Big Pine, CA, USA
N31AP
Schleicher ASW-20
The glider collided with mountainous terrain at an elevation of 11,600 feet mean sea level (msl) and was destroyed upon impact. The pilot intended to transition the area along the mountain range prior to returning to his departure point. A flight recording device was recovered from the wreckage and showed that the pilot flew 24 thermals and attempted an additional 9, and the thermaling included turns in both left and right directions. The last recording on the device showed that the glider was established in straight flight at 12,221 feet msl and then began a left turn toward higher terrain. As the left turn began, the device recorded an altitude of 12,129 feet msl and a groundspeed of 66 knots. As the turn continued, the altitude increased to 12,171 feet msl and the airspeed decayed to 56 knots. The last recording showed at altitude of 12,152 feet msl and no groundspeed was recorded. The terrain to the right of the pilot's flight path decreased in altitude and opened up to a substantial valley. The Glider Flying Handbook advises glider pilots to make all turns away from the ridge when slope soaring because a turn toward the ridge is dangerous, even if gliding seemingly well away from the ridge. Examination of the glider revealed no evidence of a preimpact malfunction of the control system.
HISTORY OF FLIGHT On July 3, 2005, about 1514 Pacific daylight time, a Schleicher ASW-20 glider, N31AP, collided with mountainous terrain in the Inyo National Park, about 15 nautical miles south-southwest of Big Pine, California, at 11,600 feet mean sea level (msl). The private pilot, also the registered owner of the glider, was operating it under the provisions of 14 CFR Part 91. The pilot sustained fatal injuries; the glider was destroyed. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot departed from the California City Airport, California City, California, about 1215, in a flight of six gliders, and planned to return that evening. In a written statement, a glider pilot flying in the group of six reported that he was the first to launch at 1200 and the accident pilot was the third to launch, about 1215. Prior to launch, it was determined that the first intended turn point would be Mount Whitney. The pilot reached Mount Whitney about 1420, and decided that the next turn point would be Coyote Flats. The pilot further stated that the lift was less than expected, so he reversed course about 6 miles south of Coyote Flats. At 1508, he was about 11,000 feet msl flying southbound, when the accident pilot passed him going northbound at 12,000 feet msl. They acknowledged each other and the pilot reported that the accident pilot sounded normal. The pilot surmised that this point was a few miles from the accident site and a few minutes prior to the accident. After 20 minutes had passed, the pilot expected to hear the accident pilot transmit a radio call so he attempted to contact him via radio. The pilot did not respond. Repeated contact attempts were made by other pilots but there was no response. When the last glider pilot returned to California City about 1830, the glider pilot group began a search effort for the accident pilot. After the initial searches were unsuccessful, the Inyo County Search and Rescue personnel were notified. On July 4th, at 1115, the wreckage was located in the mountainous terrain by the Inyo County Search and Rescue personnel. PERSONNEL INFORMATION Records obtained from the Federal Aviation Administration (FAA) showed that the pilot held a private pilot certificate for single engine land airplanes and gliders. The pilot's most recent third-class medical was issued in March 1994. The pilot's family provided a copy of the pilot's flight time logbook. Based on this logbook and interviews with friends of the pilot, his total flight time was approximately 732 hours. The pilot had flown about 30 hours in the last 90 days, 23 hours in the last 60 days, and 13 hours in the month preceding the accident. GLIDER INFORMATION The experimental Schleicher ASW-20 glider was in the exhibition and racing category, and the last condition inspection was completed June 14, 2005, at a total airframe time of 1,201.1 hours. The glider was manufactured in 1980. WRECKAGE AND IMPACT Inyo County search and rescue personnel responded to the accident site, which was located on a drainage chute of Striper Mountain in the Sierra Nevada mountain range, at an elevation of 11,600 feet msl. The crest of the mountains in the vicinity of the accident site rose between 12,300 and 12,500 feet msl. The Inyo County sheriff reported that the entire glider structure was located at the accident site. The wreckage was confined to the impact area and the nose and cockpit area of the structure were opened up and fragmented upon impact. During the initial recovery efforts, the glider wreckage slid from its original impact point and was displaced 1,000 feet below onto a glacier. Photos obtained from the initial responders showed that the glider impacted a steep rock face. The empennage section of the glider was folded over remnants of the cockpit structure. The wings remained in their respective positions but their leading edges were fragmented. Various instruments were strewn about the rock face. METEOROLOGICAL INFORMATION A glider pilot flying in the area of the accident site reported that the weather conditions included clear skies with a few scattered cumulous clouds. There were no winds aloft and there was a slight amount of turbulence associated with the thermals, which were not uncharacteristic for the flight environment. There were no abnormal weather conditions. The closest official aviation weather reporting station was Bishop, California. An aviation routine weather report was issued at 1556, and contained the following information: skies clear; visibility, 10 miles; temperature, 100 degrees Fahrenheit; dew point, -8 degrees Fahrenheit; altimeter, 29.91 inches of Mercury; wind, variable at 5 knots. MEDICAL AND PATHOLOGICAL INFORMATION The Inyo County Coroner completed an autopsy. The Federal Aviation Administration (FAA) Forensic Toxicology Research Team completed toxicological testing on specimens of the pilot. The results were as follows: 0.853 (ug/mL, ug/g) NORPROPOXYPHENE detected in Liver 0.308 (ug/mL, ug/g) NORPROPOXYPHENE detected in Spleen The tests for carbon monoxide, cyanide, and volatiles were not performed. The National Transportation Safety Board's Medical Officer reviewed the pilot's medical records obtained from the pilot's family. The records showed that over the previous year, the pilot had medical visits related to foot and shoulder injuries. The pilot was prescribed propoxyphene/ acetaminophen on June 8, 2004. There were no indications of narcotics being prescribed after June 8, 2004. TESTS AND RESEARCH The glider was recovered 2 months following the accident. The Safety Board investigator-in-charge examined the wreckage on November 18, 2005. The largest portions of the recovered wreckage were the wings. The leading edges of the wings were reduced to splinters. The wings are joined by a tongue and fork spar stub system. The right wing has two stubs that reach into the center section of the fuselage and the left stub, which is a single stub, slips between the two stubs on the right. Spar pins are used to secure the stubs together. This area was separated and sustained considerable impact damage. The flaps and ailerons were partitioned into 5- to 30-inch sections. The cabin structure was compromised upon impact and all of the control tubing was in multiple pieces. Loose instruments were found within the wreckage but their housing contents were in pieces. The empennage section was fractured from the airplane about 10 inches forward of the vertical stabilizer. Both the rudder and the elevators were dislodged from their attach points. All of the empennage control surfaces had splintered edges and sections that could not be reconstructed due to the impact damage. The glider was equipped with a Cambridge Aero 302 flight multi-function instrument. Contained within the device were an altimeter, variometer, averager, audio, accelerometer, and global positioning system (GPS) flight recording. The crushed unit was recovered from the accident site by initial rescue personnel and the data was downloaded on August 9, 2005. Two distinct flight records were contained within the unit. One record was dated July 3, 2005, and was consistent with the pilot's route of flight the day of the accident. The unit recorded the flight track data every 4 seconds. The device recording showed that pilot departed from the California City Airport. According to the flight track record, 24 thermals were used and 9 were attempted, with turns in both the left and right directions. The average cumulative groundspeed calculated for the flight was 80 knots. The last recording on the device showed that the glider began a left turn and was established in straight flight at 12,164 feet msl. A turn to the left was recorded at an altitude of 12,129 feet msl and a groundspeed of 66 knots. The track continued to the left with an approximate 50-foot gain in altitude and a decrease in groundspeed to 56 knots. The final altitude displayed on the recording was 12,152 msl with no groundspeed. Comparison of the flight track with the terrain data showed that the glider was on the eastern side of the Sierra Nevada range when the left turn towards higher terrain was initiated. The general terrain to the right of the flight track decreased in elevation and opened up into the greater Owen's Valley. ADDITIONAL INFORMATION The Glider Flying Handbook (FAA-H-8083-13) advises glider pilots to make all turns away from the ridge when slope soaring because a turn toward the ridge is dangerous, even if gliding seemingly well away from the ridge. The groundspeed on the downwind portion of the turn may be difficult to judge properly, and striking the ridge can be a serious threat. Even if above the ridge, it will be easy to finish the turn downwind of the ridge in heavy sink. Additionally, the handbook states to avoid approaching from the upwind side perpendicular to the ridge. Instead, approach the ridge at a shallower angle, so that a quick egress away from the ridge is possible should lift not be contacted. The Cambridge Aero Flight Tracking Device was released to the owner's representative on February 13, 2006. No other parts or pieces were retained.
the pilot's failure to maintain an adequate terrain clearance altitude and his decision to turn toward higher terrain.
Source: NTSB Aviation Accident Database
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