Variable geometry air-fuel injector

A combustion chamber head assembly with a variable geometry fuel injector for a gas turbine engine, comprising a combustor head defining an enclosed combustor head volume separated on its downstream side from a combustion region by an endwall which is pierced by a multiplicity of apertures including at least one fuel-air mixture aperture and a plurality of air-only apertures, at least one fuel injector assembly defining a fuel-air mixing region opening through the fuel-air mixture aperture into the combustion region, the at least one fuel injector assembly comprising a plurality of concentric rings which define a first inner annular air passage and a second outer annular air passage, a fuel nozzle located axially with respect to the annular air passages and which, in operation, sprays fuel into the fuel-air mixing region, and an airflow controller including a movable diverter member for selectively closing the second outer annular air passage and selectively opening a third passage such that air is either admitted into the fuel-air mixing region or is redirected to the third passage leading to the plurality of air-only apertures.