History of Flight
The flight departed McKinney National Airport (TKI), Texas, around 1145 central standard time, destined for Macon County Airport (1A5), Franklin, North Carolina. At 1217, while at 17,500 ft mean sea level, the pilot requested an IFR clearance to climb to 25,000 ft for an "equipment test." The airplane climbed to 25,000 ft by about 1229. At 1232, the pilot requested descent back to 17,500 ft. Radar data showed the airplane began descending before clearance. The controller asked if everything was alright; the pilot reported an "equipment issue" and canceled IFR. At 1236:39, the pilot declared an emergency. His response about the nature was unintelligible, and no further contact was established. Radar showed rapid descent from 20,400 ft at 1236:01 to 3,100 ft at 1238:13. The airplane impacted terrain about 1239.
Personnel
The pilot held a private pilot certificate issued September 6, 2016, with airplane single-engine land rating, and a third-class medical certificate issued June 1, 2016. A family member estimated he had about 250 total flight hours and about 100 hours in the accident airplane. He had recently purchased a "full face" oxygen mask and attended a high altitude/hypoxia training course about three weeks prior. The pilot-rated passenger held a private pilot certificate issued April 30, 2013, with single-engine land and instrument ratings, and a third-class medical certificate issued September 16, 2015. A family member estimated he had about 450 total hours and about 10 hours in the accident airplane.
Aircraft
The airplane, serial number 41800, was manufactured in 2007 and is also referred to as a Cessna Columbia 400. It was equipped with a Continental Motors TSIO550C engine and a Hartzell three-blade propeller, plus an anti-ice system and oxygen system. The most recent 100-hour inspections were completed June 2, 2016. The pilot purchased the airplane in August 2016. The airplane's total time was 418 hours. The most recent annual inspection was completed June 6, 2016, at 325.5 hours. On the accident morning, the airplane received 62 gallons of fuel, an oil change, and oxygen system service.
Meteorological Information
A broken to overcast cloud layer existed over Texas into Arkansas, with bases between 2,000 and 6,000 ft. The nearest weather reporting facility, Dexter B. Florence Memorial Airport, Arkadelphia, Arkansas (about 15 miles south), reported at 1256: wind 360° at 7 knots, visibility 10 miles or more, ceiling broken at 2,400 ft agl, overcast at 3,700 ft agl, temperature 3°C, dew point -2°C, altimeter 30.01 inHg. No in-flight weather advisories for turbulence, icing, or instrument conditions below 24,000 ft were current.
Wreckage and Impact
The wreckage was found in swampy, densely vegetated terrain with cypress trees, in a 4-ft-deep muddy water-filled crater. Snowfall covered much of the wreckage. Broken limbs were evident at tree tops above the crater. The airplane was severely fragmented, with pieces scattered beside the crater, and a postimpact fire ensued. The impact was consistent with a high-speed, nearly vertical, nose-down attitude. The engine and propeller were extracted. The propeller exhibited no twisting witness marks, and spinner was crushed.
Examination of recovered components: The engine could be rotated with continuity, all cylinders had thumb compression, and mud and water were expelled. The fuel pump operated and expelled a small amount of fuel. The propeller teardown showed no anomalies; blade markings indicated normal blade angle range, and bending/twisting consistent with low power or windmilling at high airspeed. Turbochargers showed no anomalies, with damage consistent with impact. The engine teardown revealed no mechanical anomalies. Flight control continuity was limited due to fragmentation; the elevator trim tab was at about 16° tab down; one speedbrake module was deployed.
Medical and Pathological Information
Autopsies of the pilot and pilot-rated passenger determined the cause of death as multiple injuries. Toxicology testing of the pilot found no ethanol or carbon monoxide; amphetamines were detected in urine (6.97 µg/ml) and blood (0.42 µg/ml). Amphetamine is a Schedule II controlled substance used for attention deficit disorders and narcolepsy, but also abused. Testing of the passenger found no ethanol; tetrahydrocannabinol carboxylic acid (marijuana inactive metabolite) was detected in liver (0.0827 µg/ml) and brain (0.0022 µg/ml); no parent THC was identified in brain.