On August 20, 2018, about 1630 Pacific daylight time, an experimental amateur built Blue Oak LLC CCK-1865 airplane, N14CK, impacted trees during an off airport forced landing near Deadwood, California. The private pilot was not injured, and the airplane sustained substantial damage to the left and right wings. The airplane was registered to Blue Oak LLC and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight, which originated from Columbia Airport, Columbia, California, about 1600.
The pilot reported that prior to the accident flight, he had completed routine maintenance that spanned a few days that he finished about midafternoon on the day of the accident. The pilot decided to make a local test flight and noted that he had a total of about 12 gallons of fuel, as indicated by the fuel sight gauges. Following a preflight inspection, he conducted a ground engine run, and taxi checks, which were normal. After takeoff, he remained near the departure airport for about 10 minutes, and decided to lengthen his flight as he did not observe any anomalies
During the uneventful flight, he was about 500 ft above ground level over mountain ridge tops when the engine lost partial power. The pilot said that he was able to maintain level flight and maneuver toward more favorable terrain before the engine lost total power. Subsequently, the pilot initiated a forced landing in a small clearing within heavily wooded mountainous terrain. During the landing roll, the airplane struck a tree and came to rest upright. The pilot added that following the accident, he noticed that the left wing fuel tank cap was not secured.
The airplane was recovered to a secure location for further examination. Recovery company personnel reported that prior to disassembly of the airplane to facilitate removal of the wreckage, the right wing fuel tank contained no fuel, and the left wing fuel tank had about one-half gallon of fuel in it. Review of a photo furnished by the wreckage recovery company revealed that 10 days following the accident, a slight amount of residue / discoloration in trail of the left wing fuel tank filler neck, and extended to the trailing edge of the fuel tank cover.
Photo 1: View of the left wing fuel tank, noting the slight discoloration in trail of the left fuel tank filler neck. Courtesy of Plain Parts.
The airplane was equipped with two 20-gallon wing fuel tanks, which gravity flowed to a fuel selector valve. The fuel selector valve had 4 selector positions, left, both, right, and off.
Examination of the recovered wreckage by the National Transportation Safety Board investigator-in-charge revealed that both wings were removed to facilitate wreckage recovery. The LyCon Exp IO-340-EXP engine, serial number L-54836-15E, remained attached to the airframe via its mounts. Throttle and mixture control continuity was established from the cockpit controls to the engine. All oil and fuel lines remained secure to their respective fittings. The top spark plugs were removed and exhibited normal operational signatures. All 4 fuel injector nozzles were removed and found to be free of debris.
The propeller was rotated by hand and rotational continuity was established throughout the engine and valve train. Thumb compression and suction was obtained on all four cylinders. The electronic magnetos produced spark on all eight ignition leads when the propeller was rotated by hand and when battery power was applied to the airframe.
The fuel lines from the fuel flow divider to the nozzles were free of debris. The fuel flow divider spring, and internal diaphragm were intact and no debris was observed. The fuel flow transducer was found free of debris. The fuel servo was intact and undamaged. The throttle plate was intact and undamaged. The fuel filter was free of debris. The fuel servo internal diaphragms were intact and undamaged. The gascolator screen was free of debris. A slight amount of debris was noted within the gascolator bowl along with residual fuel. The fuel pump switch was turned on and the fuel pump operated normally. During removal of all of the fuel lines installed on the engine, residual fuel within the airframe fuel lines, and gascolator, a total of about 6 ounces of fuel was recovered.
The left and right wing fuel tanks were found intact and undamaged. One of the two fuel caps were located within the recovered wreckage, and the vent was free of debris and obstructions. The other fuel cap was not located. The clear tube sight gauges for each wing were intact and found free of debris.