What happened
The aircraft was en route to Salt Lake City (SLC) with plans to place it on static display alongside other aircraft equipped with Solyo-conversions featuring Allison 250-C20S turboshaft engines. During the descent through 12,000 feet into the SLC area, the engine flamed out, causing the propeller to auto-feather.
The pilot restarted the engine but encountered a surge when attempting to advance power, resulting in another shutdown. After restarting the engine again, the pilot activated the engine anti-ice system. Advancing the power lever once more caused the engine to surge and quit. The pilot restarted the engine and applied alternate air. Upon advancing power, the engine surged and the power dropped to idle.
The pilot then turned off the engine anti-ice and alternate air systems, pulled the auto-feather circuit breaker, switched the start/motor switch to start, and attempted to advance power again. The engine continued to surge. Unable to restore stable operation, the pilot executed a forced landing on a mud flat in the Great Salt Lake.
The investigation
Disassembly, examination, checks, and tests of the engine, fuel control, power turbine governor, and fuel system revealed no discrepancies. However, examination of the fuel flow transducer revealed a partial blockage. This blockage was blown out during the process but could not be identified or recovered.
Findings
The primary issue was the partial blockage of the fuel flow transducer, which caused intermittent engine surges and flameouts that could not be resolved in flight.