What happened
During the landing roll of an aircraft subsequent to touchdown, the nose landing gear collapsed. The incident occurred while the aircraft was decelerating on the runway surface following a normal approach and flare.
The investigation
A post-impact inspection of the landing gear assembly revealed that a critical bolt responsible for retaining the retract arm to the bellcrank had sheared. Further examination of the failed component indicated that the bolt had been installed in the wrong direction, which was not in accordance with the manufacturer's manual. Despite this installation error, gear retraction tests conducted during the previous annual inspection showed normal tolerance, suggesting the defect may have developed or remained undetected until structural failure occurred under load.
Findings
The primary contributing factor to the accident was the improper installation of a retaining bolt. The bolt was oriented incorrectly relative to the manufacturer's instructions, leading to its eventual shear failure. This mechanical failure resulted in the collapse of the nose landing gear during the high-stress phase of the landing roll.
Safety message
Strict adherence to manufacturer maintenance manuals is critical during aircraft inspection and repair procedures. Even minor deviations in component orientation can lead to catastrophic mechanical failures under operational loads.