TDC and Send bearing to TDC question/torpedoe track question
 

Let's assume that I am manually taregting. After inputing Aob, range, and speed, I activate the TDC. Let's assume the Aob is 40 degrees bugs recht (bow right,) and the range is 4,000 meters. At 2,000 meters, I go to the sonar station, and send the bearing to the TDC. Then I return to periscope station. The Aob had moved to 0 degrees on the panel, even though that is not the correct Aob. A look at the attack map tells me that the Aob and torpedoe angle appear unchanged (now I have what appears to be the correct Aob on the Attack Map and what is clearly the incorrect Aob on the periscope screen.)(Plus on the Attack Map, the torpedoe angle appears to be unchanged.) I do understand the dynamics of the TDC operation when the bearing is sent to the TDC, and how that reset bearing affects the TDC settings (i.e. Aob), if, in fact, it does. Can someone explain this?

Also, how does information on the torpedoe angle help a captain, other than to help him visualy estimate if his torpedoe is running on a track that could intercept the target? If it is clearly an incorrect track, it tells me that the solution must be reentered. Anything else?