Colorado Aviation Accidents & Incidents

HISTORY OF FLIGHT

On April 1, 2011, about 1715 mountain daylight time, a Burkhart Grob Flugzeugbau G102 Club Astir IIIB glider, N633BG, was substantially damaged upon collision with high voltage transmission wires and terrain near Boulder, Colorado. The private glider pilot was fatally injured. The glider was registered to Mile High Youth Gliding Association, Inc., and operated by Mile High Gliding under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which operated without a flight plan. The flight originated from Boulder Municipal Airport (BDU), Boulder Colorado, at 1628.

The pilot of the tow plane reported that the glider released from the tow plane at 13,900 feet mean sea level. The tow plane pilot characterized the air conditions as bumpy with updrafts of 1,000 feet per minute in several areas.

Several eyewitnesses reported the glider in a spiral turn towards the ground. All witnesses reported seeing a steep bank angle. One witness observed the glider level off momentarily, then pitch nose up and climb, and then pitch nose down and descend.

PERSONNEL INFORMATION

The pilot, age 46, held a private glider pilot certificate issued on September 24, 2010. A review of the pilot's logbook revealed the pilot had logged 104.4 hours total time, with a majority of the flight time logged in the accident glider.

The pilot had previously been diagnosed with diabetes and had actively monitored his blood sugar level. The pilot’s last recorded blood sugar reading was taken on the day of the accident at 1450, with a reading of 58 mg/dl. It is not known what nutrition the pilot may have had prior to flight. The pilot had reported his diabetic condition to personnel at Mile High Gliding, which required the pilot to fly with glucose tablets in order to help maintain his blood sugar levels.

AIRCRAFT INFORMATION

The single-seat, low wing glider, with composite construction, serial number 5633CD, was manufactured in 1985. A review of the maintenance logbook revealed an annual inspection was completed on May 1, 2010, at an airframe time of 2,113.4 hours. On March 19, 2011, the glider wing spar spigots were inspected in accordance with Airworthiness Directive 2011-01-03 and were found free of cracks.

METEOROLOGICAL INFORMATION

At 0630, the National Weather Service (NWS), Boulder, Colorado, released a soaring forecast for April 1, 2011. The data was based off a 0600 upper air sounding taken from Denver, Colorado. The thermal soaring index was forecasted as “excellent,” with an expected 1,122 feet per minute climb between the altitudes of 13,800 and 18,100 feet mean sea level (msl). Above the thermal layer was the potential for mountain wave turbulence between 18,000 feet and 20,000 feet msl. An upper air sounding taken at 1800 remained consistent with the 0630 sounding, with winds at 20,000 feet msl from about 310 degrees at 50 knots. Satellite imagery for the Front Ran