Incident Summary
A cargo-carrying air taxi airplane experienced an engine failure during a takeoff attempt. The aircraft ran off the end of the runway and came to rest in a ditch. The pilot reported that the engine had failed.
Inspection Findings
Subsequent examination of the wreckage revealed multiple maintenance issues. The engine was equipped with incorrect spark plugs, and one magneto was found to be advanced 7 degrees beyond the proper timing. The brake system was making metal-to-metal contact, and subsequent inspection showed that the brake linings were worn down to the rivets. Additionally, the airplane was determined to be overweight at the time of the incident.
Engine Test
After replacing the spark plugs and resetting the magneto timing, the engine was run from idle to full throttle and operated satisfactorily, indicating that the identified discrepancies had been responsible for the loss of power.