"The Mark 24 Tigerfish submarine-launched dual-purpose heavyweight torpedo is a long slim cylinder with a whale nose which appears to be slightly angled from top to bottom. The four rectangular fins are faired into the after body, and the twin contra-rotating propellers, each apparently with six blades are exposed at the rear. The torpedo is roll-stabilised by controlling ailerons on retractable mid-body stub wings and is steered by hydraulically powered cruciform control surfaces mounted at the tail. No details are available about the weapon's internal organization although there is clearly an acoustic seeker in the nose and this acts either in an active or passive mode. In line with the Royal Navy policy of covert submarine operation, the torpedo is used in the passive mode whenever possible."