PURPOSE: To raise the speed of response of the whole system of combustion control by setting the operational output of a control system with a slow response speed at full closing or full opening in response to the direction of a sudden change in load and carrying out air to fuel ratio compensation regarding the operational output of a fuel flow rate control system with a fast response speed.

CONSTITUTION: A phase change-over means 32a sets the operational output of an air flow rate regulator 21 at 100% at the time when load increases suddenly to advance the phase in the direction of full opening of an air flow rate regulating valve 24. On the other hand a phase change-over means 32b sets the operational output of the air flow rate regulator at 0% at the time when the load decreases suddenly and advances the phase in the direction to open fully the air flow rate regulating valve 24. In a fuel flow rate control system 10 CV flow rate counting is sought and the degree of opening that corresponds to this is taken out of a table memory 33b of conversion for the degree of opening and this is applied to a fuel flow rate control valve 12 and control for constant air to fuel ratio is made. With this arrangement it is possible to raise the response speed for the whole fuel control system.