NTSB Identification: FTW01FA129A
Accident occurred Saturday, May 26, 2001 in Pryor, OK
Probable Cause Approval Date: 11/04/2002
Aircraft: Cessna 150, registration: N5617E
Injuries: 1 Fatal,1 Minor.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
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 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." 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.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: the failure of the glider pilot to maintain aircraft control and his delay in releasing the towrope. A contributing factor was the glider's worn elevator trim friction, which resulted in its disengagement. Full narrative available
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