20010526014641A

(-23)Glider (N9915X, a schleicher KA6-E) was observed to lift off abruptly and climb higher than tow airplane (N5617E) glider pilot stated that he got caught in "extreme updraft, the likes of which I have never seen in all of my 60 years of flying". Glider climbed higher than tow airplane causing it to nose dive and strike the runway, shortly after takeoff. Glider was able to unhook, and returned safely to airport. (.19) this is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. On may 26, 2001, at approximately 1350 central daylight time, a Cessna 150, N5617E, was destroyed when it impacted terrain during the takeoff initial climb while towing an alexander schleicher KA-6E glider, N9915X at the mid-america Industrial airport, Pryor, Oklahoma. The instrument rated private tow pilot sustained fatal injuries and the private glider pilot received minor injuries. The airplane was registered to and operated by tulsa skyhawks, inc., bixby, Oklahoma. The glider was owned and operated by its pilot. Visual meteorological conditions prevailed and a flight plan plan was not filed for the 14 code of federal regulations part 91 tow flight. The local flight was originating at the time of the accident. The glider pilot stated that at the time of the takeoff roll, the wind was out of the west, approximately 15 knots with gusts. He stated that he maintained a crab of 15 degrees into the wind in order to track down the runway 17 centerline. Shortly after lift-off, the glider encountered "severe turbulence" and was caught in an "extreme updraft." He remembers looking up at the sky, losing sight of the tow airplane, and being "jarred about the cockpit" while attempting to disengage the towrope. He recalled that his altimeter was indicating 440 feet AGL approximately mid-field of the runway at the time he released the towrope. He estimated the tow airplane to be 150 feet lower than his glider when he was finally able to release the towrope. He stated that "much of [the] runway was still ahead even though the glider had reached near pattern altitude already". While on downwind, he noticed some smoke at the end of the runway. He completed a normal traffic pattern and normal landing on the runway. Upon landing, the glider pilot realized that the tow airplane had came to a rest and was engulfed in flames on the east side of the runway. The glider pilot mentioned that his glider had a tendency to release its "full nose down" trim, which is the recommended trim lever takeoff position, and "snatching" back to the "full nose up" position. He remembered having to push forward during the initial climb to counteract this nose up effect. Witnesses were interviewed by the NTSB investigator-in-charge and by the FAA aviation safety inspector. One eye witness, who was located at the approach end of runway 17, stated that the glider was drifting to the left of the centerline and out of position. He observed the glider gain altitude "relatively abrupt" and was able to detect that the glider was "decidedly higher" than the tow airplane. He saw the glider break away to the east and thought the problem was over. He continued to observe the tow airplane and stated that from his position the airplane appeared to level off momentarily, and then "nose dived and impacted the ground." (.4) the glider pilot reported that during takeoff, he had to maintain a crab of 15 degrees into the wind in order to track down the runway centerline. Shortly after lift-off, the glider gained altitude abruptly and ascended to an altitude above the tow airplane. The glider pilot reported that he had encountered "severe turbulence" and was caught in an "extreme updraft." He remembered looking up at the sky, losing sight of the tow airplane, and being "jarred about the cockpit" while attempting to disengage the towrope. He recalled that his altimeter was indicating 440 feet AGL approximately midway down the runway at the time he released the towrope, and he estimated the tow airplane to be 150 feet lower than his glider. The glider completed a normal traffic pattern and landed on the runway. The glider pilot mentioned that his glider had a tendency for the trim lever to release from its "full nose down" trim position, which is the recommended takeoff trim lever position, and "snatch" back to the "full nose up" position. He remembered having to push forward during the initial climb to counteract a nose up effect. A witness observed the glider gain altitude "relatively abrupt" and wasable to detect that the glider was "decidedly higher" than the tow airplane. He saw the glider break away to the east and thought the problem was over. He continued to observe the tow airplane and stated that from his position the airplane appeared to level off momentarily, and then "nose dived and impacted the ground." A pilot, whose tow flight had departed just prior to the accident, reported that the wind was approximately 9 knots, and he did not experience any turbulence or gusty wind conditions. A functional check of the glider's trim operation was completed by placing the trim lever in the full nose down position (takeoff position) and then hand-tightened the wing nut, which is used to lock the lever in place. The control stick was then pulled aft, and the trim lever would release almost immediately. This procedure was repeated several times with the same result. The airplane's tow hook was found partially separated from the tail. Examination of the towrope revealed that the breakable link was broken.