N4171S

HISTORY OF FLIGHTOn December 10, 2023, about 1555 mountain standard time, a Beechcraft A36 airplane, N4171S, was substantially damaged when it was involved in an accident near Topock, Arizona. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

According to ADS-B data, the airplane departed Sun Valley Airport (A20), Bullhead City, Arizona, from runway 36 about 1533, and made a climbing right turn to the southeast. About 1535, the airplane turned left on an easterly heading and continued to climb. A summary of radio communication provided by the FAA showed that the pilot had contacted the Los Angeles Air Route Traffic Control Center (ARTCC) controller at 1141 and requested flight following services from A20 to Prescott Regional Airport—Ernest A. Love Field (PRC), Prescott, Arizona. ADS-B data showed that at 1546:49, the airplane had ascended to 11,325 ft mean sea level (msl) and began a right 180° turn.

About 1547, the pilot notified the controller that the engine was losing oil pressure and that he was returning to A20. At 1547:59, the airplane completed a 180° turn to a heading of 270° and descended to 9,650 ft msl. The data showed that the airplane descended to 6,250 ft msl over the next 2 minutes and remained on a westerly heading. At 1550, the pilot informed the controller that the engine power was set to the idle position, and he was uncertain that the airplane would make it to A20. At 1552 the controller asked the pilot if he could see any roads or freeways to make an off-airport landing, to which the pilot replied, “Not yet.” Communication between the controller and the pilot ceased at 1553, and ADS-B returns ceased at 1553:17 when the airplane’s altitude was 4,000 ft msl, the indicated airspeed was 105 kts, and the heading was 271° magnetic.

Unable to communicate with the accident airplane, the controller asked an airplane operating in the area to relay communication to the accident airplane; the pilot of the assisting airplane agreed. The pilot in the assisting airplane advised the controller that the accident pilot had transmitted that the “engine is burning up.” The assisting pilot continued to scan the area to get a visual on the accident airplane, and about 1602 reported that they may have spotted the accident airplane. About 1605, the assisting aircraft pilot visually confirmed “heavy thick smoke coming off some wreckage right at his location.” The accident site was located about 8 nm west of the last recorded ADS-B data point.

ADS-B data showed that when the airplane turned from an easterly heading to the west, it was located about 4 nm south of the Arizona proving grounds, which featured miles of wide, paved, flat surfaces. Additionally, Interstate 40 was about 4 nm west when the airplane made its turn from an easterly heading to the west (figure 1).

Figure 1. Accident airplane flight track with annotated potential off-airport landing areas. AIRCRAFT INFORMATIONAccording to the airplane’s maintenance logbooks, the last annual inspection was completed on November 1, 2023. The engine maintenance logbook indicated that when the annual inspection was completed, the total time on the engine was 2,856.4 hrs and the time since overhaul was 1,248.5 hrs. A subsequent entry in the airframe logbook dated November 3, 2023, indicated that the electroluminescent panel was removed, refurbished, and reinstalled. That maintenance entry indicated that the tachometer time and the airframe total time were 7,807.5 hrs. AIRPORT INFORMATIONAccording to the airplane’s maintenance logbooks, the last annual inspection was completed on November 1, 2023. The engine maintenance logbook indicated that when the annual inspection was completed, the total time on the engine was 2,856.4 hrs and the time since overhaul was 1,248.5 hrs. A subsequent entry in the airframe logbook dated November 3, 2023, indicated that the electroluminescent panel was removed, refurbished, and reinstalled. That maintenance entry indicated that the tachometer time and the airframe total time were 7,807.5 hrs. WRECKAGE AND IMPACT INFORMATIONThe airplane impacted rocky desert terrain while oriented on a southerly heading. The first identifiable point of contact was a boulder with blue paint transfer markings found underneath high-tension powerline wires on the north side of an unimproved road (figure 2). Fragments of the right wing’s green position light lens were found in the debris path underneath the powerlines. Additional debris within the path between the initial point of impact and the main wreckage consisted of right wing skin, a right wing rib, a fuel vent line, and a section of a propeller blade. The direction of travel from the initial point of impact to the main wreckage was oriented on a heading of about 212° magnetic and the debris path was about 132 ft in length. Additionally, between the initial point of impact and the main wreckage was a swath of terrain about 50 ft wide that exhibited thermal signatures.

Figure 2. Wreckage and debris path diagram.

The main wreckage came to rest on a heading of 333° magnetic. The engine had partially separated from the airframe and came to rest inverted. The cockpit to engine control cables for the propeller, throttle, and mixture sustained thermal damage. The propeller spinner sustained minor impact damage. All three of the wooden propeller blades separated between 9 and 12 inches outboard of the propeller hub. The instrument panel and cabin sustained impact and thermal damage. The right wing sustained impact and thermal damage, with the landing gear retracted within the wheel well. The left wing sustained impact damage but was largely intact, with the landing gear retracted within the wheel well. The left wing fuel cell was intact and was not breached. The right wing fuel cell was consumed by fire. Control continuity of the left and right wing ailerons and flaps was confirmed. The empennage was not damaged and was unremarkable. Control continuity from the cockpit to the rudder, elevator, and both trim surfaces was confirmed. The engine compartment’s upper cowling was separated from the airframe and came to rest about 3 ft from the engine. The left and right forward areas of the cowling revealed puncture signatures emanating from the inside of the cowling, with the skin curling around the exterior of the cowling (figure 3). The left side cowling sustained multiple protrusions, while the right side cowling sustained a single protrusion.

Figure 3. View of the left and right upper engine cowling protrusions.

Postaccident examination of the engine revealed that the No. 4 connecting rod was separated from the crankshaft and piston and was located adjacent to the engine. The No. 4 crankshaft journal sustained 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 not present, and there was material deformation at the base of the bearing housing and into the I-beam. The bearing end of the I-beam showed thermal discoloration that appeared white/light grey in color, with dark grey progression emanating from the trapezoidal contour at the tower base and web to the flange transition radius. The piston pin bushing was present with material deformation observed around the bushing and housing radius on both sides. The No. 4 piston connecting rod cap and bearings were fracture separated and parts of each were found in the engine sump. One of the No. 4 piston connecting rod cap bolts was found lodged between the camshaft and the crankcase. The associated connecting rod cap nut and the opposite side bolt and nut were not readily identifiable; however, metallic debris consistent with the bolt and nut was found in the oil sump. MEDICAL AND PATHOLOGICAL INFORMATIONThe autopsy of the pilot was conducted by the Clark County Coroner, Las Vegas, Nevada. The cause of death was thermal injuries, and the manner of death was an accident

An NTSB medical review revealed that the pilot’s postmortem peripheral blood and urine was positive for midazolam and ketamine. Midazolam is a benzodiazepine medication commonly administered in a healthcare setting for anesthesia and sedation. Ketamine is a dissociative anesthetic medication commonly used in a healthcare setting; it also may be misused as a recreational drug or occasionally may be administered under the supervision of a healthcare provider for treatment-resistant depression. Norketamine was detected in heart blood and was not detected in urine.

Both midazolam and ketamine have typical impairing effects. Both also are commonly administered during medical care following major injury. The tested toxicological specimens were postmortem specimens, collected after the pilot’s post-crash medical care.

The pilot’s autopsy 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 by plaque. Moderate aortic plaque with superficial ulceration was also present.

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