19981106044649A

(.19) On November 6, 1998, approximately 1225 pacific standard time, a Cessna TR182, N756YE, operated by kennewick aircraft services inc. of kennewick, Washington under contract to the U.S. Fish & wildlife service as a public-use waterfowl survey flight, struck power lines across the columbia river near Desert Aire, Washington, and subsequently crashed and sank into the river. The airplane was substantially damaged in the wire strike and subsequent water impact. After the airplane sank to the river bottom (approximately 15 feet deep), the commercial pilot-in-command of the aircraft was able to escape the aircraft and was rescued by a boat on the river, but sustained serious injuries in the accident. Two U.S. Fish & wildlife service employees aboard the aircraft, who were acting as observers for the waterfowl survey, did not escape the submerged aircraft and were fatally injured. The flight departed vista field, kennewick, Washington, and was to have been a local flight. Visual meteorological conditions were reported at the hanford, Washington, weather observation station (approximately 9 nautical miles southeast of the accident site) at 1150, and the airplane was not on a flight plan. The operator possessed an FAA waiver from the minimum altitude requirements of 14 CFR 91.119(c). This waiver authorized the pilot to operate at altitudes below 500 feet above ground level (AGL) on aerial survey flights, provided aircraft were not operated closer than 500 feet to persons on the surface. Witnesses reported that at the time of the accident, the airplane was flying eastbound (downstream) at low altitude. The airplane struck the power lines which cross the river between the priest rapids dam and the vernita bridge (where Washington state highway 24 crosses over the river), approximately 2 miles west of the vernita bridge. There are two groups of transmission lines which cross over the river at this point, a westermost (upstream) group mounted on towers rising to approximately 194 feet AGL and an easternmost (downstream) group on taller towers. The transmission line support towers on each river bank are depicted as group obstructions on the seattle sectional aeronautical chart, with the chart depicting the towers as being 280 feet AGL. The airplane struck and severed ground/support cables running between the tops of the westernmost group of towers. The FAA on- scene investigator reported that the cables the aircraft struck were 5/8 inch in diameter (the high-tension cables, mounted on supports below the tops of the towers, are approximately 1 inch in diameter.) In an initial interview with the FAA investigator conducted after the accident, the pilot told the FAA investigator that at the time he struck the power lines, the airplane was flying due east, climbing at 300 feet per minute, and was at an airspeed of 80 knots. The FAA investigator reported that the pilot told him the airplane was operating normally at the time of the wire strike, and that the pilot told him he was using the power line towers as a visual reference to indicate how high he was above the power lines. Sky conditions reported in the 1150 hanford weather observation were: few clouds (up to 2/8 sky cover) at 800 feet; scattered clouds at 25,000 feet; and visibility 15 statutemiles. (-23) on 11/06/98 at 12:25PM PST, N756YE, owned and operated by kennewick aircraft service in kennewick, WA., struck a static wire and crashed into the columbia river about six miles east of the priest rapids dam. The pilot, clif dyer, certificate number 534623389, survived and sustained a partially collapsed lung and broken ribs. His two passengers, biologists from the federal fish and game department, were pronounced dead at the scene. The pilot stated that they had just completed a water fowl survey and were heading due east to return to kennewick, WA. He further states that the aircraft was performing normally and was climbing at 300 ft/min in order to clear power lines when it struck the static wire. This static wire is a 5/8 inch steel cable suspended between two 194 foot tall power line support towers across the columbia river. They are attached to and suspended between the tops of these towers with very little catenary. The 1.125 inch aluminum power cables are suspended below the static cables with a great amount of catenary.