Accident Overview
On March 8, 2013, at approximately 1330 Alaska standard time, a Cessna 185 airplane equipped with wheel/skis, registration N185FK, sustained substantial damage during taxi on a remote, frozen, snow-covered lake near Talkeetna, Alaska. The aircraft, operated by Talkeetna Air Taxi under 14 CFR Part 135 as a visual flight rules sightseeing flight, was not damaged beyond repair. The commercial pilot and three passengers reported no injuries. Visual meteorological conditions were present, and a visual flight rules flight plan had been filed.
Flight Details
According to the pilot's account to the National Transportation Safety Board investigator-in-charge, the flight departed Talkeetna Airport for a scenic tour that included an off-airport landing on skis. After landing, while executing a left turn during taxi, the pilot felt the airplane's weight shift to the right ski. The wheel/skis began to sink into soft snow, and the aircraft nosed over. Post-accident, the pilot observed water overflow in the ski tracks.
Passenger Account
A passenger seated in the right front seat described a smooth touchdown with ample space for a long gentle rollout. At low speed, the pilot initiated a 180-degree left turn. Shortly after, the right ski began sinking into the soft snow, causing the aircraft to pitch nose-down and roll to the right. The pilot attempted to counteract by pulling aft on the control yoke and reducing throttle, but the airplane continued to nose over, coming to rest inverted.
Postaccident Examination
An examination by the operator revealed that the ski arm on the right ski had separated at the weld. The fractured component was sent to the NTSB Materials Laboratory in Washington, D.C., for detailed analysis. A senior metallurgist reported that magnified optical inspection showed features consistent with overstress separations of the welds. Small amounts of gas porosity were present in the fractured angled tube weld, but no corrosion or preexisting cracking was found. The fracture details indicated an inboard to outboard side load applied to the cross tube of the ski arm.