WPR13FA300 · Allstar PZL Glider SZD-54-2 PERKOZ

The pilot and passenger took off in the dual control-equipped glider, which used a ground-based winch launch system. Witnesses reported that the ground roll, rotation, and initial climb were uneventful with the glider maintaining a high, nose-up pitch attitude, consistent with the first phase of a winch launch. The pilot made an appropriate airspeed call to the winch operator by radio, and, a few seconds later, while the glider was about 150 to 300 ft above ground level (agl), which was well short of the typical release altitude of between 1,000 and 1,500 ft agl, the glider released from the towline. The glider maintained the same pitch angle and then banked right with an accompanying full-right rudder deflection. The glider's nose then dropped, and the glider began a right spin toward the ground and then impacted terrain in a nose-down attitude.

Postimpact examination did not reveal any anomalies with the airframe that would have precluded normal operation. The towline weak-link was intact, and the towline was continuous to the winch. The glider's line release mechanism, which could be controlled by both occupants, was functional. Given the lack of mechanical malfunction, it is likely that one of the occupants initiated the release of the glider.

The pilot, who was located in the aft seat, flew gliders regularly and was well acquainted with the airport environment, winch procedures, and accident glider operation. The passenger held an airline transport pilot license; he did not have experience flying gliders and was a passenger in the same glider earlier that day for an introductory flight.

Although the pilot's autopsy determined that he had a mildly enlarged, dilated heart and the passenger's autopsy determined that he had coronary artery disease that had been treated with a stent, neither occupant's autopsy revealed any conclusive evidence to support impairment around the time of the accident. However, toxicological analysis revealed that the vitreous urea nitrogen levels for both occupants were twice the normal levels and that their creatinine levels were normal; such results can occur in the presence of dehydration. It is possible that the high temperature (112 degrees F) that day resulted in both occupants experiencing the effects of heat stress and dehydration. Further, individuals with cardiovascular disease and dehydration may be prone to decreased cardiac output, which results in dizziness and/or degraded cognitive function.

Enough runway and overrun area remained to provide the pilot ample opportunity to perform an uneventful landing straight ahead even at the low altitude at which the glider was released. In fact, the glider club operating procedures called for a landing straight ahead following a glider release below 400 ft. The premature release and subsequent right banking turn at low altitude indicate that an unusual event likely occurred within the cabin; however, insufficient evidence existed to reach a definitive conclusion as to what occurred, including to what extent either occupant was impaired due to dehydration.

Verbatim NTSB analysis and probable cause from the NTSB dataset