Select your torpedoes with the 3 key. Repeated presses of 3 will change the width of the spread. Use narrow spreads for distant targets and wide spreads for close or multiple targets.
Once the torpedo launchers have been selected you will see the area around your ship where the launchers can bear highlighted. If the torpedoes on the side you are looking at are reloading the bearing zone has a yellowish edge. Some ships have launchers that have limited travel. Typically these come in pairs, a dedicated starboard set and a dedicated port set. Other ships have launchers mounted amid ships on a swivel. I know of no ships that can launch pointing ahead but there is at least one ship that can fire directly astern. There are some low tier ships that have single tube launchers so they do not fire a spread. Usually the minimum number of torpedoes in a launcher is two. The most that I recall in a single launcher is five. Three launches of five each is quite impressive.
With the torpedoes selected you will see a green wedge centered on your cursor. When this overlaps the bearing zone pressing the left mouse button will fire a spread. The next press of the left mouse button will fire from the next launcher in sequence, and so on.
The green wedge does not start at your ship but at about fifty meters out. This is the distance the torps travel before they are armed. Firing torps at a ship you are trading paint with will be a waste of torpedoes. The extreme end of the wedge shows you how far the torps will travel before they run out of fuel. You can also check the mini-map.The circle around your ship shows your selected weapons range. Torpedoes are not seekers. They will travel in a straight line until they hit something or run out of fuel. They are perfectly happy to damage a friendly ship. Make that a formerly friendly ship. Spamming torpedoes is not a good idea unless you are very sure no allied ship will cross their path. Even then it is typically a waste.
I'm adding this as a separate paragraph for emphasis. Before you press your torpedo release know where your team mates are. As a minimum, check the mini map. If a friendly is going to be in the path of your torps, assume your target will evade, hold your fire. The chance of killing an enemy is not worth risking a team mate. If you see a teammate going into danger tell them. I chat "ware torps". If you do hit one of your teammates with a torpedo apologize. It doesn't matter if he turned into them at the last minute. You pulled the trigger it's on you.
I have recently read arguments that players should have enough situational awareness that they should evade torpedoes fired by their team mates who are behind them.
Why should someone who has risked his ship to maneuver close to an enemy, have to abort what they are doing to get out of the way of your torpedoes, which you launched from behind their field of view? So when your team mate is lining up his shot, he has to break off his attack and look behind to see your torps, and then spend time evading? Keep in mind this game is usually won by the side that acts like a team.
Some torpedo users will fire a spread or two of torpedoes down a narrow strait to provide "area denial". My personal preference is not to deny the area to the enemy. I prefer to have the enemy enter that narrow strait where they cannot maneuver and then send my torps down. Even if I miss there is a chance they will end up clam digging on one of the islands where they are easier to kill. If you fire your torpedoes without a target by the time they get to the end of their run they will be far apart and easier to evade.
Placing your cursor on an enemy and pressing the X key will provide a lead indicator. This is a grey wedge that will appear on the sea. It is based on the heading and speed of the target and is updated continuously. Overlaying the green wedge on the grey wedge will give you the best chance of hitting a target that does not change course or speed after you launch the torpedoes.
If your target is not lost in his binocular vision he will evade. To counter this if I have two launchers that can fire on the side I'm targeting I usually select the narrow spread and launch my first spread down the grey lead indicator path. I will then take an educated guess on how my target will evade and launch a second spread along side the grey lead indicator path on the side I think he will move to. This gives me a tailored wide spread and a better chance of getting a hit.
Different torpedoes have different speeds and ranges. Know what you are packing. You can find out your weapons statistics while you are in the harbor by selecting your ship and opening the pop up window from the right side.
You can also open the modules window and find it there along with data for any module for your ship.
Torpedoes are slow. They are slow in the water so get close to minimize the enemies reaction time. Try popping out from behind an island and launching a spread. Then run away and if you've got it pop smoke. They are slow to reload. Fire your spread and go back to gunnery while your launchers reload.
Successfully evading a spread of torpedoes is defined as pulling a Farragut. David Farragut is often paraphrased in the expression "Damn the torpedoes. Full speed ahead." That's not what he actually said but you get the drift. Scholars of the Civil War will be happy to tell you that, at the time, a torpedo was what we now consider to be a naval mine. Slang expressions have little to do with fact. Don't quibble.
As was stated above "Overlaying the green wedge on the grey wedge will give you the best chance of hitting a target that does not change course or speed after you launch the torpedoes." What can we learn from that? If you think someone has targeted you, make sure you change your course and speed. Frequently. (That's good advice against gunnery as well.) Destroyers and torpedo equipped cruisers (almost all of the IJN a few USN) will telegraph a torpedo launch by getting in relatively close and turning to present their side to you. I have gone to the extreme of going from full ahead to full astern and evaded spreads that would have put me on the bottom. This is one of the reasons you should not spend all of your time at flank speed. Sometimes putting the pedal to the metal will save you. As in avoiding gunnery a predictable captain is soon a spectating captain.
When you hear the warning, look at your threat indicator and see where the torpedoes are coming from. Then get your head out of binocular mode by pressing the shift key or holding the right mouse button and try to turn to align your ship axis to run parallel to the spread. Going to flank speed may slightly increase your turning radius but it will decrease the amount of time it takes to change your heading.
Enemy torpedoes have red icons. Friendly torpedoes have grey icons. Right? Of course it's not right. ALL torpedoes are a threat. There is no such thing as a friendly torpedo.
Most ships can survive being hit by a single torpedo. Even a single torpedo hit will put a major hurt on your hit point bar.
The earlier you detect them the more likely you can evade. If you have a scout plane, get it airborne if you feel a torpedo attack is imminent. It will increase the range torpedoes are spotted.
To handle torpedoes that have been fired into a strait, that you have entered, you may want to slow down. The torpedoes spread out and open the distance between them as they travel. The longer it takes to get to you, the farther apart they will be. Line your ship up parallel to the spread and pick two of them to go between. If you must take a torpedo hit, try to make sure you will be hit by only one. Take care not to make large corrections because if you go clam digging (hit an island) you are a very easy target until you can free yourself and get underway.
Avoiding those torps closing astern; zoom all the way out and point your mouse at your stern. Pick the two torpedoes who's track is closest to your course and maneuver so they pass on either side. The trick is remembering your steering is reversed from a forward view and to make small corrections. Just make sure you wait until they are past before you make a large turn. If you hear the collision warning slow down but keep your course steady until the torps are past.
After a while you'll get used to it. I don't recommend you go looking for chances to practice, but the chances will come to you soon enough.
It is possible to outrun a torpedo if you have a large enough head start.
Torpedo Bombers: One does not begin the evasion of a torpedo bomber's torpedoes when the torpedoes hit the water. One begins by pointing the long axis of your ship at the torpedo bombers as soon as you see the TB icon. It makes it much more difficult for them to do a run on you. They want to line up on your beam. That gives them the best chance of hitting you. You want to present your bow or stern to them. Go ahead at 1/2 or 3/4 speed, and as soon as they commit either back water of go to full speed. This will mess up the targeting. If you wait for them to drop their torps you may as well have heard the keening of the banshee. It is helpful is to travel in the company of a USN cruiser. Generally speaking they have the best AA. Traveling with any other ship will provide some additional AA cover and force the carrier captain to choose a target. If you're lucky the carrier will not choose you. However a torpedo that misses its intended target can still bring an end to your battle. For dive bombers you want to present your beam instead of the long axis.
A ship in a smoke screen will not be targeted by aircraft. As flights of torpedo bombers skillfully managed are death incarnate it may behoove you to travel with a destroyer. Destroyers only get a few smoke screens. Don't waste them. Lady_Athena points out that torpedo bombers can manually drop their torpedoes and thus hit ships who thought they were safe in smoke. But as they used to say "Smoke 'em if you got 'em".
Change between wide and narrow spreads with the 3 key.
Note the yellow border on the spread indicator and bearing zones. They indicate that the launchers are loading and will not fire.
Superimpose the lead assist with the spread indicator. Note the target is out of range, but as it is heading towards you, it may be in range by the time the torpedoes get to it. If the target turns away you have wasted the spread.
Endangered Team Mate
Here your target is coming around the island and should arrive just in time to receive your torpedoes. While this sounds like a good shot, your teammate is heading for the torpedo spread as well, and this may result in a team kill. Do not launch. It's not worth it.
Grey lead assist and green spread indicator superimposed.
Green spread indicator a little to the right of lead indicator
Keep in mind that even a perfect alignment of the lead assist and the spread indicator does not guarantee a hit. It will only happen if your target does not change speed or heading or you are very close indeed. It's a judgement call. You have to decide which way you think he will turn or speed up or slow down and adjust for it. Don't expect laser guided sniper shots with torpedoes. They are not precision instruments. They just make big booms. There is no right place to hit with a torpedo. The goal is to hit with as many of them as you can.
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Added paragraph on torpedo bombers.