[BigWalleye]

Cap'n Scurvy and TorpX, I believe you are BOTH correct. Based on my reading over the years, here is how I believe that fire control was executed: The Approach Officer estimated the range, AoB, and speed, and called these out for entry into the TDC. TDC then calculated the target course. The Plotting Party kept updating the attack plot with target range-and-bearing as called out by the Approach Officer. (And AoB, as TorpX points out.) Plotting Party and TDC independently developed a firing solution, based on the two different sets of data. The solutions were checked against each other. Both solutions had to agree, or the boat commander (who usually was, but might not be, the Approach Officer) would not clear to fire. Torpedoes were not supposed to be wasted in snap shots.

IIRC, both O'Kane and Fluckey describe situations were the Plot and TDC solutions disagreed. "Check fire." There was tension and fuming while the discrepancies were resolved. (Beggin' yer pardon, but this early on a Sattidy, I am not up to finding the references.)

Range and bearing do give course, heading, and speed, but AoB immediately identifies target course changes (like zigzags).

Of course, the target range and bearing were determined mechanically, from the bearing ring and stadimeter. The AoB was judged by the Approach Officer, using the Mark I Human Eyeball. It's probably not surprising if former Approach Officers, in their post-war memoirs, sometimes emphasized the parts of their job that called for the most skill on their part.

Another observation from TorpX's excellent illustration: range and AoB data begin at 10000 yds. How hard is it for us to make any kind of range or AoB estimate at 10000? Those first long-range observations were probably easier in the R/L analog periscope view, but not a lot easier. They didn't wait until the target image was clear enough for accurate estimates, because then they would wind up basing their solution on 2 or 3 observations, like we often do. If we want to play "realistically" (in a historically appropriate manner), then we need to train ourselves to make and use good estimates at long range.