What happened
A certificated commercial pilot, serving as an Alaska State Trooper, departed from a remote lake in a float-equipped airplane as part of a two-airplane flight. The aircraft was the second plane in the formation. After the accident airplane failed to arrive at its intended destination, the lead pilot began an aerial search. The wreckage of the aircraft was subsequently located approximately a quarter-mile southeast of the lake from which it had departed.
The investigation
Investigators examined the wreckage and found that the fuel selector valve was set to the LEFT fuel tank position, and the left fuel tank was empty at the time of the crash.
A conversation between the two pilots prior to the flight was noted; the first pilot recalled discussing the use of the Cub Crafters main fuel valve with the accident pilot. The accident pilot had indicated he was not flying his normally assigned aircraft, which featured a standard Piper main fuel tank selector valve. The accident pilot expressed uncertainty regarding whether the fuel selector in this specific aircraft should be set to BOTH, LEFT, or RIGHT.
An FAA-approved Cub Crafters STC for this aircraft required a placard placed above the main fuel valve reading: "TAKE OFF AND LANDING ON BOTH ONLY." This placard was present in the wreckage. Additionally, a review of the State of Alaska, Department of Public Safety's aircraft manual revealed that there were no provisions for difference training regarding the Cub Crafters fuel system.