Evading: when to go flank speed?

[dfscott]

I've read several different opinions on evading escorts, particularly with regard to when to go flank speed and try and get some distance away. Here are some of the techniques I've heard:

1) Go flank as he passes overhead. You'll be in his baffles and he won't hear you.

2) Go flank when the depth charges hit the water -- he's already started his attack.

3) Go flank (and change direction) when the ashcans start exploding -- you need to get out of there now and he's likely moved past.

4) Same as #3, but only if you're actually getting DC'ed -- if the escort is not dumping them on you, going flank will give you away even with the explosions going off.

5) Go flank (and change depth) when you're getting the reverb ping (i.e., the loud ping-ping) -- this means he already knows where you are, so no sense trying to hide.

Ofc, this assumes a single escort -- things get more complicated with multiple ASW ships.

[Brag]

The area in which asdic or sonar looses you depends on your depth.

Imagine an inverted cone above your sub that ends at the surface.

If you are at periscope depth the cone will be smaller that the lenght of the U-boat and the escort will not lose contact till on top of you.

As you go deeper, the wider the cone will be at the surface and the further away your escort will loose contact.

When in the baffles, he can´t hear you, nor when depth charges explode.

[ryanglavin]

If its clear weather, and your caught by more than 1 ship past 1943, your just dead.

If its cloudy weather and your caught by more than 1 ship past 1943, you might get lucky.

[Scape]

Stay still. Your not going to outrun them. Keep only the bare min speed to keep depth. Wait 30 min then creep away. Once they are long range then surface and run flank to out flank conviy but not to outrun DD.

[sharkbit]

Stay still. Your not going to outrun them.

No you won't outrun them, but you may avoid the DC's raining down on you.

Still, I try to use my time at flank pretty judiciously. Slow and silent is usually best.

I get constant reports from my hydro guy when under attack.
If the bearing is starting to lag(going behind me), I'll stay silent with maybe a course change thrown in now and again. He's probably going to miss astern.

If the bearings stay pretty constant(collision course), all hell will probably be breaking loose pretty soon and I'll hit flank when I get the "Wasserbomben!!" and do a course change (and maybe depth change), pray he doesn't have hedgehogs , then cut the motors and coast when the DC's go off(and do a little more praying ). I'll start the motors back up to slow when my speed drops to 1kt.

If the bearings are starting to lead me(going toward the bow), probably a course change is in order and I'll wait and see before I pour the coals on depending on my gut feelings.

You can get a feel for the rate of bearing change and how close the destroyer is to aid in evasion and help you make the decision on course and speed changes.

Also, if you are being pinged and the escort is closing on you and the pinging stops, assume that you are out of the sonar cone. That might be the time to do something drastic, depending on the hydro information you have and your gut instinct.

[TarJak]

Rule #1 is avoid getting detected in the first place. To do this loose your eels, dive immediately to 200m+ (speed tends not to matter much but the faster you dive the better). and change course to move away from the datum of your firing point. I aim for being at least 100m depth and 1km away from the datum by the time my first torpedo hits. This means using slow speed torps sometimes or shooting at ranges of ~1500m.

The datum is where the escorts will congregate to initiate their search. The further away from this point, the harder it will be for them to locate you.

I've been playing this way for the past 6 months with careers starting in 1941 and have largely been undetected in about 85% of attacks until reaching late 1943. Things get much much harder then as there are both more escorts and they have better detection capabilities which means detection often means death.

Once getting detected though, I tend to stay silent running on a relatively steady course for most of my evasion relying on depth (230-240m), to make it harder for the escorts to get a hit. I usually only use flank when I know the DC's are coming down almost directly on my boat and run for 20 seconds from the explosion of the last DC before returning to silent routine.

[Sailor Steve]

In my experience the best time to go flank is when you can hear his propellors. If you're a 70 meters or more, when you can hear him inside your boat he's to close to know where you are. Waiting until they explode is kind of like waiting until you hear a bullet whiz by to duck. The next one might already have you. Go to flank and change your depth by at least 20 meters.

Once they're exploding, go silent again and turn your tail toward him to decrease your signature. Of course if there are several everything changes, since one of them will be listening to see where you go when you accelerate.

[Dissaray]

In my experiance, limited though it may be, flank speed is realy only warranted when you need to dodge a bulet. If you hear them pass over you and then splashes you may well be about to get hit. Dive 20-30m, go hard over so your course is oposite that of your attacker, put some distance between you, and hit flank. Diving is always preferable to going up, going up you may well intersept a charge that would have missed you otherwise. That should get you some breathing room and out from underneeth the attack. As soon as the charges start poping or you determine the ship has turned and can hear you again cut engens and coast and watch your scopes to see if he is going to re-engage you. If he dose you get to dance some more, if not slip away nice and quiet or set up to kill him for trubbling you so.

[tomfon]

The big problem are hedgehogs. If you have both of the external views disabled (external and event camera) you are in a really miserable and helpless state. There is nothing to warn you if the destroyer has hedgehogs aboard. I usually go to flank and change direction before i can hear the destroyer closing. This kind of evasion works well with one opponent. When it comes to 2+ destroyers and the weather is excellent... well, i usually kiss my crew goodbye. This is why i restrain myself from performing a convoy attack under calm seas (past mid-'43, that is)... a lesson i learned the hard way.

[Hook]

I have some techniques I worked out in the Silent Hunter 2 and Destroyer Command days. They enabled me to escape attacks by destroyers commanded by humans. I learned more about evading destroyers by playing Destroyer Command than I ever did by playing Silent Hunter alone. Two main things were that destroyers could only hear you in their front 180 degree arc and depth charges fell at 3 meters per second.

Go as deep as you can before the attack. I haven't timed it in SH3, but at 90 meters you should have 30 seconds before the depth charges explode.

Basically, if you hear his engines AND you hear the depth charges in the water warning, go to flank speed until the depth charges stop exploding. If you're going to change direction, do it near the end of this run because turning slows down your boat and you want as much distance as possible from your previous location. Don't bother trying to turn more than about 45 degrees. Changing depth slows you down as well, but I haven't measured how much.

If you don't hear his engines when you get the depth charge in the water warning, don't bother going to flank speed as he's probably going to miss and going to flank speed just lets him know where you are. This is different in SH3 as at least some ships seem to be able to hear you anywhere around the boat, not just in their front arc. This includes hearing you in their baffles.

If your hydrophones still work, either have your sonarman constantly tracking the attacker, or track him yourself. You can get a good idea where he is and what he's doing. For example, if he goes to fast speed and his bearing doesn't change for several seconds, it's likely he's setting up an attack run on your position. It may weave back and forth by a couple of degrees in this case.

It would be nice if we could get positive verification on the arcs where a ship can hear you. It was a frigate that detected me when I went to flank speed for a few seconds when I was in his baffles.

Hook

[ppk]

From my experience a destroyer will search for you where it expects you would be if you kept the course he last saw you on before making a pass. For that reason I often deliberately run at 2/3 or reload torpedoes when I know it's on to me so as to make sure to be heard, and give about 15-20 degrees of rudder when it's pinging. Then as he begins dropping the depth charges I go to flank and make a radical course change to the opposite direction and stay at flank for 20-30 seconds, checking where he is to present a minimal profile. This way he will [hopefully] be slightly put off and drop his next line of DCs somewhere else than on my head.

It goes something like this (please excuse my poor MS Paint skills )...


Of course this works better at near-critical depth and before 1943, but it's still adequate later as long as you're not getting pounded by a full horde of DDs. But then if there are only one or two DDs, it's sometimes easier to go to periscope depth and sink 'em...

[Bosje]

ideally, i want the DD to come at me from behind, slightly off to one side
say, bearing 160. only possible if you already turned away from him after the previous attack.
sonar guy tracks him when he comes back, as he starts to close in i order a turn the other way (in this case to starboard) and change depth at least 20m
all this still on silent running so the changes will not have much effect yet but they are 'pre-ordered'

then, when i am pretty sure that he has me (the ping-ping or i made a lot of noise earlier) i'll start speeding up when i can hear him from inside the boat
when the depthcharges fall i'll get to flank speed and that means my 'pre-ordered' evasion manouvre is executed swiftly

then silent again

the important thing is to only actually do this to avoid being blasted to shreds, so only use flank speed if the depthcharges are about to nail you (as far as you know).
if there's more than one escort, you will give yourself away and you'll have to keep playing that little game over and over

i often find that escorts (even multiple, even in 1943) will spend a long time blasting a certain spot where you were some time ago. if they didn't actually nail you with ping-ping and if you think you didnt make enough noise to be picked up passively... they may not actually have you and they may simply do an attackrun on your last known location from the previous run. it will appear as if they are coming right at you but in fact they're not

if they trick you into using flank speed without good cause, they'll re-acquire

at some point, they WILL temporarily lose you. the trick is to figure out when that is

steel nerves and a good sonar guy are required

god how i love that cat and mouse game

[dfscott]

Thanks, everyone, for all the excellent feedback.

I thought I'd share another version of evasion techniques -- this is based on info/pics in the GWX manual (I'm playing GWX, BTW).

[maillemaker]

Of course, by late in the war you should have noisemakers.

In which case I find it useful to go to flank speed, drop a noisemaker, and then go to 1 knot speed with a 15 degree course change.

But really, when they are on you, best just go to periscope depth and shoot them.

If you're lucky, they'll blow their own ass off with a shallow depth charge.

[ryanglavin]

Originally Posted by maillemaker

If you're lucky, they'll blow their own ass off with a shallow depth charge.

Always seems to happen late war, with extremely experienced crews, ha.