Torpedo speed.
 

In my last patrol, i track a flower class warship, it was running pretty fast. I launch 3 torpedo and they all missed by an hair. next i was forced to dive deep and play mouse and cat. I escaped without any harm. was i supposed to use faster torpedo speed against a fast target ? Whats the pros and cons of torpedo speed ?

Faster minimizes the effect of any target data errors. Slower maximises range. G7a torpedoes are steam driven and the enemy might see the bubble trails. Fast means more torpedo depth keeping failures too.