Possible Enigma application
 

Suppose there was a configurable mission setting which placed you not merely outside of visual range with the convoy, but also out of hydrophone range. On entering the game, an encrypted Bdu message would need to be decrypted, citing a known position and rough heading for the convoy. The navigation officer can chart the position of the convoy at the time stated, and estimate the current location based on the reported speed and course, and then plot a course to intercept. If by then developed, this closing to visual contact portion of the mission might be the period where a slight risk might exist of air-attack. Self-evidently, the convoy course and speed would need to be correct to (say) +/- 15%, so that it cannot be taken as correct figures to enter into the TDC, and doesn't make hydrophone checks nearing the intercept position redundant.

As the configuration requiring this proper use of Enigma and Navigating skills would likely be an unchecked box by default, it wouldn't affect most players, however "hard-core" simmers might enjoy it. One of the benefits of these necessarily longer missions would be an increased likelihood of more players than usual joining boats, and indeed more boats, whilst not increasing the likelihood of all your firing solutions being rendered incorrect because someone attacks the convoy as your torpedoes are running.

A useful facility to go hand in hand with this, is for the ability of the radio officer on a boat being able to annotate the radio log with the clear-text of received or sent messages...

Hmmm...:hmmm: (writing notes furiously)

Interesting idea. This would mean reducing the effective convoy detection range on the hydrophone to a more historical magnitude. I don't have any definitive data, but my understanding from perusing memoirs is that at the very least it was somewhere under 10 km.

I've read of hydrophone detection ranges of up to 100km, however, I suspect that related to the explosion of depth-charges or torpedoes. However, as it may reasonably be inferred that dc's and torpedoes exploding are in the region of the convoy, that would give a position line if not the location. Frankly I don't know the hydrophone range for detecting a full convoy, but I have to think it'd be considerably further than 10km, and probably 50km at least with a quiet U-boat?

I recall a particular statement that (I paraphrase) "visibility was so poor that it was easier to listen for targets on the hydrophone than to try and spot them from the bridge". Implying that ordinarily the range of assured acquisition on the hydrophone would have been shorter than the visual acquisition range. The latter is of course limited to about 10 km by the curvature of the Earth.

I think the crux of the matter is whether one is considering picking out the bearing of a specific ship, for "targeting" or for detecting the general position of the convoy as a whole. 10km sounds quite reasonable for the former, but rather too short for the latter.

It's reasonable to suppose that the distance a convoy could be detected at, is at least the routine separation of U-boats in a north/south line across the path of convoys, if not up towards double that interval.

So the question becomes, what, historically, was the interval of U-boats when seeking to gain the 1st detection of a convoy?