Why four Swordfish were the minimum useful air group

The number was an availability calculation rather than an arbitrary design preference. Four Swordfish allowed one aircraft to remain on patrol while another stayed ready to launch, with the remainder absorbing maintenance, recovery, and training demands. The same logic underpins a four-boat ballistic-missile-submarine force, where refit and readiness cycles are structured to guarantee one boat at sea. Designing around that minimum also held down the space, crew, and conversion burden imposed on a working merchant hull.