What happened
During the takeoff phase of flight, the pilot became distracted by inbound air traffic and failed to immediately retract the landing gear. Simultaneously, the aircraft engines were not synchronized, causing an unusual noise that required attention. Shortly after noticing the irregular engine sound, the pilot observed a fire developing in the vicinity of the left engine. He promptly shut down and feathered the left engine, which caused the fire to subside.
Because the hydraulic pump was driven by the left engine, the normal gear retraction system became inoperative. The pilot was forced to use the manual hand pump to operate the landing gear. After delaying the effort to pump the gear up, he realized that he would not have sufficient altitude or time to return to the departure airport. Consequently, he elected to land in a nearby grassy area with the landing gear fully retracted.
The investigation
A post-accident examination of the aircraft revealed significant fire damage located near the fuel injector and alternator. Investigators identified a fuel leak originating at the mixture control valve, part number 2522591. The O-rings surrounding the valve stem were found to be worn, allowing fuel to escape. Additionally, a teardown of the alternator showed that both the brushes and armature were worn to an extent that could produce sparking.
The density altitude at the time of the accident was approximately 8,500 feet. The combination of a fuel leak and electrical sparking from the worn alternator components likely initiated the fire. The pilot's decision to land with the gear retracted resulted in substantial damage to the aircraft structure.
Findings
The investigation determined that several factors contributed to the accident. The primary mechanical cause was a fuel leak at the mixture control valve due to worn O-rings, combined with an alternator capable of producing sparks. On the human factors side, the pilot was distracted by other traffic and delayed critical actions. The inability to synchronize the engines added to the workload and confusion during the initial phase of the emergency.
The pilot's choice to land in a grassy area with the gear retracted was a direct result of realizing he could not return to the airport after delaying the gear retraction process. The fire subsided once the engine was shut down, but the damage to the aircraft was extensive due to the hard landing on the retracted gear.
Safety message
This incident highlights the importance of maintaining situational awareness during critical phases of flight such as takeoff. Pilots should prioritize standard checklist procedures over external distractions. Regular maintenance checks for fuel system seals and electrical components are essential to prevent similar in-flight emergencies.