Lone Pine, CA, USA
N838KS
SCHLEICHER ASW-20
The pilot intended to fly along the ridgeline of a mountain range that runs south to north, accented by mountainous terrain to the west and a wide desert valley to the east. The mountain ridgeline rises between 8,000 and 12,000 feet mean sea level (msl). The glider’s datalogger recorded the glider’s position and altitude every 6 seconds as the pilot flew north along the ridgeline. The flight lasted 1 hour 12 minutes; during the last half of the flight, the glider was flying below the ridgeline and within one or two wingspans of the terrain slope. One minute before the final data point was recorded, the glider reversed course and proceeded south. The change in ground speed from 90 knots before the course reversal to 60 knots after the course reversal indicates that the glider turned into a strong southerly wind. The glider impacted the slope in a nose-low attitude and with wings parallel to the 65-degree terrain slope at 7,478-feet msl. The angle of impact is consistent with the glider being in a left turn (away from terrain) at the time of impact. No preaccident mechanical malfunctions or failures were found that would have precluded normal operation of the glider. Weather observations between two locations, one at the south end of the valley and one at the north end of the valley, indicated clear skies and warming surface temperatures. Wind magnitudes increased dramatically at the surface the hour before the accident at the northern weather observation station due to the warming surface temperatures and the developing valley breeze circulation. Typical daily orographic turbulence was most likely present near the mountainous terrain. Toxicology test results from cavity blood samples taken from the pilot revealed positive results for temazepam (sedative). The identified level of temazepam is considered to be in the therapeutic range for this medication. While it is possible that the results are reflective of the true blood level and that the pilot could have experienced some level of impairment from this medication, the investigation was unable to conlude that the pilot was impaired because the possibility of post-mortem redistribution of drugs can make the assessment of cavity blood difficult when trying to determine true blood level and impairment.
HISTORY OF FLIGHT On July 2, 2011, at 1219 Pacific daylight time, a Schleicher ASW-20, N838KS, collided with mountainous terrain 7.6 miles south-southwest of Lone Pine Airport, Lone Pine, California. The experimental category glider was operated by the owner under the provisions of Title 14 Code of Federal Regulations, Part 91. The private pilot was fatally injured, and the glider was substantially damaged. Visual meteorological conditions prevailed, and a visual flight plan had not been filed. The flight originated at Inyokern Airport, Inyokern, California, at 1109. The glider was towed airborne at 1109 from Inyokern Airport. Colleagues of the pilot stated that his intentions were to fly along the mountains of the eastern side of the Sequoia National Forrest. The glider wreckage was located along Horseshoe Meadows Road at 7,478-foot mean sea level (msl), on the eastern slope of the Sequoia National Forrest mountain range. The entire glider was in the immediate vicinity of the crash site. PERSONNEL INFORMATION The pilot, age 56, held a private pilot certificate with ratings for airplane single-engine land and glider, issued April 4, 2004, and a third-class airman medical certificate issued February 10, 2010, with the limitation that he wear lenses that correct for distant vision and possess glass that correct for near vision. Examination of the pilot’s logbook revealed that he had accumulated 339 hours of total flight time, 224 hours in gliders, and 144 hours in the accident glider make and model. His most recent flight review was performed on February 6, 2011, in a Grob 103 glider. AIRCRAFT INFORMATION The single seat, high performance glider, serial number 20599, was manufactured in 1982. Review of the glider’s maintenance logbook showed an annual inspection was performed on March 13, 2011, at a total airframe time of 1,045.54 hours. The wing span is 50 feet tip-to-tip, and the glider’s length from nose to tail is 22.3 feet. The glider was equipped with a supplemental oxygen system. METEOROLOGICAL INFORMATION Surface Observations The area surrounding the accident site was documented utilizing official National Weather Service (NWS) Meteorological Aerodrome Reports (METARs) and Specials (SPECIs). The following observations were taken from standard code and are provided in plain language, with cloud heights reported above ground level (agl). The closest weather reporting site to the accident was an Automated Weather Observing System (AWOS3) located at China Lake Naval Air Weapons Station (KNID), 3 miles northwest of China Lake, California. These observations were taken from automated equipment, and were not supplemented by a human observer. KNID was located approximately 52 miles south-southeast of the accident site at an elevation of 2,283 feet, and had a 14-degree easterly magnetic variation. The following observations were disseminated around the time of the accident: At 1156 PDT, KNID reported a variable wind at 3 knots; 10 miles visibility, clear skies below 12,000 feet; temperature of 39° C; dew point temperature of 3° C. Remarks: station with a precipitation discriminator; sea-level pressure not currently available; temperature 38.9° C; dew point temperature 2.8° C; no thunderstorm detector; maintenance is needed on the system. At 1256 PDT, KNID reported wind from 310° at 3 knots; 10 miles visibility, clear skies below 12,000 feet; temperature of 39° C; dew point temperature of -1° C. Remarks: station with a precipitation discriminator; sea-level pressure not currently available; temperature 39.4° C; dew point temperature -0.6° C; no thunderstorm detector; maintenance is needed on the system. Another weather reporting station north of the accident site was an Automated Surface Observing System (ASOS5) located at Eastern Sierra Regional Airport (KBIH), 2 miles east of Bishop, California. These observations were taken from automated equipment, and were not supplemented by a human observer. KBIH was located approximately 55 miles north-northwest of the accident site at an elevation of 4,124 feet, and had a 15-degree easterly magnetic variation. The following observations were disseminated around the time of the accident: At 0956 PDT, KBIH reported calm wind; 10 miles visibility; clear skies, temperature 29C; dew point 4C; and altimeter setting of 29.96 inches of mercury. At 1056 PDT, KBIH reported a variable wind at 4 knots; 10 miles visibility; clear skies below 12,000 feet; temperature of 33 C; dew point temperature of 3 C; and an altimeter setting of 29.95 inches of mercury. Remarks: station with a precipitation discriminator, sea-level pressure of 1008.3 hPa; temperature 32.8 C; dew point temperature 3.3 C; 6-hourly maximum temperature 32.8° C; 6-hourly minimum temperature 12.2° C; 3-hourly pressure decrease of 0.8 hPa; lightning detection system not operating. At 1156 PDT, KBIH reported wind from 160 at 15 knots with gusts to 21 knots, 10 miles visibility, clear skies below 12,000 feet, temperature of 36 C, dew point temperature of 1° C, and an altimeter setting of 29.93 inches of mercury. Remarks: station with a precipitation discriminator, sea-level pressure of 1007.4 hPa, temperature 36.1° C, dew point temperature 1.1° C, lightning detection system not operating. At 1256 PDT, KBIH reported wind from 160 at 15 knots with gusts to 23 knots; 10 miles visibility; clear skies below 12,000 feet; temperature of 37 C; dew point temperature of -1 C; and an altimeter setting of 29.92 inches of mercury. Remarks: station with a precipitation discriminator; sea-level pressure of 1007.4 hPa; temperature 37.2 C; dew point temperature -1.1 C; lightning detection system not operating. Observations from China Lake (KNID) and Bishop (KBIH) indicated clear skies and warming surface temperatures. Wind magnitudes increased dramatically at the surface from 1056 to 1156 PDT at KBIH due to the warming surface temperatures and the developing valley breeze circulation. Upper Air Sounding Data The closest upper air sounding to the accident site was from Las Vegas, Nevada (KVEF), site number 72388, located 143 miles east-southeast of the accident site with a station elevation of 2,470 feet. The 1700 PDT sounding from KVEF was plotted on a standard Skew-T log P with the derived stability parameters included (with data from the surface to 400-hPa, or 25,000 feet). These data were analyzed utilizing the RAOB (Rawinsonde Observation) software package. The sounding depicted a Lifted Condensation Level (LCL) at 20,419 feet and a Convective Condensation Level (CCL)10 at 27,951 feet. The freezing level was identified at about 17,500 feet. The precipitable water value was 0.27 inches. The KVEF sounding indicated a dry environment from the surface to 25,000 feet msl, which would not support any clouds. No layers of clouds or icing conditions were identified by RAOB. The sounding wind profile indicated a surface wind from 060 degrees at 5 knots with the wind remaining light and variable from the surface to 7,000 feet. From 7,000 feet through 18,000 feet the wind became southwesterly, and increased to 30 knots at 18,000 feet. No Low-level wind shear (LLWS) was identified by RAOB. The KVEF sounding was conditionally unstable from the surface through 17,000 feet. These conditions would have been conducive for the strong surface wind indicated at KBIH to mix vertically in the atmosphere to 17,000 feet near mountainous terrain. Such a situation could be supportive for enhanced orographic turbulence and the formation of thermals. FLIGHT RECORDERS The glider was equipped with a Cambridge Aero Instruments Model 25 Secure Flight Recorder. The unit is a flight instrument and datalogger containing sensors that detected and recorded parameters including date, time, longitude, latitude, pressure altitude, global positioning system (GPS)altitude, fix validity, and fix accuracy. The unit included an integral GPS receiver that generates International Gliding Commission (IGC)-approved secure flight logs, which are stored in non-volatile flash memory. The data was downloaded from the flight recorder and viewed using SeeYou v4.13 software by Navitor. The frequency of data recording is every 6 seconds. The data for the accident flight began at 1107:48. The glider departed Inyokern Airport via tow at 1109:40. The glider is towed to about 5,000 feet gps altitude, and released about 1114. The glider proceeds north following the 8,000- to 12,000-foot mountain ridge of the Sierra Nevada Mountains that create the western side of the Owens Valley. The glider follows the ridge line north for approximately 47 miles. From 1120 to 1145 the glider maintains altitudes between 8,500 and 10,000 feet mean sea level (msl). After 1147, the glider maintains altitudes between 9,000 and 7,000 feet msl, flying below the mountain ridge along the eastern slope. At 1218:04, the glider reverses course and proceeds back along its previous track maintaining altitudes below the mountain ridge line and flying within one or two wing spans from the terrain. Immediately upon the course reversal, the glider’s ground speed decreased from an average of 90 knots to 60 knots. The last recorded time was 1219:04, and position was approximately 720 feet north of the accident site at a gps altitude of 7,536 feet. The terrain elevation at this location is 7,427 feet (Google Earth), making the glider’s above ground level (agl) altitude 109 feet over 65-degree sloped terrain, which would place the wing tip about 25 feet from terrain. WRECKAGE AND IMPACT INFORMATION The wreckage of the glider was located by some individuals that were driving down Horseshoe Meadows Road, west of Lone Pine. The glider was on the slope below the road. The slope was measured to be 65 degrees, and characterized as loose rocks, sand, boulders, populated by scrub and numerous pine trees. The wreckage was oriented on a bearing of 090 (tail to nose). The wings remained attached to the fuselage, the tail and empennage were attached, and the cockpit was crushed from below. The pilot remained strapped into the cockpit, and was wearing an oxygen cannula. Flight control continuity was established from the cockpit controls though the L’hotelier connections out to the ailerons and elevator. Rudder continuity was established by moving the rudder and observing the rudder pedals move in concert. A Cambridge Aero Instruments, GPS Secure Flight Recorder, Model 25 (C261), serial number 0261, was recovered. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was performed on the pilot on July 11, 2011, by the Coroner’s Office of Inyo County, California. The autopsy findings state that the immediate cause of death was “Multiple traumatic injuries with exsanguination from laceration of the aorta and lungs and intracranial hemorrhages and multiple fractures.” Forensic toxicology was performed on specimens from the pilot by the FAA Forensic Toxicology Research Team CAMI, Oklahoma City, Oklahoma. The toxicology report listed the following findings: 0.076 ug/ml Diazepam detected in urine, 0.029 ug/ml Nordiazepam detected in urine, 0.921 ug/ml Oxazepam detected in urine, 0.009 ug/ml Oxazapam detected in blood, 5.465 ug/ml Temazepam detected in urine, and 0.041 ug/ml Temazepam detected in blood. Per the toxicology findings and the history provided by the accident pilot’s wife, the pilot was taking two different medications (diazepam and temazepam). These medications had not been reported to the FAA AME. Both medications are of the benzodiazepine class. Diazepam is prescribed as an anti-anxiety medication. Temazepam is a sedative hypnotic prescribed as a sleep aid. Neither medication is approved for use by airmen. Both medications may impair mental and/or physical abilities required for the performance of potentially hazardous tasks. The possibility of post-mortem redistribution of drugs can make the assessment of cavity blood difficult when trying to determine impairment.
The glider encountered a strong downward orographic wind flow and turbulence that forced it into terrain. Also causal was the pilot’s decision to operate the glider very close to the terrain.
Source: NTSB Aviation Accident Database
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