Colorado Aviation Accidents & Incidents

HISTORT OF FLIGHT

On November 2, 1996, at 1344 mountain standard time, a Schweizer SGS 1-36, N3616Z, operated by The Cloud Base, was destroyed when it broke up in flight and impacted terrain in Boulder, Colorado. The commercial pilot was fatally injured. Visual meteorological conditions prevailed at the time, and no flight plan was filed for the personal flight conducted under Title 14 CFR Part 91. The flight originated at Boulder, Colorado, on November 2, 1996, approximately 1300.

According to the tow plane pilot, the pilot of N3616Z asked him for a tow and said he would like to leave the traffic pattern on the north side and maneuver so as to reach 8,500 (feet) msl before crossing the first ridge west of the airport. The tow plane pilot said that during the tow, he found the air to be smooth with little lift in the area. The pilot of N3616Z released from the tow at 11,300 feet msl in the vicinity of the water treatment plant by Boulder Canyon.

Numerous witnesses were interviewed and seventeen witnesses submitted written statements (attached), giving their locations and what they observed. Each witness statement was numbered and their locations were plotted on a witness location chart (attached). Twelve witnesses said they heard a loud noise. The noise was variously described as a loud boom (3, 10), snap or crack (8), clap (14), or pop (15), followed by a loud shrill (2), strong whoosh (7), or rushing sound (14). Looking up, they observed the aircraft spiraling or spinning to the ground (3, 5, 8, 9, 11, 12, 13, 15). Others said it was in a steep descent (7) or went straight down (2, 6, 10, 14). One witness (14) said it was not spinning. Witness no. 5 wrote: "When I first saw it, it was slowly spinning (1,000 feet above the ground)...At about 500 feet, it stabilized and stopped rotating, then began rotating in the other direction." Witness no 9 said it was spinning "at a rapid pace," but witness no. 12 said "it was not spiraling fast, only really slow." Witness no. 11 agreed, saying "it made a slow spiral...one rotation per second."

All of the witnesses agreed that one or both wings had failed. Two witnesses (7, 9) saw the wings strike each other. Some said the wings had folded back along the fuselage (2, 5, 10, 16). One witness no. 3 said the "starboard wing practically vertical...its port (left) wing wavering and flailing somewhat aft, (then) the right wing also appeared to loose fixity to the fuselage and began also to flail and trail aft." Witness no. 14 said "the left wing was pointing upwards and the right wing (was) folded up against the left."

One witness (1), who was almost directly underneath the glider, said it fell at a high rate of speed. Another witness (12) said "it seemed to have reached terminal velocity." Based on witness locations and the direction they were looking, the glider came across the Flatirons and was heading towards the Boulder Municipal Airport. Its altitude was estimated to be between 100