A fuel-supply control system for a gas-turbine engine includes a fuel injector (47) opening into an engine combustion chamber (48), and a reservoir (23) connected to the fuel injector (47). Three fuel lines (20, 21, 22) are each connected at one end to the reservoir (23) for supplying fuel to the combustion chamber (48) via the reservoir (23) and the fuel injector (47). Electrically operable on-off metering valves (24, 25, 26) equal in number to the lines are connected in corresponding lines in such a manner that the lengths of the lines (20, 21, 22) from the corresponding metering valves (24, 25, 26) to the reservoir (23) are different from each other. A sensor (54) detects a certain engine operating condition. A controller (50) is connected to the sensor (54) for producing a pulse train whose duty cycle depends on the engine operating condition. The pulse train is fed to the metering valves (24, 25, 26) to open them periodically.