Final Report: PC-12 fuel control unit failed

Pilatus PC-12, South Bend, Ind., Dec. 14, 2004–The NTSB blamed the crash of PC-12 N922RG on the failure of the fuel control unit bellows, which resulted in a significant loss of engine power. The pilot made a forced landing on a roadway after, he said, the engine “abruptly and smoothly rolled back” shortly after takeoff from South Bend Regional Airport. The airplane’s wingtip hit two utility poles during rollout.

A contributing factor was “the pilot’s inadvertent exceedance of the engine temperature limitations during use of the manual override system,” when he tried to restore power, the Safety Board concluded.

Investigators found turbine damage consistent with an over-temperature, as well as a leak in the compressor discharge pressure sensor bellows within the fuel control unit (FCU). The leak prevented the bellows assembly from responding to throttle inputs and resulted in minimum fuel flow to the engine regardless of the throttle setting.
After this accident, an improved FCU design was retrofitted to the entire PC-12 fleet and an improved procedure for an in-flight power loss was added to the Pilot’s Operating Handbook.