I Was Wrong, Sort Of...Or RTFM!

[Sailor Steve]

We've had several discussions in the past concerning the nature of the 'Salvo Switch' when firing torpedoes. In the game, if you set for 'Salvo' it fires two, three or four torpedoes simultaneously at a single target, making it easy to get off several without redoing any calculations. The only problem with this is that torpedoes running side-by-side have a chance of wandering and colliding, and magnetic detonators might be set off by the proximity of another torpedo.

After much speculation and discussion, those of us who actually cared about such minutiae came to the conclusion that setting the Salvo Switch and selecting the tubes to be fired most likely sent a signal to the torpedo crew telling them which tubes to fire, and they did the rest.

Well, it turns out that's not quite right. I was reading the British report of the investigation of the captured U-570, and according to them the switch actually sends a signal directly to the tubes, and they do indeed fire automatically.

86. In salvo firing No. 1 selector switch is set to "salvoes" No. 2 to the particular combination of tubes to be fired. On pressing the firing pistol the first torpedo is fired and an automatic timing relay is energised which fires the remainder in succession with the minimum firing interval. This interval is stated to be 3 seconds, but it is known that later instructions have been issued that the firing interval is to be not less than 8 seconds.

http://www.uboatarchive.net/U-570BritishReport.htm
Page 20, Section 86.

So the game has it right in that salvoes are indeed fired automatically, but wrong in that they do not all fire at the same time, but in sequence. The "Later instructions" specify an interval of not less than eight seconds. I'm used to firing mine at about five, but anyone using the 'Salvo Switch' could argue that their method is historically accurate, if not perfect.