Accident Flight
The flight departed at approximately 1300 with a pilot, co-pilot, and an observer (a law enforcement officer) on board for a marijuana eradication mission operated by the Civil Air Patrol. Earlier that day, the same pilot had conducted similar missions, orbiting at altitudes between 300 and 500 feet above ground level (agl).
Witness Observations
After departure, the aircraft continued aerial observation. One witness reported that on the last pass, the airplane was seen in a large clockwise orbit at an altitude noticeably lower than the previous 300 to 500 feet agl. A sputtering noise was heard by one witness, while another stated there was no engine sound immediately before observing the aircraft depart from normal upright flight. From an altitude of about 120 to 150 feet agl, the witness saw the aircraft simultaneously nose over vertically and commence a right half roll into the terrain. The airplane came to rest inverted in a field containing cotton crops.
Post-Accident Examination
An emergency medical technician (EMT) who arrived on scene within minutes reported observing a finger-sized stream of fuel leaking from the left wing root area; the leakage lasted an estimated 15 to 20 minutes. Other personnel on scene stated they did not smell a strong odor of fuel after arriving within minutes of the crash. There was no evidence of leakage from the right fuel tank. The header tank was impact damaged. The fuel selector was found positioned to the "both" position.
No evidence of preimpact failure or malfunction of the flight controls for roll, pitch, and yaw was noted. No evidence of preimpact mechanical failure or malfunction of the engine, magnetos, or mechanical fuel pump was observed. The flaps were extended 10 degrees.
Fuel System Examination
Bench testing of the impact-damaged fuel injection servo as received revealed it flowed greater than specified service limits. After the impact-damaged mixture control shaft was replaced, the unit was flow-tested and found to flow within limits at all ranges above idle. Examination of the flow divider revealed the cover had the same safety wire pattern as the pattern used during manufacturing; bench testing of the unit revealed it operated at 2.0 psi; no contamination was noted following disassembly, and the spring was not failed. Fuel consumption calculations indicated that an estimated 15 gallons of fuel should have been on board at the time of the accident.