On June 12, 1997, at 1518 mountain daylight time, a Bell 206L-3, N207DS, operated by Delta Bravo Sierra Corporation d/b/a DBS Air, Inc., was substantially damaged when it collided with trees while maneuvering 15 miles southwest of Weston, Colorado. The commercial pilot and four passengers escaped injury. Visual meteorological conditions prevailed, and a company VFR flight plan had been filed for the nonscheduled domestic passenger air taxi flight being conducted under Title 14 CFR Part 135. The flight originated from Trinidad, Colorado, on June 12, 1997, approximately 1405. According to the pilot's accident report, this was his fourth trip of the day over the same proposed gas pipeline route. The flight was for the purpose of conducting a raptor (bird) study, and required low and slow flight over wooded areas. The pilot noted convective clouds had been building all day. The pilot said he crested a ridge and descended into the next valley following the terrain downhill. "The wind felt like it was at a momentary lull," he wrote. "As we approached the far side of this particular valley (west side), it was obvious we were going to require a climbing 360 degree turn in order to clear the next ridge." After completing about 90 degrees of the turn, the helicopter was hit by a gust of wind from the rear, causing a "significant decrease in apparent airspeed" and the helicopter settled towards the trees. The pilot said he had to decide whether to attempt completing the turn and risk striking a tree with ground speed, or attempt a landing with zero airspeed. He chose the latter. The helicopter settled into trees and rolled over on its right side.