Accident Summary
On May 2, 2023, at 1610 central daylight time, an Aero Vodochody L-39Za, N343WT, was substantially damaged in an accident near Barnhart, Texas. The pilot and a pilot-rated passenger were not injured. The aircraft was operating as a Title 14 Code of Federal Regulations Part 91 personal flight.
Pilot Report
The pilot had flown the aircraft from Ellington Airport (EFD), Houston, Texas, to San Angelo Regional Airport (SJT) earlier that day. The aircraft was refueled at SJT with 342 gallons of Jet A fuel and hangared overnight. After taking off from SJT for a local flight, while climbing through approximately 7,300 ft msl, the pilot heard a popping noise. Engine instruments indicated a rollback, with no caution lights illuminated. The pilot pitched for best glide and attempted a windmilling air start, which was unsuccessful. A second air start using the Saphir auxiliary power unit also failed. Unable to restart the engine, the pilot performed a forced landing to a dirt road in a field, during which the wings were substantially damaged.
Postaccident Examination
A visual inspection of the engine revealed white streaks in the tailpipe section. The low-pressure fuel pump was removed and disassembled, showing discolored impeller blades and a white, crusty substance on the inlet screen edge. The inlet screen and impeller blades were examined at the NTSB materials laboratory. Analysis of the substance was mostly indeterminate; it had characteristics similar to cellulose (likely plant matter), soil, and several jet fuel additives. No other anomalies with the engine or airframe were identified that would have contributed to a loss of engine power.
Fuel Analysis
A fuel sample from the aircraft's lower fuselage tank drain, taken on May 20 during disassembly for transport, tested at 55 ppm water. Recovery personnel reported that when the aircraft was de-fueled, the fuel-water separator filter clogged with water three times during transfer of 120 gallons of fuel. The aircraft had not been rained on after the accident. The FBO that refueled the aircraft tested fuel from both their Jet A trucks, finding water levels less than 15 ppm, below the 30 ppm limit. Twenty-two aircraft had been fueled from the same source without reported issues.
According to NTSB technical literature, dissolved water between 60-100 ppm at 20°C exists in conventional petroleum-derived fuels, and 50 ppm is considered acceptable. Fuel can absorb water from the atmosphere via the ventilation system or condensation. When kerosene cools, its water absorption capacity decreases, and water can precipitate and settle at the bottom due to its density.
The aircraft had a total fuel capacity of 426 gallons. Prior fueling records at EFD included 296 gallons on March 9 and 11, 2023, and 77 gallons on May 1, 2023. The aircraft was regularly hangared at EFD.