Volcano, HI, USA
N777WN
GLASER-DIRKS DG-400
The pilot was attempting to set an altitude record over the big island of Hawaii. The glider was towed to 12,600 feet mean sea level (msl) and released about 1028. Around 1245, the pilot radioed that he was in the primary wave, climbing at 1,000 feet per minute, and was at 28,000 feet (msl). He then stated that he was going to crossover to Mauna Loa. The next day search aircraft identified widely scatted debris at 10,000 feet on the southwest face of the Mauna Loa Volcano. The glider was equipped with a flight data recorder, which depicted that the glider climbed to 20,375 feet msl near the town of Holualoa, flew east-northeast and rose to 30,116 feet msl over Mauna Kea, then proceeded south-southwest to Mauna Loa and climbed to 36,846 feet msl. Three minutes and twelve seconds from the end of the recording, at 38,630 feet, the track abruptly became linear from a constant-rate turn headed in a southwest direction, with the rate of descent rapidly increasing over the next 16 seconds to 24,000 feet per minute. At the beginning of the descent, the track exhibited a pitch oscillation before the descent rate accelerated. Fifty-six seconds from the end of the recording the track suddenly reversed course 180 degrees and descended almost vertically until the end of the data. The sudden course reversal can be associated with the structural failure of the airframe from very high aerodynamic loads. A large section of the left wing was located 3.4 miles downwind from the main wreckage, indicating that the left wing separated from the airframe at a high altitude. The spar cap fractures were consistent with a negative overload of the wing. Between 1315:23 and 1315:43, the true airspeed was calculated to increase from 60 knots to 120 knots, back to 103 knots, then 180 knots, and finally 241 knots. The operating limitation section of the glider’s flight manual lists 146 knots (270 km/h) as the red line airspeed. At 20,000 feet indicated airspeed is limited to 117 knots for flutter prevention. The manufacturer stated that the airspeed limitation can be extrapolated linearly to 40,000 feet. Due to the extensive fragmentation of the airframe, the possibility of a flight control malfunction could not be ruled out.
HISTORY OF FLIGHT On January 16, 2009, about 1300 Hawaiian standard time, an experimental Glaser-Dirks DG-400 motor-glider, N777WN, collided with mountainous terrain on the southwestern slope of Mauna Loa mountain, near Volcano, Hawaii, following an in-flight structural failure. The airline transport pilot operated the motor-glider under the provisions of Title 14 Code of Federal Regulations Part 91. The pilot was killed, and the motor-glider was destroyed. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight originated at Waimea-Kohala Airport, Kamuela, Hawaii, about 1000. A member of the Mauna Kea Soaring Club that the pilot belonged to stated that the flight was an attempt to set an altitude record. The pilot's glider had been towed to 12,600 feet mean sea level (msl) and released about 1028. Around 1245, the pilot radioed that he was in the primary wave, climbing at 1,000 feet per minute, and was at 28,000 feet (msl). He then stated that he was going to crossover to Mauna Loa. At 1644, when the pilot had not returned to Waimea-Kohala Airport at the designated time, the US Coast Guard was notified of an overdue aircraft. On January 17th, approximately 1300, search aircraft identified debris at the 10,000-foot level, on the southwest face of Mauna Loa. PERSONNEL INFORMATION The pilot, age 69, held an airline transport pilot certificate for airplane multiengine land, commercial privileges for airplane single engine land, and glider, issued on May 10, 2005. He also held a flight engineer's certificate issued on July 1, 1967, and was type rated in the Boeing 737 and DC-10. An examination of his Federal Aviation Administration (FAA) medical records revealed that his most recent medical certificate was a first-class certificate issued on September 26, 1989. Flight time information was obtained from an insurance application dated April 17, 2007. The pilot reported on the insurance application that he had 15,000 hours of flight time, 812 hours in gliders, and 83.3 hours in motor-gliders. The pilot had made a previous glider altitude record attempt on April 4, 2008, in the vicinity of the Mauna Loa Volcano, where his glider reached an altitude of 33,561 feet msl. Friends of the pilot said that he was equipped with a finger blood oxygen sensing device. A video of the pilot’s previous record flight, on April 4, 2008, to 33,561 feet, indicates that the pilot did not put the device on until approximately 18,000 to 20,000 feet. The pulse-oximeter was not located or recovered from the wreckage. A colleague stated that he and the accident pilot had purchased the same pulse-oximeter, a “Check-Mate Pulse Oximeter.” The pulse-oximeter would be worn on a finger and displayed the person's pulse rate and blood oxygen level (SpO2). It did not have a low SpO2 warning alarm. A parachute was not recovered with the pilot remains nor located within the glider wreckage. Colleagues stated that the pilot did not wear a parachute on this flight due to the bulk of the cold weather gear he was wearing. AIRCRAFT INFORMATION The single seat, retractable landing gear, motor glider (S/N) 4-116, was manufactured in 1985. The motor glider was powered by a Rotax 505, 40-horsepower engine, which retracted into the fuselage behind the cockpit when not in use. According to the members of the pilot’s soaring club, the engine had been disabled by shutting off the fuel in the engine compartment. The purpose of this was to ensure the aircraft could only operate as a glider during the altitude record attempt. The glider’s maintenance logbook recorded that the last annual inspection was performed on April 2, 2008, and the total aircraft time as recorded on July 3, 2008, was 920.9 hours. The glider’s weight and balance documentation was not located. The glider was equipped with two oxygen systems. The Mountain High EDS (Electronic Delivery System) provides metered oxygen as the pilot inhales through a mask or cannula. The second system, which the pilot used for high altitudes, utilized a US Air Force surplus A-14 Diluter-Demand Regulator and a mask that covers the nose and mouth. With this system the percentage of oxygen delivered to the user is increased with increasing altitude, becoming 100 percent at an altitude of approximately 32,000 feet. The A-14 operating instructions state for cabin pressures below 30,000 feet the regulator pressure control knob is set to ‘normal’ and the diluter lever set at 'normal oxygen.' Between 30,000 and 40,000 feet the dial is set to 'safety,' which supplies oxygen to the mask at pressures above ambient. Both oxygen systems were located on the right side of the cockpit. The EDS system was located at the pilot’s right shoulder and the A-14 system was located on the right just behind his head. Friends of the pilot said he operated this regulator by feel. A radio transmission from the pilot to his ground team indicated that he changed from the EDS system to the A-14 system between 28,000 and 29,000 feet. The A-14 regulator located in the wreckage was set to the ‘normal’ position. The operating limitation section of the glider’s flight manual lists 146 knots (270 km/h) as the red line airspeed. Additionally, in the Airspeed Limits section, the flight manual states that at 20,000 feet, indicated airspeed is limited to 117 knots for flutter prevention. The provided airspeed limit table goes from 0 feet to 20,000 feet. The manufacturer stated that the airspeed limitation can be extrapolated linearly to 40,000 feet. The flight manual states that with the cockpit loads as specified (between 154-242 lbs) the center of gravity (CG) limits will not be exceeded. The following weights were used to estimate the cockpit loads; pilot - 180 pounds, cold weather clothing – 8 lbs, two oxygen cylinders – 20 lbs. Total cockpit load was estimated to be 228 lbs. Colleagues of the pilot stated that the fuel tank was at capacity (5.25 gallons), and that the water ballast system was not used. The flight manual states that “it is not allowed to carry water ballast” for flight at high altitudes or at low temperatures, and that in temperatures below 0 degrees C “it is possible that the control circuits could become stiffer. Special care should be taken to ensure that there is no moisture on any section of the control circuits to minimize the possibility of freeze up.” METEOROLICAL INFORMATION The NWS Surface Analysis Chart for 0800 on January 16, 2009, depicted the synoptic conditions over the region. The chart depicted a low pressure system with a central pressure of 947 hectopascals (hPa) south of the Alaska Peninsula with an occluded front wrapped around the low and extending southward across the eastern Pacific Ocean turning to a cold front into the northwestern Hawaiian Islands. Another developing low pressure center was identified forming north of the Hawaiian Islands near 43 degrees north latitude, with a trough of low pressure extending south-southwestward. The Hawaiian Islands were under an increasing pressure gradient from the front and was indicated by strong south to southwesterly winds across the islands, and not the prevailing tropical easterly wind flow pattern. The 500-hPa Analysis Chart for 1400 on January 16, 2009, depicted conditions in the mean atmosphere at approximately 18,000 feet. The chart depicted the wind of 55 knots over the Hawaiian Islands with a band of maximum wind of 100 knots approximately 300 miles north of the islands. The closest weather reporting facility to the accident site was from Bradshaw Army Airfield, Camp Pohakuloa, Hawaii, located approximately 16 miles north-northwest of the accident site, at an elevation of 6,190 feet msl. Certified military weather observers take observations daily between 0700 to 1500, and are closed during holidays. A special airport notice was listed in the Airport/Facility Directory indicated that high winds and low-level wind shear are common at the airport. The following conditions were reported surrounding the period: Bradshaw Army Airfield weather observation at 1255 (2255Z): wind from 130 degrees at 12 knots gusting to 21 knots; visibility unrestricted at 10 miles; a few clouds at 3,000 feet, ceiling broken at 20,000 feet; temperature 18 degrees C; dew point -5 degrees C; altimeter 30.23 inches of Hg. Remarks: sea level pressure not available, wind data estimated. The closest upper air sounding or rawinsonde observation (RAOB) was from the NWS Hilo (PHTO), Hawaii, site number 91285, located approximately 26 miles east-northeast of the accident site at an elevation of 36 feet msl. The 1200 sounding stability indices indicated a Lifted Index (LI) of 1.4, indicating a conditionally unstable atmosphere. The K-index 10 was 8.1 indicated no support for air mass type thunderstorms. The sounding wind profile indicated surface winds from 020 degrees at 12 knots veering to the south with height through 5,000 feet, with wind speeds less than 10 knots. Above 10,000 feet the winds were from the west and increased to 43 knots at 13,000 feet and continued to veer to the northwest with height through 40,000 feet. The maximum wind was identified at 33,000 feet below the tropopause with wind from 315 degrees at 57 knots. The mean 0 to 6 kilometer (km) wind was from 266 degrees at 25 knots. At the accident airplane’s last known altitude of 38,716 feet, the wind was from 315 degrees at approximately 49 knots, with a temperature of –46 degrees C, and a relative humidity of 15 percent. The accident site was located directly downwind of Mauna Loa, and the Hilo sounding wind and temperature profile supported mountain wave activity. The sounding produced a predominate wave at 24,500 feet or 400-hPa, with wind from 305 degrees at 41 knots, with a wavelength of 9.2 miles, an amplitude of 820 feet, and maximum vertical motion of 383 feet per minute (fpm), with a 90 percent potential of light turbulence. Mountain wave activity severity is dependent on wind speed, stability, mountain height, and slope steepness. Modifying the program for slope steepness with a half mountain width of 4 miles, created a predominate wave at 25,760 feet with a wavelength of 9.2 miles, amplitude of 629 feet, maximum vertical motion of 2,938 fpm, and capable of produced severe turbulence. The RAOB default mountain wave program variables, which produces the maximum potential mountain wave amplitude by using a 1 kilometer high (3,280 feet) mountain and a half width automatically adjusted to the natural wavelength of the air stream also produced a moderate to severe wave at approximately 25,000 and 29,000 feet. No waves were detected between 32,000 and 40,000 feet. The Geostationary Operations Environmental Satellite number 11 (GOES-11) data was obtained from the National Climatic Data Center (NCDC) and displayed on the National Transportation Safety Board’s Man-computer Interactive Data Access System (McIDAS) workstation. The GOES-11 visible (band 1) image at 1230, 1300, and 1330 respectively, at 2X magnification, the image depicted clear skies over the accident site. The images depict the peak of Mauna Loa to the west and Mauna Kea to the north both covered in snow. Low stratus and stratocumulus clouds were over the northern and western portions of the island, north of the departure airport of Waimea-Kohala over the Kohala Mountains and over Kona International Airport. An arch of stratocumulus type clouds is observed over the northeast part of the island in the leeside flow of Mauna Kea. A band or line of stratocumulus clouds or specifically vortex streets are observed directly east of the island downwind indicating some blocking of the wind from the mountains across the island. The Regional Atmospheric Soaring Prediction (RASP) model data over the Hawaiian Islands was obtained for the period. The RASP is a high-resolution (1-12 kilometer) meteorological forecast designed to help soaring pilots plan their flights. These high resolution charts are particularly useful for those locations where soaring conditions can vary dramatically over short distances, as in or near complex terrain. Forecasting terrain-forced phenomena, such as terrain-channeled winds and terrain-induced convergence, requires that the terrain to be resolved and RASP is capable of providing finer-scale resolution than most National Center for Environmental Prediction (NCEP) models. The accident pilot experimented with RASP model charts along with other model data for planning his flights, along with other official NWS data. Multiple pilot reports northwest of Hilo from flight crews operating a Canadian Regional Jets (CRJ2) reported moderate turbulence between 7,000 and 13,000 feet during their climb. The cruising level of flight level was not identified. Another glider pilot who was operating in the Mauna Kea area surrounding the period (also in contact with the accident airplane) indicated that he encountered smooth conditions until he descended below 5,000 feet. The Area Forecast (FA) is an aviation forecast of general weather conditions over an area the size of several states. It is used to determine forecast en route weather and to interpolate conditions at airports that do not have Terminal Aerodrome Forecasts (TAFs) issued. The NWS Honolulu office issued the area forecast at 1203, and was valid until 2400 local. The forecast for the big Island of Hawaii interior above 7,000 feet was for a few clouds at 9,000 feet with temporarily surface winds over the mountain ridges west-to-northwest at 25 to 35 knots, with higher gusts to 60 knots with isolated broken clouds at 9,000 feet with tops to 10,000 feet. The NWS issues in-flight weather advisories for Hawaii designated as SIGMET's (WS's), and AIRMET's (WA's) serve to notify en route pilots of the possibility of encountering hazardous flying conditions, which may not have been forecast at the time of the preflight briefing. The forecast available to the pilot of N777WN prior to his departure was issued at 0545 and valid until 1200. The advisories did not expect any significant IFR or icing conditions across the Hawaiian Islands, occasional moderate turbulence was expected below 10,000 feet with conditions expected to continue beyond 1200. The outlook beyond 1200 from Kauai though Maui expected sustained surface winds greater than 20 knots due to the approaching cold front. The next schedule AIRMETs were issued at 1145 and were valid until 1800, and expected the same conditions to continue through the period. The complete Meteorological Factual Report is available in the official docket of this investigation. FLIGHT RECORDERS The pilot had equipped the gilder with an EW Avionics microRecorder that was used to document the aircraft flight utilizing GPS technology, and a Sony HDR-TG1 high definition (HD) video/audio recorder. The EW Avionics mircroRecorder was continuously recording data throughout the flight. The video recorder was used by the pilot as a video diary, where the pilot would turn it on to make some commentary then turn it off. EW Avionics microRecorder The EW Avionics microRecorder is a GPS-based flight recorder capable of logging a GPS track, engine noise measurement, and barometric pressure altitude in a secure .IGC file. The flight recorder is battery-operated using internal rechargeable batteries and can operate for up to 100 hours on a single charge. Data is stored in non-volatile FLASH memory. Logging intervals are adjustable from 1 to 10 updates per second. Logged data is continuously recorded up to the internal memory limit, after which the oldest data is replaced with new data on a first-in-first-out basis. The data recovered from FLASH memory was data-mined using standard hex editing software and stored IGC data corresponding to the accident flight was identified. Recovered data included the following parameters for each recorded (logged) data point: latitude/longitude position at the time of the update; fix validity; pressure altitude; GPS Altitude; fix validity; number of satellites in view; ground speed; and engine noise measurement. The engine noise measurement parameter is facilitated by a microphone that records cockpi
The pilot's loss of pitch control and subsequent exceedance of the glider's airspeed limit for undetermined reasons.
Source: NTSB Aviation Accident Database
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