Simple, robust and systematic solutions are provided for controlling counter-rotating open-rotor (CROR) gas turbine engines. The solutions mathematically decouple the two counter rotating rotors of a CROR engine by model-based dynamic inversion, which allows application of single-input-single-output (SISO) control concepts. The current solutions allow fuel flow to be treated as a known disturbance and rejected from the rotor speeds control. Furthermore, the current control solutions allow a simple and well-coordinated speed phase synchronizing among the four rotors on a two-engine vehicle.