A head assembly for an ignition system includes a head block and a plurality of igniters seated in the head block. The head block has an issue aperture and defines an issue axis, and is configured and adapted for sealably coupling with an igniter combustion chamber. The igniters are arranged about the issue aperture and include respective ignition members arranged obliquely with respect to the issue axis for igniting fuel exiting the issue aperture irrespective to orientation of the ignition system.