LAHAINA, HI, USA
N860FE
Cessna 208B
Following a normal approach and landing, the left wing of the fixed gear aircraft dropped and the aircraft skidded on its belly-mounted cargo pod. Despite the pilot's attempt to maintain directional control, the aircraft veered off the runway to the left and down an embankment. Investigation revealed that the left main landing gear strut, a tubular spring steel assembly, was broken approximately midway between the wheel assembly and the fuselage attachment. Laboratory metallurgical analysis revealed that the strut failed due to multiple fatigue cracks that originated from an extrusion lap on the inside diameter of the strut. The lap was formed during the manufacture of the tubing from which the strut is fabricated, and caused a structural discontinuity from which the fatigue cracks initiated.
On October 26, 1998, at 0709 hours Hawaiian standard time, a Cessna 208B, N860FE, was substantially damaged when the aircraft veered off runway 02 and impacted trees during landing at the Kapalua (West Maui) airport, Lahaina, Hawaii. The commercial pilot was not injured. Visual meteorological conditions prevailed for the nonscheduled cargo flight that was operated under 14 CFR Part 135 by Corporate Air, Inc., with call sign AIRSPUR 8597. The flight departed Honolulu, Hawaii, at 0629 on the same day. The operator reported that, following a normal landing and touchdown, the pilot heard a snap sound and perceived the right wing was rising due to a gust of wind or flap malfunction. The pilot retracted flaps and applied reverse thrust. He then noted that the left wing was down, there was a scraping sound and that the aircraft was veering left off the runway. Despite the pilot's attempts to maintain directional control, the aircraft veered off the runway and traveled approximately 500 feet across a taxiway and clearway, and then about 30 feet down an embankment on the west side of the runway. Inspectors from the Honolulu Flight Standards District Office noted that there was fiberglass residue on the runway from the belly-mounted cargo pod. They also noted that the left main landing gear strut, a tubular spring steel assembly, was broken approximately midway between the wheel assembly and the fuselage attachment. The fractured gear strut was sent to the Safety Board Materials Laboratory for analysis of the failure. The metallurgist's analysis of the landing gear strut fracture is attached. The metallurgist determined that there were multiple fatigue cracks present that originated from an extrusion lap on the inside diameter of the strut. The metallurgist opined that the lap was formed during the extrusion process of the tubing from which the strut is manufactured, and caused a structural discontinuity from which the fatigue cracks initiated. The fatigue cracks grew in service to a maximum depth of 0.24 inches prior to the strut fracture.
Structural failure of the main landing gear strut due to metallurgical fatigue. The fatigue cracks originated at an internal structural flaw placed in the part during manufacture.
Source: NTSB Aviation Accident Database
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