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 14 CFR Part 91. The pilot was killed, and the motor-glider was destroyed. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated at Waimea-Kohala Airport, Kamuela, Hawaii, about 1000.
A member of the Mauna Kea Soaring Club stated that the flight was an attempt to set an altitude record. 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 he was going to crossover to Mauna Loa. At 1644, when the pilot had not returned, the US Coast Guard was notified of an overdue aircraft. On January 17, 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 certificate and was type-rated in the Boeing 737 and DC-10. His most recent FAA medical certificate was a first-class certificate issued on September 26, 1989. According to an insurance application dated April 17, 2007, he had 15,000 hours total 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, near Mauna Loa, reaching 33,561 feet msl.
Friends said the pilot was equipped with a finger blood oxygen sensing device. A video of the previous record flight indicated he did not put the device on until approximately 18,000 to 20,000 feet. The pulse-oximeter was not recovered from the wreckage. A colleague stated they had purchased the same model, a “Check-Mate Pulse Oximeter,” which displayed pulse rate and blood oxygen level (SpO2) but had no low SpO2 warning alarm.
A parachute was not recovered with the pilot remains nor located within the glider wreckage. Colleagues stated the pilot did not wear a parachute due to the bulk of cold weather gear.
Aircraft Information
The single-seat, retractable landing gear motor glider (serial number 4-116) was manufactured in 1985. It was powered by a Rotax 505, 40-horsepower engine, which retracted into the fuselage behind the cockpit. According to soaring club members, the engine had been disabled by shutting off the fuel in the engine compartment to ensure the aircraft operated only as a glider during the altitude record attempt. The last annual inspection was performed on April 2, 2008, and total aircraft time as of July 3, 2008, was 920.9 hours. The weight and balance documentation was not located.
The glider was equipped with two oxygen systems: a Mountain High EDS (Electronic Delivery System) and a US Air Force surplus A-14 Diluter-Demand Regulator with a mask. The A-14 regulator was set to the ‘normal’ position in the wreckage. A radio transmission indicated the pilot switched from the EDS to the A-14 system between 28,000 and 29,000 feet.
The flight manual listed 146 knots as the red line airspeed and stated that at 20,000 feet, indicated airspeed is limited to 117 knots for flutter prevention. The manufacturer stated the airspeed limitation could be extrapolated linearly to 40,000 feet.
The fuel tank was at capacity (5.25 gallons), and the water ballast system was not used. The flight manual stated that water ballast is not allowed for high altitude or low temperature flight.
Meteorological Conditions
The NWS Surface Analysis Chart for 0800 on January 16, 2009, depicted a low pressure system south of the Alaska Peninsula with an occluded front extending southward, and another developing low north of the Hawaiian Islands. The islands were under an increasing pressure gradient with strong south to southwesterly winds.
The 500-hPa Analysis Chart for 1400 showed wind of 55 knots over the islands and a band of maximum wind of 100 knots about 300 miles north.
Bradshaw Army Airfield, about 16 miles north-northwest of the accident site, reported at 1255: wind from 130 degrees at 12 knots gusting to 21 knots; visibility 10 miles; few clouds at 3,000 feet, ceiling broken at 20,000 feet; temperature 18°C; dew point -5°C; altimeter 30.23 inches Hg.
The closest upper air sounding from Hilo (PHTO) at 1200 indicated conditionally unstable atmosphere (Lifted Index 1.4). The wind profile showed surface winds from 020 degrees at 12 knots veering to the south through 5,000 feet. Above 10,000 feet, winds were from the west increasing to 43 knots at 13,000 feet, veering to the northwest through 40,000 feet. Maximum wind was at 33,000 feet from 315 degrees at 57 knots. At the glider’s last known altitude of 38,716 feet, wind was from 315 degrees at about 49 knots, temperature -46°C, and relative humidity 15%.
The sounding supported mountain wave activity, with a predominant wave at 24,500 feet (400-hPa) with wind from 305 degrees at 41 knots, wavelength 9.2 miles, amplitude 820 feet, maximum vertical motion 383 fpm, and 90% potential of light turbulence. Modifying for slope steepness created a wave at 25,760 feet with maximum vertical motion of 2,938 fpm and potential for severe turbulence. No waves were detected between 32,000 and 40,000 feet.
GOES-11 satellite imagery at 1230, 1300, and 1330 showed clear skies over the accident site. The Regional Atmospheric Soaring Prediction (RASP) model data was used by the pilot for planning.
Multiple pilot reports northwest of Hilo from CRJ2 crews reported moderate turbulence between 7,000 and 13,000 feet. Another glider pilot in the area reported smooth conditions until descending below 5,000 feet.
The Area Forecast issued at 1203 valid until 2400 local forecast for the Big Island interior above 7,000 feet: few clouds at 9,000 feet with temporary surface winds over mountain ridges west-to-northwest at 25 to 35 knots, gusts to 60 knots, isolated broken clouds at 9,000 feet tops to 10,000 feet.
AIRMETs issued at 0545 and 1145 expected occasional moderate turbulence below 10,000 feet and sustained surface winds greater than 20 knots due to an approaching cold front.
Flight Recordings
The glider was equipped with an EW Avionics microRecorder (GPS-based) and a Sony HDR-TG1 video/audio recorder.
The microRecorder data showed the flight began at 0902:51 at Waimea-Kohala. The glider took off, flew south-southwest to ride lift near Holualoa, then east-northeast over Mauna Kea, then south-southwest over Mauna Loa. The final 20 minutes showed s-turns searching for lift. The glider reached a maximum pressure altitude of 36,846 feet (GPS altitude 38,716 feet) at 1314:59. During the last 3 minutes 20 seconds, ground speed varied between about 75 mph and 150 mph with a period of about 10 seconds. At 1315:47, ground speed leveled at about 20 mph at GPS altitude 31,439 feet. The recording ended 42 seconds later at GPS altitude 11,825 feet, indicating a descent rate of about 28,000 fpm.
A plot of the last 6 minutes showed large radius curves consistent with controlled constant rate turns. Three minutes and twelve seconds from the end, at 38,630 feet, the track became linear heading southwest, and the rate of descent increased to 24,000 fpm over 16 seconds. Fifty-six seconds from the end, the track reversed course approximately 180 degrees and descended almost vertically.
True airspeed calculated between 1315:23 and 1315:43 increased from 60 knots to 241 knots.
The video recorder captured nine files from just before takeoff to about 52 minutes before the accident. The last recording ended at 1223:32. No further recordings were made.
Wreckage and Impact Information
The wreckage was located on the southeastern slope of Mauna Loa on a steep slope of barren lava rock. Hawaii Volcanoes National Park rangers retrieved the glider. A Plexiglas debris field was near the fuselage. The canopy emergency release knob was in the stowed position and appeared not activated. The left wing was severely damaged from its root outboard for approximately 5 feet, located 3.44 miles southeast of the main wreckage. The remaining outboard section appeared relatively undamaged, and the spoiler moved freely. Its detachable one-meter tip extension appeared almost undamaged; its I-beam spar extension appeared damaged. The right wing was with the main wreckage, badly damaged and fractured in pieces. Its spoiler extension tubes were not damaged, but the spoiler was bent and deformed, consistent with ground impact forces. The right wing’s detachable tip extension appeared undamaged; its I-beam spar extension appeared undamaged. Both detachable tip extensions were found detached. The horizontal stabilizer and elevator control surfaces were not located.
Examination of the wing spar carry-through revealed that the left wing bottom skin had failed in compression, and the top skin had failed in tension, consistent with an upward wing bending load. The wing root structure exhibited substantial leading-edge deformation and compression failure on the upper surface, consistent with a negative (downward) wing bending load.