What happened
On July 24, 2008, a float-equipped Cessna A185F, registration N6320N, collided with terrain during takeoff from Lake Nahwatzel near Shelton, Washington. The flight was a personal cross-country trip with a planned destination of Auburn, Washington. Weather conditions at the time were visual meteorological conditions with a 10-mile visibility and light winds.
Witnesses observed the aircraft land on the lake and taxi to the center, where the engine was shut down. Two individuals were seen exiting the aircraft and sitting on the pontoons for approximately 30 minutes before returning to the cockpit. Following several taxi maneuvers across the lake—which witnesses noted appeared to be an attempt to roughen the glassy water surface—the aircraft departed toward the northeast.
As the airplane reached an altitude of approximately 100 feet, clearing the trees, witnesses observed the wings wobbling. The aircraft then rolled sharply to the left and entered a nose-down descent into the terrain. The impact was followed by a post-crash fire that destroyed the aircraft. The pilot and one passenger sustained 2 fatal injuries.
The investigation
Investigators examined the wreckage at the accident scene and at a maintenance facility. The aircraft came to rest inverted in a wooded area approximately 0.14 miles from the shoreline. The fire had consumed much of the cabin, wings, and the front portion of the floats.
An examination of the engine, a Teledynam Continental Motors IO-520-D, revealed the following:
- The fuel selector valve was unobstructed.
- Spark plugs showed no mechanical deformation, and electrodes appeared normal for standard operation.
- A borescope inspection showed no mechanical deformation of the valves, cylinder walls, or internal cylinder heads.
- The crankshaft would not rotate, but no metal debris was found in the oil screen, and the oil pickup screen was clean.
- While the accessory section and induction system sustained severe thermal damage from the fire, no mechanical anomalies were found that would have prevented normal operation.
- The propeller hub remained attached to the crankshaft, though one blade separated and was found in the impact crater.
Control continuity was established for the ailerons, rudder, and elevators.