Exemplary embodiments are disclosed of variable frequency drive (VFD) controllers with engine fail-over and systems including the same. In exemplary embodiments, a system includes a controller configured to be operable for controlling a VFD that drives a motor (e.g., a three-phase AC motor, etc.), which, in turn, drives (e.g., mechanically spins, etc.) a first pump. The same controller is also configured to be operable for controlling an engine (e.g., a diesel engine, etc.), which, in turn, drives (e.g., mechanically spins, etc.) a second pump. The system is configured to failover from the motor to the engine in response to a VFD communications failure.

An apparatus and method for reducing a pressure differential across a turbine 19 of a gas turbine engine 10 during a shaft break event, comprises a pressure equalization apparatus 200, 300, 400, 500, 600, 700 configured to introduce a pressurised fluid into a core airflow A at a region directly downstream of the turbine 19 in the event of a shaft break to directly increase a local pressure at the downstream region 29 of the turbine 19 and thereby reduce the pressure differential across the turbine 19. The reduction in the pressure differential may result in a reduction in the acceleration of the turbine 19.