An annular combustor for a gas turbine engine, comprising: an inboard liner extending longitudinally fore to aft, the inboard liner having a forward section and an aft section; an outboard liner spaced radially outboard of and circumscribing the inboard liner, the outboard liner having a forward section and an aft section; a bulkhead extending between a forward end of the inboard liner and a forward end of the outboard liner and cooperating therewith to define a combustion interior volume extending fore to aft from the bulkhead to an annular combustor exit boundary extending between an aft end of the inboard liner and an aft end of the outboard liner; a plurality of combustion air admission holes formed in the inboard liner, each air admission hole having a center, the plurality of combustion air admission holes arranged with the respective centers of the plurality of combustion air admission holes disposed in a circumferential row; and a plurality of combustion air admission holes formed in the outboard liner, each air admission hole having a center, the plurality of combustion air admission holes arranged with the respective centers of the plurality of combustion air admission holes disposed in a circumferential row; wherein in longitudinal section, the combustor interior volume includes a forward volume (V 1) extending fore to aft from the bulkhead to an annular boundary (P 1) extending between an aft end of the forward section of the inboard liner and an aft end of the forward section of the outboard liner, an aft volume (V 3) extending fore to aft from an annular boundary (P 2) extending between the centers of the row combustion air admission holes in the inboard liner and the centers of the row of combustion air admission holes in the outboard liner and the annular combustor exit boundary; and an intermediate volume (V 2) extending fore to aft from a forward end interfacing with an aft end of the forward volume (V 1) to an aft end interfacing with a forward end of the aft volume (V 3); characterised in that the forward volume (V 1) represents from about 30% to about 40% of the combustor interior volume; in that the intermediate volume (V 2) represents from about 10% to about 20% of the combustor interior volume; and in that the aft volume (V 3) represents from about 40% to about 60% of the combustor interior volume. an inboard liner extending longitudinally fore to aft, the inboard liner having a forward section and an aft section; an outboard liner spaced radially outboard of and circumscribing the inboard liner, the outboard liner having a forward section and an aft section; a bulkhead extending between a forward end of the inboard liner and a forward end of the outboard liner and cooperating therewith to define a combustion interior volume extending fore to aft from the bulkhead to an annular combustor exit boundary extending between an aft end of the inboard liner and an aft end of the outboard liner; a plurality of combustion air admission holes formed in the inboard liner, each air admission hole having a center, the plurality of combustion air admission holes arranged with the respective centers of the plurality of combustion air admission holes disposed in a circumferential row; and a plurality of combustion air admission holes formed in the outboard liner, each air admission hole having a center, the plurality of combustion air admission holes arranged with the respective centers of the plurality of combustion air admission holes disposed in a circumferential row; wherein in longitudinal section, the combustor interior volume includes a forward volume (V 1) extending fore to aft from the bulkhead to an annular boundary (P 1) extending between an aft end of the forward section of the inboard liner and an aft end of the forward section of the outboard liner, an aft volume (V 3) extending fore to aft from an annular boundary (P 2) extending between the centers of the row combustion air admission holes in the inboard liner and the centers of the row of combustion air admission holes in the outboard liner and the annular combustor exit boundary; and an intermediate volume (V 2) extending fore to aft from a forward end interfacing with an aft end of the forward volume (V 1) to an aft end interfacing with a forward end of the aft volume (V 3); characterised in that the forward volume (V 1) represents from about 30% to about 40% of the combustor interior volume; in that the intermediate volume (V 2) represents from about 10% to about 20% of the combustor interior volume; and in that the aft volume (V 3) represents from about 40% to about 60% of the combustor interior volume.