycles. The National Transportation Safety Board Materials Laboratory conducted a metallurgical examination on the fractured bolt. The examination revealed that the bolt failed in reverse bending fatigue. The bolt held the down lock drag brace joint link to the airframe structure.
Maintenance History
The airplane’s last one-year/100-hour/200-hour inspection was performed on September 14, 2010, at an airframe total time of 8,053 hours. At the time of the accident, the airframe had accumulated a total time of 8,124 hours. The airplane’s manufacturer maintenance manual calls for and indicates when to check for proper rigging of the nose gear down lock system. Manufacturer Service Bulletin No. 188, dated July 13, 1981, was developed due to several incidents where improper adjustment of the down lock mechanism led to failure of the nose landing gear. The service bulletin requires inspection of the mechanism for proper adjustment (rigging). As a result of this incident, the manufacturer published a Service News letter, dated September 5, 2011, outlining the importance of proper rigging of the down lock mechanism, making reference to Service Bulletin No. 188, and informing maintenance personnel and operators to obtain the correct rigging tools.