WPR13FA053

The noninstrument-rated pilot’s failure to maintain clearance from terrain while maneuvering around weather.

The noninstrument-rated pilot departed on a visual flight rules cross-county flight. Visual and instrument meteorological conditions prevailed throughout the area around the time of the accident. Review of recorded radar data provided by the FAA (which did not record altitude) and recovered GPS data depicted the flight departing and proceeding on a south, southeasterly course then turning left to an easterly heading toward the intended destination; the last recorded radar return was about 1.5 miles northwest of the accident site. Throughout this timeframe, recorded GPS altitudes varied between 8,000 and 12,300 feet, however, an ascent to 13,450 feet mean sea level (msl) was recorded just before the end of recorded GPS data, about 22 miles west of the accident site. Examination of the accident site revealed that the airplane impacted trees and mountainous terrain on a southwesterly heading just below the top of a ridgeline at an altitude of about 10,030 feet msl. A postaccident examination of the airframe and engine revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation. AIRMETs for instrument meteorological conditions, mountain obscuration, and moderate icing conditions were in effect throughout the area about the time of the accident. Geostationary Operational Environmental Satellite (GOES) imagery indicated that clouds with tops of 16,700 feet msl were within the accident area, however, the cloud bases could not be determined. There was no evidence that the pilot obtained a weather briefing for the flight. Wreckage impact signatures and radar data were consistent with a right turn away from the flight's intended destination just before the accident. It is likely that the pilot did not maintain sufficient altitude above the mountainous terrain while attempting to maneuver around the instrument meteorological conditions at the time of the accident.

A portable Garmin handheld GPS unit was located during wreckage recovery. The GPS was subsequently sent to the NTSB Recorders Laboratory, Washington, DC, for further examination. The data recovered from the GPS unit showed that following departure from Stevensville, the flight ascended to about 9,500 feet mean sea level (msl), and remained between 9,000 and 10,000 feet for about 25 minutes. The data depicted a climb to about 10,500 feet over a 2 minute time frame, before descending about 8,000 feet and remaining between 8,000 feet and 9,500 feet for about 27 minutes. The data further depicted that the flight climbed to about 12,300 feet over a 12 minute time frame before a descent was observed to about 8,700 feet across 19 minutes. The remaining 27 minutes of recorded GPS data depicted that the flight climbed from 8,700 feet to an altitude of 13,450 feet at the last recorded data point near Freedom, Wyoming, about 22 miles west of the accident site. Examination of the recovered airframe revealed that the forward portion of the fuselage from the rear seats forward was fragmented. The aft portion of the fuselage from the rear seats was crushed aft to about 12 inches aft of the baggage door. The upper half of the vertical stabilizer and rudder were separated. The outboard halve of the left horizontal stabilizer and elevator was separated. The right horizontal and elevator remained attached; however, was impact damaged on the inboard leading edge and bent upwards about mid span. Both wings were fragmented into multiple pieces. The instrument panel was fragmented into multiple sections with numerous instruments displaced. The tachometer was located and displayed 1,700 rpm and 889.4 hours. Control cable continuity was established from the empennage to the rear doorpost bulkhead. Both aileron control cables were located and exhibited signatures of tension overload. The left flap cables exhibited tension overload. The right side flap cables were cut by recovery personnel. The fuel selector was in the "right fuel tank" position. The flap bar was in the stowed position. Examination of the Continental P-Ponk Aviation O-470-50 engine revealed that it was separated from the engine mount structure via all its mounts. The starter, right magneto, propeller, oil cooler, external oil filter, and carburetor were separated from the engine. The top spark plugs, starter adapter, and the vacuum pump were removed. The crankshaft was rotated by hand using a hand tool attached to the engine crankshaft. Continuity was established throughout to the rear of the engine and valve train. Thumb compression and suction was obtained on all six cylinders. All six cylinders were inspected using a borescope; all of the cylinders, valve faces, and pistons displayed normal operating signatures. The left magneto remained attached to the engine and was intact. The magneto was removed and the magneto drive shaft was rotated by hand. Spark was produced on all six terminals. The right magneto was separated from the engine and was intact. The magneto drive shaft was rotated by hand. No spark was produced on all six terminals. The right magneto was installed on a magneto test bench and produced spark on all six posts. The carburetor was impact damaged to the bottom portion of the float bowl. The mixture arm was separated. The throttle arm moved from stop to stop freely by hand. The fuel screen was removed and found free of debris. The carburetor bowl was removed. The floats were intact and as the bowl was removed, one float separated. The needle valve was intact. The vacuum pump drive coupling was intact and undamaged. The drive coupling would not rotate by hand. The vacuum pump was disassembled and the vane and rotor assembly was damaged. A postaccident examination of the airframe and engine revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation. The Sublette County Coroner conducted an autopsy on the pilot on November 28, 2012. The medical examiner determined that the cause of death was "…multiple blunt force trauma..." The FAA's Civil Aeromedical Institute (CAMI) in Oklahoma City, Oklahoma, performed toxicology tests on the pilot. According to CAMI's report, carbon monoxide, cyanide, volatiles, and drugs were tested, and had negative results. A National Transportation Safety Board (NTSB) staff meteorologist prepared a factual report for the area and time frame surrounding the accident. The National Weather Service (NWS) Surface Analysis Chart for 1400 depicted a regional high-pressure center of 1018 hectopascals (hPa) in northwestern Colorado. Station models in the region of the accident site generally depicted a light and variable wind; however some stations reported wind magnitudes of 10-15 knots. Southwest of the accident site, stations were reporting cloudy conditions, while stations northeast of the accident site were reporting relatively clear sky conditions. A regional Next-Generation Radar (NEXRAD) mosaic for 1345 did not identify any areas of reflectivity close to the accident location. Unofficial weather observations were retrieved from the Bridger Teton National Forest Avalanche Center station DEABT, which was located about 4.5 miles to the west of the accident site at an elevation of approximately 10,350 feet. Data recorded at 1345 was temperature -2.8 degrees Celsius, dew point -3.4 degrees Celsius, relative humidity 94 percent, wind from 217 degrees at 7.8 knots, gusting to 13.9 knots. Jackson Hole Airport (JAC) in Jackson, Wyoming, was located approximately 37 miles north-northwest of the accident site at an elevation of 6,451 feet. At 135, JAC reported a wind from 190 degrees at 6 knots, visibility of 8 miles, snow showers between 5 and 10 miles from the airport, few clouds at 3,500 feet above ground level (agl), ceiling broken at 5,000 feet agl, overcast cloud base at 8,000 feet agl, temperature of 4 degrees Celsius (C) and dew point temperature of -1 degrees C, altimeter setting 30.06 inches of mercury. Geostationary Operational Environmental Satellite (GOES)-13 and GOES-15 visible and infrared data indicated that there were clouds in the accident area. While it can be difficult to discriminate meteorological cloud from snow-covered terrain in individual visible images, an animation of the visible imagery surrounding the accident time assisted in identifying the meteorological clouds in the area. GOES-13 infrared data indicated cloud-top brightness temperatures near the accident site at 1345 were approximately -16 degrees C, which, when considering the NAM model sounding, corresponded to cloud-top heights of about 16,700 feet. GOES-15 infrared data indicated cloud-top brightness temperatures near the accident site at 1330 were approximately -15 degrees C, which, when considering the NAM model sounding, corresponded to cloud-top heights of about 16,100 feet. Cloud bases for the area surrounding the accident site were not determined. An Airmen's Meteorological Information (AIRMET) advisories issued at 0745 for areas of Wyoming that included the accident site. The AIRMETs advised of mountain obscuration and moderate icing between the freezing level and flight level 220. At 1345, two AIRMETs were issued for areas of Wyoming that included the accident site. The AIRMETs advised of mountain obscuration and moderate icing between the freezing level and flight level 220. For further information, see the weather study report within the public docket for this accident. It was not determined if the pilot obtained a weather briefing for the flight. The four-seat, high-wing, fixed-gear airplane, serial number (S/N) 18253398, was manufactured in 1961. It was powered by a Continental P. Ponk O-470-50 engine, serial number 291076-R. The airplane was also equipped with a McCauley D3A34C401-C adjustable pitch propeller. Review of the aircraft maintenance logbooks revealed that the most rec