Wooden fins improved an air-dropped torpedo's behavior in flight, while a tension wire helped it enter the water in a shallow belly flop. That arrangement worked best over relatively smooth water. A rising wave could overtake the descending torpedo, break the wire, or disrupt its entry. In suitable conditions, a shallow entry helped the torpedo run straight and true. The interpretation here is that crews judged the weather and removed the wire in high seas, allowing a deeper nose-first entry before the torpedo rose to its running depth. Accounts of crew preferences strongly suggest that practice, but the manual establishing the doctrine has not been located. The precise rule therefore remains unconfirmed.
Notable Point · 1:00:57-1:03:09
Why rough seas complicate Swordfish torpedo entry
Wooden fins and a tension wire aided shallow torpedo entry, but rough North Atlantic water made wire use a matter of uncertain doctrine.