Elizabethton

The pilot and three passengers departed on a cross-country flight. Shortly after the airplane climbed through 26,600 ft, the pilot stopped responding to air traffic control instructions. According to ADS-B data, the airplane continued climbing to 34,000 ft, then flew at that altitude along its flight plan waypoints, turning southwest to overfly the intended destination about 1 hour later. The airplane continued flying for about another hour along a relatively constant track and altitude before entering a spiraling descent and impacting terrain. United States Air Force (USAF) pilots intercepted the airplane about 2 minutes before it began the spiraling descent. They observed no breaches of the airplane structure or doors, no smoke in the cockpit or passenger cabin, and no oxygen masks deployed in the cabin. One occupant was observed slumped over in the pilot seat and no movement or other occupants were observed in the cabin. Based on the lack of response to air traffic control communications, ADS-B data showing the airplane following its flight plan waypoints at the altitude last assigned by air traffic control, and the USAF pilot observations, it is likely that the pilot of the accident airplane became incapacitated during the climb to cruise altitude. It is also likely the airplane trajectory was then directed by the autopilot until a point at which it was no longer able to maintain control. The pilot had medical conditions, including high blood pressure and high cholesterol, that represented some increased risk of an impairing or incapacitating cardiovascular event. In addition, the pilot had prior prescriptions for medications that could be impairing if used too recently before flight. However, there was no evidence of the pilot being at exceptionally high incapacitation risk, or of using medications inappropriately. Based on the accident circumstances, it is likely that all the airplane occupants were incapacitated due to a common environmental condition, such as loss of cabin pressurization. Maintenance records indicated that, at the time of the accident flight, five items were overdue for inspection, including the co-pilot oxygen mask. About 4 weeks before the accident flight, maintenance personnel noted 26 discrepancies that the owner declined to address, including several related to the pressurization and environmental control system. Furthermore, 2 days before the accident flight, maintenance personnel noted that the pilot-side oxygen mask was not installed, and the supplementary oxygen was at its minimum serviceable level. At that level, oxygen would not have been available to the airplane occupants and passenger oxygen masks would not have deployed in the event of a loss of pressurization. No evidence was found to indicate that the oxygen system was serviced or that the pilot-side oxygen mask was reinstalled before the accident flight. Altitude-related hypoxia, although not verifiable from forensic medical evidence, likely explains the incapacitation of the airplane occupants. According to the FAA Pilot’s Handbook of Aeronautical Knowledge, impairing effects from hypoxia are often vague and are experienced differently by different individuals; they include confusion, disorientation, diminished judgment and reactions, worsened motor coordination, difficulty communicating and performing simple tasks, a false sense of well-being, diminished consciousness, and, if conditions aren’t remedied or mitigated, death. Between 30,000 and 35,000 ft, the time of useful consciousness for a pilot to take protective action against hypoxia, including donning an oxygen mask and descending, is about 1/2 to 2 minutes. These times depend on multiple variables, including medical factors, with substantial variation among individuals. The times are decreased by about half when depressurization is rapid. However, gradual depressurization can be as dangerous or more dangerous than rapid depressurization because of its potential to insidiously impair a pilot’s ability to recognize and respond to the developing emergency until the pilot is no longer effectively able to do so. Cognitive impairment from hypoxia makes it harder for affected individuals to recognize their own impairment. Based on the available information, it is likely that the airplane occupants became hypoxic due to a lack of oxygen during the flight and became incapacitated. However, the reason for the loss of pressurization, and whether it was rapid or progressed over time, could not be determined.

The pilots were conducting a visual flight rules cross-country flight with three passengers onboard. The preflight, departure, and cruise portions of the flight were uneventful. During the initial approach to the airport, the flight crew discussed having some difficulty visually acquiring the airport. They also discussed traffic in the area and were maneuvering around clouds, which may have increased the pilots' workload. As the approach continued, the airplane crossed a ridgeline at 710 ft above ground level (agl), which triggered a terrain awareness and warning system (TAWS) alert. Further, the flight crew made several comments about the airplane flying too fast and allowed the airspeed to increase well above the reference speed (Vref) for the approach. At 1535:57 (about 1 minute 52 seconds before landing), the pilot pulled back the throttles to idle, where they stayed for the remainder of the approach. In an attempt to slow the airplane for landing, the pilot partially extended the speedbrakes when the airplane was below 500 ft agl, which is prohibited in the airplane flight manual (AFM). Five seconds before touchdown, the airplane's descent rate was 1,500 ft per minute (fpm), which exceeded the maximum allowed for landing per the AFM of 600 fpm. When the airplane first touched down, it was traveling about 18 knots above Vref. The pilot did not extend the speedbrakes upon touchdown, which the landing checklist required, but instead attempted to deploy the thrust reversers immediately after touchdown, which was a later item on the landing checklist. However, the thrust reversers did not unlock because the airplane bounced and was airborne again before the command could be executed, which was consistent with system design and logic: the thrust reversers will not unlock until all three landing gear are on the ground. The airplane touched down four times total; on the third touchdown (after the second bounce), when all three landing gear contacted the runway, the thrust reversers unlocked as previously commanded during the first touchdown. Although the pilot subsequently advanced the throttles to idle, which would normally stow the thrust reversers, the airplane had bounced a third time and had already become airborne again before the thrust reversers could stow. When the airplane became airborne, the system logic cut hydraulic power to the thrust reverser actuators; thus the reversers would not stow. The thrust reversers were subsequently pulled open due to the aerodynamic forces. The pilot attempted to go around by advancing the throttles when the airplane was airborne. However, the electronic engine controls prevented the increase in engine power because the thrust reversers were not stowed. When the airplane touched down the fourth and final time, the pilot attempted to land straight ahead on the runway; the airplane touched down hard and the right main landing gear then collapsed under the wing. The airplane departed the paved surface and came to rest about 600 ft beyond the runway threshold. The passengers and crew eventually evacuated the airplane through the main cabin door, and the airplane was destroyed in a postaccident fire. A postaccident examination of the airplane systems, structure, powerplants, and landing gear revealed no evidence of mechanical malfunctions or anomalies that would have precluded normal operation. The airplane's approach was unstabilized: its airspeed during the approach and landing well exceeded Vref and its descent rate exceeded the maximum allowed for landing just seconds before touchdown. Both the pilot and copilot commented on the airplane's high speed several times during the approach. During short final, the pilot asked the copilot if he should go around, and the copilot responded, "no." Although the copilot was the director of operations for the flight department and the direct supervisor of the pilot, the pilot stated that the copilot's position did not influence his decisions as pilot-in-command nor did it diminish his command authority. Neither the pilot nor copilot called for a go-around before landing despite awareness that the approach was unstabilized. As the airplane touched down, the pilot failed to follow the AFM guidance and used the thrust reversers before the speedbrakes. According to the airplane manufacturer's calculations, the airplane could have stopped within the length of runway available if the airplane had not bounced and the speedbrakes and wheel brakes were used at the point of the first touchdown. After the third touchdown, when the airplane became airborne again, the pilot attempted a go-around; the AFM prohibits touch-and-go landings after the thrust reversers are deployed. It is critical for pilots to know the point at which they should not attempt a go-around; a committed-to-stop (CTS) point is the point at which a go-around or rejected landing procedure will not be initiated and the only option will be bringing the aircraft to a stop. Establishing a CTS point eliminates the ambiguity for pilots making decisions during time-critical events. The FAA issued Information for Operators 17009, "Committed-toStop Point on Landings," to inform operators and pilots about the importance of establishing a CTS point; however, the director of operations was not aware of the concept of a CTS point during landing.

The ATP and his passenger were en route to pick up a patient for transport to a VA hospital. The destination airport was uncontrolled, and VFR only. The pilot cancelled with ATC and reported the field in sight. The airport was reporting VFR conditions, but rising, mountainous terrain existed to the northeast, and local authorities reported that the top third of the mountain was obscured in clouds during the morning of the accident. After cancelling IFR, no subsequent radio calls were received from the flight, and the flight did not arrive at its destination. The wreckage was found several hours later near the crest of holston mountain, 1/2 mile east of the Holston mountain VOR. An examination of the wreckage indicated the aircraft impacted upsloping, wooded terrain, while at a climb angle of 8°. Disintegration of the wreckage was indicative of a high speed impact. No evidence of mechanical malfunction or failure was found during the examination of the wreckage. Both occupants were killed.