tdc-pk
 

in the torpedo fire control manual there is mention of a gyro matched light being on and a mention of a correct solution light being on before launch.
I dont see any lights on except the green triangle in auto mode

I'm afraid the game's TDC/PK isn't the same as the real deal. So do not consider that document as a manual. Actually, the game's manual isn't even to be trusted.

Go watch the video's in the subskippers bag of trick thread to learn the various ways of using it.

http://i.ytimg.com/vi/1Y58dWSILYY/hqdefault.jpg

There is a light in the bottom right corner of your scope view tdc/torp setting console. When it's lit up it's operating on 'memory', so to speak - meaning you sent it a course and speed of the target and it still predicts position based on those qualities. When it's off it's ready for fresh info - you lock onto the target and it'll update. If you click the light again, it'll track from those settings whether you're looking through the scope or the scope is down.

I once popped up the scope and 'locked' on a target, thinking the data refreshed but unfortunately I didn't disengage the light/old data tracking. The old data was tracking a different freighter. So instead of two hits apiece, the first frieghter was hit with 4. Argh.