History of Flight
On March 30, 2013, about 1600 central daylight time, a Schleicher Alexander Ka7 glider, registration N12053, impacted terrain after an in-flight wing separation near the Littlefield Municipal Airport (KLIU), Littlefield, Texas. The commercial pilot and passenger were fatally injured. The glider was destroyed. The glider was operated by the pilot under 14 CFR Part 91 as a personal flight. Visual meteorological conditions prevailed, and no flight plan was filed. The local flight originated from KLIU about 1545.
Witnesses observed the glider riding thermals. It appeared to come out of a thermal and execute a tight loop. They heard a loud sound, then saw the glider spinning. During two rotations, a portion of the right wing separated and fell. The glider continued spinning into the ground.
The tow pilot stated he towed the glider to 2,800 feet AGL, then released. He landed about 5 minutes later and joined witnesses. After about 5 minutes, the glider was north at about 2,000 feet AGL, nose low, appearing to spin. The right wing seemed broken but not completely separated. During the spin, about half of the right wing separated. The glider made about 4 rotations before impact.
Personnel Information
The pilot, age 78, held a commercial pilot certificate for airplane single-engine land, multiengine land, and glider, issued March 3, 2010. He held a second-class medical certificate issued April 26, 2012, with a limitation for glasses available for near vision. His logbook was not recovered. On the April 26, 2012 medical application, he reported 12,695 total flight hours and 120 hours in the previous 6 months.
The passenger, age 14, was seated in the rear seat.
Aircraft Information
The two-seat, forward-swept-wing glider was manufactured in 1965 by Alexander Schleicher in Germany. A standard-normal airworthiness certificate was issued May 12, 1965. The glider was not approved for aerobatic maneuvers. Maintenance records showed major maintenance and repairs on May 30, 1997. The most recent annual inspection was completed April 1, 2012.
Meteorological Information
At 1553, an automated weather station at Lubbock International Airport (KLBB), 32 miles southeast, reported wind variable at 4 knots, visibility 10 miles, few clouds at 9,000 feet, broken cloud layer at 30,000 feet, temperature 29°C, dew point -4°C, and barometric pressure 29.94 inHg.
Wreckage and Impact Information
The glider impacted terrain on the northeast side of the airport. The main wreckage was on flat terrain, inverted, on a southwesterly heading. Wooden components were mostly shattered; metal tubular components were bent and damaged. The empennage was twisted toward the cockpit, facing southwest.
Portions of the right wing were found east and southeast of the main wreckage. The outboard section separated near the inboard aileron attachment point. The separated section was about 15 feet long, mostly intact. The spar was fractured and splintered at the separation. Metal aileron controls were fractured in overload and bent downward. The control tube tore through the wing fabric laterally from the connection point to the inboard point.
Additional Information
The British Gliding Association (BGA) issued Mandatory Aircraft Inspection 042/07/2004, Issue 3, effective March 31, 2006, requiring wing inspections every five years on Schleicher Ka7 gliders. This followed a 2004 Ka7 wing failure in England investigated by the UK AAIB. The inspection addressed urea formaldehyde adhesive degradation due to age and damp conditions. No records indicated the inspection was completed on the accident glider. The FAA did not issue an Airworthiness Directive on this issue.
Medical and Pathological Information
An autopsy of the pilot on April 1, 2013, determined the cause of death as blunt force injuries. Toxicology testing revealed 23 mg/dL ethanol detected in muscle and caffeine detected. According to the FAA Civil Aerospace Medical Institute, the ethanol was consistent with postmortem putrefaction. No tested-for drugs were detected in the liver.
Tests and Research
The outboard section of the right wing was examined at the NTSB Materials Laboratory. The wood wing section was fractured and splintered. Cracks were observed on many adhesive joints. The adhesives were degraded and poor. Upper and lower spar caps were constructed of three and two layers of wood, respectively, bonded with urea formaldehyde adhesive using scarf joints. Fractures in the scarf joints were relatively flat with adhesive on the tapered surface, mainly cohesive, with no evidence of wood or smooth adhesive interface from the mating side. Fractures in both spar caps were consistent with combined tension and torsion. The adhesive holding ribs was brittle; pieces separated during handling. Rib markings noted a date of 1959. Pieces of spar, ribs, and skin were disassembled by hand with varying effort. Wood material appeared mostly dry with no moisture staining, except mold and moisture stains observed at the leading edge interior skin and adjacent structure.