Buffalo, WY, USA
N731BJ
CESSNA P210N
The pilot departed on a visual flight rules (VFR) cross-country flight. Recorded automatic dependent surveillance – broadcast (ADS-B) data showed the airplane ascended to a cruise altitude of 17,450 ft mean sea level (msl) where it remained for about 9 minutes, 17 seconds until a descent was observed. The data showed the airplane descended 2,050 ft in 12 seconds, followed by brief 175 ft ascent. The airplane then descended 1,075 ft during the final 4 seconds of ADS-B data, which equated to about a 12,000 ft-per-minute descent rate. The last recorded ADS-B target was located about .46 miles northwest of the accident site, about 5,680 ft above ground level (agl). A witness located about 4 miles south of the accident site reported that they heard the airplane and it sounded fine until they heard a distinct over-rev of the engine, followed by the sound of the impact. Fire crews were responding to reports of a wildland fire when they located the wreckage of the airplane in rugged mountainous terrain. Based on High-Resolution Rapid Refresh (HRRR) sounding and satellite imagery, the airplane most likely encountered instrument meteorological conditions (IMC) with moderate and greater convectively induced turbulence during the last 5 minutes before the accident. Postaccident examination of the recovered wreckage revealed no evidence of any preexisting mechanical malfunction that would have precluded normal operation. The outboard 65 inches of the right wing was not located within the recovered wreckage. Given the high descent rate recorded during the final few seconds of the flight, coupled with the missing section of the wing, it’s likely that the airplane broke up in flight following an encounter with moderate or greater turbulence while in IMC. The autopsy examination was limited by the condition of the pilot’s body so it could not be determined if there may have been an impairing or incapacitating event. While the impairing anxiolytic medication diazepam and its metabolites were found in liver tissue, there were no blood specimens available to determine if the medication was at a therapeutic level. Thus, whether the pilot’s medical conditions and effects from his use of diazepam were a factor in this accident could not be determined from the available medical evidence.
HISTORY OF FLIGHTOn July 14, 2022, about 1231 mountain daylight time, a Cessna P210N, N731BJ, was destroyed when it was involved in an accident near Buffalo, Wyoming. The pilot and passenger were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. Recorded ADS-B data showed the airplane departed from Powell Municipal Airport, Powell, Wyoming, and flew along a southeasterly course while it ascended to an altitude of 17,450 ft msl. The airplane remained at that altitude for about 9 minutes 17 seconds until it descended to an altitude of 15,400 ft msl within about 12 seconds (see Figure 1). The data showed that about 2 seconds later, the airplane ascended to 15,575 ft msl, which was followed by a descent to 14,500 ft msl over the last 4 seconds of recorded ADS-B data. The last recorded data point was located about .46 miles northwest of the accident site at an altitude of 5,680 ft agl. Figure 1: Plotted ADS-B Data According to local law enforcement, fire crews were responding to reports of a wildland fire when they located the wreckage of the airplane in rugged mountainous terrain about 14 miles west-northwest of Johnson County Airport, Buffalo, Wyoming. A witness who was riding a horse about 4 miles south of the accident site reported that they heard the accident airplane, and it “sounded normal until just before impact.” The witness stated that they heard a “distinct over-rev of the engine and then heard the impact.” METEOROLOGICAL INFORMATIONThe accident site was located between a high-pressure and low-pressure system that had a weak pressure gradient over the area. The closest official weather reporting site to the accident site was at Johnson County Airport (BYG), Buffalo, Wyoming, located about 12 miles east of the accident site at an elevation of 4,970 ft. The National Weather Service Aviation Weather Center display image for 1245 depicted general VFR conditions being reported over Wyoming with clear skies below 12,000 ft, visibility unrestricted, and variable winds, with temperatures ranging from 82º F to 90º F. The GOES-16 visible imagery showed the development of an area of clouds in the immediate vicinity of the accident site. The image from 1226 depicted clouds over the general route of the last 5 minutes of the flight. The GOES-16 infrared imagery at 1231 depicted an area of cumulus clouds over the eastern slopes of the Big Horn Mountains and in the vicinity of the accident site. The radiative cloud top temperatures in the vicinity of the accident site ranged to 253 Kelvin or -20º C, which corresponded to cloud tops near 26,000 ft based on the HRRR sounding. The clouds were moving to the east and did not remain stationary. The atmosphere was characterized as unstable with the Lifted Index (LI) 17 of -4.9, and the Convective Available Potential Energy 18 of 1,005 Joules/kilogram (J/kg), with the downdraft CAPE (DCAPE) of 841 J/kg, which supported the development of thunderstorms as indicated by the HRRR sounding from 1300 MDT. The sounding-derived maximum vertical velocities in potential convective updrafts was 45 meters/second or 90 knots. The sounding also supported strong thermals to about 18,000 ft with the estimated maximum lift of 757 ft per minute (fpm). The Universal Rawinsonde Observation analysis program depicted the potential for scattered alto-cumulus clouds at 9,500 ft agl (16,625 ft msl) near the accident airplane’s cruising level. No record that the pilot received a formal weather briefing was found. WRECKAGE AND IMPACT INFORMATIONLocal law enforcement reported that the wreckage impacted a hillside within mountainous terrain. Due to limited site accessibility access, the National Transportation Safety Board did not travel to the accident site. Examination of the recovered wreckage revealed that the outboard portion of the left wing from wing station (WS) 112 to the wingtip end rib was recovered. The speed brake was observed around WS 112. The inboard portion of the left wing spar was intact from WS 25 to WS 41. Wing structure between WS 41 to WS 112 was not identified within the recovered wreckage. Three of the four left wing fittings/lugs remained attached, and one wing fitting was separated. The wing fitting/lug fracture surface was consistent with overload. The recovered portions of the left wing exhibited varying degrees of impact and fire damage. About 27 inches of the outboard left aileron was located within the recovered wreckage. The right wing spar exhibited a 90° bend between WS 25 to WS 94. The spar continued outboard to WS 143. Wing structure from WS 143 to WS 208 was not identified within the recovered wreckage. The right aileron bell crank, which was located about WS 170, was observed within the recovered wreckage; however, it had separated from the right wing structure. The wing structure other than the main wing spar was separated and not identified within the recovered wreckage. The right wing main spar lower lugs were missing and severe heat/thermal damage was observed within their respective areas. No identified remains of the right aileron or flap were observed within the recovered wreckage. The right speed brake was found in the recovered wreckage. The fuselage was severely fragmented and mostly consumed by fire. Portions of the instrument panel, doors, door posts, seats and instruments were located throughout the recovered debris. The outboard 35 inches of the left elevator, including the left counterweight, was recovered. The right elevator counterweight and a 12-inch outboard portion of the right elevator was observed within the recovered wreckage. Additional portions of the right elevator, right trim tab, and portions of the right horizontal stabilizer were identified within the recovered wreckage. About 37 inches of vertical stabilizer rear spar and 31 inches of rudder remained attached, which included the center and lower hinges. A portion of the rudder and stabilizer were identified within the recovered wreckage and exhibited significant thermal damage. The left and right aileron bellcranks were located within the recovered wreckage. Both the aileron and balance cable remained attached to both bellcranks. One pulley was observed in debris from the area of the cabin, which contained 3 control cables. The elevator aft bellcrank was observed. The push pull tube remained attached to both elevator torque tubes. The aft bellcrank up and down cables remained attached. The rudder control cable was not located within the recovered debris except for a portion of cable that remained attached to the forward rudder control bell cranks. Examination of the recovered engine revealed that it was impact and thermally damaged. Rotational signatures were observed throughout the compressor, with multiple stages of blades bent opposite the direction of rotation. Continuity was established throughout the compressor aft to the gas producer turbine. The gas producer turbine (N1) rotated freely by hand. No evidence of any thermal distress was observed throughout the turbine. All engine controls were not located within the recovered wreckage. MEDICAL AND PATHOLOGICAL INFORMATIONAn autopsy was performed for the Johnson County Coroner. According to the autopsy report, the cause of death was “multiple blunt force injuries from airplane crash (instantly).” No brain, heart, or lungs were available for examination. Toxicology testing performed by the Federal Aviation Administration Forensic Sciences Laboratory detected ethanol in the pilot’s muscle tissue at 0.027 grams per hectogram (gm/hg), but not in his liver tissue. N-propanol was also detected in his muscle tissue but not in his liver tissue. Tissue samples were described as having undergone putrefaction. The antianxiety medication diazepam was detected in the pilot’s liver tissue at 12 nanograms per gram (ng/gm) but not in his muscle tissue. Diazepam’s metabolite temazepam was detected in liver tissue at 503 ng/gm and muscle tissue at 121 ng/gm; its metabolite oxazepam was also detected in liver tissue. The high blood pressure medications chlorthalidone and atenolol were detected in the pilot’s liver and muscle tissue; these two medications are generally considered non-impairing. No blood specimens were available for toxicology testing. Ethanol is a social drug commonly consumed by drinking beer, wine, or liquor. It acts as a central nervous system depressant; it impairs judgment, psychomotor functioning, and vigilance. Ethanol is water soluble, and after absorption it quickly and uniformly distributes throughout the body’s tissues and fluids. The distribution pattern parallels water content and blood supply of the tissue. Ethanol can be produced after death by microbial activity, often in conjunction with other alcohols such as n-propanol. Extensive trauma increases the spread of bacteria and raises the risk of ethanol production after death. Diazepam, commonly marketed as Valium, is a sedating benzodiazepine available by prescription as a controlled substance and used to treat anxiety; it is also useful to help treat muscle spasms, alcohol withdrawal, and seizures. It is metabolized to the active metabolites nordiazepam or temazepam. These compounds are further metabolized to the active metabolite oxazepam. Diazepam and its metabolites carry the warning that they may impair the mental and physical ability to perform hazardous tasks. Drowsiness, fatigue, and muscle weakness are commonly reported side effects. Even low doses can cause confusion, slowed reaction times, and impairment of vigilance and psychomotor and cognitive skills. Diazepam has a half- life of 21 to 82 hours; temazepam has a half-life of 3 to 13 hours; and oxazepam has a half-life of 2 to 25 hours.
The pilot’s decision to continue the visual flight rules flight into localized instrument meteorological conditions, which resulted in an encounter with convective turbulence and a subsequent loss of control and in-flight breakup.
Source: NTSB Aviation Accident Database
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