Accident Details
On October 18, 2010, at approximately 1715 eastern daylight time, a Schempp-Hirth Ventus B/16.6 glider, registration N188XP, sustained substantial damage during a forced landing near Warren-Sugarbush Airport (0B7), Warren, Vermont. The certificated private pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight, which originated at 0B7 at about 1400. The flight was conducted under 14 CFR Part 91.
According to a telephone interview, the pilot stated the glider was towed to about 1,600 feet above ground level, then climbed using ridge and thermal lift to 14,000 feet. During the return flight, he used the airbrakes multiple times to maintain a 500 foot-per-minute rate of descent. Entering the traffic pattern, he encountered moderate to strong turbulence. On the downwind leg, he experienced a strong lifting force and deployed the airbrakes fully to counteract the lift. When turning to base leg, he flew out of the lifting air into an extremely strong downdraft. He tried unsuccessfully to retract the airbrakes. Unable to reach the airport due to wind and sink rate, he selected a field south of the airport for an off-airport landing. The glider collided with trees short of the field and came to rest suspended approximately 40 feet above the ground.
Pilot Information
According to FAA records, the pilot held a private pilot certificate with ratings for airplane single-engine land and glider. He did not hold a current FAA medical certificate, which was not required for glider flights. The pilot reported 3,500 hours of flight experience, with 2,200 hours in the accident glider make and model, and 23 hours in the previous 90 days.
Glider Information
The glider was manufactured in 1986 and registered to the pilot in December 1987. It was a single-seat, high-performance, flap-equipped, T-tail glider. Maintenance records showed the last conditional inspection was on June 2, 2010, at 2,297.1 total hours. The pilot reported total time at the accident as 2,334 hours.
Weather Conditions
At 1651, weather reported at Edward F Knapp State Airport, Montpelier, Vermont (12 miles northeast) included wind from 300° at 9 knots gusting to 19 knots, overcast at 6,500 feet, 10 miles visibility, temperature 6°C, dewpoint -2°C, and altimeter 29.86 inHg.
Post-Accident Inspection
After the glider was lowered from the trees, an FAA inspector examined it. Inspection revealed substantial damage to the right wing spar about 10 feet from the fuselage; the fuselage had minor damage, and the horizontal stabilizer, tail, and left wing were undamaged. Flight control continuity was established. The dive brake handle was found to bind on the interior of the cockpit when deployed beyond the fully deployed position. The airbrake control tube and dive brake guide tubes were not lubricated. Rotating the handle back to the retracted position freed the handle to move normally. In a second interview, the pilot presumed that negative G forces from turbulence caused his arm to pull the handle beyond its normal upper limit.
The Ventus-2b Maintenance Manual states to lubricate all accessible control circuits and connecting points in the aileron and airbrake control circuits and hinges. However, the glider maintenance manual did not specifically mention lubrication of the airbrake guide tubes, nor did it specify grease type or application method. The mechanic who performed maintenance stated he lubricated the airbrakes only as prescribed in the manual and did not lubricate the guide tube for the airbrake system in the cockpit because it was not specified.