[UKönig]

Your U-boat and you
*A new Captain's guide*

So, You've decided to become a U-boat Captain...
Congratulations! You are about to embark on a rewarding (life threatening) career.
Fortunately for you, I, Kapitanleutnant Johan Konig, have put together this little survival guide, which hopefully will help you survive the war.

Your boat.
Is obsolete, even when brand new. It has not made many advances since the end of 1918. Primarily must travel on the surface in order to make any gains. Speed, without any improvements to the engines, is rarely faster than 17 knots. Multiply knots by 1.4 to get kilometers per hour, which is about 23.8 in this case. Now compare 24 km distance to the vastness of the Atlantic and you can instantly see what kind of a disadvantage this is. Now lets' try the underwater speed. 7 kts = 9.8 km per hour. We have golf carts that go faster than this. Your bicycle can go faster than this, hell, even a dog sledding team running the Itadtrod race can go faster.
One of the big problems became that the merchant ships themselves were able to make faster speeds, slower when the weather was bad, but, the U-boats became too slow versus the ships they were intended to hunt. The prey got leaner and the U-boat (lion) got fatter, to put in another parlance.
To start with, stay on the surface whenever possible. Fight on the surface, whenever possible. Take advantage of your higher diesel output. If your target can't shoot back, and conditions favor it, attack with the surface weapons (they cost less per shot than a torpedo, and war is expensive, even to a dictatorship).
Only dive to keep the element of surprise. Experience will teach when is the best time to keep stealth. Usually after the target spots you, it will start taking zig-zag actions. Unless or until they spot you, they should go on sailing innocently.
Later in the war, as aircraft and radar sets become more plentiful and efficient, you will have to spend most of your time in transit underwater. If you'll refer back to the pitiful maximum of 10km per hour, you can see how convoys can get away with ease.
You come up only to recharge your batteries. Man the AA guns any chance you get, they may be the only thing that can buy you enough time to crash dive.
If possible, turn your boat into the windward side of the attacking aircraft. The plane gets too much wind on the wing as it banks, and it's forced outward. Doesn't make that much difference, but the U-boat needs every inch of space it can get. Literally.
If forced to dive in proximity of destroyers, evasion will depend on several factors.
Firstly, the shallow waters of the English channel will provide adequate protection from ASDIC detection or passive listening systems, like the hydrophones, due to the fast currents that flow through there. Anything up to 12 knots. All that rushing water disturbs the sensors and makes them inaccurate. Sweep wires or drag lines will probably be used at that point, and those should still work just fine. Too bad. The North sea is a little bit different. Because the water and ocean currents are more diffuse, and not being forced through a channel, ASDIC and hydrophones work well enough.
There, often times, a U-boat's best defense (if they could not run away), was to sit on the ocean floor, turn off all non-essential machines and electrical equipment, and stay as quiet as possible, in the hopes that the Tommies above will lose interest and leave, or mistake the U-boat for an unusual rock formation, or maybe a sunken trawler, but either way, biding time and hoping for them to 'go away' is a last resort.
And if they *do* score a hit, it could break open a fuel bunker (those saddle tanks on the sides), releasing their contents back to the surface. And an oil slick is unmistakable evidence of a direct hit. If that happens, they will never go away until your air runs out. If that happens you have only two options. Choke to death on carbon dioxide poisoning, or, alles ausblassen, and blow ballast to emergency surface. If they did things correctly, you *may* get a chance to surrender, before they blow you to pieces with their naval artillery, as they were just sitting there, waiting for you. It's not cool to be *that* popular.
If you are fighting in deep water, at the beginning, you have the advantage of depth. In 1939 to about 1942, like Jan. 1942, the greatest depth a wasserbom could drop to was about 498 feet. By staying under that, the U-boat was relatively safe. The surface attackers can hear you, they can ping you, but they can't *reach* you. It was like in the Pacific. The Japanese could rarely hit US submarines because they simply did not set their charges deeply enough. One careless comment from a US politician changed all that though...
In any case, by 1942, do not think that depth will protect you. Only not being in the area of depth charges will be effective at 'not getting sunk'.
Going to silent running only works on the passive systems, if they hit you with the active systems, there pretty much is nothing you can do about it.
Tricks there include changing depth, going deeper, or shallower, hit full speed when you hear the splashes, try to jink left or right, depending (here I like to use exterior view). Hit silent running again after the first few charges go off because those underwater blasts cause big bursts of static in the earphones. Their own weapons provide the cover for you to hide behind.
If you are being attacked by more than one destroyer, the odds are very much not in your favor. If the Hunter-Killer group contains more than 3, the odds are very much that you will not get away. When using depth charges, the attacking destroyer must move quickly, or else they will get hit by the water column when the charge goes off. Going over 13 knots messes up most ASDIC sets, so the attack run makes a blind spot for you to hide in. Unfortunately, when more ships are attacking, the others go just fast enough to ping you, and radio that information back to the attacking ship. They draw a net around you that you simply cannot out run.
To further reduce the U-boat's chances, the Allies developed the 'hedgehog', a device for throwing depth charges in a forward, eliptical pattern, ahead of the attacking ship. This served two purposes. Firstly, it cut off any dash to the left or right, once the attack run had begun, and secondly, the charges only detonated when they made contact with the hull, which meant, fewer blind spots to hide in. Contact was not lost when explosions were heard. Which thirdly made the U-boat easier to kill. Because they know exactly where you are. You think you are hiding, but, you are not.
Nowhere else is the axiom "speed is life" more applicable than in the U-boat war. The boats simply were not fast enough. Some attempt was made to correct this defect, what with the Type-21s and 23s , but it was too little too late.
Above all, try to keep going. The only times you should be 'all stopped' are when you are conducting a search and destruction of contraband, when you are on the bottom, hoping against all hope that your attackers will go away, or when you are dockside, being repaired or fitted out.
Enjoy your new career, and your spiffy white U-boat command cap option, and rest assured, that 8 out of every 10 U-boats failed to return from patrol...