Accident Summary
On October 9, 2017, about 1616 mountain standard time, an experimental Nanchang China CJ-6 airplane, registration N8NW, was substantially damaged during a forced landing near Buckeye, Arizona. The pilot sustained serious injuries and the passenger sustained minor injuries. The flight was conducted as a Title 14 Code of Federal Regulations Part 91 personal flight.
The pilot reported that the takeoff, climb, and cruise were uneventful. During descent toward the destination airport, the engine began to vary in pitch and rpm. The pilot checked the fuel quantity; both main tanks indicated 60 liters. He enriched the fuel mixture and turned on the auxiliary fuel pump. Although fuel pressure appeared good, the engine eventually lost power as the airplane slowed.
Unable to glide to an airport, the pilot initiated a forced landing to a clearing at a construction site. During the landing, the left wing impacted an obstacle, causing the airplane to veer out of control and resulting in substantial damage to the fuselage and wings.
Engine Examination
Postaccident examination of the engine revealed that the crankcase sustained impact damage to the lower side. The propeller and spinner were attached to the crankshaft propeller shaft. Manual rotation of the crankshaft established rotational continuity throughout the engine. All cylinders exhibited compression and suction in the proper firing order.
The left magneto was removed and manually rotated; spark was observed from the coil lead, but the mechanical advance was sticking. The right magneto produced spark during manual rotation. The forward spark plugs were removed and showed oil residue on the electrodes and evidence of normal wear.
Fuel System Findings
The engine-driven rotary gear fuel pump was examined. The pump’s vanes and drive shaft showed no anomalies, and the drive shaft rotated freely by hand. However, fuel was noted on the accessory side of the pump. Further examination revealed a ruptured diaphragm on the drive shaft. The diaphragm, designed to prevent fuel system contamination, had remnants on the accessory side and was located inward from its original position. The ruptured diaphragm could be consistent with a potential source of fuel system contamination from air or oil.
The fuel header tank was empty. The fuel line from the gascolator to the engine was intact. Engine accessories mounted to the rear of the engine were intact except for the oil reservoir, which had impact damage. The fuel lines were removed and were clear of debris. The three-bladed propeller had all blades separated about 1 foot from the hub.
No additional evidence of pre-impact mechanical anomalies was found during the engine examination.