The hoped for improvements in surface performance were achieved as the class developed and further changes in power were made, but in underwater performance there was little gained over the Hollands.
During the building of A1, it was decided that greater torpedo capability was required and from A2 onwards two bow tubes were fitted, side-by-side. So many modifications were made to the various boats during the building programme, that the A Class could almost be considered as four classes: A1; A2 to A4; A5 to A12 and A13, the diesel version.
