History of Flight
On December 10, 2023, at about 1555 mountain standard time, a Beechcraft A36 airplane, registration N4171S, was substantially damaged when it impacted terrain near Topock, Arizona. The pilot sustained fatal injuries. The flight was operated as a personal flight under Title 14 Code of Federal Regulations Part 91.
According to ADS-B data, the airplane departed Sun Valley Airport (A20) in Bullhead City, Arizona, from runway 36 at about 1533. It made a climbing right turn to the southeast and then turned left to an easterly heading, continuing to climb. The pilot had contacted the Los Angeles Air Route Traffic Control Center (ARTCC) at 1141 requesting flight following services to Prescott Regional Airport—Ernest A. Love Field (PRC) in Prescott, Arizona. At 1546:49, the airplane reached 11,325 ft mean sea level (msl) and began a right 180° turn.
At about 1547, the pilot notified the controller that the engine was losing oil pressure and that he was returning to A20. By 1547:59, the airplane completed the 180° turn to a heading of 270° and descended to 9,650 ft msl. Over the next two minutes, it descended to 6,250 ft msl while maintaining a westerly heading. At 1550, the pilot informed the controller that the engine power was set to idle and that he was uncertain of reaching A20. When asked by the controller at 1552 about roads or freeways for an off-airport landing, the pilot replied, “Not yet.” Communications ceased at 1553, and ADS-B returns ended at 1553:17 when the airplane was at 4,000 ft msl, an indicated airspeed of 105 kts, and a magnetic heading of 271°.
A pilot of another aircraft in the area relayed that the accident pilot had transmitted that the “engine is burning up.” At about 1605, the assisting pilot visually confirmed “heavy thick smoke coming off some wreckage right at his location.” The accident site was located about 8 nautical miles west of the last ADS-B data point. ADS-B data also indicated that when the airplane turned from east to west, it was about 4 nm south of the Arizona proving grounds, which featured wide, paved, flat surfaces, and about 4 nm west of Interstate 40.
Aircraft Information
The airplane, a Beechcraft A36, had its last annual inspection completed on November 1, 2023. At that time, the engine had accumulated 2,856.4 total hours and 1,248.5 hours since overhaul. A subsequent airframe logbook entry on November 3, 2023, indicated that the electroluminescent panel was removed, refurbished, and reinstalled, with a tachometer time and airframe total time of 7,807.5 hours.
Wreckage and Impact Information
The airplane impacted rocky desert terrain while on a southerly heading. The first identifiable point of contact was a boulder with blue paint transfer located underneath high-tension powerline wires on the north side of an unimproved road. Fragments of the right wing’s green position light lens were found in the debris path under the powerlines. Additional debris included right wing skin, a right wing rib, a fuel vent line, and a section of a propeller blade. The debris path was about 132 ft long, oriented on a heading of about 212° magnetic, and included a swath of terrain about 50 ft wide with thermal signatures.
The main wreckage came to rest on a heading of 333° magnetic. The engine partially separated from the airframe and came to rest inverted. The cockpit-to-engine control cables for propeller, throttle, and mixture sustained thermal damage. The propeller spinner had minor impact damage, and all three wooden propeller blades separated between 9 and 12 inches outboard of the hub. The instrument panel and cabin sustained both impact and thermal damage. The right wing sustained impact and thermal damage with the landing gear retracted; the left wing was largely intact with the landing gear retracted. The left wing fuel cell was intact, while the right wing fuel cell was consumed by fire. Control continuity of the ailerons and flaps was confirmed, and the empennage was undamaged. Control continuity from the cockpit to the rudder, elevator, and trim surfaces was verified.
The engine compartment’s upper cowling was separated and came to rest about 3 ft from the engine. The left and right forward cowling areas exhibited puncture signatures emanating from the inside, with skin curling around the exterior. The left side cowling had multiple protrusions, and the right side cowling had a single protrusion.
Postaccident examination of the engine revealed that the No. 4 connecting rod was separated from the crankshaft and piston and was found adjacent to the engine. The No. 4 crankshaft journal showed material deformation with dark grey/black thermal signatures. The main bearing gallery and crankshaft oil passage were unobstructed. The No. 4 connecting rod bearing shoulders were absent, with material deformation at the base of the bearing housing and into the I-beam. The I-beam end showed thermal discoloration appearing white/light grey, with dark grey progression from the trapezoidal contour. The piston pin bushing was deformed. The No. 4 piston connecting rod cap and bearings were fracture-separated, with parts found in the engine sump. One of the cap bolts was lodged between the camshaft and crankcase; the associated nut and opposite bolt and nut were not readily identifiable, but metallic debris consistent with them was found in the oil sump.
Medical and Pathological Information
An autopsy conducted by the Clark County Coroner in Las Vegas, Nevada, determined the cause of death as thermal injuries and the manner as accident. An NTSB medical review found that postmortem peripheral blood and urine tested positive for midazolam and ketamine. Norketamine was detected in heart blood but not in urine. Both drugs have typical impairing effects and are commonly administered during medical care following major injury. The specimens were collected after the pilot’s post-crash medical care. The autopsy also identified focally severe coronary artery disease, with up to 75% narrowing of the left anterior descending coronary artery and 25% narrowing of the right coronary artery, as well as moderate aortic plaque with superficial ulceration.