This is the heart of the game. Instead of relying on the "locking" feature, you manually input a target's range, bearing, angle on bow (AOB), and speed. Mastering this allows you to fire from long distances or difficult angles where the auto-targeting often fails.
These specialized torpedoes (available later in the war) can be programmed to travel in a zigzag or ladder pattern. This is incredibly effective when firing into the middle of a dense convoy where a straight-running shot might miss. Stiller Jäger 3
When being hunted by destroyers, toggle "Silent Running" immediately. This stops all non-essential repairs and reloading, which are noisy and give away your position to enemy sonar. This is the heart of the game
Historically and in-game, U-boats were most dangerous when used as "submersible torpedo boats." Attacking on the surface at night gives you a speed advantage over most merchant ships and makes you very hard to spot. These specialized torpedoes (available later in the war)
When an aircraft is spotted, every second counts. Keying the crash dive command and immediately setting your planes to "hard dive" can be the difference between escaping or being destroyed by depth charges.