If you're trying to use the simplified O'Kane 90° method...
When we talk about firing down a 0° torpedo track, that doesn't mean you point the aiming wire at 0°. If you do that, your torpedo won't track 0°, it'll veer to the left or right 5-10°. If you entered no solution at all... it'll track a straight line down the 0° gyro path, but you'd have to point the aiming wire with a 10°-20° lead for a better point of impact. In which case you've just totally ignored the TDC completely and you're playing as if WWI technology is all you have to work with.
To use the TDC, you'll need to setup a firing solution such that you'll be holding the aiming wire steady on about a 10° or 20° mark (depending on target speed) and then as points of interest pass the wire, you can fire and your torpedos should track a straight line to the target (0° gyro angle shot).
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