2007 Kapowsin Air Sports accident

The 2007 Kapowsin Air Sports accident occurred on 7 October 2007, when a Cessna 208 Caravan on a flight from Star-Snake River Skydiving Airport in Idaho to Sheldon-Sanderson Field, Washington went out of control and crashed 55 kilometres west-southwest of Naches, Washington. All 10 occupants of the aircraft were killed in the accident.

Accident sequence

After a weekend trip, the group of nine parachutists and the pilot were on their way back to their skydiving base at Shelton-Sanderson Field in the US state of Washington. The pilot had flown several skydiving flights that day and had landed in the early afternoon at Star-Snake River Parachuting Airport in the US state of Idaho to prepare the aircraft for the flight home. The Cessna was to fly through a weather zone in which cloud layers, turbulence and icing conditions were to be expected, which is why the pilot obtained comprehensive information about the weather along the route. He delayed the departure until the weather conditions had improved to the point that he assumed he could conduct the flight under visual flight rules. The aircraft took off from Snake River Skydiving Airport in Star, Idaho at 17:50 local time. About two hours later the aircraft was in the airspace of the state of Washington; it was dark, and that evening the moon illuminated the area only slightly because of the cloud layers through which the aircraft was flying. According to the satellite images and the cockpit voice recorder recordings, the aircraft most probably flew through an area with a broken or overcast cloud layer that extended below and above its flight altitude. There had probably also been lee waves in the area, which could be accompanied by icing conditions. The recorded radar data suggested that the pilot probably tried to manoeuvre the aircraft above, below or around the side of the cloud layer in order to fly out of the rain clouds. He had evidently done this while trying to continue the flight under visual flight conditions. The aircraft probably entered a cloud layer within the last three minutes of flight and was possibly exposed to icing conditions and turbulence. Control of the aircraft was lost shortly thereafter.

Accident investigation

After the accident, the National Transportation Safety Board (NTSB) took over the investigation into the cause of the crash. The accident investigation found that the aircraft's angle of attack had increased significantly within a few moments immediately before the crash. The performance data indicated a stall. The aircraft, which by design did not have a pressurised cabin, had maintained an altitude of 14,000 feet for an hour. Immediately before the crash, after successively flown 360-degree turns in which the aircraft climbed and descended again, it had reached altitudes of 15,000 feet. No oxygen equipment was used on the flight. At such altitudes, pilots can suffer hypoxia without experiencing noticeable symptoms of it. The pilot was certified only for visual flights.

The NTSB concluded that the most probable cause of the accident had been the pilot's failure to maintain sufficient airspeed while manoeuvring the aircraft to avert a stall. Contributing factors were given as his possible partial incapacitation due to hypoxia, as well as knowingly flying through an area in which adverse weather conditions prevailed. Clouds, turbulence and darkness, which suggested that instrument flying had been called for but not carried out, had also contributed to the circumstances of the accident.