The I-400's cylindrical aircraft hangar was about 31 metres long and 3.5 metres in diameter, with a thick rubber gasket sealing its door. Hydraulics opened the door from inside, but an external handwheel and rack-and-spur gear could open it when the powered system failed. That simple fallback reflects a submarine service accustomed to demanding redundancy from new equipment. A faster hydraulic system minimized exposed time on the surface, yet operational experience warned against relying on it alone. The contrast is a useful rule of thumb rather than an absolute distinction between experienced and newly expanding submarine forces.
Notable Point · 39:43-42:41
A manual hangar-door backup encoded hard-won experience
The hangar's external handwheel backed up its hydraulics, illustrating why experienced submarine services preserve simple fallbacks for sophisticated machinery.