Quote:
Originally Posted by Sniper297
I don't know how you figure the TDC didn't have lead angle capability, target speed, relative bearing, and AOB equals lead angle - which was automatically updated in the torpedo gyrocompass. Put the crosshairs on the target, hit the button to send the latest bearing to the TDC, which sets the gyro angle for the correct lead angle, and shoot. Don't even need to know the lead angle, TDC sets that automatically.
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We are talking about 2 different uses of the term "lead angle". I used it in the sense of shooting at a moving target,where the shooter "leads the target" to compensate for target motion. The TVR provides this lead angle, deflection angle, aim point offset, call it what you will, for the Approach Officer (or German equivalent). The TDC does not.
As you correctly described it, the TDC continuously updates the torpedo gyro angle setting, based on the target estimated position from the Position Keeper. It is fully automatic. Once the target position, course, and speed have been entered, the Approach Officer can point the periscope at a seagull. If the correct target position, course, and speed have been entered in the TDC, and IF the target course and speed do not change, then the torpedo will intercept the target. At firing time, the Approach Officer is out of the fire control loop.
For a variety of reasons, some more valid than others, there were US skippers who prefered a less automatic fire control procedure. The "Dick O'Kane" Constant Bearing Technique is an example. Once the fire control party has determined gyro angle for the desired torpedo impact geometry, the Approach Officer observes through the periscope until the target crosses an offset aim point (based on estimated speed) and gives the command to fire. ("Fire on the wire.") The TDC Angle Solver is used to calculate the gyro setting - and set the gyro - but it does not provide any assistance in determining the aim point offset. There were tables and rules of thumb for this.
The TVR, on the other hand does not have a fully automatic mode, because it does not have a Position Keeper. Once target position, course, and speed are entered and the TVR is activated, the TVR calculates an impact point based on the current periscope bearing and sets the gyro angle accordingly. The TVR does automatically introduce an aim point offset, based on target position, course, and speed. The Approach Officer needs to put the periscope wire on the intended impact point on the target. If target position, course, and speed were entered correctly, the torpedo will impact the target at the aim point. This allows for a spread to be fired simply by moving the periscope. It also allows for rapid shifting of targets in a convoy, where all ships have the same course and speed, and approximately the same range - TVR data do not have to be changed.
The TDC and TVR reflect two distinctly different design philosophies - computer automated fire control versus computer assisted fire control. Which is better? Coke or Pepsi?