Submarine And Anti-Submarine

Discussion in 'The War In The Air' started by Peter Clare, Aug 23, 2016.

  1. Peter Clare

    Peter Clare Very Senior Member

    I obtained this document very many years ago, I have no idea where from (Its an age thing) Thought I would post it on here for the interest of others. Posted in sections as I found it easier :)

    It was ---- Originally produced by H.Q Coastal Command October 1942 - Reproduced May 1943.

    SUBMARINE AND ANTI-SUBMARINE

    1. THE U-BOAT

    General and Constructional

    In any contest of skill, whether in peace or war, the more one knows about one's opponent, the more chance one has of success. This statement is probably more true in the case of Anti-Submarine warfare than in any other form of air operations and for that reason every crew engaged on this type of work should have a thorough grasp of the general characteristics and limitations of the U-Boat. We are lucky in having captured the U-57o, now H.M.S. "Graph", as from her we have obtained not only complete constructional details of the typical 517 ton class U-Boat, but full details of her performance and limitations and so are able to work to known data.
    Primarily, the U-Boat is a warship, to whom the power to dive at will gives the gift of invisibility. But working under water and sometimes at great depths, she must be immensely strong to withstand the pressure of the water, and even stronger to withstand the under-water blast of depth charges and bombs. Practically every U-Boat likely to be met at sea consists of a pressure hull built to withstand these great strains and stresses, outside which are various fairings, casings and tanks built to give streamline shape to the pressure hull and conning tower, to provide a flat upper deck and also fuel and buoyancy tanks.
    The pressure hull of a U-Boat is the strongest structure ever produced in marine architecture. Built of i" high tensile steel, it is cylindrical in shape as being the best section to withstand the great pressures likely to be encountered. Joints are both welded and riveted. Ribs, bulkheads and, in the lower part of the hull, the sides of tanks, add greatly to the rigidity. All hatches, bulkhead doors, torpedo tube doors, glands for propeller shafts and periscopes, hydroplanes and rudders and such fittings are also designed to withstand pressure and under-water blast. The conning tower is an oval-shaped pressure-tight structure made of even heavier gauge high tensile steel than the hull. It is built over the centre of the boat and has two heavy hatches, the upper leading to the bridge and the lower to the control room. These two hatches, together with a large induction pipe leading from the after-end of the bridge to the engine room, and possibly a voice pipe, are normally the only openings into the U-Boat when she is at sea. The inside of the pressure hull is divided into a number of water-tight compartments by bulkheads in which small but heavy circular doors secured by clips are fitted. While these add to the general strength of the boat they are not conducive to comfort or rapid movement from compartment to

    Crampted U-Boat.png

    compartment. The accommodation for the crew is of necessity very cramped and on long cruises is made worse by the carriage of spare torpedoes and provisions. While on patrol, to add to the general efficiency of the boat and the speed of diving, but adding still more to their discomfort, the crew have to live and sleep at their stations.
    All U-Boats have a flat upper deck extending nearly the whole length of the boat. This deck, usually made of wood slats, is about 2 ' 6 above the crown of the pressure hull and is supported by light girders. From the deck to the pressure hull is a casing of thin plating provided with a large number of holes to allow free flooding and to avoid air pockets when diving. Inside this casing are stored wires and ropes, non-perishable stores, spare torpedoes, safety buoys, ready-for-use gun ammunition, a few high-pressure air bottles and such-like articles. Similarly, the conning tower is streamlined by a light casing which forms the bridge, bridge-screen and A.A. gun platform.
    From the bottom of the casing to about the centre line of the U-Boat and centrally for about one-third of her length streamline blisters of r steel are built, and the space between them and the pressure hull is divided into a number of compartments on each side. These form the external main ballast and fuel tanks. To complete the boat streamline fairings are fitted to the bow and stern. In addition to giving her a reasonable streamline form, this outer hull provides brackets for the rudders and hydroplanes and propeller shafts, torpedo tubes, anchor hawse pipes and all the other fittings which go to the make-up of a ship.
    The fuel tanks in a U-Boat are of the self-compensating type; that is, they are always open to the sea at the bottom. Fuel is taken from the top of the tanks and, as it is used, so its place is taken by sea-water, Both internal and external ballast tanks are provided. The external tanks, like the fuel tanks, are permanently open to the sea at the bottom. Internal tanks are provided with large valves in the base, known as Kingstons. These valves would be closed in harbour, but are always open when at sea. In the top of all the tanks are " vent-valves" and " blow-valves". The vents open to the outside of the boat and let the air out when the tanks are being flooded. The " blows ", on the other hand, allow high-pressure air into the top of the tanks to force the water out and thus add buoyancy to the boat. At sea it is normal for a U-Boat to fill, or partially fill, some ballast tanks and then close the vents. The water cannot rise higher, due to the cushioning effect of the air locked in the top of the tanks, and in this state the boat is said to be " riding on her vents". To fill the tanks, therefore, it is only necessary to open the vents and release the air.
    For observation when submerged, the U-Boat is provided with two periscopes which are about 3o ft. long. The top three feet of each fines away in diameter so that the portion showing above water will only make a small feather. The foremost, or search-periscope, has a top diameter of about four inches surmounted by a 5-inch " blob ". It is fitted just ahead of the conning tower but inside the fairing of the bridge structure with the eye-piece in the control room. This instrument passes through a gland in the pressure hull and the lower part houses, when lowered, into a well let into the floor boards. Lenses give powers varying from r f to 6 magnifications and a prism gives sky search up to the vertical. This periscope would be used during normal periscope watch when on diving patrol.
    The attack-periscope is used in the later stages of submerged attack, and for this reason the top diameter is only 1.5 inches. This glass also has powers of i f to 6, but the top prism only allows for a search of 40° above or below the horizon; enough to cater for roll and pitch. In this case the eye-piece is in the conning tower, and the instrument is trained by pedals, the operator sitting on a bicycle saddle. This periscope passes through a gland in the roof of the conning tower, and houses in a pressure-tight well extending from the roof of the control room nearly to the keel. As this periscope is operated from the conning tower it is some 81 ft. higher than the foremost one.
    There are two sets of machinery in the U-Boat; Diesel engines for propulsion on the surface, and electric motors for use when submerged. The motors also serve as dynamos for charging the batteries when on the surface. U-Boats on the surface combine high speed with very long range at cruising speed. The maximum speed of U-570 was found to be about 175 knots, at which speed her endurance was 2,690 miles. On the other hand, at a speed of 6.25 knots the endurance worked out at 13,750 miles. The normal cruising speed would probably be in the neighbourhood of 8.5 knots which would give an endurance of about 10,000 miles. When travelling submerged on both motors the maximum speed proved to be about 7.5 knots, when the battery end urance was only two hours. At I knot, however, the batteries would last for 70 hours. This does not mean that the boat could remain submerged for that time, however, for the air would become foul long before that, and no Captain would be prepared to run his batteries flat. Normally, a U-Boat would never remain submerged for more than 20 hours at a stretch, but in case of serious hunting might remain down for as long as 3o hours. A general arrangement diagram of the 517 ton class U-Boat is shown at the end of this book.
    A few words should be included concerning the seaworthiness of U-Boats.
    In conditions of moderate sea and swell, that is to say, when "white horses" are visible and the wave crests are about thirteen feet high, the U-Boat proceeding head to sea can maintain an efficient lookout at a speed of about 5 knots. If the sea is rough and the swell heavy the maximum speed will be 3 knots. Higher speeds than these are possible by day if the bridge is evacuated and lookout is maintained through the watchkeeping periscope. If speed is increased without evacuating the bridge, the lookouts will be more concerned about their own safety than with that of the boat, for at times the bridge is apt to disappear 3 feet under water.
    In a moderate sea and swell proceeding with the sea about 43° on either bow, speed can be increased to 9 knots.
    If the sea is between the beam and the stern, although "pooping" does not occur to any dangerous extent, the boat will roll and remain listed to one side or the other long enough for the lower side of the bridge to fill with water. Under such conditions speed is unlikely to be in excess of 10 knots.
    In bad weather water is kept out of the boat by closing the conning tower hatch, and the air for the main engines is drawn through the outboard induction pipe. This is a large pipe, about 2 feet in diameter, of pressure hull strength. It leads from the after end of the bridge, through a valve underneath the cannon platform, then aft between the pressure hull and the casing for a distance of about 25 feet, and then passes through a valve in the pressure hull to the engine room.
    The above remarks apply to a U-Boat which has its "blister" main ballast tanks full of oil fuel. When all external fuel has been consumed these tanks can be used as normal ballast tanks which, when empty, give 5o per cent. more buoyancy, and therefore, great seaworthiness and stability to the boat. Thus a homeward bound U-Boat can be expected to have a better performance in bad weather than one which is outward bound. In other words, she will be able to proceed at higher speed on the surface with the conning tower hatch open. If, therefore, the blister tanks can be holed by machine gun or cannon fire this additional buoyancy is lost and speed must be reduced and possibly the bridge evacuated.
    From the above remarks certain important facts emerge. Firstly, the best target for machine gun and cannon fire on a surfaced U-Boat is the lower after end of the conning tower and the casing from the conning tower aft for 25 feet. Also the blister tanks along the midship section of the boat. Secondly the rather poor performance of the 517 ton U-Boat in a sea more than 'moderately rough' necessitates closing down the bridge and only keeping watch through the periscope. This makes rough weather hunting conditions as good as hazy conditions for surprising the U-Boat on the surface.
    The above description applies to the 517 ton class, but the broad principles are similar for all types. However, brief notes on the main types of enemy U-Boats follows:—

    GERMAN.

    I. 25o ton class. Length 136 feet. Speed on surface 13 knots, submerged 7 knots. Torpedo armament-3 bow tubes. Guns—one 20 m.m. A.A. This class is not likely to be encountered at sea except possibly on Coastal convoys.
    2. 500 and 517 ton class. Length 206-213 feet. Speed on surface 164-174 knots, submerged 74 knots. Torpedo armament 4 bow and 1 stern tube. Guns—one 3.5 inch and one 20 m.m. A.A. Some have been modified to carry mines.
    3. 712 and 740 ton class. Length 233-245 feet. Speed on surface 184 knots, submerged 8 knots.
    Torpedo armament-4 bow and 2 stern tubes. Guns —one 4.1 inch and two 20 m.m. A.A. Some have been modified to carry mines.
    4. 1,000 or 1,200 ton Cruiser Class. (About 30 boats.) Length 28o feet. Speed on surface 16 knots, submerged 7 knots. Number of torpedo tubes not known. Guns, probably one 4.1 inch forward and one 37 MM. aft.
    5. 1,600 ton class. (About ro.) Length 290 feet. No other details known, but some may be fitted as mine-layers.
    6. Broad beamers, or ' Mikh Cows'. (About 15.) Tonnage between 1,200-1,600 tons. Length, 213 feet, which is the same as the 517 ton class, but the beam is 25 feet as against 20 feet outside saddle tanks as in the latter class. No information is available about performance or torpedo armament, but they have two guns, one forward and one aft of the conning tower, probably HA/LA of 37 m.m. They are probably used solely as supply boats and are easily recognised by their squat appearance, with the conning tower slightly aft of amidships.

    ITALIAN.

    There are so many types of Italian U-Boat that it is only possible to give details of the most numerous.

    I. St. Bon Class. 1,461 tons. Length 288 feet. Speed on surface 18 knots. Torpedo armament 14-18 inch tubes. Guns—two 3.9 inch and four m.g's.
    2. Marconi Class. 1,036 tons. Length '251 feet. Speed on surface 18 knots. Torpedo armament eight 21 inch tubes. Guns—two 3.9 inch and four m.g's.
    3. Gemma Class. 620 tons. Length 198 feet. Speed on surface 54 knots, submerged 84 knots. Torpedo armament six 21 inch tubes. Guns—one 3.9 inch, two 13 m.m. A.A.

    JAPANESE.

    Similar remarks apply as in the case of Italian U-Boats.

    1. Improved I 5. Class. 1,900 tons. Length 343 feet. Speed on surface 17 knots, submerged 9 knots. Torpedo armament—six 21 inch tubes. Guns—one 5 inch, two light A.A.
    2. I I to I 4 1,955 tons. Length 320 feet. Speed on surface 17 knots, submerged 9 knots. Torpedo armament—six 21 inch tubes. Guns—two 5.5 inch, two light A.A.
    3. RO 60-68. 988 tons. Length 25o feet. Speed on surface 16 knots, submerged io knots. Torpedo armament six 21 inch tubes. Guns—one 3 inch, one light A.A.
     
    Last edited: Aug 23, 2016
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  2. Peter Clare

    Peter Clare Very Senior Member

    2. DIVING

    As has been stated previously, a U-Boat is provided with various ballast tanks, some of which are inside the pressure hull and some outside in the saddle tanks. When all these tanks are empty the U-Boat is a normal surface vessel. Actually, there are three types of tanks: main ballast, both internal and external; trimming tanks at bow and stern for maintaining or adjusting under-water trim, and " Q " or quick diving tanks placed by the centre of gravity in the saddle tanks. All these tanks can be flooded or blown at will, as can the fuel tanks in case of emergency.
    The U-Boat dives by taking in water ballast and by the use of her hydroplanes. The design of the tankage is such that, when the main ballast tanks are flooded she should, theoretically, be the same weight as the water which she displaces and should be on an even keel. This is known as diving trim and in this condition she will either float with her conning tower awash, or will just sink. By going ahead on her motors and placing the hydroplanes to dive the boat submerges, and thereafter the desired depth is maintained by the use of the hydroplanes. By flooding her '0' tanks in addition to her main ballast, the U-Boat will have negative buoyancy and will sink.
    When in an area where air attack is expected, a U-Boat will normally proceed " trimmed down", that is, with certain ballast tanks full or nearly full, and by using fine adjustment she can run with her upper deck awash. showing only her bridge structure and gun. On the alarm being given all vents would be opened to flood the tanks and at the same time the hydroplanes would be set to dive. The Diesels would be stopped and motors started and from this state she could submerge in about 25 seconds, thereafter
    gaining depth at the rate of about feet per second.
    On reaching about 6o feet depth the Q" tanks would be blown to regain normal diving trim, and it is probable that the high pressure air would be kept on until it was heard roaring out of the tanks. A short discharge of air would follow the water while the valves were being closed, and this causes the " eruption " or " explosion " often noticed by pilots after the release of depth charges.
    A U-Boat in rough weather prefers to dive beam on to a sea and may alter course to reach this position. On the other hand, she will, if possible, surface head on to the sea. A submarine forced to dive as a result of air attack may, and probably will, alter course after diving The turning circle is so slow, however—it takes her 21 minutes to turn 180° and 5 minutes to turn 36o°—that some part of her hull will be on her original line of advance for about 3o seconds after " dipping ". She may also make a last-moment turn on the surface before diving to throw the opponent off the track. Actually, this may be an advantage to the aircraft as it slows down the speed of diving and rate of descent and increases the time taken to submerge by about to seconds.
    When submerged, a submarine's endurance is limited by (a) battery capacity on which depends propulsion, cooking, heating and auxiliary machinery, (b) high-pressure air for blowing tanks and (c) the condition of the air breathed by the crew.
    A submerged U-Boat is propelled by her electric motors, the current for which is provided by batteries which weigh up to 15o tons. This huge dead weight has to be accepted as the Diesels, which draw their air through the conning tower hatch or a large induction pipe, cannot be used while the boat is diving. The battery compartments are situated under the living quarters forward and aft of the control room and are weak spots in the boat due to the vulnerability of the battery containers, and the risk of chlorine gas, should the acid spill and mix with sea-water.
    The Diesel engines are used to charge the batteries and at sea this would normally be done at night while on passage. The U-Boat can either run on one engine and charge on the other with the propeller unclutched, or can run and charge at the same time. In an area where the danger of air attack is serious, there is no need to charge continuously, but this can be done an hour or so at a time, whenever conditions seem suitable. The fact remains, however, that about 5 hours a day must be spent charging when the U-Boat is making the passage submerged.
    The state of his batteries provides the U-Boat Captain with one of his major sources of anxiety, particularly during the months of long daylight. It takes a long time to charge if they are almost completely exhausted and thus, as has already been stated, a boat will never stay submerged for more than 20 hours if it can be avoided.
    A U-Boat diving with a full charge has a battery endurance of 7o hours at about i knot, but only about two hours or so at full speed. Crash dives and evasion tactics need bursts of high speed which take a heavy toll of the batteries, so the more a U-Boat can be harried after an attack, the more chance there is of forcing her to the surface with exhausted batteries.
    A U-Boat carries only enough high-pressure air to blow her tanks completely a limited number of times. Some of the air bottles are stowed inside the boat close to the hull, and the remainder in the casing. All are connected to the H.P. air line and

    Captain U-Boat.png

    are charged up by an air compressor while on the surface. If a U-Boat is forced, by air attack, to dive frequently and without the chance to replenish the used H.P. air she may have to come to the surface and remain there.
    The fresh air which a U-Boat takes down when she dives would, if not purified, be just fit to breathe at the end of 36 hours. A man absorbs oxygen and exhales CO2, a poisonous gas; when working hard, he uses up five times as much air as when asleep, so the more he is harried the more air he will use and the less time can he spend below. U-Boats carry a device for eliminating CO2, and re-oxygenating the air, but the air may become " unbreathable" from other causes.
     
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  3. Peter Clare

    Peter Clare Very Senior Member

    3. STRATEGY AND TACTICS

    The whole German U-Boat organisation is controlled by Vice-Admiral U-Boats. He is directly responsible to the German High Command and has a close liaison with the Reconnaissance Aircraft Command.
    On completion, a U-Boat runs her trials either in the Baltic or off the Norwegian Coast. She then proceeds to sea on her first short war cruise, which is more in the nature of a shake down and, if all goes well, will join a running flotilla at a Biscay Port on completion of this cruise. Thereafter, she will carry out regular patrols, returning to the French Port for rest and repairs. In fact, facilities at the French Ports are now such that it is only very seldom that U-Boats return to Germany once they have left.
    When the present war started U-Boats usually attacked their targets submerged and in daylight. Not fully realising, at that stage, their danger from Asdic detection, they paid heavily. They soon changed their tactics and now at least 75 per cent of our losses are caused by surface attack at night.
    When a convoy is located by either enemy aircraft or a U-Boat details of it are passed to U-Boats in the area by their Headquarters. As soon as the first U-Boat arrives she will shadow from a long distance on the surface and act as a homing beacon for others who will have been instructed to join the pack. When four, five or more boats have collected they will generally attack on the surface and by night, the attacks in some cases being concerted, but more often " free for all ".
    It is impossible to lay down any hard and fast rule for a U-Boat's tactics leading up to the attack, as a successful submarine Commander must be an individualist and seize his opportunities as they arise. However, the probable normal tactics would be to shadow from astern or on the quarter of the convoy during the forenoon and then gradually work round the beam to fine on the bow by dark. After dark she will probably come in at high speed on the surface, attack and withdraw, still on the surface. In fact, on clearing the scene of the attack the Captain will prefer to remain on the surface, so retaining high speed, all-round view and better manoeuvrability. He will have the legs of corvettes and trawlers and can even draw a sloop a long way from the convoy. If a sloop or destroyer appears likely to pick him up he will dive and take avoiding action. In any case, if not seriously molested, he will re-load his torpedo without delay, and, when conditions are suitable, will rejoin the pack ready to attack once more. If, on the other hand, the convoy is heavily escorted, the U-Boat may not come in close but may fire a salvo "into the brown". From this it will be seen that, if the first U-Boat to sight the convoy is put down by air attack before she has homed the pack, the convoy is at least given a respite until she is again located.
    It is even more impossible to lay down any tactics for the U-Boat which locates a single unescorted ship. The Commander will certainly attack either by torpedo or gunfire whenever he locates a ship and that is why stragglers from convoys are in such danger. If his torpedo hits, he will probably surface. If he misses he will probably do the same so as to chase the ship and attack with gunfire. It is on these occasions when the look-outs may be so engrossed watching their victims that they may be taken completely by surprise.
    The action of a U-Boat on being attacked is also a matter which will vary with the individual Captain. Some will dive straight down to a great depth to get out of the lethal range of Depth Charges as quickly as possible, but may alter course when down to 6o—ioo feet. Some will put on helm as soon as the conning tower has dipped to throw the attacking aircraft off the track. Others will put on helm first and then dive, even though this does increase the time taken to get under and reduces the speed. Some may stay shallow and take violent avoiding action under water while others may prefer to stay on the surface and fight back. Whatever the tactics may be, however, the sooner the aircraft can get in his attack, the greater the chance of success.
    If the U-Boat is successfully to avoid air attack, the lookout must be of a very high order. While on the surface four men are employed on these duties. They stand back to back, each searching an arc of goO. They are supplied with excellent binoculars, and, as the watches are changed frequently, they do not suffer unduly from eye strain. In clear weather they will sight an aircraft at such a range that the boat can dive in plenty of time to avoid attack, but skilful use of sun and cloud cover will defeat them, as an aircraft will never be heard in time to avoid attack. In a heavy sea the lookout will never be nearly so efficient, as glasses and eyes will be filled with salt spray and, in fact, glasses will be almost useless.
     
  4. Peter Clare

    Peter Clare Very Senior Member

    4. THE EFFECT OF AIR ATTACK ON A U-BOAT

    The next point that should be studied is the effect, both material and moral, of air attack. It must be remembered that the target presented to the aircraft is only the pressure hull which, in the case of a 500- tonner, is only about 165 feet long and 15 feet in diameter. The lethal range of the present weapons is so small, and the hull of the U-Boat so immensely strong, that only a very near explosion will cause lethal damage. For this reason most accurate bombing is essential.
    The amount of damage sustained by a U-Boat attacked by depth charges will probably vary somewhat with the particular part of the hull most affected. An explosion some 3o feet ahead of the conning tower, if correct for depth, is probably the most productive. The following damage could be caused by air attack.
    A very near explosion would split or crush the pressure hull, and the boat would fill and sink. Unless the hole was very large, however, it would probably be possible for the U-Boat, by blowing everything, to struggle to the surface for a short time to permit the crew to abandon ship, though this is not invariably the case.
    A near explosion would cause leaks in the hull and also in glands and connections through the hull. It frequently jams the hydroplanes in the rise or dive position, causing the U-Boat to break surface or dive to a dangerous depth. Fuzes would blow and lamps and instruments would break. Battery cells may be broken. Oil from the external tanks would leak and show on the surface, but, of course, such oil is no proof that a U-Boat has been seriously damaged. And high pressure air might leak into the boat with dangerous or, at least, very unpleasant, results.
    A more distant explosion might cause a number of defects such as cracked battery cells causing chlorine gas and loss of power; broken lights, damage to instruments and compasses, jammed rudder and similar small defects, troublesome but not really serious. Again, oil might be forced out of the external tanks, but this is no proof of damage.
    The effect of the 20 m.m. cannon or machine gun fire on the pressure hull of the U-Boat is negligible, but if fire is concentrated on the bridge the crew will be kept below and prevented from manning their A/A Armament. It should be remembered that a wounded man is a serious embarrassment in a U-Boat, and if the wound is bad enough the boat may be forced to return to base.
    To describe the effect of air attack on the crew, it would be as well to describe in some detail the sequence of events. As soon as an aircraft is sighted the alarm rattles are pressed and sound their raucous note throughout the boat, while at the same time the few men on the bridge tumble down below, slamming the conning tower hatches after them. The rattles alone are enough to bring the heart into the mouth, especially as only those few men on the bridge know what it is all about. Orders are passed, Diesels stopped and motors started, the vents opened, planes put hard to dive and the boat assumes a steep angle down by the bows. Even with all tanks flooding, motors running at full power and planes hard to dive, the boat will take 25 seconds to submerge and those 25 seconds must seem like an age. And all this time the whole crew are in a state of tense anxiety waiting for the inevitable.
    Then perhaps the plops of the depth charges hitting the water will be heard and in two or three seconds the explosion. This is quite different from the explosion of a bomb on land and is difficult to describe. Imagine being inside an empty tank and having the outside hit by a gigantic sledge hammer. Multiply this noise a hundred-fold and you will have some idea of what happens. The crash of the exploding depth charges will leave the crew dazed and half-stunned for a time, lights will go out, there may be the

    Effects.png

    ominous sound of water spurting through a leak, and then the hurried examination of the boat for signs of damage. Cracked batteries may be discovered by the smell of chlorine gas, motors or Diesels may be out of action, there may be leaks in the hull or jammed planes. It may be found necessary to surface and then there is another period of acute anxiety waiting to see if the aircraft has any more depth charges left. Even if no damage has been done, the effect of the attack will last. All the crew will be jumpy and on edge. The effect of further attacks will be cumulative and if they can be kept up day after day one or more of the crew will finally crack. A classic example of the result of cumulative moral effect was the case of U-57o. This boat had an unlucky first—
    and last—war cruise. On proceeding up the Norwegian Coast, she dived to avoid an attack by a Hudson, hit the bottom and stove in her bows. This necessitated a three months refit. Eventually, she sailed again and after many alarms for aircraft, she arrived in her billet, where she was sighted and attacked by an aircraft of No. 269 Squadron. This attack did practically no damage and left her quite seaworthy. She could have dived and would probably have returned safely to her base, but the crew had had enough and so surrendered. Thus, although the Captain of an aircraft seldom has the supreme satisfaction of ascertaining the material and moral results of his encounters with U-Boats, he may rest assured that a good attack is never wasted.
     
  5. Peter Clare

    Peter Clare Very Senior Member

    PART II.-ANTI-SUBMARINE

    5. ANTI-SUBMARINE OPERATIONS

    General and Training of Crews

    Having dealt briefly with the U-Boats themselves, we now come to the conduct of Anti-Submarine operations. This type of work is the most monotonous and unspectacular of any flying carried but by the Royal Air Force. Crews may fly for hundreds of hours over the sea without sighting a single U-Boat but at last the chance will come and then the Captain has only a minute or so in which to carry out his attack. But however boring the work may be, its vital importance to the successful prosecution of the war cannot be over-emphasized. At the time of writing the Germans have a U-Boat fleet of more than 30o boats, so that even if every building-yard in Germany were completely destroyed by bombing, there would still be a formidable fleet which could work more or less indefinitely from ports in occupied countries. The search for these craft in the wide stretches of the oceans would be a hopeless task, but there are two areas through which they all must pass, i.e., between Scotland and Iceland and to and from the Biscay ports. It is in these areas, and on Convoys which have been reported and are being shadowed, that we must concentrate on the location and destruction of the enemy.
    Every U-Boat which puts to sea on patrol is a very real menace to our vital sea communications and, owing to the huge areas to be covered, only aircraft are in a position to patrol them with any chance of success. This is a heavy responsibility and it is up to every single member of every air-crew to shoulder his fair share. The more the U-Boats are attacked while on passage the more frequently will they change their tactics. It is the job of the A/S planning staff at Headquarters, Coastal Command, to anticipate every new move and be ready for it when it comes. They indicate to Groups the most likely areas to be covered and it is up to the air-crews to seek out and destroy any U-Boats in that area. To achieve this aim is not an easy matter and the problem will be divided into various phases, each of which will be dealt with separately.
    Accurate Anti-Submarine bombing is by far the most difficult task that is given to any pilot in the R.A.F. to perform. The problem which is presented to him is to get a straddle with a fairly close spaced stick of depth charges on an unseen and moving target, using as his aiming mark the fixed and visible swirl. To add to his difficulties he must get down from operational height to 5o feet and deliver his attack within a matter of one or two minutes if he is to be successful, and the lethal range of under-water weapons is so small that an error of only a couple of feet may make all the difference between a kill or only damage. Finally, no sight is yet provided, but the bombing has to be done by eye. Successful results can only be achieved by constant practice, but unless such practice is organized and taken seriously by the crews, it will simply be a waste of flying hours. The whole question of what are the most suitable practices for the job has been given the most serious consideration by the Staff at Headquarters, Coastal Command, in consultation with many experienced air-crews, and the following is a brief summary of the conclusions drawn. In the first place, the whole success of the attack depends on the ability of the pilot to fly at 5o feet within fine limits. This may sound simple, but it really is not so. The span of, say, a Sunderland is 113 feet. Flying at 5o feet would be only about a half-span above the surface. This low flying should be practised at frequent intervals. Then the pilot often has to lose a lot of height quickly and be in the correct position to attack as soon as he has reached bombing level. This is not easy to do and unless some well-defined scheme has been thought out and practised he may find himself at 5o feet and a long way from

    Crew alert.png

    his target. So he should practise this whenever the opportunity offers and reach such a stage of training that he can reach 30 feet and the perfect attacking position simultaneously. Next, as in any other type of bombing, the pilot must be able to place his stick where he means to and this can best be achieved by bombing a fixed target or even a smoke float. The next stage is to place the bombs at a given distance from a fixed target to represent the placing of the stick ahead of the fixed swirl. These four practices form the basis for all successful anti-submarine attacks and, though towed or submersible targets may teach tactics, it is constant practice on the fixed targets which ensures accurate bombing. The need for constant practice is vital, but to add interest, the practices may be combined with tactical exercises. For instance, the pilot may fly round the target at operational height and at a range of, say, three miles. At any time another member of the crew could tell him " U-Boat in sight, course so-and-so ". The pilot would then dive in to attack, open bomb doors, etc. On the way in to attack, the Captain would be informed " U-Boat has dived", after which he would have to place his bombs at a correct distance "ahead" of the target.
    The next problem to be studied is the most efficient employment of the crew while on patrol. In the first place, it will be understood that successful A/S patrolling is ioo per cent dependent on good crew drill and discipline. As has been stated already, this type of flying is deadly monotonous and a crew can only be kept awake and efficient if the Captain and
    Senior members set an irreproachable example. The maintenance of an efficient look-out is an art which can only be learnt from long experience, but any look-out can be improved by good drill. To begin with, it is no good searching the horizon. When flying at 4,000 feet the horizon is 83 miles away, so the uselessness of looking there will be appreciated. The search should be much closer to the aircraft than that. A haphazard look-out will be no good. Unless properly organized, gaps will be left in the search, while other areas will be covered twice. A good Captain will give the various members of the crew certain fixed areas to cover in relation to the aircraft. The members of the crew so detailed should sweep their areas slowly and constantly while on duty, while at the same time the S.E., if in use, should be under constant observation: Obviously, no man can keep up such a look-out with any degree of efficiency for a prolonged period, so the Captain should arrange a routine system of reliefs. As this depends on the size of the crew, it is impossible to lay down any rules for reliefs, but every look-out must have his regular stand off period as frequently as can be arranged. When off watch, whether he is the Captain or the junior member of the crew, he must relax completely and rest. Looking over his relief's shoulder is no rest! It should be pointed out that, whatever system of reliefs is adopted, it should be an absolute routine and worked punctually to time. Haphazard arrangements lead to irregular turns of duty and irritation among the crew.





    Crew alert 2.png


    Good look-out brings its own reward. It is often said that so-and-so has all the luck. He always runs across the U-Boats. This is not a fact. If some individual crew in a Squadron does obtain more sightings than the others it is a clear sign of good look-out; not luck. The U-Boats are there for all to see if they know how to look.
    While on the subject of crew discipline, the Captain of the aircraft must realize that his responsibility does not begin and end in his aircraft. It is his duty to see that his crew are well looked after on the ground, especially before early flying or after a late landing. In fact, he must see to their general welfare while they are together. He should interest them in their duties generally; discuss operations with them, encourage them to put up ideas of their own; all operational instructions or memoranda should be studied with them, while discussions of their own, and other attacks, are of great value. In fact, he should make his crew feel that they are all essential parts of the machine, and not just pieces which have got in by mistake. Familiarity between Officer and N.C.O. members is not to be encouraged and is not appreciated. A little personal interest is, and will make all the difference in a crew.
    It is not surprising that crews are kept as one entity throughout their operational tour.
    Finally, in preparing the air-crews for attacks on U-Boats, the Squadron Commander must shoulder a heavy load of responsibility. It is for him to ensure that ample training is carried out, but, at the same time, he must take a personal interest in each crew to ensure that the crews themselves are interested in their work and do not treat their practices as a necessary evil, to be finished as quickly as possible. Weak crews should be given every encouragement and should not be penalized in any way. He is responsible for keeping his Squadron in touch with all the orders, instructions and general information circulated to Stations and generally for keeping his crews keen and efficient. As it is the duty of the Captains of aircraft to look after the well-being of their crews, so it is the duty of the Squadron Commanders to do the same for the Captains. He must also ensure that they are, in fact, taking a real interest in the well-being of the crews. And finally, he must keep a strict watch on every crew. Bad attacks due to excitement or similar reasons are to be expected once or twice, but a crew whose work is consistently bad should be suspect. No chance can ever be wasted of seeking out and attacking U-Boats. A crew lacking interest and discipline will never succeed in this type of work and must, for the good of the Squadron and Command as a whole, be discarded.

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    Last edited: Aug 23, 2016
  6. Peter Clare

    Peter Clare Very Senior Member

    6. U-BOAT HUNT AND SEARCH

    A trained and well-disciplined crew on A/S Patrol will leave nothing to chance. Their training and knowledge of the job in hand will be such that as soon as a U-Boat is sighted their reactions will be absolutely automatic and correct. Once on patrol, watches will be set and reliefs organized, and from that moment onwards no part of the sea will ever be left unsearched.
    The first thing which the Captain has to decide is at what height to fly. The look-outs in the U-Boat are experts on their job and constantly on their toes. There are two apparent ways of defeating them; firstly, by the use of the most perfect camouflage which it is possible to devise and, secondly, by the Captain of the aircraft putting his wits against the enemy and making the best use of any natural cover which he can, such as clouds, sun, rain, showers, etc. The situation is most difficult when the sky is clear and the visibility good. On such occasions the U-Boat will probably be on the surface, as the Captain will be prepared to back his look-outs against those in the aircraft. On at least two out of every three occasions he will be right and will dive without being seen. But he will not win every time. It is proposed to see how best to ensure that an attack is possible. If a look-out is comfortable, he will be far more efficient. When he is searching for a low-flying aircraft he is in a reasonably comfortable position, but, when looking for those at a greater height, his head is back and his neck strained. It follows that he will search the lower sky more efficiently than that area higher up. It would appear, therefore, that the higher the aircraft flies the more chance he has of seeing without being seen, and, from the point of view of sighting only, this is probably true. From the tactical point of view, however, there must be a limitation to this height. Most of the aircraft engaged on A/S operations are large and heavy and consequently take time to lose height and carry out an attack from a low level. If the aircraft were flying at, say, io,000 feet, it is almost certain that he would be seen by the U-Boat while he was losing height, and the latter would have plenty of time to dive and be at a safe depth before any attack could be delivered. The height must, therefore, be a compromise, and at the time of writing 5,000 feet has been found most satisfactory in either clear weather or when the clouds are above that height. The introduction of dive brakes or tail parachutes may, and almost certainly will, make a variation of this height desirable, but, though tactics are unlikely to vary in broad principle, such detailed changes are issued from time to time in Tactical Memoranda and Instructions.
    When clouds are present the task of the Captain of the aircraft is not so difficult, but, even so, it is no easy one. The tactics to be employed must be left largely to him and he must assess the actual conditions and use his own judgment. As a general guide, however, it is suggested that, if the cloud is 5/ioths or less, and below 5,000 feet, the aircraft should fly at about 500 feet above the cloud, while, if there are more than 5/Ioths, the Captain should make the maximum use of cloud cover compatible with accurate navigation. Within the broad limits laid down the Captain has ample opportunity to use his wits, studying conditions of light and cloud and flying in such a way as to get the maximum concealment without spoiling the chances of sighting an unwary U-Boat. That a U-Boat can be surprised even in conditions of good visibility is a fact which has been proved time and again
    Finally, every object sighted or contact made should be treated as a U-Boat. The approach should be made as for an attack and, if at the last moment the object is recognized as non-submarine, the aircraft can resume patrol and no harm has been done. On the other hand, if the Captain closes to investigate before attacking, the U-Boat will certainly dive and leave him with no target.
    A word of warning is necessary. Whales look very like U-Boats and oil streaks seem an irresistible attraction to some pilots. While a whale may be mistaken for a U-Boat when first sighted, the pilot should not remain long in doubt. It is much smaller than a submarine, never remains on the surface for long and it does not have the large and distinctive swirl of the diving U-Boat. Oil sighted on the surface practically never originates from a U-Boat. Diesel oil is very light, almost the viscosity of paraffin, and is hardly noticeable unless present in large quantities. Even so, it only has the effect of deadening the sparkle of the sea and looks rather like oil in a puddle. Thick oil, or oil with clearly defined edges, invariably comes from a wreck. Oil streaks may appear to move, or even alter course, but this is the result of under-water currents. Thus, due to the improbability of a U-Boat being present, orders have been issued that oil streaks are not to be attacked.
     
  7. Peter Clare

    Peter Clare Very Senior Member

    7. ANTI-SUBMARINE TACTICS-ATTACKS ON U-BOATS

    The detailed tactics for the actual attack on a U-Boat and the weapons to be carried will vary from time to time, but the broad principles of attack will not change. The aim of the pilot must be to deliver his attack with the least possible delay. To do this we must attack from whatever direction presents itself. Though the pilot is instructed to attack without delay and is given complete freedom of action, there may be times, as, for instance, when there is good cloud cover or where a lot of height has to be lost, when the
    Captain has time to choose his direction of attack. In such cases it is better to attack along the track of a U-Boat from astern. In such circumstances he has the wake and swirl to give him his accurate line of approach, and if he uses the swirl itself as an aiming mark he will still get at least one of his stick within lethal range if he releases his D.C.'s within 15 seconds of the U-Boat diving.
    In spite of the remarks in the preceding paragraph, there is one occasion when the pilot may wish to with‑hold his attack. This is when the U/Boat mans all guns and produces an intense and accurate volume of fire while the aircraft is running in to attack. This is an indication that the U/Boat is not going to dive, and it is up to the Captain of the aircraft to decide whether he will continue the attack or stand off in an attempt to silence the U/Boat's fire. It should be borne in mind that in anything but calm weather, the U/Boat's guns crews are firing from slippery and moving platforms.
    As no bomb sight is available at present, accuracy can only be achieved by attacking from a very low height, and, if possible, all attacks should be delivered from 5o feet. Having reached his objective, the pilot will release the load as ordered from time to time in Tactical Instructions, but whatever he may be carrying, his object is to place the centre of his stick on the centre of the U-Boat. He must, therefore, know exactly where to aim. In the case of a visible U-Boat all the pilot has to do for line is to steer his aircraft so that he will track over the conning tower. This holds good whatever direction of approach he is committed to. The problem is purely range, i.e., when to press the release so that the stick shall explode with its centre under the conning tower. If using a stick of four depth charges spaced to 35 ft. and attacking up the track, the first D.C. must be aimed to hit the water 5o ft. short of conning tower ; for other lines of approach increase this distance as the bearing draws forward up to a maximum, which is reached when attacking down the track in which case the first D.C. must hit the water loo ft. short of conning tower.
    If using a stick of six D.C.'s spaced to 35 ft., the distances for the first D.C. are 'coo ft. short of conning tower for up the track increasing to 200 ft. short of conning tower when attacking down the track. The forward and downward speed of a diving U-boat is, fortunately, known exactly, so the calculation of the point of aim is simple.
    To calculate the exact spot at which to aim, allowance must be made for the forward travel of the U-Boat, half the length of the stick and the forward travel of the A/S weapons under water. In fact, the pilot must aim at a certain distance ahead of the swirl and also a certain distance short of the calculated spot. The first is a variable and the second a constant for any given weapon and length of stick. The actual figures will vary slightly with the weapon in use, but to give an example of how the calculations are made, the following, correct for the Mk. VIII D.C., will be taken:—

    Forward speed of U-Boat.....................10 ft. per sec.
    Downward speed of U-Boat.................1.5 ft. per sec.
    Time of flight of D.C.'s in air................ 2 secs.
    Time of flight of D.C.'s in water........... 3 secs.

    If, then, the point of release is reached 15 seconds after the U-Boat has submerged, the point of aim should be calculated as follows.—

    Time from submersion to release of D.C.............. 15 secs.
    Time from release of D.C. to detonation...............2 + 3 = 5 secs.
    Time from submersion to explosion of D.C.'s.......20 secs.

    In 20 seconds the U-Boat will have travelled 20 X I0 =200 ft., so the point of aim for the centre of the stick should be zoo ft. ahead of the swirl.
    At first sight it may appear that a complicated mathematical problem is involved in every attack, but this is not so. The time from the release of the D.C.'s to detonation is a constant for any given weapon so long as the height is accurate, so it is possible to construct a simple table thus, using the figures given above:—

    Time from submersion to release of D.C.'s,

    0 secs., 5 secs., 10 secs., 15 secs., 20 secs., 25 secs., 30 secs.

    Distance to aim ahead of swirl,

    50 ft., 100 ft., 150 ft., 200 ft., 250 ft., 300 ft., 35o ft.

    It is a simple matter to make a scale to fit on the face of a stop-watch so that the pilot can read off the distances at a glance.
    Having decided on the point where the centre of the stick is to fall, the first bomb must be aimed to fall a certain distance short. This distance is a constant for any given weapon, length of stick and spacing. Assuming a stick of 6 D.C.'s spaced at 25 ft. and that the forward travel of the D.C.'s under water is 40 ft., the pilot should aim to place his first depth charge

    62/65 ft. (half the stick length) +40 ft. (forward travel of the depth-charges under water), or say roo ft. short of the position where the centre of the stick should be—thus, if the weapons are released, say, 8 seconds after submersion, the first one should fall roo ft. short of a point 130 ft. ahead of the swirl. Judging distances at sea is a difficult problem, but, luckily, the U-Boat herself provides a yard stick, Tests with H.M.S. 'Graph' have shown that the horseshoe shaped white water of the swirl is almost exactly roo ft. long by 80 ft. broad.
    One other case must be considered: that is, when the U-Boat is located at periscope depth. Under such circumstances, the speed will probably be about 2 knots (3'4 ft. per second). Using the same figures as-before, the time interval between release and detonation of the depth-charge is 5 seconds, in which time the U-Boat will have moved 5 x 3.4 = 17 ft. The aim should, therefore, be at a point 17 ft. ahead of the periscope feather. Once more, it must be stressed that all the data given above relate to the Mk. VIII or Mk. XI Depth-Charges. They will not be correct for any other weapons, but similar reasoning must be used to obtain the appropriate figures.
    The next question which arises is, how long after submersion is it worth-while carrying out an attack? This depends on various factors and the decision must rest with the Captain, but the following points are issued for guidance. After 3o seconds the U-Boat will have travelled 300 ft. forward and 45 ft. downward. In the same time she may have altered course 30° one way or the other, and her position will be so uncertain that it is not worth carrying out an attack if the aircraft is on a normal A/S patrol and has plenty of petrol in hand. If, on the other hand, the U-Boat is approaching a Convoy or other surface craft, the very fact that D.C.'s are dropped may keep her down and prevent an attack from developing. In such a case it would probably be best to drop only one or two charges and leave the remainder in case another opportunity presents itself. In brief, if there is any chance of another opportunity presenting itself, depth-charges should not be wasted, but every possible step must be taken to prevent an attack being carried out on shipping.
    Photographs are most useful when attacks are being assessed and also photographs of U-Boats taken before and after the attack may provide technical information of great value. Every endeavour should, therefore, be made to obtain a complete set of photographs of the attack, using both the fixed mirror and the hand held cameras. Some member of the crew should be detailed to attend to this as a matter of routine, as soon as a U-Boat is sighted.
    Immediately the attack has been made, the whole story must be passed to Base, who must be kept fully informed. The information which is of immediate importance is the position, course and speed of the U-Boat when first sighted and at what time: whether it was sighted on the surface in the first instance or if only the periscope was seen; and whether it was attacked. Further, if serious damage has obviously been caused to the Boat and she has been forced to the surface disabled or partially disabled, Base must be informed at once so that follow up action may be taken. In fact, Base must be kept fully in the picture the whole time. The details of the signals to be sent should be well known by all crews, who should also have a thorough knowledge of the signal book in use.
    There is one important point which must be borne in mind. The crew of an aircraft which attacks a submerged U-Boat are in no position to estimate whether they have scored hits or not and are not to include such estimations in their signals. Faulty estimations only lead to confusion in the organizing of any follow up which may be ordered. The only time when a hit may be claimed is in the case of a hit with a bomb which is actually observed on a surfaced U-Boat.
     
  8. Peter Clare

    Peter Clare Very Senior Member

    8. ACTION AFTER AN ATTACK

    When considering what action to take after an attack, the Captain of the aircraft should always try to put himself in the U-Boat Captain's place and think what would worry him most if the position were reversed. The following paragraphs are based on remarks of one of our own submarine Commanding Officers and would, presumably, apply equally in the case of a U-Boat.
    When the U-Boat is forced to crash dive by an actual or potential air attack, the Captain will probably take her down to 90 or too ft. for half an hour or so and will then come up to have a look round through his periscope. If he sees the aircraft still in the vicinity, he says: 'Oh! Hell take this blasted aircraft!' and stays down for another half an hour, when he comes up for another look, and so on. Finally, the aircraft reaches the limit of its endurance and has to leave. The U-Boat then surfaces and gets on with her passage. This has been merely irritating to the U-Boat. She could have been worried much more.
    Suppose that within a few minutes of the attack the aircraft had gone away from the scene for 20 to 30 miles and remained there for half an hour or more. The U-Boat Commander would then have come up to periscope depth, had a look round and, seeing the coast clear, would have surfaced to proceed on his main engines. Thus, in due course, when the aircraft returns to the scene, making all the use he can of cloud cover or the sun, there is every chance that the U-Boat will be re-sighted on the surface, very near to the position of the original dive, or along the track which was noted on first sighting. The aircraft may or may not have expended his depth charges on the first dive. If he didn't, he will get his chance again now. If he did, a dummy attack should be made just the same. The U-Boat will have to do another hurried crash dive, using up a lot more battery power, and everyone, from the Captain downwards, will be fed up with having the passage interrupted again. The Captain will not know whether it is a new aircraft with another load of depth charges and everyone will be waiting anxiously for the depth charge explosions once more. If petrol allows, the procedure should be repeated, and once again the U-Boat will be forced under, by which time the crew will be getting jittery. Besides, each
    attacked. Further, if serious damage has obviously been caused to the Boat and she has been forced to the surface disabled or partially disabled, Base must be informed at once so that follow up action may be taken. In fact, Base must be kept fully in the picture the whole time. The details of the signals to be sent should be well known by all crews, who should also have a thorough knowledge of the signal book in use.
    There is one important point which must be borne in mind. The crew of an aircraft which attacks a submerged U-Boat are in no position to estimate whether they have scored hits or not and are not to include such estimations in their signals. Faulty estimations only lead to confusion in the organizing of any follow up which may be ordered. The only time when a hit may be claimed is in the case of a hit with a bomb which is actually observed on a surfaced U-Boat.
    crash dive uses up a lot of battery power, and high-pressure air is used each time the boat re-surfaces. Both these commodities are very precious to a U-Boat. Everyone's nerves will be frayed, to say the least, and should a relief aircraft arrive, it is more than likely that he in turn may sight the exasperated U-Boat, who may well make a false move while making yet another dive.
    Every time a dummy attack is made machine-gun fire should always be opened on the U-Boat. A lucky hit may be scored on a periscope or some electric lead or high-pressure air line, which is extremely irritating to the U-Boat crew, who have to repair or plug it. Besides, the rattle of bullets on the hull is not a pleasant sound to those inside the boat, and a burst will certainly relieve the feelings of the aircraft crew.
    A U-Boat's crew at sea in an area patrolled by aircraft are always in a state of tension. The rattles which give the signal for a crash dive are sudden and startling, even to a veteran crew. Only three or four men know why they have been sounded, how close the enemy is and what to expect next. If this signal is sounded several times in a few hours, the inexperienced members of the crew are apt to get more and more rattled and are, therefore, quite likely in the end to open the wrong valve, or fail to close the right one. An aircraft has the power, if the Captain uses his imagination, to cause more heart fluttering among a U-Boat crew than any other craft used in A/S warfare.
    There is one occasion when baiting procedure should not be carried out, and that is when a first-class attack has been carried out on a U-Boat. Every captain of aircraft must know in his heart of hearts when he has done a really accurate attack on a visible U-Boat or even on one which has only submerged up to to seconds before release. In this case the aircraft should remain over the spot as long as possible so as to observe after results. It is even more important to do so if oil has appeared or if air has continued to rise for more than a minute. By remaining over the spot at low altitude it may be that " bits and pieces " will be detected that otherwise would never be seen if the aircraft goes off on baiting procedure.
     
  9. Peter Clare

    Peter Clare Very Senior Member

    9 INTERROGATION

    So that a complete study of weapons and tactics may be made and every possible lesson extracted from each attack, it is necessary to have a full and accurate account of the incident. Further, every attack is assessed by an Admiralty committee, and it is only by putting up a full story, supported by photographic evidence, that the crew will get full credit for their efforts.
    On landing after an attack it is probable that the crew will be both tired and excited and will not be in a fit state to give a reasoned and connected account of the incident. However, it is essential that some account of the action should be available for immediate information, and so the crew are interrogated immediately on landing and the Coastal Command Form Orange is completed and forwarded to Command Headquarters and the Admiralty. Though giving a general account, the information in this Form is seldom accurate or complete.
    When the crew is throroughly rested, the second interrogation takes place. As it is necessary to obtain complete tactical details of the attack, this interrogation is taken by the Squadron Commander with the Intelligence Officer and any other specialist Officer he may call in to assist him. This interrogation should take the form of a round table discussion and the whole attack thrashed out in the light of the evidence of the various members of the crew and of the photographs. Any unusual incidents should be given special care and the most accurate description possible obtained of any oil or bubbles, wreckage or any other after-effects which may be seen after the attack. The most important points to be cleared up are the accurate time interval between the submersion of the U-Boat and the release of the depth charges, the angle of attack relative to the track of the U-Boat and the distance of the stick ahead of the swirl. Again, it should be remembered that the length of the white water in the swirl is roo ft. When the whole matter has been thoroughly discussed, a connected account should be written out and read over to the crew. If they have no additions or alterations to suggest, the Form U-Boat is completed and forwarded to Command Headquarters and Admiralty.
    Even then the matter is not finished. All crews who can be spared, and particularly those who have carried out a promising or interesting attack, are invited to attend a further meeting at Command Headquarters, where a third interrogation is held by the Naval and Anti-Submarine Planning Staffs. As those Officers are in personal contact with many crews from all Groups, they have a broader view of the picture than a local Squadron Commander or Intelligence Officer can be expected to have. Once more the interrogation takes the form of a general discussion, but a large collection of photographs of U-Boat attacks is available and very often doubtful points or difficult descriptions can be cleared up by comparison with these photographs. From this last interrogation the final account is made out and is in due course submitted to the Admiralty Assessment Committee for their final decision. Incidentally, the personal contact maintained between crews and the Staff of Command has proved of the greatest value to both.
    In conclusion, it can be repeated that A/S Warfare is the most important task that the R.A.F. is called upon to perform. To achieve success, which is so necessary for the safety of our sea communications, constant practice is essential, and, in addition, crews should be kept informed of all the latest developments in equipment and tactics. The essentials of successful A/S warfare are perfect crew drill and discipline, alertness and constant training. Good hunting!

    After attack.png


    Thats all folks
     
    spidge, alieneyes, Harry Ree and 2 others like this.
  10. Trackfrower

    Trackfrower Member

    Excellent stuff.

    Lawrence
     
  11. Harry Ree

    Harry Ree Very Senior Member

    A comprehensive document without doubt as Peter states issued by Coastal Command.Information issued probably to those involved in anti U Boat duties at the start of their specialist training.

    One thing noted is the absence of any reference to ASV (information which would be restricted from an open document) which was the tool to gain access and expose the vulnerability of the submarine from a relatively long range while on the surface.In the case of the Kreigsmarine,their U Boat force fared badly as ASV was developed and along with the breaking of the Kreigsmarine naval codes,happy hunting for them was a thing of the past.

    The success of the Allies anti U Boat operations in the so called Battle of the Atlantic ensured that manpower and war material could be built up in preparation for the Normandy landings.
     
    Peter Clare likes this.
  12. Clint_NZ

    Clint_NZ Member

    Interesting stuff.
     

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