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On September 12, 2009, at 1453 Pacific daylight time, a Schweizer SGS 1-34 glider, N7656, impacted the ground in a nose down attitude following a separation of the tow line at the Skylark Field Airport (CA89), Lake Elsinore, California. The pilot/owner operated the glider under the provisions of 14 Code of Federal Regulations (CFR) Part 91, as a personal flight. The pilot, the sole occupant, was killed. The glider sustained substantial damage. Visual meteorological conditions prevailed for the local area flight, and no flight plan had been filed.
A Federal Aviation Administration (FAA) airworthiness inspector responded to the site, and interviewed witnesses and the tow airplane pilot. The tow pilot reported that while on the takeoff roll he was manipulating the flight controls due to what he thought was either a crosswind, or the movement of the glider. The tow plane lifted off the ground about 65 miles per hour (mph). He felt what he thought was slack in the tow line and tried to slow down using back pressure. The tow pilot then felt the airplane surge forward as if the tow line had been released. He looked back to confirm that the glider had released and saw it in a sharp right turn and then hit the ground. The tow plane pilot looked back at his altimeter and noted that the tow plane's altitude was between 225 to 250 feet at the time.
Ground witnesses reported that from their viewpoint, it appeared that the glider released from the tow airplane, and then veered sharply to the right before it entered into a nose dive prior to impacting the ground. One of the witnesses reported that while still on the ground the glider was pulling towards the right, but before it lifted off the ground it had corrected itself.
During the inspection of the glider, the FAA inspector established flight control continuity. The FAA inspector also reported that the tow line broke at a point called the weak link. The FAA inspector indicated that the link was in good condition and showed no signs of wear.
A review of FAA airman records revealed that the 70-year-old pilot held a pilot certificate with ratings for glider aero tow only. The pilot held a third-class medical certificate issued on April 7, 2008. It had the limitations that the pilot must wear corrective lenses.
A reissuance of the pilot's private pilot certificate was dated May 21, 2009, and showed his ratings as airplane single engine land and sea, and glider. A corresponding logbook entry revealed that the pilot passed his airplane single engine sea check ride. A review of excerpts of the pilot's logbook by the National Transportation Safety Board investigator-in-charge estimated a total of 192.9 hours of glider time; with 15.6 hours logged between February and August 2009. The pilot's estimated total time was 817.7 hours.
MEDICAL AND PATHOLOGICAL INFORMATION
The Riverside County Sheriff-Coroner, Riverside, California, completed an autopsy on September 15, 2009. The cause of death was listed as multiple blunt force trauma. The coroner's report noted that the pilot initially survived the accident, but succumbed to his injuries during surgery. According to the pilot's wife, he had flown gliders for over 30 years, and he was not taking any prescription medication. However, he was blind in his right eye, but did not need to wear corrective lenses.
The FAA Forensic Toxicology Research Team, Oklahoma City, Oklahoma, performed toxicological testing of specimens of the pilot. Analysis of the specimens contained no findings for carbon monoxide, cyanide or volatiles. The report contained the following findings for tested drugs: atropine and lidocaine detected in blood and lidocaine detected in urine.
The weak link is a safety line that is designed to "break" (release) under sudden or extreme loads to protect/ensure that the airframe of the glider is not damaged. The weak link can break at low altitude, causing an inadvertent release.
If the glider pilot or the tow plane pilot are not able to release the tow line via the primary or secondary release mechanisms, the glider pilot can attempt to snap the weak link with a sharp movement of the glider.
In the glider flying handbook, under 14 CFR Part 91 section 91.309, the tow rope has a required strength to be within a range of 80 to 200 percent of the maximum certificated weight of the glider.