Accident Overview
On September 23, 2011, at approximately 1330 Alaska daylight time, a high skid-equipped Bell 206B3 helicopter, registration N204PA, sustained substantial damage during a tail rotor strike while maneuvering to land on the Harding Ice Field, about 10 miles west of Seward, Alaska. The helicopter was owned and operated by Pathfinder Aviation of Homer, Alaska, as a visual flight rules (VFR) public use passenger flight in conjunction with the National Park Service (NPS) under 14 Code of Federal Regulations Part 135. The commercial pilot and two passengers were not injured. Visual meteorological conditions prevailed at the time of departure, and company flight following procedures were in effect. The flight originated at about 1320 from a remote site on the Harding Ice Field.
Flight Details
According to the operator's report and subsequent conversations with Pathfinder Aviation’s director of operations, the purpose of the flight was to transport two NPS employees to a remote snow-covered site on the Harding Ice Field to collect snow samples. The mission required brief stops at various predetermined sites along a prearranged route. The director of operations noted that when the pilot departed from the previous site en route to the next site, weather conditions were “good VFR.” As the flight progressed towards the upper elevations of the ice field, the pilot encountered overcast layers and flat light conditions. As the pilot slowed the helicopter to make a precautionary landing, and while on approach, the aircraft touched down early. After the initial touchdown, the pilot hover-taxied the helicopter to an area about 20 to 30 yards beyond the initial touchdown point, then landed the helicopter in the deep snow. After landing, the helicopter tipped backwards as the aft portion of the skids settled into the deep snow, and the tail rotor blades subsequently struck the snow. There were no preaccident mechanical problems reported with the helicopter.
Passenger Account
In a written statement to the NTSB dated September 24, a passenger reported that while traveling from one landing site to another, visibility deteriorated rapidly, making it very difficult to discern any topographic features of the snow-covered ice field. He estimated the helicopter’s height above the ice to be 100 feet as the pilot began slowing, and then the helicopter unexpectedly touched down. After the initial touchdown, the helicopter continued to hover momentarily, and then the pilot immediately landed the helicopter, causing it to tip backwards. Photos of the accident site provided by the passenger show expansive, smooth, featureless, snow-covered sloping terrain.
Post-Accident Inspection
According to Pathfinder Aviation’s director of operations, a company maintenance technician was flown by helicopter to the site to inspect the helicopter for damage before it could be ferried back to Seward. Finding no apparent damage, the helicopter was started, ground run, and hovered. While hovering, a tail rotor driveshaft coupling separated, and the pilot performed a hovering autorotation back to the snow-covered ice field. As a result, the helicopter sustained substantial damage to the tail rotor drive shaft assembly.
Recommendations
In the recommendations section of the operator's NTSB 6120.1 form, the director of operations noted that future pilot training would include formal flat light and whiteout training, as well as added training on judgment and decision making regarding weather.