Abstract: A variable orifice combustor unit 10 comprises an annular combustion chamber 12 extending about a central axis 14 and ending in a discharge nozzle 16. Charging of the chamber 12 takes place from combustion fuel and air supply chambers 18 and 20 via a fuel charging orifice array 22 and an air charging orifice array 24. The orifices 28.1, 28.2 of the orifice arrays 22, 24 are positioned and slanted at the same forward angle in the direction of the nozzle 16 to the effect of their central axes 38, 40 cutting along the longitudinal centre of the combustion chamber 12. The cross sectional sizes of the orifices 28 are adjustable by means of an orificed displaceably mounted cyndrically shaped covering body 44 for the fuel charging side and an orificed cylindrical body 58 for the air charging side both being displaceable in the direction of the axis 12.