Torpedo Evasion

[Molon Labe]

Post your torpedo evasion tactics here!

To start everyone off, I recommend reading the torpedo evasion chapter in Timmy G's TACMAN. (http://www.subguru.com/missions/SCHQ_TACMAN_PDF.zip (http://www.subguru.com/missions/SCHQ_TACMAN_PDF.zip)))

It was intended for Sub Command, but the games are similar enough that the lessons there are 90% true of DW. (The relevant change in DW is that torpedoes now explode when they hit decoys, which actually makes evasion in DW much simpler.)

[Molon Labe]

I'll go first. :wink:

The first thing everyone needs to keep in mind about receiving torpedo evasion advice from others is that we might be wrong. There are a lot of variables at work--including the mindset of your opponent--which make absolute "rules" of evasion elusive. New players--and experienced players for that matter--should always be open to experimenting with new tactics to see what works best for them (and against different opponents).

First Actions
"Conn, Sonar, Torpedo in the water bearing 320!" This is the most important audio warning you will receive in DW, and it is critcal that you act quickly but calmly to keep yourself in the fight. You should not react impulsively to the TIW (torpedo in the water) warning; you first must have information to know what the right course of action is. Bear in mind that it is crucial that this assesment is done very quickly if there is any chance that the torpedo is very close (for example, because it was air-dropped).

Identify the Weapon: Knowing the type of weapon is absolutely critical to deciding what to do. While knowing the EXACT class of torpedo is not usually necessary, you need to know if the torpedo was launched from a sub, ship, or was air dropped. Upon receipt of the TIW warning, immediately make a mental note of the bearing and decide whether or not it corresponds with the known bearing of any contacts...it is usually safe to assume that a TIW on the bearing of a contact came from that contact.

After noting the bearing, immediately switch to your narrowband sonar sensors. If you are going to fast, slow down, unless you are absolutely confident you know the type and location of the weapon. Scroll through the possible classes of all weapons on all arrays. (You should also assign trackers and/or mark all weapons at this point)

Noteworthy weapons types:
sub launched:
MK 48 ADCAP: ASW/ASUW torpedo used by US submarines, 27nm range
65cm: ASW/ASUW torpedo used by the Akula, 27nm range
USET-80: ASW/ASUW torpedo used by Kilos, 11nm range
TEST: Wireguided ASW/ASUW torp fired from Kilos, 40 kt top speed
53-65K: ASUW torpedo used by Kilos and Akulas, may also be used on submarines but must be very accurate to acquire
Shkval: 200knot torpedo fired from Akulas, 6nm range.
UUV: The Unmanned Underwater Vehicle produces a TIW warning. It tends to be quieter than torpedoes (although it is loud when cavitating).

ship launched:
Mk 50: Standard OTS (over-the-side) torpedo on US ships
Mk 46: US OTS torpedo
53cm: Standard Russian OTS torpedo

air-dropped:
Mk 50: Dropped from P-3s and Helos.
Mk 46: Dropped from P-3's, Helos, and ASROCs from surface ships
type 40: Dropped from the SS-N-27 ASW (Klub-ASW) missile, has a 65knot top speed
UGMT-1: Dropped from the SS-N-15 and -16, has a 41knot top speed and a weak warhead.

You must use the information you have to quickly assess the whether or not the weapon presents a threat to you. Note if the weapon was fired from an allied platform, if so, you can probably relax (although friendly fire is always a possibility). Also note wether or not the weapon was air dropped. An air-dropped weapon may have been delivered VERY close to your sub, if that is the case you need to know NOW. Note the intensity of the noise on the NB, and also BB sonar.

In addition to the narrowband classification, you can use the following characteristics to identify an air-dropped torpedo:

*ASROC torps (such as the Type 40) ping immediately upon entry.

*All ASROC torps, and sometimes Mk50s and 46s, are set to Circle. If you use
US subs the doppler shift will be clear on the NB sonar. (The lines will appear to "swerve") Over time, the motion will be visible on the BB sonar as well (the history will look "squiggly"). Please note that this is only true if the weapon is circling, not if it has acquired and is homing!

*A contact that pings once or twice, then is silent for several seconds, then repeats, is probably a circling torpedo that has NOT acquired anything.

*Several TIWs from multiple directions is indicative of a "bracket" attack by ASROCs. If this is the case, you may wish to skip the NB sonar assesment and commence evasion action IMMEDIATELY.

*A large amount of bearing drift for a "loud" (i.e., close) torpedo is an indication of an air-dropped torpedo that is close aboard that has not yet acquired (but soon will)--or less likely, a passive homing torp that is in the terminal homing phase.

Evading an Air-Dropped Torpedo.

Air dropped torpedoes are the most dangerous because you have very little time to react. A torpedo dropped nearly on top of your boat often cannot be evaded. I cannot stress enough that, if you are being opposed by hostile air platforms and you believe they have detected you, either come shallow to prepare to use the SAM launcher, or at least convince the enemy pilots that you intend to do so. A P-3 or helo that can park a torpedo within 1nm of you with impunity will kill you, it is up to you to use your deterrent capability to force the airdales to fire from 2.5 nm away or greater.

Once you have determined that an air-dropped torpedo has been dropped nearby, you should turn away from it and accelerate. If it acquires, your best chance for survival is to get the sub pointed directly away from it, and to release a decoy directly between your boat and the torpedo. After releasing your decoy, you should turn to get the weapon out of your baffles so that you can track it by its pings...Auto TMA may be your friend in this case, as it is very quick and very accurate. Also be aware that a spoofed torpedo heading toward a decoy behind you will produce an active intercept bearing that shifts astern of you. If the bearing holds constant, the torpedo is on an intercept course for you....turn away from the weapon and release another decoy.

Also be aware that air dropped Mk46s and Mk50s may be set to passive homing. This is a rarely used but potentially deadly tactic if you are only expecting active weapons. You can usually ID a passive weapon by marking it in Broadband and checking its speed in DEMON (torps have a TPK of 30). Torps set to maximum speed are probably active, torps slowed down to 45 knots or lower may be passive....plus the whole not pinging thing is a pretty good hint (provided that the weapon has in fact enabled!).
If a weapon is dropped very close aboard in front of you, or if weapons are closing from multiple directions, evasion gets more difficult. Desperate may be a better word. If a weapon is in front of you and close, do not order a course change--order the rudder directly. Stabilizing the turn may be difficult afterward, but you need to get the boat turned in order to survive, and you don't have time to waste.

If you cannot get the boat pointed away from a weapon either because of proximity or quantity, put the (or one of the) weapon(s) abeam of you. Fire decoys when it is close, and maneuver radically. There is some probability that a weapon that is turning to try to maintain its lock on you will break off and chase a CM instead. Turning towards previously released decoys might work--sometimes torps will break their lock on the sub and attack nearby decoys even if the torp already had the sub locked up. Also, if a torp passes close by a decoy, the torp's seeker is temporarily washed out--if this happens close enough to the sub, the sub may be able to escape the detection cone before it locks back on.

Prayer might help too. I have to admit that last paragraph is not solid advice, just remarks based on my observations of replays. If anyone else knows of any desperation manuevers that are effective, please post them, because I honestly don't have any good suggestions.

Evading a Ship-Launched Torpedo (or any non-wireguided active/passive torpedo)

These are the least dangerous of all ASW torpedoes. They are usually very short ranged weapons (the 53cm is above average at 10nm, the Mk50 does 7), so they can probably be outrun unless you are very close to the shooter. If you cannot outrun the weapon, there are (at least) two solid evasion tactics.

*If you succeed in forcing airdales to drop from several miles off, these tactics may be relevant for those as well*

One method is to release a decoy immediately, then run away at an obtuse angle to the torpedo. This removes you from its acquistion cone and opens range; when the torpedo enables it will hopefully acquire the decoy before it acquires you.

If you're short on decoys or want to stay close, hold on to your decoy and run at a right angle to the incoming weapon. With luck, you will escape the acquisistion cone and it will pass harmlessly by. Make sure you turn toward the torpedo as it drifts behind you in order to keep your active intercept pointed at it; also slow if necessary to monitor it on passive sonar. If it turns towards you, turn away from it and release decoys.

In the rare case that a wakehomer is fired at you, run as quickly as possible at a right angle to the weapon. Do not cavitate, or the weapon may acquire you as it would a skimmer. The greatest threat is if the weapon comes close enough to you to aquire regardless of your speed, in which case there isn't anything you can do to escape (at least not that I'm aware of)

[Molon Labe]

Evading a Sub-Launched Torpedo
Don't be duped by UUVs! A UUV launch will produce a TIW report, but obviously does not place you in danger. If you get a TIW on the bearing of an enemy sub, be sure to classify the "weapon." The UUV's giveaways are its sometimes quiet signature, its narrowband signature (often looks like a 688I or SLMM, it's also the only 60hz object to come from Russian/Chinese subs), a speed of 5 knots (TPK=30), and a launching platform patrolling at 4 knots or less.

In most cases, you should observe the torpedo briefly to see if there is any bearing drift which might indicate that you are not the target (just make sure not to dismiss an air dropped torp with bearing drift!). The exception to this rule is if you are fired on by a Kilo at very close range (no other sub should get that close) or by a Shkval, in which case you should commence an evasion routine immediately after IDing the weapon and assigning a tracker.

The Shkval Supercavitating Torpedo If your opponent is driving an Akula, be very aware of this threat. Do not allow the Akula to get within 6nm of you; be especially careful around blind corners.
Fortunately, the Shkval is easy to identify. There very few other objects that share a similar signature, and it is extremely noisy. If you believe you have Shkvals incoming, go to maximum non-TA failing speed immediately. If you are just barely 6nm away, turn directly away from them. Otherwise, run at a right angle to them. The damage done by Shkvals depend on depth, so you should run either very deep or very shallow to minimize the damage. The Shkval has a maximum depth of 398m (1306ft), so the Seawolf can get under it if the bottom is cooperative. You should also waste no time getting counterfire torpedoes in the water set to very short enable ranges...it is very possible you will be unable to return fire in a matter of seconds.

Wireguided ASW Torpedoes: The majority of weapons launched at you by other submarines will be of this class. These weapons are extremely dangerous because there is a human behind them, resteering them to match your every move, even steering them around decoys.
Your best bet to survive a wireguided torpedo attack is to degrade your opponent's ability to steer the weapons. That means firing snapshots as soon as possible...if you're in an Akula or Kilo, consider using an ASROC to put the pressure on more quickly. When your enemy speeds up to evade, their sonars will be washed out and they will lack crucial sonar data to know what you are up to.

CLEAR DATUM. Don't be where your opponent thought you were. Consider trying to fake out your enemy instead of running in a straight line. Running one direction, then turning the other way after your opponent accellerates is a good way to get him to resteer his torps in the wrong direction. Also, while a 90 degree evasion course is the best way out of the acquisition cone, it is very easy for your opponent to predict where you will be. Running at an obtuse angle will not only change your bearing, but your range as well. Increasing the range will also give your torpedoes more of a chance to close in on him, putting him under more pressure to stay at high speeds or even killing him, preventing him from resteering.

Keep in mind that the enemy is probably using Auto TMA, which will be very accurate as long as you are on a steady course. Changing course frequently will help to throw it off a bit. Also, if there is terrain you can use to block the enemy's LOS, consider using it (of course, it blocks your LOS as well, making your counterfire less effective!).

Track the Incoming: You should have placed a tracker on all incoming weapons back when you first went to narrowband to ID them. During your evasion routine, you should periodically slow to get new bearing info on the incoming weapons, and to assign trackers to torps that you could not mark earlier because of overlap. (Be careful not to lose your tracker on your enemy, the BSY-1 will automatically reassign trackers when you run out. Use your bow and hull array trackers too!). If you can get Broadband contacts, do so--this will allow you to get DEMON info. Torps set to 45 knots or lower are probably passive homing; if you notice one and you do not have passive decoys loaded, you may want to consider popping an active out now and reloading the tube with a passive decoy.

Monitor the active sonar sweeps with the intecept, and mark them as frequently as possible (or use Active Intercept Autocrew). A torpedo that pings several times at long intervals, possibly fading out for a time and then resuming, is probably snaking and has not found a target. If the torpedo is pinging on short intervals (maybe about 2 seconds or less?) and then it has probably acquired a target. If the intercept bearing is drifting astern, then it has probably acquired a decoy behind you. If the bearing holds steady, it has probably acquired you.

Also consider using UUVs. A UUV will pick up incoming torps very easily, and will provide very good locating data when merged with data from your sub's arrays. The UUV will also continue to record bearings while you are running at high speed. The downside of using UUVs is that they can be tracked by your opponent, confirming his TMA solution on you, and that they clutter the TMA plot with many unnessesary contacts (which usually pop back up if dropped!)....this in turn degrades the performance of the Auto TMA and may result in crucial updates being delayed.

By tracking the incoming torps, you will have an impression of whether or not your evasion routine is working. Change course as needed to get yourself away from the re-steered torpedoes (or if faced with a good spread, get away from as many as possible to make the work of your CMs easier).

Decoy the Threats. There are two basic ways to use decoys. One way is to leave them far behind you in the hope that your enemy will believe you are there, causing his torpedo to home in on the decoy while you are safely somewhere else. Unfortunately, decoys take time to reload so this tactic is not always prudent. It is also a good way to waste decoys, since your enemy will probably be competent enough to resteer his torps to your actual location. If you have been attacked by multiple torpedoes, and you are successful in preventing your opponent from resteering, then this tactic may be necessary and effective. Placing the decoy near the lowest speed on the SSP while driving your sub near the highest speed might help make the decoy the preferred target.

The other way to use decoys is to break the lock of a weapon that is homing on you. As mentioned earlier in this post, this works best when you turn away from the torpedo to place the decoy directly between you and the weapon. Always remember to turn after decoying to make sure that the torp is homing on the decoy so that you will know if you need to fire the second tube!

And always, always, remember to reload your decoy tubes!

An Afterthought: Watch your Aspect! I haven't specifically looked at aspect angles in regard to torpedo evasion, but considering how important aspect is in active sonar returns, I would imagine that, when a torpedo is choosing between two returns it will "prefer" the stronger one. This probably has a lot to do with why decoys are more effective when the sub is pointed away from the torpedo and the decoy is between the sub and the torpedo (return strength should be dependent on aspect and proximity). When moving at right angles to the weapon, or turning to track it, keep in mind that you may be presenting a better target to weapons that have not yet settled on a decoy. For this reason, its also probably a good idea to wait several seconds after popping a decoy before turning, this gives the torpedo a chance to lock onto the decoy first.

EDIT: I'd like to revise my position on delaying the turn. As Fish points out below, getting the torpedo to lock onto the torpedo is made easier by turns that make the seeker sweep over the torpedo. Instead, I would suggest presenting the minimum aspect possible during such turns as you can under the time constraints... It's a tradeoff, like many things in naval warfare sims.

[Molon Labe]

Origninally posted by Amizaur on the Subsim Review Forums:
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I have to admit that I'm yet to master this art :-) but know few things you should do or should NOT do when avoiding.

The most important thing is to not cavitate !!! If you cavitate then you become HUGE target for both active AND passive torpedo seeker. Second thing is - at first launch both passive and active decoy - from time to time happens an active torpedo that acquire and home with passive seeker - especially a loud cavitating target. Then no wonder that you can launch 20 active decoys with no effect http://www.subsim.com/phpBB/images/smiles/icon_smile.gif. Later you may load only active decoys, but at first launch both - passive and active. Third thing - sometimes it's good to slow down after relasing a decoy and turning - again it's not sure why this works but often works - if you continued on flank (even not cavitating) torpedo would ignore decoy and follow you, if you slow down to 5kts it suddenly finds decoy more attractive :-). This can have something to do with the fact that currently in DW noisy target is simultaneously a bigger active sonar target, so by slowing down you reduce your active signature in comparison to a decoy.
But second best of all tactics is to not allow torpedo to acquire you in first place so get your boat away from it's sesnor cone ! After enemy launches a torpedo set course perpendicular to torpedo bearing (or make a 180deg turn if torpedo is from the side already) and run as fast as you can without cavitating, you have fair chance that when torpedo enables you'll be so far to the side to be outside it's seeker cone.
This is much easier when torpedo seeker cones are more realistic, for example in L&A mod where Mk-46's seeker has 1500m acquision range and Mk-50 around 2300m - in comparison with 4500m for both in stock DW.

And the best tactics off all and I believe this is primary tactic used by real life sub captains http://www.subsim.com/phpBB/images/smiles/icon_smile.gif is to not get shot at in the first place http://www.subsim.com/phpBB/images/smiles/icon_wink.gif because if you get, any evasion tactic is not 100% sure and you can die eventually....

So try to shoot at the target cargo ship from max range (which is outside range of Perrys torps), it would be also good to launch from the rear (wait till targets passes by and maneuver to be behind them, only calculate carefully your torpedo range then because targets are opening the range) and after launch immediately turn away and run to be as far from the frigate as possible - again not cavitating if possible, so rather for deeper waters.
You can also find a (distant) place where the bottom shape will hide you from the frogate if you place yourself on the bottom (so you in underwater valley and between you and the frigate would be a shallower area) - after launch run to this place and lay on the bottom.

Or you can close to the frigate for 100-200yds and follow it everywhere, even surfaced - it won't hurt you as long as you stay very close ;-)
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NOTE: DW 1.04 corrected the bug that makes active SL's depend on passive SL's.--ML

[Fish]

Excelent tips!
I want to add something. A torpedo always try to "lead" your course, in other words he is taking the shortest way.
When one or more torps acquired your boat, going say 000, turn away to 030, wait a few seconds (depends on how close they are), cavitate if you can. Then launch decoys as told before (active/passive) and turn hard away, say 330, slow down at the same time. The torp lost you and turns back to 000, finding a nice fat juicy target, your decoy.
This was a nice tactic in SC, and should work in DW.

On the UUV, when launched below 520 feet, and hold there, your enemy does NOT recieve TIW. :)

[Molon Labe]

Excelent tips!
I want to add something. A torpedo try to "lead" your course, in other words he is taking the shortest way.
When one or more torps acquired your boat, going, say 000, turn away to 030, what a few seconds (depends on how close they are), cavitate if you can. Then launch decoys as told before (active/passive) and turn hard away, say 330, slow down at the same time. The torp lost you and turns back to 000, finding a nice fat juicy target, your decoy.
This was a nice tactic in SC, and should work in DW.

On the UUV, when launched below 520 feet, and hold there, your enemy does NOT recieve TIW. :)

A very good point.... You can increase the possibility of the decoy being acquired in this fashion. Or, as JoGary put it, you try to "drag" the torpedo's seeker across the CM. It is definitely more effective than dropping while facing exactly away.

[Molon Labe]

Here's a visual example of dragging the torp sensor over decoys. The turn in this example is harder than what Fish describes since it was done with LW/Ami installed and the torpedo will not explode on the decoy--so the sub needs to get clear before the torp passes the decoy.

http://home.insightbb.com/%7Enotenoughsand/torpevasion1.jpg
http://home.insightbb.com/%7Enotenoughsand/torpevasion2.jpg
http://home.insightbb.com/%7Enotenoughsand/torpevasion3.jpg

Of course, it's a bit trickier without show truth on, but it helps to see what's actually happening so that you can put a mental picture together when you're doing it "for real."