NTSB Identification: LAX04LA203.
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Accident occurred Saturday, May 08, 2004 in Reno, NV
Probable Cause Approval Date: 01/31/2006
Aircraft: Schleicher ASW-20, registration: N126PS
Injuries: 1 Fatal.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The glider entered a stall and spin while attempting a return to runway maneuver following an overload failure of the towrope in the takeoff initial climb. During takeoff, the towrope between the tow plane and glider broke while the glider was about 300 feet above ground level. The glider pilot reversed course and attempted to return to the departure runway. The tow plane pilot said that when he looked back the glider was in a left turn with its heading passing through 030 degrees when the right wing suddenly dropped downwards and the glider appeared to descend vertically, nose down. The glider made about 1/2 a clockwise rotation, nose down, before it impacted the desert. The Safety Board Materials Laboratory examination of the towrope and safety link revealed: 1) The towrope was worn by abrasion and sunlight at the glider connection end, which had substantially reduced the strength of the rope at the failure location; 2) the worn end of the rope was about 60 percent weaker than the unworn end; 3) the towrope failed due to overloading at the knot; and 4) the unworn end of the towrope and the safety link met the tensile strength required by 14 CFR 91.309. The rope area around the knot connecting the towrope to the safety link was wrapped in a protective layer of duct tape, and therefore, the rope condition at the failure point could not be easily examined by the pilot during a towrope preflight inspection. Examination of the glider revealed no evidence of preimpact malfunction or failure of the flight control system. The tow plane pilot reported that there were gusty winds and turbulence present at the time. The ASW-20 Flight Manual includes a section titled "Dangerous Flight Attitudes," which contain a number of cautionary statements and warnings pertaining to stalled flight. Full control deflections will result in wing dropping, whereas full-deflected controls in opposite directions with stick pulled completely back will case rapid wing dropping. Initiated from turning flight the wing dropping is more rapid than from level flight. Full deflections of opposite rudder and aileron deflections will lead to a spin. The Federal Aviation Administration produced "Glider Handbook, AC 80-83-14" contained a very brief section about towrope inspection and essentially stated that the rope should be inspected for excessive wear without defining what that means.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: the pilot's failure to maintain an adequate airspeed margin while performing a return to runway maneuver, which led to a stall and spin. Factors in the accident were: 1) the deteriorated condition of the glider towrope, which resulted in towrope failure during a critical phase of the tow; 2) the duct tape covering over the abraided portion of the failed rope end that made inspection of the rope difficult; and, 3) the gusty winds and turbulence. Full narrative available
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