WPR13FA312

The pilot’s decision to continue flight into instrument meteorological conditions, which resulted in his failure to maintain situational awareness and sufficient altitude to clear mountainous terrain.

The instrument-rated pilot departed on a visual flight rules cross-county flight. Review of radar data showed the airplane departing and then proceeding on a northeasterly heading toward the intended destination. For the first 35 minutes of flight, the airplane remained below 10,000 ft mean sea level (msl). The airplane then ascended to a maximum altitude of 17,000 ft msl, initiated a descent, and turned north. As the airplane continued to descend through 14,300 ft msl, it turned west. (The airplane operated above 10,000 ft msl for 1 hour 8 minutes.) The data then showed the airplane perform a series of 360-degree descending turns. During the series of turns, the airplane descended to 6,200 ft msl and then ascended while turning east. The last recorded radar target was located about 12 miles west of the accident site at an altitude of 9,800 ft msl. Examination of the accident site revealed that the airplane impacted mountainous terrain just below the top of a ridgeline at an altitude of about 10,679 ft msl. Airmen's meteorological information for instrument meteorological conditions (IMC), mountain obscuration, and moderate turbulence conditions below 18,000 ft were in effect throughout the area about the time of the accident. Satellite imagery depicted a layer of low clouds over the area with a thick, overcast layer of clouds over the accident site. Weather radar imagery depicted scattered echoes within the immediate vicinity of the accident site, which indicates that precipitation was falling over the area. However, due to the possibility of beam blockage from the higher terrain, the full extent and intensity of the precipitation over the accident site could not be determined. It could not be determined if the pilot obtained a weather briefing before the flight. A postaccident examination of the airframe and engine revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation. Wreckage impact signatures and radar data were consistent with continued flight toward the intended destination before the accident. It is likely that the pilot was attempting to maneuver around the IMC but did not maintain situational awareness and sufficient altitude above the mountainous terrain and entered IMC at the time of the accident. As noted, the airplane operated 1 hour 8 minutes over 10,000 ft msl; this included 42 minutes over 14,000 ft msl. The Federal Aviation Administration requires pilots to use supplemental oxygen when flying over 14,000 ft msl; however, no evidence was found that supplemental oxygen was available to or used by the pilot. The duration of flight at these altitudes without supplemental oxygen could have resulted in the pilot experiencing hypoxia, which can cause various symptoms, including headache, decreased reaction time, impaired judgment, euphoria, visual impairment, and drowsiness. The pilot's decision-making was likely significantly impaired during this period, and the radar track showed that the airplane turned away from and flew northwest beyond the intended destination. However, the data then showed the airplane descend and remain below 10,000 ft msl for the last 17 minutes of recorded data as the flight track changed direction back toward the original destination. During this period, it is likely that the symptoms of hypoxia would have largely abated.

HISTORY OF FLIGHT On December 17, 2012, about 1234 Pacific standard time, a Mooney M20F airplane, N9524M, was destroyed when it impacted terrain while maneuvering near Yosemite Valley, California. The airplane was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91. The private pilot, sole occupant of the airplane, sustained fatal injuries. Visual meteorological conditions prevailed, and a flight plan was not filed for the personal flight. The flight originated from the Santa Ynez Airport (IZA), Santa Ynez, California, about 1027 with an intended destination of Mammoth Lakes, California. A family member of the pilot reported the airplane overdue to local law enforcement the evening of December 17, 2012, after becoming concerned when the pilot had not arrived at his intended destination. The Federal Aviation Administration (FAA) issued an Alert Notification (ALNOT) for the missing airplane at 2309. An emergency locator beacon signal was not reported during the search and rescue operation. Search and rescue operations by Civil Air Patrol and local authorities were suspended on December 21, 2012. The wreckage was located by a visitor to the Yosemite National Park on July 7, 2013, near Vogelsang Peak. Review of radar data provided by the FAA revealed that following departure from IZA, the flight flew in a north easterly direction while ascending to about 8,500 feet mean sea level (msl). The data showed that the flight remained at 8,500 feet for about 22 minutes before initiating an ascent. About 4 minutes into the ascent, the flight ascended above 10,000 feet msl and leveled off at 14,500 feet msl 17 minutes later. The flight remained at altitudes around 14,500 feet for about 11 minutes before initiating an ascent. The data showed that about 18 minutes later, the flight leveled off at 17,000 feet msl, and remained there for about 1 minute before starting a descent as the flight initiated a left turn to a north westerly heading. The radar data further depicted that the flight turned to a westerly heading while descending through 14,300 feet about 10 minutes following the start of the descent. About 19 minutes into the descent, the data showed that the flight began to perform several descending 360-degree turns over the course of about 12 minutes, of which the lowest recorded altitude was 6,200 feet msl. The data further depicted that the flight began an ascent and turned to a south easterly course at an altitude of 8,800 feet msl. The flight continued an ascent for about 8 minutes until radar contact was lost. The last recorded radar target was located about 12 miles west of the accident site at an altitude of 9,800 feet msl. PERSONNEL INFORMATION The pilot, age 68, held a private pilot certificate with an airplane single-engine land and instrument-airplane ratings. A third-class airman medical certificate was issued on March 3, 2011, with no limitations stated. The pilot reported on his most recent medical certificate application that he had accumulated 3,000 total flight hours. Review of the pilot's logbook revealed that as of the most recent logbook entry dated October 16, 2012, he had accumulated 3,033.8 hours of total flight time, of which 0.2 hours were within the previous 90 days to the accident. No actual instrument or simulated instrument flight time was logged since April, 2009. AIRCRAFT INFORMATION The four-seat, low-wing, retractable-gear airplane, serial number (S/N) 670101, was manufactured in 1966. It was powered by a Lycoming IO-360-A1A engine, serial number RL-4167-51A, rated at 180 horse power. The airplane was also equipped with a Hartzell adjustable pitch propeller. The airplane logbook records were not located. METEOROLOGICAL INFORMATION A National Transportation Safety Board (NTSB) staff meteorologist prepared a factual report for the area and time frame surrounding the accident. The southwest section of the NWS Surface Analysis Chart for 1300 depicted a low pressure system at 1013-hectopascals (hPa) over northern Idaho with a cold front extending southwestward into Nevada and northern California, where some cyclonic circulation was noted and the front became stationary, before turning back into a cold front and extending southward along the California coast. A trough of low pressure extended over western Nevada into Arizona. The accident site was located in the warm air sector immediately ahead of the approaching cold front, and west of the trough over Nevada. A 6 to 9-hPa pressure gradient existed over the eastern California and Nevada in the general location of the accident, suggesting a strong localized pressure gradient over the mountains. The NWS National Radar Mosaic from the National Climatic Data Center (NCDC) for 1230 depicted several areas of precipitation associated with rain and snow showers were depicted over northeastern California along the Sierra Nevada Mountains and in the vicinity of the accident site. The upper air sounding at 1600 from the NWS Reno (KREV), Nevada, located approximately 110 miles northwest of the accident site indicated a surface wind from 250 degrees at 24 knots with little variation in direction with height through 18,000 feet. The mean 0 to 6 kilometer (or 18,000 feet) wind was from 259 degrees at 68 knots. With the level of maximum wind was identified at 300-hPa or 30,000 feet with a wind from 260 degrees at 156 knots. The wind profile was favorable for the development of mountain wave activity with a predominate wave near 8,900 feet capable of producing severe turbulence and updraft of 1,545 feet per minute (fpm). The Geostationary Operational Environmental Satellite (GOES)-15 visible image recorded at 1230 depicted a layer of low clouds with a thick overcast layer of clouds over the accident site. A defined edge of the clouds was in the vicinity of Mammoth Lakes and Bishop California, which did not change significantly, or move with time were identified with orographic type clouds. Other defined lenticular clouds perpendicular to the wind flow were identified over southern Nevada immediately downwind from the Sierra Nevada Mountains. The image for 1235 from the Weather Surveillance Radar-1988 (WSR-88D) located in Hanford, California, depicted a large area of scattered echoes along the windward side of the Sierra Nevada's and extended into the immediate vicinity of the accident site, with echoes of 10 to 35 dBZ, which suggests that precipitation was falling over the area. However, due to the possibility of beam blockage from the higher terrain, the full extent and intensity of the echoes over the accident site could not be accurately determined. An Airmen's Meteorological Information (AIRMET) was current for mountain obscuration and moderate turbulence below 18,000 feet over the route and the accident site. Review of recorded weather data from the Mammoth Yosemite Airport (KMMH), located 30 miles southeast of the accident site revealed at 1235 wind was from 320 degrees at 8 knots gusting to 19 knots, visibility unrestricted at 10 miles, scattered clouds at 5,000 feet, ceiling broken at 7,000 feet, temperature 5 degrees Celsius (C), dew point -4 degrees C, altimeter 29.96 inches of mercury. A review of the observations from 0800 through 1400 indicated strong southwesterly winds of 25 knots with gusts to approximately 40 knots prior to the accident, with VFR conditions prevailing at the airport. During the evening hours after 2100, the weather deteriorated with IFR conditions in light to moderate snow, which continued into the morning hours of December 18. Columbia Airport (O22), located approximately 53 miles west-northwest of the accident site at an elevation of 2,119 feet, recorded weather data at 1235 was wind from 160 degrees at 7 knots, visibility 1 ½ miles, Ceiling overcast at 400 feet, temperature and dew point 9 degrees C, altimeter 30.01 inches of Hg. For