An electric power management system of a vehicle may interconnect a power plant, a propeller drive unit, and a battery via a bus. A command limiting controller may direct the operation of the power plant and the propeller drive unit in fast and slow modes of operation, the fast mode of operation operating at a higher bus voltage than at a slow mode of operation. The command limiting controller may generate a bus current to drive the propeller drive unit according to a command limiting, voltage-versus-current curve that adjusts the bus current depending on an amount of voltage on the power bus; where the command limiting curve includes a minimum voltage portion, a maximum voltage portion and a control range therebetween having upper and lower voltage limits and upper and lower current limits for enhanced reliability and stable control of the propeller drive unit.