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Old 06-12-2018, 09:53 PM   #1
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Default tracking convoys

tracking convoys by hydrophones

this post takes a look at how to track convoys or warship taskforces, i have heard a few people in both sh3 and sh4 forums say its impossible to track them over the years, its not really, and this post is going to deal with how they can be tracked.

in the pic below, it shows a map view of a 16 merchant ship convoy, with 3 escorts, the point, and flank security. it also shows a map view of the angle tool, which will represent the needle, or pointer of the hydrophones. the track is a ninety here, it makes explaining easier, but this can also be any angle, its also better if the player assumes the role of the sonarman, before the ai sonarman butts in. if that doesnt happen, then the ai sonarman will announce targets he has identified, if that happens, hes going to identify the closest warship, which will always be the point escort, or he will identify the closest merchant in distance, whatever, its always going to the the closest ship to the submarine in distance. unfortunately, once hes id'ed those ships, its impossible to get him to switch to a different ship, because these ships are not the ones to track in a convoy, but all is not lost here, the point is unreliable, it will turn to port or starboard to search, or speed up and slow down, on the base course, and the closest merchant ship propellers are mingled with a bunch of others from the convoys merchants, making that ship impossible to track.

the best scenerio is to get to the hydrophones while every ship in the convoy are still, "unknowns", so that the player can id the ship to be tracked.

the pic shows an approach of a convoy from the port quarter, but its the same for the other quadrants in the circle, just from different directions.

if the player/sonar operator had the pointer of the hydrophones and began to sweep from zero degrees to 270 degrees, the first ship's propellers he will hear will be the escort at point, the soundcone will be 20 degrees, just the word, "unknown" written in the notepad for 20 degrees, if he continues to sweep toward 270, hopefully theres a gap in the bearings after sweeping by the escorts screws, where theres no propeller beats heard, continue sweeping toward 270, the next ships screws he's going to hear will be the closest merchant to the submarine in bearings, not the closest one in distance.

this is the ship to be tracked, becus you can follow its screws, its sound is out ahead of every other propeller in the convoy, and cant be lost in a background of multiple screws. its labelled unknown if it was found before ai, so the player now id'es the ship as merchant, the ai sonarman will report the merchants bearing, leave all the others as unknowns, just going to concentrate on this one ship, becus its following the convoys base course.

a player might try to find that merchants bearing, but often it will be masked by the other propellers of the ships nearby, the sonarman knows he cant track the merchant ships screws in that group of propellers, and so he moves the hydrophone needle to the right, to the merchants forward fringe bearing, becus no other propeller sound other than the id'ed merchant will be on that bearing, knowing the sound cone is twenty degrees, he moves the needle to the right until hes on the last bearing that he can hear the merchants screws, the next bearing to the right of that is where the screws drop out and is no longer heard.

the sound cone is the bearing of the target, and ten degrees to the left of the target and ten degrees to the right of the target, if a merchants bearing is zero degrees, merchants propellers will be heard at 350 degrees and at 10 degrees, these are the fringe bearings, its sound is also heard thru out the range of 350 to 10 degrees.

so by tracking one ship by its forward fringe bearing, (fringe bearing plus or minus 10 = real bearing) its bearing is known and can be plotted, and there are certain conditions in the sounds of the hydrophones where a pretty good range estimation can be made, two vital parts of the map plot, from there speed and course estimations can be estimated, if a player was to conduct approach and torpedo attacks submerged.

there maybe times when this leading ship (closest in bearings) as in the first pic cannot be used to track a convoy, becus its screws cannot be determined, or ai sonar has id'ed multiple ships that makes it impossible to find, so there is still a way to track the convoy, and thats by tracking the merchant that is the furthest in bearings from the submarine. for this one , a player would track the ship using the trailing fringe bearing. these two ships are the ships to be tracked in the conduct of a submerged attack to also use with the speed formula from the torpedo fire control manual to determine the convoys speed.

Her gun crew had guts, however, for from her canting bow came a half dozen well-aimed rounds. How they pointed and trained their gun on that tilting platform will long remain a wonder, and their dedication in keeping up the fire until they went under would be a matter of pride to any nation.

O'Kane, Richard. Clear the Bridge!: The War Patrols of the U.S.S. Tang
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