Accident Narrative
On August 23, 2022, about 1145 mountain daylight time, a Piper PA-30 Twin Comanche, N4009Y, was substantially damaged when it was involved in an accident near St. Ignatius, Montana. The pilot and passenger sustained no injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
According to the pilot, he was repositioning the airplane to a nearby airport about 15 miles north for an annual inspection. The passenger added that during the preflight, the left engine popped and sputtered for about 5 minutes before starting, but eventually ran smoothly. The pilot stated the engine start and runup were normal. Both engines continued to idle for about 25 minutes as the pilot completed the checklist. The pilot verified that both engine RPM needles matched, and he taxied the airplane to the runway. He positioned the airplane on the runway, advanced the throttles to full power and departed to the west on runway 26. He stated that, as the airplane transitioned through ground effect, he applied “a lot” of right rudder. Shortly after the airplane crossed the end of the runway, the pilot observed powerlines in his flight path and rolled the airplane to the left to avoid contacting the lines. Subsequently, the airplane impacted a road and cartwheeled to a stop.
Postaccident Examination
Postaccident examination of the airplane and engine did not reveal any preimpact mechanical anomalies. The fuel system for each engine was traced from each wing tank to the fuel servo at the engine through the fuel selector, which rotated normally and was unobstructed. The left fuel servo was recovered and further tested by the manufacturer; it revealed no mechanical anomalies that precluded normal operation.
Fuel Analysis
Both left- and right-wing tanks had green-colored fuel, not consistent with aviation grade gasoline or automotive fuel. The pilot reported that the fuel had been in the wing tanks for over two years. A sample from the left tank was recovered for testing, which revealed the presence of sodium (Na), potassium (K), copper (Cu) and nickel (Ni). Sodium and potassium have numerous natural sources including water/moisture, dust, and soil. Nickel and copper are often found in aviation fuel system components. According to aviation gasoline manufacturers, the presence of copper can cause the color of aviation gasoline to change from blue to green, particularly in fuel that has been in an aircraft for an extended period.