What happened
The pilot was repositioning the aircraft back to its home base following a series of revenue flights. One month prior to the accident, the pilot had refueel the auxiliary tanks at a different airport, but had not utilized those tanks since that time. Approximately 20 minutes after takeoff, the pilot switched the left and right engines to their respective auxiliary fuel tanks. Thirty minutes later, the pilot returned the engines to the main fuel supply.
Following this switch, the right engine began to surge and subsequently stopped running. Although the engine restarted after the pilot activated the fuel boost pump, it quit again five minutes later; subsequent restart attempts were unsuccessful. Shortly thereafter, the left engine also began to surge and produced only partial power.
With decaying altitude and power in the remaining engine, the pilot diverted to an alternate airport. Upon approaching the airport, the pilot determined the aircraft was too high to land with a tailwind and circled to land into the wind. During the base leg, due to the presence of power lines and the rapid loss of altitude and power, the pilot decided to land straight ahead in a field. During the landing roll, the aircraft collided with a ditch. There were no injuries reported.
The investigation
Examination of the left and right main fuel filters revealed a foreign substance. Laboratory analysis identified this substance as polyacrylamide, a manmade synthetic polymer used as an agricultural soil amendment to reduce erosion.
An inspection of the fueling facility found that refueling employees lacked formal or on-the-job training. There were no records indicating that delivery system filters had been inspected or replaced. Maintenance for the fuel truck, delivery system, and storage facility was performed by employees only on an as-needed, time-permitted basis. Additionally, the fuel truck was improperly labeled, and the fuel nozzle was found in a compartment among dirt, gravel, and other contaminants without any protective caps or covers.