N6500WCessna P210N · 1981

On August 29, 2018, about 2035 mountain standard time, a Cessna P210, N6500W, was destroyed when it was involved in an accident in Prescott, Arizona. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The purpose of the flight was for the pilot to acquire night currency by performing practice takeoffs and landings at the Prescott Regional Airport (PRC). He initially requested clearance from the ground controller to takeoff from runway 21L and stay in the pattern, but the controller told the pilot that the traffic pattern was full. The controller then told the pilot he could depart from and stay in the traffic pattern for 21R, which the pilot accepted.

A review of the radar track data indicated that after departure, the airplane joined a right traffic pattern for runway 21R (see figure 1). On the downwind leg, the track was not parallel to the runway and neared the approach end. The track then progressed into a long teardrop-shaped 180° turn; about 2.8 nautical miles (nm) from the approach end of runway 21R, the airplane's heading turned right toward the runway. At 2032:59 the tower controller stated to the pilot, "just verifying you're lining up for runway 21R." Four seconds later the pilot replied, "roger that, 21R, 6500W." At 2033:19 the controller told the pilot to go around.

Figure 1: Radar Track

The last recorded data point was at 2034:17 and about 740 ft northeast of the accident site. At that time, the airplane was about 5,050 ft mean sea level (msl), which was about 145 ft above ground level (agl), at a ground speed of 99 kts. At 2034:24, the controller again told the pilot to go around, to which another pilot in the pattern responded that the airplane was on fire.

The pilot had flown 32.1 hours in the accident airplane over the course of 12 flights. The pilot was based out of Prescott and recorded performing 10 landings at the airport in the accident airplane. The pilot’s personal logbooks revealed that the last time he flew in nighttime conditions was in November 2017. The logbook entry indicated that the flight occurred at PRC in a Cessna 172; the total duration of the flight was 1.8 hours, of which 0.9 hours was at night.

A review of the maintenance records revealed that, on July 24, 2018, the airplane underwent maintenance for the air conditioning system and the vacuum pumps at a tachometer time of 2,210.8 hours.

According to the U.S. Naval Observatory, Department of Astronomical Applications, the phase of the moon was waning gibbous (just past full) with 87% of the moons visible disk illuminated. Sunset was at 1859 and civil twilight was at 1925. Moonrise was at 2105 and at the time of the accident the moon was about 7.4° below the horizon (including refraction) on an azimuth (heading) of 82°.

A review of the maintenance records revealed that, on July 24, 2018, the airplane underwent maintenance for the air conditioning system and the vacuum pumps at a tachometer time of 2,210.8 hours.

The accident site was located in desert terrain about 1,890 ft from the runway 21R threshold (see figure 3). The wreckage was found distributed over a 240-ft distance on a median magnetic track of about 222°.

Figure 3: Accident Site in Reference to the Airport

The main wreckage consisted of a majority of the airframe and engine, which came to rest on a heading of about 270°. The remaining wreckage was found adjacent to the main wreckage; it principally consisted of the outboard left wing, the nose landing gear doors, a propeller blade, and nose cowling pieces.

The first identified points of contact consisted of disrupted dirt and grass on the flat desert terrain. The markings started as two nearly parallel indentations in the vegetation and dirt, spaced about 110 inches apart continued southwest toward the main wreckage. A center indentation appeared about 96 inches down the debris field and was spaced equally between the right and left craters. The craters were consistent in size and orientation to that of the landing gear wheels.

Numerous parallel ground scars that were located perpendicular to the direction of the center indentation, consistent with propeller slashes.

The fuselage came to rest upright and was partially consumed by fire. The inboard section of the left wing still had the partially consumed aileron and wing flap control surfaces attached. The outboard section was about 10 ft from the main wreckage and consumed by fire. Flap cable continuity was established from the control surface to the cockpit area; the flap handle was in the 10° position. The flap actuator jackscrew was examined, and the exposed threads was consistent with the flaps being extended between 5° and 10°. Flap cable continuity was established from the control surface to the cockpit area. The aileron cable continuity was established from the control surfaces to the control yoke assembly.

The right wing remained affixed to the fuselage with the aileron and wing flap control surfaces still attached at their respective hinges. The outboard section had less burn than the main wreckage and fuel was found in the right-wing fuel tank. Fuel system continuity could not be established due to the amount of impact and thermal damage that the airplane sustained.  Fuel was present in the left outboard wing tank.  The fuel selector valve was found in the "LEFT" position. Trace amounts of fuel were recovered from the fuel manifold.

The main landing gear up lock mechanism is in the main gear wheel well; however, the boots were burned so the condition could not be determined. The nose gear steering boots' condition could also not be determined.

The engine was intact. Investigators achieved manual rotation of the crankshaft by rotation of the crankshaft propeller flange. Thumb compression was established in all cylinders. Valve train continuity was observed, with equal lift action at each rocker assembly; oil was found in the rocker box areas on all cylinders.

Investigators removed the upper spark plugs of all cylinders; they were light gray in color. According to the Champion Aviation Check-A-Plug AV-27 Chart, these spark plug signatures corresponded to lean to normal engine operation. A borescope examination of the cylinders revealed no foreign object damage, no evidence of detonation, and no indication of excessive oil consumption. Lack of combustion deposits was consistent with low hours since overhaul and/or a lean operation.

The upper spark plugs were reattached to their respective leads and rotation of the crankshaft resulted in a visible spark at each plug; the impulse couplings were audible during rotations.

Disassembly of the fuel manifold revealed trace amounts of liquid consistent in odor to that of 100LL Avgas; there was no evidence of debris and the diaphragm was pliable. Inlet screen for the fuel metering unit was clear. The throttle body was thermally damaged. The mechanical fuel pump was intact as was the sheer shaft of the drive coupling.

The turbocharger exhibited no apparent damage and the impeller rotated freely by hand. The controller was thermally destroyed, the wastegate actuator was intact, and the respective oil lines were still attached. The vacuum pumps were removed; the vanes were all intact. Light scoring could be seen on the outside housing of both. The sheer shaft was intact.

Two of the propeller blades were in the hub, one of which was partially consumed by fire. The remaining blade was found in the debris field. The two blades that were not thermally consumed exhibited leading-edge polishing and gouges, with the tips curled aft.

The engine examination revealed that the flange on the exhaust manifold was cracked at the front crossover tube. The fracture features were consistent with reverse bending fatigue. This is a fatigue crack propagation mechanism whereby cracks initiate on opposite surfaces of a component that is being bent back and forth. The cracks propagated inward from opposite surfaces until the remaining material cross-section could no longer bear the stress, resulting in the material fracturing from overstress.

A computerized tomography (CT) scan of the heat exchanger revealed that there were several areas with significant voids. It could not be determined if these voids would create a complete gas path from one side to the other. The Cessna representative stated that even if there was a complete gas path, the pressure on the pressurization side of the heat exchanger is higher than the ram air pressure and, therefore, would leak into the side going overboard rather than being introduced into the cabin air.

The Federal Aviation Administration's (FAA) Airman Information Manual (AIM) addresses illusions encountered on approaches to landing in chapter 8-1-5. It states that a "narrower-than-usual runway can create the illusion that the aircraft is at a higher altitude than it actually is." It further states that a pilot who fails to recognize this illusion will "fly a lower approach, with the risk of striking objects along the approach path or landing short."

The AIM chapter additionally addresses runway and terrain slopes illusions, stating that an, "upsloping runway, upsloping terrain, or both, can create the illusion that the aircraft is at a higher altitude than it actually is." Again, it warns that pilots who fail to recognize this illusion will fly a lower approach.

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According to the autopsy performed by the Yavapai County Medical Examiner, the cause of death was smoke inhalation and thermal injuries.

Toxicology testing performed by the Federal Aviation Administration's Forensic Sciences Laboratory identified 35% carboxyhemoglobin in blood and ibuprofen in urine. There was no ethanol or cyanide detected in the blood samples.

Carbon monoxide (CO) is an odorless, tasteless, colorless, nonirritating gas formed by hydrocarbon combustion. In the body, CO binds to hemoglobin with much greater affinity than oxygen, forming carboxyhemoglobin; elevated levels result in impaired oxygen transport and utilization. Nonsmokers may normally have up to 3% carboxyhemoglobin in their blood; heavy smokers may have levels of 10 to 15%. Acutely low levels of CO may cause vague symptoms like headache and nausea but increased levels (40% and above) lead to confusion, seizures, loss of consciousness, and death.

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