"A to Z" Use of Tools in this File
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Use of the tools in this file begins when first sighting the enemy.
I. On first sighting, achieve constant bearing to compute target speed:
Quickly eyeball AOB and turn the boat to roughly match the enemy's course.
Ensure the TDC is set to accept bearings from the UZO.
Pick one ship and observe through the UZO how its bearing changes, using a feature such as the funnel as a guide.
Adjust speed in such a way that the bearing only slightly moves.
(hint: use the "both engines 10 slower" EOT setting to achieve speeds between the main EOT settings)
Adjust course in small increments (preferably away from target) and observe the bearing change after each adjustment
until the bearing line doesn't move off that spot on the target for at least a couple minutes. This exercise may take 10-15 min
but the information gleaned pays dividends.
At that constant bearing, have the TDC operator read off the exact bearing to the 10th degree and input in tab 2 Speed Calculation
section as Constant Bearing.
Estimate as closely as possible the AOB at this bearing and have it entered into the TDC, and input into tab 2 Speed Calculation
section as Original AOB.
Read calculated target speed from tab 2 Speed Calculation section and have entered into TDC for reference.
Enter own course into tab 2 Speed Calculation section and make note of the resulting target course. We will use this for comparison
later in overtaking the target.
II. Begin overtaking the target and plot to refine course/speed estimate. If already ahead of target, skip this section:
Accelerate to desired speed and turn to begin overtaking the target.
Once speed stabilizes, enter it in the Range Calculation section of tab 1 as Own Spd.
Enter estimated target speed from tab 2 in the Range Calculation section of tab 1 as Tgt Spd.
Find a reference point on the target ship and start the timer, having TDC read off the exact bearing and
entering it into Range Calculation section, 1st Brg. Mark own position on map.
After exactly 1 minute, recenter on reference point on ship and have TDC read off exact bearing and enter
into Range Calculation section, 2nd Brg.
Have TDC read off AOB at 2nd bearing, and enter into Range Calculation section, AOB @ b2.
Read target range as calculated in meters at bottom of Range Calculation.
Enter own course into Range Calculation section, Own Course, and use this target range and the 1ST true bearing
calculated below it to start a plot, using own marked position on map. Plot the target's course from this point, marking off
where he'd be at intervals of 5 minutes (or any desired interval) along his course based on the speed estimate.
Observe the target at these time intervals, estimating AOB and comparing observed bearing and rough
range to the plotted points to further refine target course/speed.
Alternatively, you could also forego the Range Calculation section and simply perform a plot using ranges derived from
AOB and target length. See the Plot tab - fill in the section for the correponding observation. The reason for keeping a
record of previous observations is that, if and when you estimate a more-accurate AOB, you will need to go back and
readjust the AOBs of the previous observations by the same amount, thus truing up your plot (because the ranges will
Use the AOB estimated at intervals to further refine the enemy course estimate using the Attack Disk section
of tab 2 (Course from AOB). This section has a "Difference" field which compares the new course to the one originally
estimated. Adjust the Original AOB in the Speed Calculation section of tab 2 by the amount of the difference so the difference
zeroes out. This "trues up" the initial speed estimate from the constant bearing method for the new AOB.
If so desired, use this more refined course to adjust the AOB in the Range Calculation section to "true up"
the initial plot point and adjust the plot for the change in the speed estimate, going back and forth
in this manner further refining course and speed, if time allows.
DO NOT FORGET TO UPDATE THE AOB IN THE TDC FOR ANY NEW ESTIMATES THROUGHOUT!
III.Check/determine target speed while closing with target:
Having achieved a position far enough ahead where the approach can begin, turn toward and start approach.
As target becomes more clear, continue refining the AOB (and thus target course) using the Attack Disk section in
tab 2 (Course from AOB), adjusting the Original AOB in the tab 2 Speed Calculation to further refine speed.
When close enough to see the masttips clearly, obtain a range by entering mast height, scope marks and magnification
in the Speed Calculation section of tab 1. Alternatively, if you've plotted his track using the 0 AOB method in the tutorial,
read range off where the bearing intersects his track.
Pick a ship and a reference point on that ship and perform the "1-minute" timing exercise as before, noting exact bearings
and entering these along with own speed and AOB at 2nd bearing in the appropriate fields in the Speed Calculation section of
tab 1 (adjust AOB as necessary if appears different from observation).
Read off calculated target speed and enter into TDC (along with any new AOB estimate).
As a triple-check (or double-check in case plot wasn't done), you can do the "fixed-wire" method of checking speed. Turn
bow-onto target and time how long it takes for the target to cross the wire (irrespective of AOB), then calculate speed:
Target length / seconds x 1.94
The disadvantage here is the need to either stop or turn bow-on, which can be very impractical during an approach.
IV. Shoot while minimizing gyro angle while turning:
Every subsimmer has that "aha" moment eventually in their time while hunting high and low (some will get that joke, some won't)
when they realize that, the smaller the gyro angle is at the time you shoot (i.e. the less the torpedo has to turn), the less range matters
as a TDC input. At a 0 gyro angle, range has no impact to the solution at all. And so, historically, commanders strove to shoot at as close
to a 0 gyro angle as possible to eliminate range as a factor. It is still a good idea to at least input a rough estimate of range into the TDC