CEN16FA086

The non-instrument-rated pilot's decision to fly the airplane in instrument meteorological conditions at high altitude for greater than 30 minutes without the use of supplemental oxygen which resulted in hypoxia, and a subsequent loss of control. Contributing to the accident was the pilot's use of multiple impairing medications.

The noninstrument-rated private pilot was conducting a night cross-country flight in the piston-engine-powered, unpressurized airplane. According to the radar track data and ATC transcript, the pilot flew between about 14,000 ft and 18,000 ft for about the last 40 minutes of the flight. Review of weather information indicated that the airplane was likely operating in instrument meteorological conditions for most of the flight, with icing possible below 14,000 ft. About 10 minutes before the accident, the air traffic controller observed the airplane had climbed through 18,000 ft. The air traffic controller subsequently informed the pilot that he would require an instrument flight rules (IFR) clearance to fly at that altitude and asked the pilot if he wanted to file IFR.  The pilot responded, "that would be great, I just want to get over [this] so I can get back down." The controller also asked the pilot if the airplane was IFR-equipped and -capable, to which the pilot responded that he was IFR-equipped. During subsequent communications with air traffic control, the pilot's communications became inconsistent and the airplane began flying erratically with changes in direction and altitude during the final minutes of flight. The airplane entered a series of descending turns before experiencing an in-flight break-up. Examination of the wreckage revealed no preimpact mechanical malfunctions or anomalies that would have precluded normal operation. Although the airplane was equipped with a home-built system of medical-grade oxygen onboard, the valves on the bottles were found in the off positions; since the valves were inaccessible from the cockpit, was not possible for the pilot to have used oxygen during the flight. As altitude increases, the partial pressure of oxygen in the air decreases, leading to hypoxia. The FAA Aeronautical Information Manual (AIM) notes that hypoxia is a "state of oxygen deficiency in the body sufficient to impair functions of the brain," and "the effects of hypoxia are usually quite difficult to recognize, especially when they occur gradually." The AIM also states that between 12,000 and 15,000 ft "judgment, memory, alertness, coordination and ability to make calculations are impaired, and headache, drowsiness, dizziness and either a sense of well-being (euphoria) or belligerence occur." It also states "pilot performance can seriously deteriorate within 15 minutes at 15,000 ft. FAA regulations (14 CFR 91.211) require a pilot to use supplemental oxygen when operating above 12,500 ft in excess of 30 minutes and during the entire flight time when operating above FL140. The pilot's inconsistent communications and erratic flight track was characteristic of a state of hypoxia, and hypoxia likely resulted in the pilot's inability to maintain control of the airplane. Toxicological testing of the pilot revealed the presence of multiple central nervous depressants and a total of 6 psychoactive substances in his system (diazepam, nordiazepam, hydrocodone, dihydrocodeine, norcyclobenzaprine, and zolpidem). While there is no direct conversion between the liver and kidney levels and blood or serum levels of these drugs, the presences of even lesser amounts of all 6 substances in combination strongly suggests the pilot was influenced by the effects of the multiple medications he was using. It is likely that the combined effects of the 6 impairing substances he was using contributed to his unsafe decision making, which led to him to initiate the flight in the dark, over mountainous terrain, in instrument meteorological conditions, and without ensuring ready access to his oxygen system.

HISTORY OF FLIGHT On January 14, 2016 about 1745 mountain standard time (MST), a Beech C-35 single-engine airplane, N2025D, was destroyed when it impacted terrain near Meeker, Colorado. The private pilot was fatally injured. The airplane was privately owned and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. Instrument meteorological conditions prevailed, and no flight plan was filed for the personal flight, which departed Provo Municipal Airport (PVU), Provo, Utah, about 1620, with an intended destination of Granby-Grand County Airport (GNB), Granby, Colorado. Radar data indicated that, after departure, the airplane circled and climbed to an altitude about 12,000 ft mean sea level (msl) in the general area of PVU before turning east toward mountainous terrain. [Note: All radar and/or air traffic control data is reference in ft msl in this report.] The airplane continued to climb as it traveled east, reaching about 14,500 ft about 1641. The airplane maintained between about 14,000 ft and 14,500 ft until about 1653, when it descended to just below 13,000 ft. The pilot contacted air traffic control at 1704, traveling east-southeast, and was issued the current altimeter setting. The airplane continued in the same direction after initial check-in and began a climb again, the airplane had climbed above 18,000 ft by about 1736. At 1736, the controller confirmed the airplane's altitude, advised the pilot he would require an instrument flight rules (IFR) clearance to fly above 18,000 ft, and asked the pilot if he wanted to file IFR. The pilot responded, "that would be great, I just want to get over (unintelligible) so I can get back down." The controller then asked if the airplane was IFR -equipped and -capable, to which the pilot responded that he was IFR-equipped. The controller subsequently cleared the flight direct to GNB and issued a block altitude between 17,000 ft and 19,000 ft. Just after the pilot received the block altitude, the accident airplane stopped climbing about 18,400 ft; the controller subsequently asked the pilot if he could maintain 19,000 ft. The pilot responded that he was in the clouds, and the controller again asked if he could maintain 19,000 ft; the pilot responded, "we're getting there." The controller then instructed the pilot to maintain 19,000 ft. Radar data indicated that, after reaching about 18,700 ft, the airplane abruptly descended to about 17,400 ft, turned to the north, and climbed back up to about 18,500 ft. The controller advised the pilot he observed him turning north asked the pilot if he was okay, to which the pilot responded, "a little bit." Radar data indicated that the accident airplane then turned to the west, descending more rapidly as the airplane entered a right spiral. At the onset of this change in direction and descent, the controller advised the pilot that he observed him in a turn and descending and asked if he was in control, to which the pilot responded, "uh yes." The controller then advised the accident pilot not to descend lower than 11,000 ft and cleared him to descend and maintain 11,000 ft. The controller advised "that's lowest I can get you." The pilot responded "alright (unintelligible) clear there." The controller advised he did not have any [weather] reports for that area and asked if he was planning to head back to the west, to which the pilot responded, "I'm at seventeen now". The controller then advised the pilot he observed him doing some "S turns" and asked if he was proceeding to Grandby or heading back to the west. There was no response from the pilot. After two more attempts by the controller to reach the pilot, the pilot responded, "I hear you fine (unintelligible)." About 1744, the controller advised the accident pilot that Meeker airport was at his 3 o'clock and 17 miles, and there was an unintelligible response. There were no further recorded transmissions from the accident pilot. The last radar target correlated with the accident aircraft was at 1743:33 and about 14,100 ft; however, OpsVue track data continued to record, showing the airplane in a continued descent until 1744:13 and about 10,300 ft before track data terminated. OpsVue is a commercially available web-based flight tracking program. The track is derived from a combination of several surveillance sources that are combined and a "mosaic" type of flight track is produced. PERSONNEL INFORMATION The pilot, age 62, held a private pilot certificate with a rating for airplane single-engine land. The pilot did not have an instrument rating. No pilot logbooks were available for review. On his most recent Federal Aviation Administration (FAA) third-class medical certificate application, dated November 6, 2015, the pilot reported about 600 total hours of flight experience, with 20 hours in the previous six months. The medical certificate was issued with a limitation that he: must have available glasses for near vision. AIRCRAFT INFORMATION Review of preaccident photographs of the airplane showed the airplane was equipped with a homebuilt oxygen system consisting of two oxygen tanks, two vinyl oxygen masks, and the associated vinyl oxygen supply tubing. The two oxygen tanks were attached to the fuselage wall behind the bulkhead on the left side of the airplane. The oxygen supply tubing attached to each tank and ran forward toward the cockpit area. The valves on the tanks were not able to be accessed to start or stop the flow of oxygen from the cockpit. The airplane model has a service ceiling of 18,500 feet MSL. METEOROLOGICAL INFORMATION Although the pilot checked weather information prior to flight with Lockheed Martin Flight Service (LMFS), the data and weather information discussed was not able to be retrieved for this investigation. There was no indication that the pilot received any additional weather briefing information before the flight. At the time and location of the accident, AIRMETs were active for IFR conditions, mountain obscuration, moderate icing below 12,000 ft, and moderate icing between the freezing level and 17,000 ft. The Area Forecast valid at the time of the accident predicted an overcast ceiling at 10,000 ft with layered clouds to 25,000 ft. Visibility of 3 miles, mist, and light snow were forecast through 1700 with visibility increasing to 5 miles with mist after 1700. Meeker Coulter Field Airport (EEO), Meeker, Colorado, was located about 18 miles east of the accident site, at an elevation of 6,415 ft. The 1653 observation included calm wind, 9 miles visibility, light snow, an overcast ceiling at 3,900 ft agl, temperature -2°C, dew point of -8°C, and an altimeter setting of 29.89 inches of mercury. Remarks included: station with a precipitation discriminator, snow began at 1648, sea level pressure 1018.0 hPa, 1-hour precipitation trace, 6-hour precipitation trace, temperature -2.2°C, dew point -7.8°C, 6-hour maximum temperature of -0.6°C, 6-hour minimum temperature of -6.7°C, and 3-hour pressure increase of 1.0 hPa. The 1753 observation included calm wind, 10 miles visibility, an overcast ceiling at 4,300 ft agl, temperature -2°C, dew point temperature -7°C, and an altimeter setting of 29.89 inches of mercury. Remarks included: station with a precipitation discriminator, snow ended at 1658, sea level pressure 1017.1 hPa, 1-hour precipitation trace, temperature -2.2°C, dew point temperature -6.7°C. A North American Mesoscale (NAM) model sounding was created for the accident site for 1700. The sounding indicated a relatively moist vertical environment from 9,000 ft through 15,000 ft. This environment would have been conducive to cloud formation between 9,000 ft and 15,000 ft. The cloud tops likely extended higher, up to 19,000 ft according to satellite imagery and weather radar data. Icing (clear, rime, and mixed) was indicated between 9,000 ft and 14,000 ft. The 1700 MST NAM sounding was also c