Incident Overview
Description
The crew of C-GNAA, a Beech King Air, were taxiing for takeoff on the gravel strip at Patuanak, SK. The flight was a medevac flight with 5 people on board. During the taxi, the nosewheel of the aircraft went into a sinkhole, breaking the nosegear fork assemby and collapsing the nosegear. Both propellers struck the ground, disabling the aircraft on the runway. There were no reported injuries. The failure of the fork was at the weld assembly as identified in Airworthiness Directive 87-22-01 R1. There was a 150 hour repetitive requirement to check the weld for cracks by means of a liquid penetrant inspection, and this was done by a NDT firm in Fort McMurray 120 hours prior to the accident. When the nose gear of C-GNAA entered the soft area, it jammed hard over against the steering stop and imparted a twisting moment to the weld. Preliminary indication is that the weld failed in overload. It had been known for years that the Patuanak strip is sandy and has loose gravel areas. When the weather is hot and dry, soft spots will appeared, especially near the sides of the runway. The strip was not designed for aircraft with narrow tires such as a King Air.
Primary Cause
Weld failure due to overload, exacerbated by sandy conditions and loose gravel on the Patuanak strip.Weld failure due to overload, exacerbated by sandy conditions and loose gravel on the Patuanak strip.Share on:
