Work on a 30 mm anti-torpedo capability extends the close-in-defence problem below the waterline. The Type 31 frigate's 57 mm and twin 40 mm battery is then considered as point defence for a carrier or another high-value unit. In this concept, the frigate sits between the protected unit and incoming weapons instead of serving primarily as a distant radar picket. Weapon calibre, escort position, and task-group role therefore have to be considered together.
Notable Point · 3:14-5:04
Gun defence above and below the waterline
The Type 31 discussion links medium-calibre air defence with developing 30 mm anti-torpedo fire, showing how gun systems may protect a task group in more than one direction.