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View Full Version : What just happened?? Torps made a big turn!


ESPY
02-17-08, 05:38 PM
Maybe someone can help me figure out what I just did wrong in setting up my firing solution for a single merchant using mostly sonar. Not really a noob, but trying "no map updates" for the first time (running 1.4 + TM + RSRD). Had pretty good success against a convoy earlier in the patrol and when I came across this single merchant in rough waters at night I thought I'd try putting one or two fish in it instead of taking it out with guns.

So I was sending range and bearing info to the TDC from the hydrophone station. My first incorrect assumption was that since the "estimate speed" function was fixed in 1.3 that if you sent range and bearing to the TDC twice, that you could then use the estimate speed button. But that told me "not enough data." Si I guess that only works when you have a target lock in the scope??? No problem, I know several other means to figure speed. The contact was reported as medium speed so I estimated 8 kts and fed that initial value to the TDC.

I't seems like feeding bearing data to the TDC would take the place of feeding an AOB, but I wasn't sure so I went ahead and estimated AOB and fed it to TDC. Is that right or wrong? It seems like "send bearing" makes the same adjustment to the TDC that "send AOB" does. Anyway, after giving it an AOB I turned on the PK.

As time went by I continued to feed range and bearing data. The range values read by the SO were matching very close to the PK so I was pretty satisfied with my speed setting and didn't bother updating it. But I did notice that the TDC did not seem to be updating the bearing/firing solution. I sent a bearing and then let the target change bearing by 5d and when I looked at the PK the bearing on the lower dial of the PK still read the previously sent bearing.

Just to be sure, I fed AOB again before I shot. Well, didn't work. I found and locked the target with the scope and fired two fish and the both made a big right turn as they left. I checked the attack map and sure enough, the solution showed a turn.

So where did I go wrong? Bottom line, I sent speed and AOB to the TDC manually and sent the range by way of the SO. And yet it behaved like I had not sent one of the pieces of data. Hmmmph, what am I missing?

SP

Rockin Robbins
02-17-08, 08:07 PM
It seems like "send bearing" makes the same adjustment to the TDC that "send AOB" does. Anyway, after giving it an AOB I turned on the PK.

SP

Actually, no. The bearing tells you what direction from the bow the target bears. The AoB is how the computer gets the target course to project movement at a certain speed along that course. So "send bearing/range" and "send AoB" are very different.

So range and bearing plot the present position of the target, AoB/course gives the target a direction of movement and the speed is self explanitory. Without all three you do not have a solution.

It is also very important which order you send the three parameters to the TDC. The first two inputs should be speed and AoB/course. The order for those two is not important, although in practice you will develop them together on the plot. The last parameter you send is very important, and must be the range/bearing. If you find you did it in the wrong order, you can just repeat inputting a new range/bearing and your TDC will be accurate. New data replaces old, just like a spreadsheet.

Have you checked out WernerSobe's video on sonar only targeting (http://www.subsim.com/radioroom/showpost.php?p=677410&postcount=82)? I'll bet you'll find your problem really quickly by checking that off. Check it out and check back!:up:

ESPY
02-17-08, 08:49 PM
Thanks for the suggestions Rock. After further thought, I realized the error of my thinking regarding the AOB vs bearing. That was why I went ahead and entered an AOB anyway...I wasn't sure if that was right or not. But despite doing so, still had problems. It may relate to the sequence...I think the last data I entered was AOB.

I have seen WernerSobe's video...I guess I'll watch it again. But if I send range and bearing to TDC from the SO, I don't also need to send it manually from the data entry tool, right?

Thanks,
SP

Paajtor
02-18-08, 05:11 AM
No, for the TDC it doesn't matter where it gets it's data from...as long as it gets them.:D