Section IV - "Fast 90 Advanced" Manual Targeting
Ok.... so you've mastered turning your U-Boat into a perpendicular course to your target and then deploying your torpedoes. However, sometimes turning to that course does not fit with the overall tactical situation you are presented with. For example, maybe you would prefer NOT to turn directly towards that escort that is protecting the convoy. Or maybe you are playing submerged catch-up to your targets and just can't quite get ahead enough to turn 90 degrees into the target course and still have an acceptably low gyro deviation from 000 (remember, the more the gyro deviates from 000, the more prone to error and thus the higher the probability of a miss).
Fast 90 Advanced is for you Kapitaen!
Step #1 - Calculate a Course Perpendicular to the Target
This is identical to Step #1 in the Fast 90 Basic Section.
Step #2 - Turn to your Desired Course
The process of turning your U-Boat (i.e. clicking on the outer ring of the Compass Gauge) is identical to Step #2 in the Fast 90 Basic Section.
However, you may, within the limits of your torpedo gyro, turn your U-Boat to any course you desire.
In this example, using the Target Course of 56 degrees calculated in Section I and the Perpendicular Course to Target of 326 degrees calculated in Section III, I turn the U-Boat to a heading of 013 degrees:
Above: New course set of 013 degrees.
Step #3: Enter Speed and Torpedo Settings in TDC
This is identical to Step #3 in the Fast 90 Basic Section. If you need a refresher course, please go there.
DO NOT PROCEED TO STEP #4 UNTIL YOU ARE ON THE NEW COURSE HEADING!
Step #4: Calculate Scope Bearing for TDC Calibration
Unlike calibrating the Scope & TDC in Fast 90 Basic method, pointing at 000 degrees will not work because your course is NOT perpendicular. Since your bow is not on a perpendicular course, you must rotate your scope to the Perpendicular Course to Target instead and THEN calibrate the TDC as done in Fast 90 Basic.
To calculate the bearing to rotate the scope to in preparation for TDC calibration, we can utilize either the Navigation Map, or mathematical computation.
OPTION A - Determining Scope Bearing Using the Navigation Map
Create a Course Line for your U-Boat Bearing 000 degrees
Since we are now moving down a new bearing ourselves, we need to extend a ruler line from the bow of our U-Boat to several kilometers in the distance. Simply select the Ruler Tool and draw a line bearing 000 from your U-Boat's bow.
Extend a course line from your U-Boat's bow bearing 000 degrees. Note how the line drawn corresponds to 13 degrees on the compass.
Use the Protractor to Create a Perpendicular Line that Intersects your New Course Line
Identical to how we used the protractor to create a 90 degree perpendicular course in Step#1 of the Fast 90 Basic Section, do the same here but make sure that it extends long enough to intersect the new U-Boat course line you have drawn in the previous step.
Above: Make sure that the perpendicular course line extends through the U-Boat line drawn above.
Measure the Angle of Intersection Between Your Course Line and the Perpendicular Course Line
Using the Protractor Tool one last time, measure the angle created by the intersection of the Course line for your U-Boat and the Perpendicular Course Line drawn from the target's course. This angle is the bearing from the bow of your U-Boat that you will set the scope to during calibration.
Above: The protractor tools reveals that you need to turn your scope 47 degrees to port for TDC calibration.
Calculate the Scope Bearing from the Angle Measurement
Now that you have the angle measurement from the step above, you need to calculate what bearing to
turn the scope to in order to calibrate the TDC.
The answer depends on whether the target is to your port or to your starboard.
TARGET TO PORT
Scope Bearing = 360 - Angle Measured Above
TARGET TO STARBOARD
Scope Bearing = Angle Measured Above
EXAMPLE: After doing the charting, the angle of intersection of the U-Boat course line and the perpendicular line is 47 degrees. Since the target is to our port (left) side, we calculate 360 - 47 = 313 degrees.