What happened
Prior to departing on an air ambulance mission carrying one patient and two medical crewmembers, the pilot requested that 40 gallons of fuel be added to the multiengine airplane. During the refueling process, a line service technician added 20 gallons of fuel to each wing tank. While the pilot was present and assisted with replacing the fuel caps, the specific type of fuel was not verbally specified during the request.
During the initial climb phase, a crewmember notified the medical dispatcher that the aircraft needed to return to the airport due to smoke emanating from the right engine. Witnesses observed smoke trailing the aircraft, and some reported seeing flames following the impact with the terrain. The aircraft struck the ground in an upright, eastbound orientation, which led to a postimpact fire that destroyed most of the airframe.
Findings
Investigations determined that the multiengine airplane, which utilized two reciprocating engines, was misfueled with Jet A fuel instead of the required 100LL aviation gasoline. Although labels near the fuel filler ports explicitly stated "AVGAS ONLY," the presence of the smell of jet fuel at the scene and refueling records supported the conclusion of a fuel error. Postaccident engine inspections confirmed internal damage consistent with engine detonation.
This error was facilitated by the equipment used by the fixed-base operator. The fuel truck was equipped with a small-diameter nozzle that could fit into the aircraft's aviation gasoline filler ports. Had the truck been equipped with an oversized nozzle, as recommended by industry standards, the accidental insertion of the jet fuel nozzle into the smaller port would have been prevented. Ultimately, the failure of both the pilot and the technician to verify the fuel type resulted in the engine detonation and subsequent loss of power.