Manual Targeting Failure

[Zosimus]

So I've started playing with 100 percent realism (under a new name so I can preserve my old games, if I choose). I was out for a cruise in my fine U-boat when night fell and, as usual, I went underwater. I figure I might be able to find things visually by day but at night hydrophone is better.

A few hours into my cruise I was rewarded with a contact: Merchant, closing, long range, slow. A look at the map showed me that it was somewhere to my SSE and a quick measurement with the protractor soon had me heading 167º at 2 knots. A couple of minutes later another contact showed the ship heading west and so I set course 225º, zoomed in, and dropped a mark on the contact location. Another minute later and I had the apparent ship course of 75 to port, which I worked out to be 285 and a quick line showed its apparent course. I set course for 270º and surfaced the boat.

Once I woke the watchman up and got him on lookout I calculated a line that would intersect and set course at 10 knots. About 5 minutes later I had success: Ship spotted. So I zoomed in, and dropped a mark on its location and started the stopwatch. 3:15 later I placed another mark and measured: 0.7 heading 70º to port. A few minutes later I rechecked and found that the heading was closer to 69º and I drew a line across my map showing the merchant's course.

As I was already slightly ahead I picked some place up yonder and drew a perpendicular line and a circle with a radius of 0.6 and sent the ship gunning there at 14 knots. Along the way I thought better of that and sent the ship a little to the NE of that location with three waypoints leading me to my final location: The final two on the line of approach. As I drew close to my destination I slowed to 1 knot and maneuvered my way in quite slowly.

Despite my best efforts, I found that I drifted nearly 100m in towards the anticipated target, so I set the range at 500m, speed 7 knots, and raised the observation periscope a bit. The bearing was already at 0º and I set AOB 90º starboard and called for periscope depth. It takes awhile to get under when you are at all stop.

It was no more than a minute underwater and I got hydrophone contact and a line showing the merchant on the anticipated course. I raised the observation periscope and tried to find the ship, but I noticed the gyroangle wasn't updating. Worried, I returned the scope to 0º, hit F6 and rechecked my settings. Once done, I switched off of manual settings and went back to the observation periscope. At that point when I moved the scope I saw the gyroangle updating. Perfect!

All stop and waiting for the merchant to come into range everything seemed perfect. I lowered the observation scope and switched to the attack scope. I clearly saw the English flag and so I felt confident and when the gyroangle said 355 I flooded tube 1. At gyroangle 000 I clicked fire and hit F6. I watched proudly as my torpedo streamed out over the distance toward the target. It seemed perfect, at first, but the torpedo passed astern of the merchant.

I know you weren't there to see me, but any ideas what I might have done wrong?

[Pisces]

Well, the 3 minute 15 second plot is good for getting a quick fix on his speed. But it isn't that accurate. It's better to take an average over a few intervals. 4 intervals are 13 minutes. Which is just long enough what the stopwatch can show. 12 minutes on the small handle, and another lap of the big one. And you get the speed known to a quarter of a knot. Much better the TDC won't take anyway.

But if the target really was at 500 meters in front of you then it should have hit anyway. 1 knot of speed difference alone cannot make that much of a miss at this distance.

The target can speed up if it does see the bubble wake of the type 1 torpedo. So it may have tried to dodge it successfully. Remember the near Tramp Steamer in the torpedo academy mission? How sure were you of your stealth?

Other than that I can only imagine the Torpedo speed setting bug messing up the TDC when switching between tubes with a type 1 and type 2 with different speed settings. In the future you can check this manually if it is correct with a rule of thumb (assuming near 90 AOB):

Lead angle= 60 * Target speed / Torpedo speed

[maillemaker]

It was no more than a minute underwater and I got hydrophone contact and a line showing the merchant on the anticipated course. I raised the observation periscope and tried to find the ship, but I noticed the gyroangle wasn't updating.

Yup, forgetting to turn the TDC on and off can ruin an attack, for sure.

3:15 will give you the exact speed [i]if you are 100% certain of the ship's position at the start and stop of the time.

If you are 100% realism without map updates, then your map solution may not be 100% certain.

I try to shoot at less than 1000 meters, and I still miss, too. It all comes down to knowing their speed accurately.

Steve

[Zosimus]

I'm still not sure why I missed, but I've had better success now that I always set the torpedo depth to 2 meters rather than 5.

[Zosimus]

Yeah I had that happen once, but I figured it out long before I took the shot. The gyroangle was showing zero on the wrong side of the 0º bearing.

[maillemaker]

Yup, that's happened to me before, too.

Also I have tried down-the-throat shots at pursuing destroyers only to realize after firing that I forgot to dial the target speed back down to zero...

Steve