NTSB Factual Report

On July 29, 2000, at 1500 central daylight time, a Let L-23 Super Blankit non-powered glider, N105LW, was destroyed when it impacted trees following a separation of the towrope and loss of control during the initial takeoff climb from the Houston Gliderport, Waller, Texas. The glider was registered to and operated by The Soaring Club of Houston, Houston, Texas. The private pilot, who held a glider rating, sustained fatal injuries. Visual meteorological conditions prevailed and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 personal flight. The local flight was originating at the time of the accident.

According to the pilot of the towplane, the takeoff from runway 17 was normal and while climbing through 600 feet agl he initiated a left turn to the east. He reported that as the airplane was turning he "felt the glider release from the tow," and he then banked hard left to give way to the glider. Subsequently, the pilot received a radio transmission that the glider had crashed, and he returned to the airport. Upon landing it was evident that the tow rope had separated, and the glider pilot had not released in the normal manner.

According to witnesses, the initial climb-out "appeared quite normal" and "as usual, at the end of the airport the tow plane commenced a left turn." However, the glider continued straight ahead and it entered a climb. The glider was 250-300 feet agl when it began a "very uncoordinated turn to the right," and as it turned through 90 degrees, the "nose of the glider dropped and it entered a spin." Subsequently, the glider completed 1-2 turns before impacting trees and the ground. One witness, who was part of the airport crew and a wing runner for the gliders, stated that "it was picture-perfect for soaring," and "all other flights that day were without incident and none of the pilots of the Blankit that day had mentioned any problems."

The separated sections of the rope were removed from the glider attach point and from the tow plane by an FAA inspector. The rope was sent to the NTSB Investigator-In-Charge for examination. The rope was separated approximately 25 feet forward of the attach point on the glider, and the rope's fibers, at the separation point, appeared frayed and uneven. The remainder of the rope appeared clean and was free of abrasions, knots, and nicks. According to Soaring Club personnel, the rope was 5/16-inch polypropylene, with a breaking strength of 1,300 pounds.

According to FAA records and the pilot's flight logbook, the pilot was issued a private pilot certificate (single-engine land) on September 19, 1970, and a glider rating on April 30, 2000. He had accumulated a total of 118.4 flight hours, of which 26.2 flight hours were in gliders. His last FAA third class medical certificate was issued on June 14, 1992, and there was no record of the pilot having been issued an FAA medical certificate since that time. Additionally, the FAA does not require a pilot to hold a medical certificate to pilot a glider.

An autopsy was performed by the Office of the Medical Examiner of Harris County, Houston, Texas. Toxicological tests were performed by the FAA's Civil Aeromedical Institute, Oklahoma City, Oklahoma. The tests were negative for carbon monoxide, cyanide and ethanol. The tests revealed the following; Bupropion present in blood and urine, bupropion metabolite detected in blood and urine, 0.034 (ug/ml, ug/g) diphenhydramine detected in blood, and diphenhydramine detected in urine. Bupropion is a prescription mediation (commonly known by the trade name Wellbutrin) used in the treatment of depression, attention deficit hyperactivity disorder, and smoking cessation. Diphenhydramine is an over-the-counter antihistamine (commonly known by the trade name Benadryl) used in symptomatic management of allergic symptoms and also for its sedative, antitussive and antispasmodic effects.

The American College of Physicians-American Society of Internal Medicine conducted a study (Effects of Fexofenadine, Diphenhydramine, and Alcohol on Driving Performance) on the effects of diphenhydramine on driving performance. The results of that study indicated that "Participants had significantly better coherence after taking alcohol or fexofenadine (Allegra) than after taking diphenhydramine...After participants took diphenhydramine, driving performance was poorest, indicating that diphenhydramine had a greater impact on driving than alcohol did."

NTSB Probable Cause

the pilot's failure to maintain control of the glider while maneuvering. Contributory factors were the in-flight separation of the tow rope and the pilot's physical impairment from his use of diphenhyrdramine.