The U.S. SUBMARINE WAR
  in the PACIFIC  1941 - 1945


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Silent Hunter - WW II submarine simulation
USING RADAR
A tutorial for Silent Hunter: the World War II Pacific submarine warfare simulation
Valor at Sea.com



 [ Background info ] [ The Tools ] [ Using RADAR ]


The RADAR function in Silent Hunter can be a tricky endeavor, but with a little basic math and fair amount of practice, you can become proficient in its use. Regardless of whether you employ the automatic or manual TDC modes, mastering the RADAR function will add a whole new dimension to Silent Hunter. Included in this page is a simple but effective method for utilizing the RADAR. The procedure described below will work well, but will require course alterations to insure an intercept. What tends to be confusing about the RADAR function is the difference between the bearings in degrees relative to your compass heading and the bearing in degrees relative to your sub. Gain an understanding of that concept and you're well on your way.

But first, a little background . . . .

RADAR (Radio Detection And Ranging) was initially installed on US sub's during the latter part of 1941 when the USS Plunger field tested the first version during an actual war patrol. It was a rather primitive and unreliable setup called the SD. Having a limited range (6 - 10 miles), it was non-directional and primarily useful in detecting enemy aircraft.

A major technological improvement came in 1942 with the development of the SJ RADAR. Designed as a surface search system, it provided exact range and bearing and redefined many of the tactics (particularly night surface attacks) employed by the skippers. Further advancement in RADAR technology came about in 1943 with the PPI (Plan Position Indicator) or "improved SJ" system. When one commonly thinks of a RADAR screen, the improved SJ comes to mind. It translates the RADAR pulse information into a picture, with all bearings relative to the sub at the center.

Silent Hunter models these system particularly well. The early war S-boats have no RADAR and thus must rely on gut instinct and visual sighting. In the career mode, you will receive equipment upgrades as your patrol dates correspond with the historical use of the improved systems.

One major concern of US sub skippers was the fact that prior to the war Japan had developed a reliable and accurate radio direction finding (RDF) system in the Pacific. In fact, they were way ahead of the United States in that category. The Japanese were detecting and pinpointing US naval vessels well before Pearl Harbor using their RDF. While the IJN's ability to detect RADAR signals was well known, it was unclear whether Japanese warships possessed a RADAR system of their own. In fact, IJN RADAR appears to have been limited to aircraft carriers and battleships.

 

THE TOOLS

Silent Hunter accurately models the SD, the SJ and the PPI RADAR systems used by US submarines during WWII. The graphic below is of the PPI. The actual screen controls will vary from system to system as historical improvements and advances were made depending on the year you are in.

Silent Hunter Radar

1) Toggles between on/off, PPI and A scope.

2) Allows you to toggle between "rotate" and "focus". It can lock on to a contact to determine bearing and range.

3) SD on/off.

4) Allows you to adjust the range scale. Particularly useful in PPI when making a night surface approach, or executing an intercept maneuver.

5) Range to contact dial.

 

INTERCEPTING A CONTACT 
USING RADAR

The following method allows you to turn "bow on" to a contact bearing.

 

 Let's assume for this exercise that your sub has a heading of 030. This heading is in terms of a compass bearing. With due North being 0 degrees, this means that you are traveling in a direction 30 degrees relative to due north.

Silent Hunter bearings

 

Now let's assume that the picture on the right is your RADAR screen. While it looks exactly like a compass in the graphic, the difference is that the RADAR bearings are relative to your sub and not to North. Your bow would be 0 degrees, your starboard (right side) beam would be 90 degrees. The stern is at 180 degrees and 270 off the port (left side) beam.

The graphic shows a RADAR contact at a bearing of 240. Now you need to figure out what heading to take to try to intercept the contact.

Silent Hunter Radar contact

 

Here's what we know:

A) The sub was at a compass heading of 030.
B) RADAR picked up an unknown contact bearing 240 from the sub.

To find the correct course heading to take, add the two figures.

240 + 030 = 270

By turning the sub's bow in the RADAR graphic to 30 degrees, and laying it over the compass image you can see that the RADAR contact pip lines up with 270 degrees on the compass.

 

Silent Hunter Radar

 

Now . . . suppose you are on a course heading of 240 degrees and RADAR reports a contact bearing 311 . . . .

240 + 311 = 551

Obviously this needs to be adjusted because there are only 360 degrees in a compass circle. In this situation simply subtract 360 from the figure.

(240 + 311) - 360 = 191

The correct "bow on" heading course would be 191. Hit the F7 key to take you to the gauges screen, or the F4 key to take you to the bridge. Find 191 on the compass and click. You are now on your way and have completed the first step in conducting a successful contact intercept.


To summarize:

1) Compass heading bearings are relative to due North.

2) Radar bearings are relative to your submarine, with your bow being at 0 degrees, regardless of your actual direction of travel.

3) Adding your course heading to the RADAR contact bearing (or subtracting 360 as necessary) will put you in a direction to intercept the contact.


THE RADAR APPROACH

Now that you have determined the bearing, range and probable location of the contact and you have initiated a course change to execute an intercept, you will need to monitor the RADAR screen until you can make a visual sighting. The above model turns you in the direction of the contact. Unless the ships are anchored in port, the bearing and ranges will change constantly as the ships continue their transit. You will need to order additional course changes to adjust for their movement. If you are in the period that has the PPI, lock on to the closest contact and take a look at the range dial. See if the range is increasing, meaning they are heading away or decreasing. A convoy at too great a range may be impossible to catch if they are heading away from you. 

As you begin to close the distance between your sub and the approaching targets, change the range ring settings to give you a clearer picture of what the convoy looks like. The larger "blips" are your bigger targets. You will also be able to locate the escorts too; found usually hanging around the perimeter of the group. Don't be confused by the super large blips . . . it's probably interference from a land mass, but you can check your charts just to be sure. As you gain experience and confidence in reading the RADAR screen you'll be able to alter your course well in advance of the convoy for the best possible attack position. I have found that by keeping the oncoming targets bearing in the neighborhood of somewhere between 315 and 45 I can generally work into a fairly good set up.

One method that navies use to reduce the threat from a submarine attack is the "zig zag". You can see the challenge of trying to determine the exact heading or target solution when your contact changes course so often. Obviously, this can be particularly frustrating when you are on a final attack approach and the target zigs away just before you were ready to fire your torpedoes.

Silent Hunter zig zag

Tracking a zig zagging convoy can try one's patience, but it is most certainly "do-able" with RADAR. For those who want to duplicate the methods used by WWII skippers, you can come to a full stop and note the bearing info from your RADAR screen. Doing this several times, and plotting the course will give you a pretty good picture of their actual heading. Make sure to change the range ring settings (arrow 4 in the Tools graphic) as you begin to cut the distance between your sub and the convoy.

An inexpensive and reusable plotting board can be made by simply taking a piece of 8 x 11 sheet of paper and drawing a large circle. Find the center and place a large dot. Now, around the outer edges of the circle pencil in the compass bearings from 0 to 350. You can actually make it in 5 or 10 degree increments. Obviously the smaller the increment the more accurate your data will be. You can insert the copy into a clear plastic presentation page cover and use an dry erase marker or grease pencil to add the contact points.

A "cheat" method of countering the zig zag is to turn your sub "bow on" to the contact and increase your time compression so that you have virtually a constant picture of the convoy's movements. Adjust your course gradually using the arrow shortcuts to keep them on track.

 

CHARTS PATROL

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Silent Hunter Commander's Edition

Silent Hunter
Commander's Edition

 
   

 


 
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