IS-28B2 N6388V accident near Wallis, Texas

Probable cause

The pilot’s failure to maintain adequate airspeed during an emergency situation, which resulted in an aerodynamic stall and subsequent impact with terrain. Contributing to the accident was the pilot’s acute coronary event, which resulted from his severe coronary artery disease, prior physical exertion, and the stress of the emergency situation.

NTSB analysis

A witness reported that, before launch, the pilot installed the tail dolly on the glider, and the ground crew then assisted him pull the glider near the normal launch position about midfield. Another witness reported that the pilot then assisted the passenger and the lapchild into the front seat of the glider and ensured that the restraints were properly latched and snug. The pilot then got in the rear seat, and he secured his own lap belt and shoulder straps. Several witnesses noticed that, after takeoff, the tail dolly was still attached to the glider, and the glider operations dispatcher made a radio call to "abort...abort...abort." The takeoff continued, and several witnesses observed both the tow plane and the glider lift off normally. When the tow plane was about 50 feet above ground level (agl), the glider suddenly pitched nose up about 45 degrees, and the tow plane disconnected from the glider and turned left. The glider subsequently turned right and continued to climb steeply until it was about 150 to 200 feet agl. The glider then began what appeared to be a controlled left turn with the nose level. While the glider was turning, witnesses saw it suddenly pitch nose down and descend. Wreckage evidence showed that the glider impacted terrain at a 30- to 45-degree nose-down angle. The glider's rapid, near-vertical descent is consistent with the pilot's loss of control of the glider because of an aerodynamic stall. An on-scene examination of the wreckage revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation.

Two other pilots reported that they had previously inadvertently made takeoffs in the same model glider with the tail dolly still attached. Both of them reported that the flight characteristics did not change in that condition. A postaccident weight and balance calculation showed that the glider's weight and balance were still within the allowable range with the addition of the tail dolly.

At the time of the accident, the pilot had cardiac hypertrophy and severe coronary artery disease. His physician had examined him 3 days before the accident and had ordered several tests. It is likely that, if the pilot had undergone a stress test, he would have failed it, and further evaluation would likely have led to a coronary artery bypass graft operation in the following few days. The pilot's wife reported that the pilot had spent the day of the accident engaging in strenuous activity, including teaching students and moving the glider around. Given the extent of coronary artery disease found on the pilot's autopsy, it is likely that the pilot's sudden awareness of the emergency situation (takeoff with the tail dolly attached) and physical exertion before the flight led to an acute coronary event and that this event contributed to his loss of control.

Text from the NTSB. Open the NTSB docket for CEN12FA378 for the full record.