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Mon, Apr 26, 2010

NTSB: Fatal Wave Flight Due To Loss Of Control

Pilot Was Going For Altitude Record

A well-known glider pilot, David Bigelow (69), lost his life last year while flying Hawaii's amazing mountain wave action in pursuit of an altitude record. Bigelow was a highly-experienced flyer, and a retired Air Force captain, as well as a former commercial airline pilot and member of the Mauna Kea Soaring Club. Bigelow's flight that was an attempt to set an altitude record, and was not his first such effort -- in April 2008, Bigelow had ascended to an absolute altitude of 33,561 feet. During the January 2009 attempt, the aircraft reached an ultimate altitude of 38,630 feet but broke up in flight, killing Bigelow.

The NTSB's report, released over the weekend 'determines the probable cause(s) of this accident as follows: The pilot's loss of pitch control and subsequent exceedance of the glider's airspeed limit for undetermined reasons.'

Full NTSB Report -- WPR09FA089

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.


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.

File Photo-Glaser Dirks


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.”

File Photo-Glaser Dirks


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.

File Photo-Glaser Dirks


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 cockpit noise.

Data corresponding to a logged flight dated January 16, 2009, began at 0902:51 with a latitude/longitude position fix corresponding to Waimea-Kohala Airport. The glider took off from Waimea-Kohala and flew south-southwest to ride lift that was near the mountains behind the town of Holualoa. The flight then proceeded east-northeast to ride the lift up again over Mauna Kea. The flight then proceeded south-southwest to rise up over Mauna Loa, where the flight abruptly ended with a rapid descent almost directly down. The final 20 minutes of the flight shows the glider entering the area from the north and making one s-turn searching for lift before proceeding a short distance further. The glider began s-turning upwind, then turned back to the north. After flying a short distance, the glider began exploring the area just downwind of Steaming Cone, making one left 360, followed by a right 360. The glider began to make a second right 360 when the rapid descent ensued. The recording ended approximately 1 minute later. The glider reached a maximum pressure altitude of 36,846 ft (38,716 ft GPS derived altitude), at 1314:59; about 1 minute 40 seconds before the end of the recording. During the last 3 minutes 20 seconds of recorded data the ground speed is seen to begin rapidly varying between about 75 mph and 150 mph with a period of about 10 seconds. After the first cycle the GPS altitude begins to decrease, and after about 2 ½ cycles the ground speed begins to drop dramatically. At 1315:47, the ground speed levels off at about 20 mph with a GPS altitude of 31,439 ft. The recording ended 42 seconds later at a GPS altitude of 11,825 ft; an equivalent descent rate of about 28,000 fpm.

A plot of the glider’s track during the last 6 minutes of the recording illustrates large radius curves consistent with controlled constant rate turns. Three minutes and twelve seconds from the end of the recording, at 38,630 feet, the track abruptly becomes linear, heading in a southwest direction, and the rate of descent rapidly increases over the next 16 seconds to 24,000 feet per minute. Fifty-six seconds from the end of the recording the track suddenly reverses course approximately 180 degrees, and descends almost vertically until the end of the data.

The true airspeed of the glider can be estimated using the ground speed provided by the microRecorder datalogger, and calculating the rate of descent using the altitude recorded at 4-second intervals. Wind affects can be disregarded because the southwest track that is being examined is perpendicular to the prevailing winds of 315 degrees at 38,715 feet, effectively eliminating headwind or tailwind components. The true airspeed was calculated using simple trigonometric functions as the resultant vector between the rate of descent and ground speed. Between 1315:23 and 1315:43, the true airspeed is calculated at 4-second intervals to increase from 60 knots, to 120 knots, 103 knots, 180 knots, and finally 241 knots.

File Photo-Glaser Dirks

HDR-TG1 Video Recorder

The Sony HDR-TG1 is a High Definition (HD) digital video recorder capable of recording video at full 1920 x 1080 HD resolution. The video recorder was damaged beyond repair due to impact forces. A 4GB memory stick was found within the unit. The memory stick showed signs of minimal damage and was readable using a standard card reader attached to a PC. Nine MTS (MPEG Transport Stream) files were recovered from the memory stick. These files were named 00000.MTS through 00008.MTS. These files were converted to the WMV (Windows Media Video) standard and viewed on a standard PC running MS Windows.

The video files recovered represented segments of the accident flight covering the period from just prior to takeoff to about 52 minutes prior to the time of the accident. For every file, the video captured a view directly forward from a position near the pilot’s head, showing a wide-angle view of the external environment. The pilot’s knees were just visible in the bottom of the view. None of the cockpit instruments were visible and no other part of the pilot was visible.

File 00000.MTS, 1001:04-1003:20, glider takes off from runway.

File00001.MTS, 1020:36-1027:59, pilot reported reaching 10,000 feet, stated that the winds aloft were 227 degrees at 30 knots, released the tow line, and made a left turn.

File 00002.MTS, unknown, 4-second snippet.

File 00003.MTS, 1032:21-1036:44, pilot stated he is in a wave at 13,300 feet and climbing. Sounds consistent with supplemental oxygen use were recorded.

File 00004.MTS, 1052:47-1055:40, pilot reported a 300-foot-per-minute (fpm) rate of climb, winds aloft of 282 degrees at 48 knots. At 1054:27, another glider made a radio call announcing their approach to 20,000 feet. At 1055:10, pilot stated he’s passing 14,000 feet at 300 fpm.

File 00005.MTS, 1125:25-1128:07, pilot states he’s passing 17,000 feet in weak lift. At 1125:55, he reported that the oxygen is on, and his blood saturation was about 90 (%). At 1126:31, the pilot reported winds aloft of 290 degrees at 44 knots. Sounds consistent with supplemental oxygen use were recorded.

File 00006.MTS, 1159:09-1201:34, pilot stated he as at the top of the Hualalai wave at 20,700 feet. At 1159:47, he reported his blood oxygen is 89(%). At 1201:34, the pilot radioed that he is starting to head towards Mauna Kea. Sounds consistent with supplemental oxygen use were recorded.

File 00007.MTS, 1211:58-1217:37, the pilot stated he’s close to Mauna Kea at 18,800 feet. At 1215:47, the pilot made a radio call reporting that he was in lift passing through 17,000 feet at 400 fpm. At 1217:01, the pilot stated the pressure of the first oxygen bottle was 1,000 (psi), blood oxygen is 93 (%). Sounds consistent with supplemental oxygen use were recorded.

File 00008.MTS, 1222:05-1223:32, the pilot stated he was passing 20,000 feet at 800-900 fpm. At 1223:32, the pilot reported he is at 21,000 feet. Sounds consistent with supplemental oxygen use were recorded.

No further recordings were made after 1223:32.

The entire GPS Factual Report and the Digital Video Factual Report are contained in the official docket of this accident investigation.


The wreckage was located on the southeastern slope of Mauna Loa on a steep slope of barren lava rock.

The glider was retrieved by Hawaii Volcanoes National Park rangers. They reported a Plexiglas debris field near the fuselage wreckage. The canopy emergency release knob was found in the stowed position; it appeared to not have been activated. The left wing was severely damaged from its root outboard for approximately 5 feet, and was located 3.44 miles southeast of the main wreckage. The remaining outboard wing section appeared relatively undamaged and the spoiler moved freely. Its detachable one meter tip extension appeared almost undamaged; its I-beam spar extension, which was used for assembly, appeared damaged. The right wing was located with the main wreckage, was badly damaged and fractured in pieces. Its spoiler extension tubes were not damaged, but the spoiler itself was bent and deformed, and is consistent with damage as a result of ground impact forces. The right wing’s one meter detachable tip extension appeared undamaged. Its I-beam spar extension appeared undamaged. During the wreckage examination, both detachable tip extensions were found detached. The horizontal stabilizer and elevator control surfaces were not located or identified during the examination.

Examination of the wing spar carry though revealed that the left wing bottom spar cap fracture surface exhibited a flat face, and carbon fibers that were bent and buckled in a manner consistent with compression loading. The upper spar cap fracture surface was jagged with carbon fiber ends extending at different lengths, consistent with tension loading.

The cockpit, fuselage, and empennage were shattered into unrecognizable pieces. A lap belt tongue and shoulder belt tongue remained engaged in the seat harness rotary buckle. The A-14 oxygen regulator knob was set at ‘normal.’


An autopsy was performed on the pilot on January 20, 2009, at the Hilo Medical Center, by the Department of Pathology, Hilo, Hawaii. The autopsy findings state that the immediate cause of death was multiple traumatic injuries.

Forensic toxicology was performed on specimens from the pilot by the FAA Forensic Toxicology Research Team CAMI, Oklahoma City, Oklahoma. The toxicology report stated no ethanol was detected in muscle or lung tissue, and none of the listed drugs were detected in muscle tissue.


According to a recent textbook on aviation medicine, “When an altitude of about 39,000 feet is reached, breathing 100 percent oxygen, the alveolar oxygen tension falls to … a similar value to that reached at 10,000 feet when breathing air.” (Gradwell, DP. Hypoxia and Hyperventilation, in Ernsting’s Aviation Medicine, Fourth Edition (Eds. D.P. Gradwell and D.J. Rainford), Edward Arnold, London, 2006, p. 45).

Data from the Hilo airport surveillance radar (ASR) for the 30 minutes prior to the accident was reviewed. No traffic was identified as being in the vicinity of the glider prior to the accident.

FMI: www.ntsb.gov/ntsb/brief.asp?ev_id=20090117X00043&key=1


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