Cessna 208-B Nose Gear Failure at Ibiza Airport (EC-IHD)

Incident Overview and Damage Assessment On Friday, August 27, 2004, at 03:52 local time, a Cessna 208-B with registration EC-IHD, operated by Alaire, landed at Ibiza Airport after departing from Palma de Mallorca. The aircraft was engaged in a domestic commercial cargo operation. During the landing roll, the crew applied reverse thrust and experienced a strong vibration in the nose wheel. They subsequently deactivated the reverse thrust and attempted to decelerate using only the brakes, but the vibration intensified. Shortly after, a metallic noise was heard, and the aircraft's nose dropped, causing the propeller to strike the pavement. The aircraft continued to move on its forward fuselage until it came to a stop. The crew, consisting of a 30-year-old pilot-in-command and a 22-year-old co-pilot, were uninjured and evacuated the aircraft under their own power. The aircraft sustained minor damage to the nose gear, propeller, and forward fuselage. ## Technical Investigation and Findings A post-incident inspection revealed that the nose gear had pivoted forward and slightly to the left because its drag link had detached. The drag link is secured to the nose gear by two bolts. The right-side bolt was found to be broken, while the left-side bolt was bent. Neither bolt was fully threaded into the housing, with the broken bolt missing 3.3 mm and the bent bolt missing 2.8 mm of thread engagement. Metallurgical analysis indicated that the broken bolt failed due to bilateral bending fatigue. Two fatigue cracks initiated at opposite positions along the root of the first thread and grew inward until a central band remained, which then fractured under overload. The bent bolt showed early signs of a similar fatigue process, suggesting it had experienced lower load levels than the broken bolt. ## Probable Cause and Analysis The investigation concluded that the nose gear folded due to the failure of one of the bolts connecting it to the drag link, which maintains the gear in a vertical position. The bolt failure was attributed to bilateral bending fatigue caused by an applied tightening torque that was lower than required. The analysis suggested that the bolt was subjected to bending stresses rather than the intended shear stresses, likely due to incorrect tightening. The fact that the broken bolt was less deeply threaded than the bent bolt indicated a difference in tightening between the two, with the broken bolt likely being less tight and thus experiencing greater bending stress.