What happened
Following its departure, the Cessna aircraft was observed flying at a low altitude above a treeline. During this phase of flight, the plane experienced a sudden roll to the left, which led to an impact with the wooded terrain. An eyewitness noted that gray smoke was emanating from the left engine prior to the collision. At the time of the crash, the landing gear remained in the extended position, and the propellers had not been feathered.
Findings
Post-accident inspections of the wreckage identified that the spark plugs in the left engine were covered in heavy soot and appeared black. Investigators determined that the aircraft had not been updated in accordance with Cessna multi-engine service bulletin 88-3. This specific bulletin required a modification to the fuel system to allow the pilot to manually control the output pressure of the auxiliary fuel pumps, rather than relying on an automatic system. While both engines were found to be functioning correctly during a subsequent test stand evaluation, the failure to implement the fuel system modification was a key finding. The accident resulted in three fatalities and no survivors.