NTSB Identification: SEA08CA129.
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Accident occurred Saturday, May 10, 2008 in Tehachapi, CA
Probable Cause Approval Date: 06/30/2008
Aircraft: Schleicher ASK-21, registration: N361KS
Injuries: 2 Uninjured.

NTSB investigators used data provided by various entities, including, but not limited to, the Federal Aviation Administration and/or the operator and did not travel in support of this investigation to prepare this aircraft accident report.

The glider was being towed to altitude by a tow airplane. During the takeoff initial climb, the spoiler handle was not locked and the spoilers momentarily extended twice and although the pilot felt that he had to input forward control forces, he did not visually check the position of the spoiler control handle. The tow pilot then gave a rudder wave signal to the pilot telling him to check the spoilers; however, because the spoilers appeared retracted when the pilot verified their position, the glider pilot misinterpreted the tow pilot and released the glider from the tow airplane at approximately 100 feet above ground level. The glider pilot force-landed the glider in a field. During the landing, the empennage broke from the remainder of the glider. The glider pilot did not report any mechanical malfunctions with the glider.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The pilot's inadequate preflight procedures and failure to check the spoiler control position, which resulted in the inadvertent deployment of the spoilers during takeoff. A contributing factor was the pilot's misinterpretation of the tow pilot's instructions.

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