History of Flight
On November 14, 2009, at approximately 1215 central standard time, an Augustine David L Sonex experimental light sport airplane (serial number 332) was substantially damaged when it impacted terrain one mile north of Burnet Municipal Airport – Kate Craddock Field (KBMQ), Burnet, Texas. Visual meteorological conditions prevailed. The personal flight was conducted under 14 CFR Part 91 without a flight plan. The commercial certificated pilot was fatally injured. The cross-country flight departed Shirley Williams Airport (44TE), Kingsland, Texas, around 1145 and was en route to Spicewood Airport (K88R), Spicewood, Texas.
According to a friend, they had flown to an Experimental Aircraft Association meeting earlier that morning and were returning home. The accident pilot reported he was “breaking off” to return to K88R, then five minutes later said he was having difficulties and reversing course to land on runway 01 at KBMQ. That was the last transmission the friend heard. A flight medic in the area heard the pilot report “something really wrong with the airplane,” followed by an emergency declaration.
One witness saw the airplane descending low as if to land in a field, then bank hard right and descend “straight nose down.” Multiple witnesses reported the airplane cleared trees and nosed over in a nose-low attitude before impacting terrain between two rows of trees.
Personnel Information
The pilot, age 81, held an airline transport pilot certificate with multiengine land and sea ratings and several type ratings, plus a commercial certificate with single-engine land and glider privileges. He was issued a third-class medical certificate on December 13, 2005, with the limitation “must wear corrective lenses.” He held a valid Class C driver’s license from Texas. His personal logbook was not located; at his last medical application he reported 12,124 hours total time. On an insurance application dated January 1, 2008, he reported 12,000 hours total time and zero hours in the accident airplane make and model, with a biannual flight review date of August 22, 2006.
Aircraft Information
The airplane, an Augustine David L Sonex, was issued a special airworthiness certificate on August 21, 2004, for experimental amateur-built operations. It was powered by a Jabiru 3300A engine with a two-blade Sensenich propeller. The airplane was registered to and operated by the accident pilot and maintained under an annual condition inspection program. Records showed a condition inspection completed on October 6, 2009, at an airframe total time of 189.9 hours.
Meteorological Information
The closest official weather observation station was at Burnet Municipal Airport – Kate Craddock Field, one nautical mile south of the accident site. The 1210 METAR reported winds variable at 5 knots gusting to 14 knots, visibility 10 miles, scattered clouds at 2,000 feet, temperature 22°C, dew point -16°C, and altimeter 29.90 inHg.
Wreckage and Impact Information
The accident site was just north of the approach end of runway 19 in level terrain, with tall deciduous trees nearby. Elevation was 1,280 feet msl. The debris field measured 20 by 20 feet and included the fuselage, empennage, both wings, and the engine/propeller assembly. The airplane was recovered and relocated to Lancaster, Texas, for examination.
Medical and Pathological Information
The Travis County Office of the Medical Examiner performed an autopsy on November 15, 2009. The report concluded the pilot died as a result of blunt force injuries. Toxicological tests by the FAA’s Civil Aerospace Medical Institute were negative for all substances tested.
Tests and Research
An NTSB investigator examined the wreckage on December 22, 2009. The airplane had been cut in two aft of the crew seats. Both wings showed aft accordion crushing. The empennage was unremarkable. Control continuity was verified for aileron, elevator, and rudder. The engine remained attached; continuity was established by rotating the propeller by hand, with rocker arm movement and compression observed.
The airplane had two fuel tanks: forward and aft. The forward tank was empty; the aft tank contained fuel. The forward fuel selector was set to main; the aft selector was off. The forward tank contained a white substance lining its interior, broken into pieces. The finger strainer was about 80% blocked by a similar white substance. The tank and debris were sent to the NTSB Materials Laboratory. FTIR analysis identified the white substance as polyurethane. The tank was made of polyethylene. The finger screen had a 32 mesh size.
Prior to NTSB recovery, an FAA inspector removed the carburetor and sent it to the engine manufacturer without NTSB oversight. Examination revealed corrosion and an unknown substance buildup on the jet needle, preventing proper fuel-air mixture.
Additional Information
Sonex Aircraft, LLC stated the kit included a 16-gallon cross-linked polyethylene fuel tank. Builder guidance recommended a 16 mesh finger strainer. In June 2008, revision B of the fuel tank guide stated that if a leak occurred, the only acceptable repair was tank replacement. Revision C (March 2010) warned against using sloshing compound, noting it would not adhere to plastic and would plug the fuel system.
According to the airplane builder, the forward fuel tank began leaking 10 to 20 hours into operation. He applied Por-15 fuel tank sealant to stop the leak rather than replacing the tank. The airplane flew an additional 100 hours without issues before being sold to the accident pilot. Maintenance records did not document this repair. Por-15’s instructions did not address use in plastic tanks, and the manufacturer confirmed the sealant was not designed for plastic applications.
The mechanic who performed the last condition inspection reported no anomalies with the airplane, engine, or fuel tank and was unaware of any leaks. He noted the fuel bowl and main fuel line were contamination-free, but he did not inspect the finger screen as it was not routinely removed.