[Heibges]

I have found it easiest just to enter the values into the TDC myself.

Manual TDC Steps

1. Spot your target.
2. Determine targets course.
3. Using Matching Speed Method, determine targets speed. Basically, turn onto the same course as your target, and adjust your speed until there is no change in bearing.
4. Enter the Speed into the TDC.

5. Determine AOB. If you are on a perpendicular course to your target's course (not to be confused with 90° AOB) there is a defined relationship between AOB and Bearing. REMEMBER, this is true only if your courses are perpendicular to each other.

Targets Moving Right to Left
Bearing 45° = AOB 45° port
Bearing 20° = AOB 70° port
Bearing 10° = AOB 80° port

Targets Moving Left to Right
Bearing 315° = AOB 45° starboard
Bearing 340° = AOB 70° starboard
Bearing 350° = AOB 80° starboard

If the target is 1200m or under, my Firing Point leads the target by 10°.
If the target is over 1200m, my Firing Point leads the target by 20°.

6. Determine Range. It is much easier to measure the length of the target as opposed to the height. Especially in rough weather. This is the MILS method for determing range. Mearsure the length of the target using the scale on the periscope, and compare to the range chart.

Target..............1200m.........1000m.........80 0m........600m
C2 Merchant........6................8...............1 0............12
C3 Merchant........7................9...............1 1.5..........14

Practical Example

I spot a target on the horizon . I figure out the target is on course 180°. I turn onto course 180°, and adjust my speed so there is not change in Bearing with the Target.

I enter this speed into the TDC.

I plot out my overhaul manuever based on target course and speed.

I plan my Firing Point to be about 1000m from target.

Based on whether the target is moving right to left or left to right, I determine if AOB will be Port or Starboard.

I enter AOB 80° pt or stb into the TDC.

My last course correction of my overhaul maneuver should put me on a perpendicular course with the target.

I measure the length of the target using the scale on the periscope.

Enter this range into the TDC.

Make sure I am between 300 and 1200m. If it is then AOB is OK.
If range is greater than 1200m change AOB to 70 pt starboard.

Wait for target to reach Firing Point and fire your eels!