WPR17FA008

The noninstrument-rated pilot's decision to depart on and continue a flight over mountainous terrain into forecast instrument metrological conditions, icing, and hazardous wind conditions that exceeded the airplanes performance capabilities and resulted in an uncontrolled descent and collision with terrain.

The noninstrument-rated private pilot was returning to his home airport along a mountainous route that he had traveled multiple times in the accident airplane. After landing for fuel at an intermediate airport, he called his wife and reported that the landing was challenging due to strong winds. He subsequently departed on the final leg of the flight, and shortly after departure, he sent her in-flight photographs which revealed limited visibility, dust storms, and lenticular cloud formations in the general direction of his intended route. The flight progressed on a relatively constant track for the next 2 hours, during which time the airplane encountered significant headwinds, which reduced its ground speed to about half of its typical cruise speed. As the airplane approached the high terrain of the Sierra Nevada mountain range, the flight track began to deviate left and right with rapid climbs and descents. During the last 1.5 minutes of flight, the airplane descended from 10,800 ft to the last radar-recorded altitude of 9,700 ft. Snow, rain, and strong wind hampered the search effort, and the wreckage was found 3 days after the accident covered in snow at an elevation of 8,630 ft, about 3,300 ft south of the last radar target and about 50 miles short of the destination airport. The debris field and airframe damage was consistent with a high-speed, right-wing-low impact. The airplane was equipped with a 406MHz emergency locator transmitter (ELT), which should have provided search and rescue teams with an accurate location of the wreckage, however, due to the severity of the impact, the ELT detached from the airframe and thereby its antenna. The pilot's injuries were determined to be non-survivable. Examination of the airframe and engine did not reveal any anomalies that would have precluded normal operation. About 30 minutes before the accident, an air traffic controller issued the pilot a frequency change, which the pilot read back correctly. Although the airplane's flight path continued, the pilot never made radio contact with the next controller, and neither that controller nor the previous controller was able to reach the pilot despite numerous attempts. It is possible that, during this portion of the flight, the pilot was occupied with maintaining control as the airplane began to experience the effects of downdrafts and mechanical turbulence while approaching mountainous terrain from the lee side. A storm was passing through the area at the time of the accident with high winds, mountain obscuration, and precipitation; these conditions were both predicted and widely disseminated in published weather products. Weather analysis revealed that, during the final minutes of flight, the airplane likely either entered or was drawn into instrument meteorological and airframe icing conditions after encountering downdrafts with velocities that exceeded the airplane's climb capability. It could not be determined whether the impact was the result of spatial disorientation after entering the instrument conditions, the encounter with downdraft conditions, or some combination of the two. Additionally, the pilot did not use his shoulder harness, and his lap belt appeared to be loose at the time of impact. He had struck his head on the cabin roof during a prior turbulence encounter, so it is possible that this happened again, leading to some form of incapacitation during the final minutes of the flight. Furthermore, none of the airplane's cargo, including folding chairs, water canisters, coolers, tools, and clothing had been secured. These items most likely began to shift during the downdraft encounters, possibly becoming a distraction, or even interfering with the pilot. Although the pilot did not receive an official weather briefing before the accident flight, he was likely using a tablet-based mobile application and ADS-B device that would have provided him with weather information; additionally, conversations with his wife about the flight and interactions with air traffic control personnel regarding a temporary flight restriction (TFR) in the area indicated that he had a source of aviation weather and flight information. After departing on the flight, the high wind conditions were apparent to the pilot given the airplane's slow ground speed, and the lenticular cloud conditions reflected the presence of mountain wave activity. Additionally, pilots on the air traffic control approach frequency that the pilot was tuned to were discussing landing options given the high wind conditions in the area. The presence of clouds at and above his flight level during the latter parts of the flight would have been obvious to the pilot. The worsening weather conditions in the region (in particular the extreme surface winds at area airports), along with the TFR, which was located just below the final segment of his route before crossing over a large lake and into remote, mountainous terrain, may have contributed to the pilot's reluctance to discontinue the flight and land. Additionally, his familiarity with the area and route, along with the relative close proximity of his destination, may have lulled him into a false sense of security, predisposing him to continue the flight.

A meteorology report was compiled by an NTSB weather specialist. The following is a summary of the complete report, which is contained in the public docket. Upper Air Charts The National Weather Surface (NWS) Storm Prediction Center constant pressure charts for 1700 depicted mid-level troughs just east and west of the accident site at 700-hPa. Troughs typically act as lifting mechanisms where enhanced lift, gusty winds, fronts, clouds, and precipitation can occur. Troughs and frontal boundaries near mountainous terrain also act to aid in the mixing of low-level air, allowing for the possibility of low-level wind shear, mountain waves, and turbulence. In addition, at 500-hPa, there was a mid-level trough west of the accident site, while at 300-hPa the accident site was located in the exit region of a jet streak, where enhanced lift, clouds, and precipitation can occur. There was a southwest wind around 50 knots at 700-hPa with the wind becoming westerly by 300-hPa. The wind increased to 80 knots by 500-hPa with a wind speed of 70 knots at 300-hPa above the accident site. Surface Observations The two closest official weather stations to the accident site were Lake Tahoe Airport (TVL), South Lake Tahoe, California, located 10 miles east-southeast at an elevation of 6,269 ft, and Minden-Tahoe Airport (MEV), Minden, Nevada, located 22 miles east-northeast at an elevation of 4,731 ft. From 1153 through 1453, observations from TVL indicated 10 miles visibility, wind generally out of the south-southwest at 17 to 21 knots gusting between 28 and 32 knots, and scattered/broken cloud layers. By 1453, clouds were broken at 4,400 ft agl with a ceiling at 7,500 ft agl. A special weather observation was issued at 1545, indicating 4 miles visibility, moderate rain, scattered clouds at 2,700 ft agl, and an overcast ceiling at 3,300 ft agl. At 1553, 1 minute after the accident, TVL reported visibility at 4 miles with moderate rain, scattered clouds at 2,400 ft agl, broken ceiling at 2,900 ft agl, overcast skies at 3,400 ft agl, temperature 8°C, dew point 5°C, and an altimeter setting of 29.87 inches of mercury. MEV reported similar observations throughout the afternoon, with visibilities ranging from 7 to 10 miles, with a brief period of light rain and 3-miles visibility during the 1415 report. At 1555, 3 minutes after the accident, MEV reported 8 miles visibility, few clouds at 3,300 ft agl, broken ceiling at 4,800 ft agl, overcast skies at 5,500 ft agl, temperature 9°C, dew point 6°C, and an altimeter setting of 29.87 inches of mercury. A 1455 observation issued for RNO shortly before the airplane passed over its Class C airspace included wind from 210° at 28 knots gusting to 41 knots, few clouds at 5,500 ft agl, scattered clouds at 7,000 ft agl, broken skies at 8,500, 18,000, and 22,000 ft agl. The closest weather reporting station to the destination airport, was Placerville Airport (PVF), Placerville, California, located at an elevation of 2,585 ft, 20 miles north of Jackson JAQ (elevation 1,694 ft). An observation at 1555 indicated wind from 190° at 13 knots, gusting to 20 knots, broken clouds at 3,400 and 5,000 ft, and an overcast ceiling at 9,000 ft. Sounding The closest official upper air sounding was from Reno, Nevada, located 43 miles northeast of the accident site at an elevation of 4,970 ft. Data derived from the 1700 sounding indicated a freezing level at 10,734 ft, with relatively dry conditions east of the Sierra Nevada mountains and a cloud layer likely near 10,000 ft. The sounding wind profile indicated wind speeds of 45 knots at 9,000 ft, with several layers of clear air turbulence indicated between the surface and 14,000 ft. The analysis of the sounding data also indicated that mountain wave conditions were likely near 10,000 ft with updrafts and downdrafts of about 2,645 ft per minute. Mountain wave conditions were also likely at 14,000 and 20,000 ft. Satellite Data Visible and infrared data from the Geostationary Operational Environmental Satellite number 15 (GOES-15) indicated that cloud cover at the accident site began around 1153 and rapidly increased in coverage from the Nevada and California border westward during the time of the flight. Lenticular cloud formations between Winnemucca and South Lake Tahoe were also observed. Based on infrared imagery and the vertical temperature profile provided by the 1700 Reno sounding, the approximate cloud-top heights over the accident site were 18,500 ft at 1545. The visible and infrared imagery indicated that there was extensive cloud cover across the accident site at the accident time, with cloud cover increasing in coverage and height with time. In addition, the lenticular clouds were likely indicative of the mountain wave conditions near the mountainous terrain. Weather Radar Data The closest NWS Weather Surveillance Radar-1988, Doppler (WSR-88D) was from Reno, Nevada, (KRGX) located 61 miles northeast of the accident site at an elevation of 8,299 ft. Level II and III radar data for base reflectivity images for the 0.5° elevation scans initiated at 1545, 1548, and 1551 indicated that the airplane flew through 5-30 dBZ base reflectivity values (light to moderate echo intensity) along the route of flight during that period. The precipitation targets moved from southwest to northeast. Due to terrain, the radar signal was likely blocked near the accident site, and it is possible that more precipitation was present in the area than indicated in the images. The weather radar data indicated that the accident flight likely flew through icing and instrument meteorological conditions while above 10,000 ft msl around the accident time. SIGMETs SIGMET November 1 was issued for the accident area before the flight departed and warned of occasional severe turbulence below 15,000 ft msl due to strong low-level winds and mountain wave activity, with strong updrafts and low-level wind shear. AIRMETs AIRMETs Tango, Zulu, and Sierra, valid for the accident period and location, were issued before the flight departed WMC and again at 1345. The AIRMETs forecast moderate icing conditions between the freezing level (which was between 6,000 and 11,000 ft msl) and 22,000 ft, instrument meteorological conditions with ceilings below 1,000 ft agl, visibility below 3 miles in precipitation and mist, and mountain obscuration conditions due to clouds, precipitation, and mist. Area Forecast The Area Forecast for the northern Sierra Nevada area, issued at 1245 and valid at the accident time, predicted a broken ceiling at 10,000 ft msl with cloud tops at 25,000 ft, widely scattered light rain showers, and a south wind of 35 knots with gusts to 45 knots. The forecast predicted a transition later in the afternoon to an overcast ceiling of 8,000 ft msl, with visibility between 3 and 5 miles in light rain and mist. Terminal Aerodrome Forecast TVL was the closest site with a NWS Terminal Aerodrome Forecast (TAF). The TAF valid at the time of the accident was issued at 1028 and included wind from 190° at 32 knots with gusts to 45 knots, greater than 6 miles visibility, a broken ceiling at 6,000 ft agl, and wind shear at 2,000 ft agl with wind from 250° at 65 knots. National Weather Service High Wind Warnings The NWS Reno office issued high wind warnings at 0408 for the accident area, with another at 1429 warning of southwest wind between 25 to 35 mph with gusts to 70 mph, and gusts on the Sierra Ridge of up to 115 mph. Wind and Temperature Aloft Forecast The NWS Winds and Temperature Aloft forecast for (KRNO), issued at 1259, indicated wind at 6,000 ft from 220° at 38 knots, at 9,000 ft from 220° at 63 knots with a temperature of 4° C, and at 12,000 ft from 230° at 61 knots with a temperature of -1° C. Weather Research and Forecasting Model Simulation A Weather Research and Forecasting Model (WRF) simulation indicated that,