Aircraft Accident/Incident Report

Minden, Nevada 89423
Saturday, October 23, 2004 12:40 PDT

The motorized glider broke apart during a personal flight. The pilot told an acquaintance at the airport that he intended only a short flight. The acquaintance noted that the pilot did not have oxygen and offered to loan the pilot some; however, the pilot reiterated that he only intended on doing a short local flight. The glider was not equipped with gyroscopic flight attitude reference instruments. Witnesses reported hearing an engine rev up and down prior to hearing a loud bang. Several of the witnesses observed the aircraft falling from the base of the clouds with separated wings and debris following behind. Review of the weather in the area of the accident revealed there were unstable wave conditions that were reported as rapidly changing by another glider pilot. The pilot witness said the wave conditions were not very strong, nor was the mountain wave very well established. The air gap between the mountain cap cloud and the downwind lenticular clouds was rapidly closing and opening, creating an area that one moment was free of clouds and the next moment completely obscured. There were also reports of moderate turbulence in the accident area and freezing levels were reported above 9,200 feet in clouds and precipitation. The cloud tops were reported to be between 15,000 and 16,000 feet, while the bases were between 8,000 and 9,000 feet. Review of the glider's radar data revealed it was flying along a southerly heading at 14,600 feet mean sea level (msl). The glider's radar track then depicted the glider making a turn toward the northeast and enter two spiraling right turns with a rapid descent. The glider descended from 14,600 feet to 9,200 feet in 1 minute, which was the last radar return received. Post-accident examination of the composite wings revealed the right wing spar failed in two locations while the left spar failed in four locations. All of the fractures were consistent with an overload failure and were not associated with any obvious manufacturing defects. No preimpact anomalies were noted with the flight controls. The never exceed and maneuvering speeds of the glider were 135 and 100 knots, respectively. The limit load factor was established at +5.3/-2.65. The pilot did not wear a parachute due to previous back injuries and pain. He had not had a current medical certificate for more than 7 years prior to the accident, and review of his medical history revealed he had a number of medical conditions that could have resulted in an incapacitation event; however, the autopsy results were inconclusive in determining the likelihood of this possibility. He was also taking some potentially impairing medications such as brompheniramine and diazepam; however, no blood samples were available, and it was not possible to determine precisely when the drugs might have been used nor the level of potential impairment at the time of the accident.

the pilot's likely inadvertent entry into instrument meteorological conditions created by the rapidly changing cloud conditions that resulted in his spatial disorientation and exceeding the glider's ultimate design loads while in a spiral dive, which resulted in the overload failure of the wings.