What happened
On May 28, 2020, an Aero Commander 500S, registration N909AK, was involved in an accident near Aniak, Alaska, during the initial climb phase of flight. The aircraft, which was operated by the Alaska Division of Forestry, had recently undergone refueling at a local vendor. Following the refueling process, the pilot completed necessary paperwork, boarded three passengers, and taxied to Runway 29.
During the early stages of the climb, the pilot reported experiencing what appeared to be mechanical turbulence, followed by a noticeable drop in climb performance and a loss of power in the engines. As the aircraft began descending at a rate of approximately 400 feet per minute, the pilot identified a landing site consisting of shallow water and terrain. The subsequent off-airport landing resulted in substantial damage to the aircraft and caused serious injuries to the pilot and all three passengers.
Findings
Investigations into the accident revealed that the aircraft's reciprocating engines had been inadvertently serviced with Jet A fuel. The ground service personnel involved in the refueling process noted that they were unfamiliar with the specific aircraft and had consulted the pilot regarding the location of the fuel filler port and the grounding strap. During the transaction, the fueler asked the pilot if additive was desired, to which the pilot declined.
While the fueler recorded the fuel type on the receipt, the post-accident examination confirmed the use of incorrect fuel. Although a placard was located near the fuel port indicating that a minimum grade of 100/100LL aviation gasoline should be used, the placard was noted to be slightly degraded. The mismatch between the required aviation gasoline and the Jet A fuel provided led to the engine power loss during takeoff.