Accident Overview
On April 19, 2019, at approximately 1340 Pacific daylight time, a Nanchang CJ-6 airplane, registered as N621JM, sustained substantial damage during an accident near Grass Valley, California. The pilot and passenger received minor injuries. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Sequence of Events
According to the pilot, after an uneventful landing on runway 25—a 4,657-foot-long by 75-foot-wide asphalt runway—the landing roll was extended due to traffic on one of the taxiways. As the airplane approached the intended taxiway, the pilot applied left rudder and lightly depressed the brake handle. About 30 degrees into the left turn, the brakes failed, and the airplane departed the asphalt taxiway surface. Facing obstructions and downsloping terrain ahead, the pilot applied right rudder and engine power to realign with the runway. Shortly after, the airplane overran the departure end of the runway, became airborne while traveling downslope, then touched down and struck a dirt berm. It subsequently collided with a fence, nosed over, and came to rest inverted. The fuselage and both wings sustained substantial damage. The wreckage was recovered to a secure location for examination.
Postaccident Examination
Examination of the aircraft revealed that the brake cable had separated from the brake handle. The cable thimble, clevis pin, and cotter pin remained attached to the brake control handle. The separated cable portions were forwarded to the NTSB Materials Laboratory for further analysis.
Laboratory examination determined that the cable was constructed of seven strands, each composed of seven metal wires (7x7 construction). The configuration of the thimble and cable contour between two fracture points was consistent with a hand-tucked splice joint forming a thimble-eye termination. Scanning electron microscope inspection of the cleaned cable fracture surfaces showed that six of the seven strands exhibited relatively flat fracture surfaces oriented normally to the wire axis, indicative of a progressive fracture mechanism such as fatigue. Only one strand and a few individual wires showed minor elongation at the fracture location. Details are available in the Materials Laboratory Factual Report in the public docket.
Logbook Records
No specific entries regarding the brake cable were found in the airframe logbook.