HISTORY OF FLIGHTOn September 22, 2024, at about 1248 Pacific daylight time, a Nanchang CJ-6A airplane, N313YK, and a Yakovlev Yak 52 airplane, N5287, were substantially damaged when they were involved in a midair collision near Lancaster, California. The pilot of the CJ-6A was fatally injured and the pilot of the Yak 52 received minor injuries. Both airplanes were operated as Title 14 Code of Federal Regulations Part 91 personal flights. According to the pilot of the Yak, they had planned to fly in formation with the Yak as the lead airplane and the CJ-6A following the Yak off its right wing as the “dash 2” (wingman). During the uneventful flight from Watsonville, California, they briefed their detachment procedure over a shared radio frequency. The plan was for them to accelerate from 210 kph to 250 kph, at which time the pilot of the CJ-6A would pitch up and bank left to continue his flight to Payson, Arizona, while the pilot of the Yak would continue straight and level and proceed to San Diego, California. The pilot of the Yak stated that, immediately after they accelerated to their planned speed, he observed the CJ-6A pitch up and bank left. After looking away briefly, he observed the CJ-6A abeam as it began to overbank to about 120° and approached the Yak in an approximately 35° nose low attitude. After the airplanes collided the pilot noticed that his propeller blades had separated, at which time he lost sight of the CJ-6A. A witness observed the CJ-6A roll right four times and then impact the ground, which was immediately followed by a plume of dust. The pilot of the Yak made a left turn as he looked for a suitable place to land and eventually touched down on a nearby road. Figure 1. Flight track of N5287 (Yak) movements at the time of the accident and after. PERSONNEL INFORMATIONAccording to the Red Star Pilots Association (RPA) website, the organization is composed of over 500 members operating a variety of jet- and propeller-driven aircraft, including Yak and Nanchang airplanes. A family member reported that the accident pilot had owned the Nanchang CJ-6A for about 10 years and had been a member of RPA for about that same length of time. The RPA also reported that the pilot was the president of the organization at the time of the accident. The RPA maintains a Formation Manual that includes instructions on the fundamentals of formation flight and covers basic and advanced maneuvers. In 1993 RPA formed a Formation and Safety Team (FAST) to develop and codify standards for formation flying throughout the warbird community. The manual serves as the basis for these fundamentals, which include wingman procedures and techniques, operating procedures, contingency procedures, communications procedures and techniques, hand signals, and aircraft signals. According to the president of RPA, the maneuver that the two pilots had briefed was not covered in the RPA manual and is not something the organization teaches in its FAST formation training courses. According to the association, the RPA formation manual and 14 Code of Federal Regulations Part 91.11 do not prohibit other formation maneuvers as long as they are thoroughly briefed by the participating pilots. WRECKAGE AND IMPACT INFORMATIONThe CJ-6A came to rest upright in desert terrain oriented on a northwestern heading at a field elevation of about 2,310 ft mean sea level. Most of the major structural components of the airplane were accounted for at the accident site except the left elevator. The left side antenna from the vertical stabilizer was located about 0.5 nautical miles west of the main wreckage. A ground scar was located beneath the right wing, and another ground signature was located under the engine. The empennage, which was loosely attached to the aft fuselage, was composed of the vertical stabilizer, both horizontal stabilizers, and the right elevator. The CJ-6A displayed multiple paint transfer signatures, score marks, tears, gouges, and separations. The left wing contained a 3-foot-long tear about midspan, with wooden propeller fragments inside the wing. Yellow paint transfer marks and light grey or white scuffing and track marks were observed aft of the tear. The scuffing was oriented about 25° to the right of the longitudinal axis of the airplane. White/light grey scuffing was also observed on the outboard top skin of the left horizontal stabilizer oriented 47° to the right of the longitudinal axis. The left elevator was not recovered. The leading edge of the left horizontal stabilizer exhibited a chordwise tear and was deformed from midspan to the stabilizer tip, with an impression and paint deterioration at the leading edge of the horizontal stabilizer tip. Additional light grey striated marks were observed on the top skin of the aft fuselage that tracked aft and to the left of the longitudinal axis of the airplane. These fuselage striations were just forward of the leading edge of the vertical stabilizer, which was crushed and partially separated from the fuselage. Postaccident examination of the CJ-6A revealed no preimpact mechanical anomalies or malfunctions with the airframe or engine that would have precluded normal operation. Figure 2. CJ-6A damage signatures after midair collision. The Yak came to rest upright on the right edge of a road about 1.5 nautical miles southeast of the CJ-6A oriented on a southeast heading at a field elevation of about 2,350 ft mean sea level. The airplane’s major structures were accounted for at the accident site. The left wing exhibited a long chordwise tear from about mid span to the trailing edge surrounded by numerous paint transfer marks. The top of the cowling was crushed, a portion of the cowling had separated, and both propeller blades had separated at their blade roots. The left wing of the Yak exhibited white/light grey scuffing that was oriented 47° relative to the longitudinal axis of the airplane. An arching red paint transfer mark that had an approximate diameter of 4 ft 7 inches was observed on the top skin of the inboard left wing. The left-side canopy plexiglass at the aft cockpit was broken and a portion of the left-side canopy frame was bent. About midspan was an approximately 1-ft-7-inch-long gouge along the chordwise axis of the left wing that terminated in a concaved depression. The pilot of the Yak reported no preimpact mechanical malfunctions or anomalies that would have precluded normal operation. Figure 3. Yak damage signatures after midair collision. Occupant Information MEDICAL AND PATHOLOGICAL INFORMATIONAn autopsy of the CJ-6A pilot was completed by the County of Los Angeles, Department of the Medical Examiner, Los Angeles, California. According to the autopsy report, the cause of death was blunt force trauma and the manner of death was an accident. Toxicological testing by the County of Los Angeles Department of the Medical Examiner Forensic Sciences Laboratories detected ethanol at 0.054 g/dL in the pilot’s cavity blood. Further toxicological testing by the FAA Forensic Sciences Laboratory detected ethanol at 0.058 g/dL in the pilot’s cavity blood and at 0.036 g/dL in his gastric contents. Ethanol was not detected in his vitreous fluid. N-propanol was detected in the pilot’s cavity blood and gastric contents, but not in the vitreous fluid. Ethanol is the intoxicating alcohol in beer, wine, and liquor, and, if consumed, can impair judgment, psychomotor performance, cognition, and vigilance. N-propanol is another alcohol that can be produced by microbes in a person’s body tissues and fluids after death. Detection of n-propanol in a postmortem specimen potentially is indicative of postmortem microbial activity in the specimen with or without associated ethanol production.