Accident Details
On June 4, 2014, about 1530 Pacific daylight time, a North American AT-6C, registration N13372, impacted trees and terrain following a loss of engine power near South Prairie Airport (02WA), Buckley, Washington. The airplane was substantially damaged. The airline transport rated pilot in the front seat and the airline transport pilot rated passenger in the aft seat were fatally injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight. The flight originated from 02WA about 2 minutes prior to the accident.
Witnesses reported observing the airplane take off from runway 34 with the engine sounding normal. About 15 to 30 seconds after passing the departure end, the engine began to "sputter." The airplane initiated a right turn to an easterly heading, followed by a left 270-degree turn with erratic ascents and descents. Throughout the turn, the engine seemed to power up and then lose power. As the airplane turned south toward the airport, the engine lost complete power, and the airplane descended into trees. A video recorded by a witness showed the airplane departing normally without any smoke or abnormalities.
Family members reported that the airplane had recently been sold by the passenger to the pilot, and the flight was part of a checkout. The pilot and passenger had conducted a local flight earlier that day lasting 1 to 1.5 hours before returning for lunch.
Aircraft Information
The airplane was a two-seat, low-wing, retractable-gear tailwheel aircraft, serial number 88-13372, powered by a Pratt & Whitney R-1340-AN engine rated at 550 horsepower, with a Hamilton Standard variable pitch propeller. It had dual flight controls, but was typically flown from the front seat due to the landing gear handle location. Fuel was carried in two 55.2-gallon wing tanks. The left tank had two delivery ports for main (35.2 gallons) and reserve (20 gallons) positions.
According to family of the former owner, the airplane had 30 to 35 gallons of fuel per side, with 31 gallons added the day before the accident. About 1 to 1.5 years before the accident, a new fuel selector valve was installed, but initially two valves were replaced as the first did not operate as expected. The airplane had flown little since, though numerous ground runs were conducted. The most recent annual inspection was on November 12, 2013, at a Hobbs time of 976.7 hours. A fuel selector valve was installed on August 31, 2012. At the time of the accident, the airplane had 2 hours since the annual inspection and 3.3 hours since the valve replacement.
Wreckage Examination
The accident site was about 1.25 miles northeast of 02WA in heavily wooded terrain. Initial tree contact was at about 70 feet height. The wreckage debris path was 238 feet long on a heading of 147 degrees magnetic. The fuselage came to rest on its right side, partially inverted, with the engine partially attached. The left fuel tank contained fuel; the right tank was empty. The fuel selector valve assembly was intact and found in the left tank position, slightly away from the detent. However, the right wing fuel line was connected to the fuel selector valve outlet port, and the engine supply line was connected to the right fuel tank port on the valve. This configuration would prevent fuel flow from the left tank to the engine when the selector was in left main or left reserve; fuel would instead flow from the left to the right tank. If the selector was in the right tank position, fuel would reach the engine. Both fuel handles moved freely, and the indicator plates were loose.
Examination of the engine revealed rotational continuity, thumb compression on all cylinders, and the carburetor throttle plates in the open position. The propeller remained attached; one blade was bent aft 90 degrees. Magnetos produced spark. The carburetor was impact-damaged with one float separated and crushed; the other float was intact but contained liquid internally. No evidence of sooting was found in the exhaust. Flight control continuity was established for all primary surfaces, with separations consistent with tension overload.
Medical Information
Autopsies of both pilots determined cause of death as multiple blunt force injuries. The front seat pilot had a heart weight of 450 grams with 30-50% coronary atherosclerosis. Toxicology detected acetaminophen and rosuvastatin. The rear seat pilot had a heart weight of 310 grams with over 50% coronary atherosclerosis and 80% occlusion of the left anterior descending artery. Toxicology detected sertraline, desmethylsertraline, and salicylate. Neither pilot's medical history was determined to be a factor in the accident.