Accident Cessna 208B Grand Caravan N430A,

ASN Wikibase Occurrence # 321860

Date:	Sunday 7 October 2007
Time:	19:59
Type:	Cessna 208B Grand Caravan
Owner/operator:	Kapowsin Air Sports
Registration:	N430A
MSN:	208B0415
Year of manufacture:	1994
Total airframe hrs:	9604 hours
Engine model:	Pratt & Whitney Canada PT6A-114A
Fatalities:	Fatalities: 10 / Occupants: 10
Aircraft damage:	Destroyed, written off
Category:	Accident
Location:	ca 55 km WSW of Naches, WA - United States of America
Phase:	En route
Nature:	Parachuting
Departure airport:	Star-Snake River Skydiving Airport, ID
Destination airport:	Shelton-Sanderson Field, WA (SHN/KSHN)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
A Cessna 208B, N430A, was destroyed when it collided with terrain near Naches, Washington. The commercial pilot and nine passengers were killed.
The pilot was returning a group of skydivers to their home base after a weekend of skydiving. He flew several jump flights, and then stopped early in the afternoon to prepare the airplane for the flight home. The flight was planned into an area of clouds, turbulence, and icing, which the pilot had researched. He delayed the departure until he decided that he could complete the planned flight under visual flight rules (VFR). The flight departed Star (ID92), Idaho, about 1750 PDT, en route to Shelton (SHN), Washington. The accident occurred at night with little illumination of the moon, and the airplane was in an area of layered clouds. A detailed analysis of the weather conditions revealed that the flight probably encountered broken to overcast layers both below and above its flight altitude. The satellite and sounding images suggested that it was possibly in an area of mountain wave conditions, which can enhance icing. The recorded radar data indicated that the pilot was likely maneuvering to go around, above, or below rain showers or clouds while attempting to maintain VFR. The airplane likely entered clouds during the last 3 minutes of flight, and possibly icing and turbulence. It was turning when it departed from controlled flight, with the angle-of-attack increasing rapidly. The unpressurized airplane was flying at over 14,000 feet mean sea level for more than 1 hour during the flight. It reached 15,000 feet just prior to the accident in sequential 360-degree turns while climbing and descending. Supplemental oxygen was not being used. At these altitudes, the pilot would be substantially impaired by hypoxia, but would have virtually no subjective symptoms, and would likely be unaware of his impairment. The pilot had logged over 2,000 hours of total flight time, with nearly 300 hours in this make and model of airplane. He was instrument-rated, but had only logged a total of 2 hours of actual instrument flight time. Company policy was to fly under visual flight rules only, and they had not flight-checked the pilot for instrument flight.

PROBABLE CAUSE: "The pilot's failure to maintain an adequate airspeed to avoid an aerodynamic stall while maneuvering. Contributing to the accident were the pilot's impaired physiological state due to hypoxia, the pilot's inadequate preflight weather evaluation, and his attempted flight into areas of known adverse weather. Also contributing were the pilot's inadvertent flight into instrument meteorological conditions that included clouds, turbulence, and dark night conditions."

Accident investigation: