What happened
During a mosquito control mission involving the dispersal of Scourge insecticide, an unidentified aircraft was observed flying at a low altitude. A witness reported hearing the engines throttle back, rev up, and then sputter. The observer noted that the right engine appeared to be sputtering because the propeller was turning slowly. Following this, the aircraft pitched up, rolled to the right, and descended into the ground. The impact resulted in an immediate fire.
The investigation
The on-scene inspection of the propeller assemblies revealed specific damage: one blade on the left propeller assembly was curled aft while the other was curled forward. On the right propeller assembly, one blade was curled aft and the other remained straight.
Both engines were subsequently disassembled for detailed inspection. Investigators found that crankshaft rotation produced proper camshaft, valve, and accessory drive continuity in both engines. There were no anomalies identified within the lubrication, induction, fuel injector, exhaust, or ignition systems of either engine. Examination of the cylinders and spark plugs showed normal color and burn patterns. While most cylinders produced compression, the right engine's number 6 cylinder did not. However, the manufacturer determined that the intake and exhaust valve springs in that cylinder had lost tension due to exposure to the post-crash fire. Both propeller governor controls were found in the high rpm position.