Originally Posted by joegrundman

In the extreme case, you are travelling parallel to the target track and intending to fire more or less at a gyro angle of 90 degrees. it is fine to do this, but you must have a very good range estimate. The reason range suddenly becomes so critical is because of torpedo tube parallax, which is to say the difference between the position of the scope view and the torpedo once it has completed its turning circle. With a 90 degree shot this is significant. The TDC will have programmed a converging course for the torpedo to meet at the range you have given. Unless that range is accruate, it could easily follow a very different angle and miss the target altogether.