History of Flight
On April 30, 2020, about 1200 Pacific daylight time, a Piper PA-23-250 airplane, registration N6521Y, was substantially damaged when it struck terrain near Hemet, California. The pilot was fatally injured. The flight was conducted as a Title 14 Code of Federal Regulations Part 91 aerial survey mission.
According to a fellow company pilot operating a similar flight in the area, the accident pilot was assigned to photograph two parcels, designated flight plan 223 (FP223) and flight plan 224 (FP224). These plans specified a north-to-south track at 8,500 ft msl ±300 ft, with a groundspeed of 120 to 130 knots.
Review of recorded camera data showed the pilot selected FP224 first. Before entering FP224, he communicated with a colleague, stating he was "about to be on station." Between 1140 and 1210, the pilot made two distress radio calls.
ADS-B data indicated the airplane departed CNO about 1131, climbed to approximately 8,500 ft msl, and tracked southeast at about 164 knots groundspeed for roughly 42 miles. About 5 miles northwest of Diamond Valley Lake, it descended to 8,100 ft and decelerated to 130 knots before turning east. The airplane proceeded east for about 15 miles, passing near a camp with buildings at a valley base, then continued east for 3 miles before turning north, consistent with approaching FP224's southern boundary. About a minute later, before entering FP224, the airplane initiated a left turn and descent, traversing through FP223 to the southwest, maintaining the new heading for about 3.5 miles until crossing over the camp again. It then began a right turn and continued descending. The last ADS-B point, recorded at 1200, showed the airplane at about 4,400 ft msl (1,000 ft agl), 177 knots groundspeed, and roughly 950 ft northeast of the accident site.
Aircraft Information
The airplane was manufactured in 1967. According to the operator, it was maintained under an annual inspection program, with the last annual inspection completed on November 21, 2019. In April 1994, the airplane was modified to carry a Kodak Hite experimental camera system, later replaced by an Eagleview proprietary digital camera. This camera system recorded flight parameters including pitch, roll, altitude, heading, and speed.
Wreckage and Impact Information
The accident site examination revealed the airplane impacted steep mountainous terrain and came to rest inverted about 15 miles west of the intended survey area. The debris path measured about 240 ft in length, oriented downhill on a heading of approximately 239°. The first identified point of impact was a shallow indentation in sandy soil at the top of a ridgeline at an altitude of 3,606 ft msl.
The fuselage sustained substantial damage throughout. The right propeller was not located at the site; examination of the fracture site indicated overload separation.
Post-accident visual examination of the aileron control cable revealed multiple broken wires protruding from the strands, with a separation fracture located between the left aileron bellcrank and the cable junction for the control yokes. Laboratory examination by the NTSB materials laboratory showed the cable consisted of six strands wrapped around a central core strand. All strands fractured at approximately the same location, perpendicular to the cable direction. Two strands exhibited little fraying, while the other four showed local fraying up to 0.5 inch from the fracture surface. The core strand exhibited fraying several inches from the fracture surface. Further examination revealed numerous wires fractured by overload and others by fatigue, with some cracked by fatigue then fractured by overload.
Medical and Pathological Information
Toxicology testing by the FAA Forensic Sciences Laboratory detected tetrahydrocannabinol (THC) and its primary metabolite 11-hydroxy-delta-9-THC in the pilot's urine at 0.9 ng/mL and 12.3 ng/mL, respectively; neither was detected in cavity blood or liver tissue. THC's inactive metabolite, carboxy-delta-9-tetrahydrocannabinol (THC-COOH), was detected in cavity blood, urine, and liver tissue at 7.1 ng/mL, 89.9 ng/mL, and 376.2 ng/g, respectively. Toxicology testing by the coroner's office was positive for cannabinoids in the pilot's blood.
Additional Information
The Piper Aztec service manual, in the Annual/100 Hour Inspection Procedure, states: "Examine cables for broken strands by wiping them with a cloth for the entire length. Visually inspect the cable thoroughly for damage not detected by the cloth. Replace any damaged or frayed cables."