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Torpedo Attack

This view of an S Class boat gives an idea of the spaciousness(!) of the Control Room.

Rolling back the years to World War Two, a submarine's success or failure was much more of a 'solo effort' by the captain. There was very little that the rest of his crew could do to assist an attack from a dived submarine, other than to follow the captain's instructions. Sometimes attacks had to be carried out instantly and there was just no time for a boat to come to full 'Diving Stations', so the Captain would often have to start an attack by relying on the members of the ship's company on watch at the time, with help from others as they could reach the Control Room. Most attacks had to be carried out in daytime, with a visible target. The nights were usually spent re-charging batteries, often requiring a submarine to vacate an attack area and returning at daylight. The human interface between a dived submarine and the outside world consisted mainly of the eyes of the Officer of the Watch and the ears of the hydrophone/ASDIC (Sonar) operator.

"Captain to the Control Room! -
Sound the Alarm - Diving Stations, Diving Stations"

Pre-war material for public consumption

Captain arrives at the search periscope in 7 seconds. The periscope has been lowered - we don't want a target - or its escorts - noticing a tell-tale periscope wake. A quick report from the OOW gives the bearing of the contact. "Up periscope" - a quick look at the target, taking in as much information as possible - from the first visual contact with the target, depending on the quality of the sighting, several pieces of information can be gleaned: 1. What the target is, its validity/nationality/value etc. 2. What (rough) direction it's going in (Target Course) 3. How the submarine lies in relation to the target (the 'Angle on the Bow' - putting yourself on the target's bridge, where would our submarine bear, relatively, to the target's course?) 4. An estimate of the target's speed - experienced captains could make good estimates from the length of the bow wave, while an experienced Asdic operator could make a close guess from the target's engine noise and the timing of propeller revolutions. 5. Approximate range. A visual estimate by the captain, again supported by a good Asdic estimate. In a captain's 'first look' at the target, only a rough estimate of range would normally be made; on later 'looks', if a target's funnel or mast height were known, or could be discovered from recognition books, the periscope's split prism rangefinder could be used - a second image of the target is swung upwards by a small dial on the periscope, superimposing the target's image above the original, the difference between the images measured as an angle - in seconds or minutes of a degree - producing a range by trigonometry (the angle on the split prism and a known or assumed height of the target being used to give an angle and one side of a triangle).

More pre-war public relations information. Click for larger versions

Right, so we can make a provisional estimate of our best course for firing and on what bearing we may be firing. Can we reduce the 'Closest Point of Approach' (CPA) by moving position? How many torpedoes? Let's try three - we'll try to get one on the centre of the target, one just in front and one astern. This will hopefully ensure success if there are any inaccuracies in our target speed calculations or if the target decides to speed up or slow down. This works like this: We've decided that the target is moving at 11 knots - If three torpedoes were fired in a salvo then the first would be fired to hit a 12 knot target, the second to hit for 11 knots, and the third to hit the ship if it were travelling at 10 knots. Torpedo spread across the target's track would be achieved by applying a time interval between torpedo discharge or by observation of the target through the periscope with the CO applying his deflection angle against different parts of the ship (e.g. bow, middle, stern). Salvo size would be varied (provided you had sufficient weapons) depending on the importance of the target, and once again the CO had to apply fine judgement - torpedoes were about £3000 each, while the shells required for a gun action were considerably cheaper. A major target may be worth a 6 torpedo salvo (£18,000), but a Greek caique or an Eastern junk would be a better target for the gun. Time for a second look at the target. "Up periscope" A quick all-round look first, both on the horizon and in the air, then we'll get back to the target's estimated position. The Torpedo Control Calculator (TCC) can give us the estimated target bearing, based on the last information we put in, plus the time difference since the last look, including the difference in the submarine's own position. One of the officers would be manning the TCC, and he'd have a slide-rule in his hand as a backup. (The TCC was an electrically driven mechanical fire-control calculator for torpedoes, usually operated by a junior officer. Unlike similar machines in U.S. or German service, it did not provide a continuous solution and had to be re-set at each fresh periscope observation, making the wartime RN submarine captains some of the finest mental mathematicians in the world.)

Lt. Lynch Maydon at the periscope of HMS/M Umbra. The British 'Fruit Machine', or Torpedo Control Calculator  more accurately known as a "Submarine Torpedo Director Mk.II". Although supplied from the gyro compass this machine did not track continuously and had to be completely reset at each observation.

The periscope assistant, often a Telegraphist, could put the periscope on the bearing without the captain's eyes leaving the viewer. What have we got this time? a. Target BEARING - does it match with our earlier speed estimates or is it behind or in front for the suggested target speed? A new bearing will enable us to calculate a fairly accurate target speed, but... b. Is the Target COURSE correct? If we use the rangefinder on the new bearing we will have two positions on the chart - we can refine both course and speed information from that. c. The Target's RANGE "Down Periscope." This look has provided the data above to 'feed' to the TCC (Fruit Machine) for calculation: Distance Off Track - (the distance between the S/M's course and the Target Course) b. Director Angle (the difference in angle from where the bow will be pointing at firing and the actual angle between the bow and the target - the 'aim-off') c. Torpedo Track Angle (the angle relative to the target that the bow must be to achieve a straight running hit). OK, we've now got the target's speed and course fairly accurate so, in theory, we know where the target will be the next time we look. So we now know our best firing course, based on the target's movements. But at what moment should we fire the first torpedo so that it blows the target's bow off? What time lag should we use between torpedoes? We know how fast the target is going, and on what line, and we know how fast our torpedo runs, so we have another trigonometry puzzle. The TCC will give us the answers (with luck). We must make sure that the boat is aligned with the firing bearing. And don't forget to open the torpedo tube bow caps! How many torpedoes? If (say) three torpedoes were discharged in a salvo then the first would be fired to hit a 10 knot target, the second to hit a 9 knotter (the estimate), and the third to hit the ship if it were travelling at 8 knots. Torpedo spread across the target's track would be achieved by applying a time interval between torpedo discharge or by observation of the target through the periscope with the CO applying his deflection angle against different parts of the ship (e.g. bow, middle, stern). Salvo size would be varied (provided you had sufficient weapons) depending on the importance of the target, and once again the CO had to apply fine judgment. The largest salvo in history was fired by Lieutenant (later Vice Admiral Sir) Arthur 'Baldy' Hezlet who, as Commanding officer of HMS Trenchant during WWII, sank the Japanese battle-cruiser Ashigara which he hit with five torpedoes out a salvo of eight from a range of four thousand yards! Such was the strategic importance of the target, but with the submarine unable to close the range, this brilliant CO applied all the logic discussed above, and achieved his aim by covering all eventualities. The captain's assessments of all three parts of the 'attack triangle' will determine the point at which you want to arrive, the ideal firing position being 1000 yards on the target's beam. Arrive at this point a minute or two late, or be out of position, and the attack could stand little chance of success. Other factors to 'compute' would be the target length and angle on the bow (i.e. its virtual length), its draught, prevailing sea-state and visibility, and then and any evasive movements that the target may be using. Remember to think of the state of the battery capacity (to get to the firing point, let alone later evasion if required). Last look - a firing look. "Up periscope" The 'Periscope Reader' will put the periscope onto the firing bearing, provided by the 'Fruit Machine'. There it is! Right on time! When the bow crosses the centre of the viewfinder, 'Fire One'. The buttons on the Torpedo Order Instrument are operated. Now the target's bang in the middle, 'Fire Two'. Now the stern crosses - 'Fire Three'. "Down 'scope, 120 feet, Port 15, steer 180." The Asdic operator reports, "All torpedoes running,sir!". "How long to first hit, Pilot?" "85 seconds, sir".... (With acknowledgements to the late Dave Perkins, of Nova Scotia, Canada, for his technical know-how! He will be greatly missed). (Left) Lt. J.C.Y. Roxburgh RN, (Flag Officer Submarines in 1970-1971) at United's periscope. The 'Fruit Machine' can just be seen in the background, slightly to the left of the periscope.

This extract from the book 'Submarine Command' by Ben Bryant is worth a look: Everyone is inclined to invest their own trade with an aura of black magic, and perhaps I too am biased. But I do believe that submerged attack, with the facilities submarines had in 1914-18, was far from easy. Lack of money for development between the wars found our submarines in 1939 with no advance in torpedo control over their 1914-18 forebears. The difference was that they now had to compete with World War II opposition, though this fortunately also had its weaknesses. In support of my contention, it is a fact that in 1914-18 the Germans found that a handful of their C.O.s achieved a preponderance of their sinkings. Others just had not got the knack, the seaman's eye. Accordingly, the Germans devised attack computers and accommodating torpedoes which would alter course, so as to take much of the strain off the C.O. The Americans went further and evolved a truly wonderful computer and backed it up with radar ranging. The attack I describe is an attack as used with considerable success by the British World War II C.O.s. Nature seems to have equipped the British more generously with seaman's eyes--the ability to calculate velocity triangles in your head, on data judged by eye, and to do them when, if not actually frightened, at least under considerable pressure. In the days when the exploits of Sealion and Safari made headlines in the press, I found myself described as "dashing". I can think of few more unsuitable adjectives to use in a trade where the needle business, the closing stages of attack, was carried out at a speed of three knots or less. I had the honour, after the war, to be head of the submarine service when Churchill unveiled the submarine memorial in Westminster Abbey. I remember he attributed to us an "ice cold brain in danger". I do not claim this attribute personally; but it certainly describes the kind of intellect I should have liked to have had as a submarine C.O.; the dashing part was best left to those less interested in survival. During an attack your speed was restricted so as to avoid detection. Then you had to point the whole submarine to aim your torpedoes; it took about four minutes, in reasonable circumstances, to turn your boat ninety degrees; it could take considerably more if the escorting vessels were being difficult. At reasonable firing ranges, say under 2,000 yards, the target was crossing your sights much faster than you could swing the boat; you had to be lined up in advance. Then you had to attack from ahead. You had not got the speed to catch up. The ideal firing position was about 600 yards on the beam of the enemy, though anything between 500 and 1,500 yards was fair enough. Outside that range you were starting to rely upon having made very good estimations of enemy course and speed--to calculate the angle to aim ahead--and you were asking more of your torpedoes, though actually our torpedoes had a magnificent range, getting on for 10,000 yards, which was just about double that of the Americans and Germans. At its best a torpedo would only run to within a degree of the course set; and at its worst was more likely to torpedo you than the enemy. The element of luck entered increasingly outside a range of 2,000 yards. Long range shots could, and occasionally did, work; but they were more suitable for a browning shot at a line of ships than at a single target. Calculation of enemy course was done by eye and was not all that difficult with practice. The line of his masts and funnel and his side would give you this if you were fairly fine ahead. An experienced C.O. would expect to get the enemy course within 5 degrees if within 45 degrees of right ahead of the target. From further to one side it became increasingly difficult. Some ships were far more difficult than others; camouflage painting did not help or the light might be difficult. Judging speed was more difficult. First and foremost you had the type of ship and what she was engaged upon. That gave you a clue as to the probable range of speeds she might be doing. Bow waves were deceptive, they depended upon the wind and sea and the shape of the ship's hull. Stern waves, when you could see them, were more help. A ship going fast tucks down her stern, a destroyer at speed will have a stern wave mounting higher than her quarter deck. But again this is only a rough guide. Then there were the revolutions of her engines; the Asdic operator could make a shot at counting the beat of the propellers. It was difficult, but some were quite good at it. Then you had to decide what revolutions per knot of speed that type of ship would be doing; they varied enormously according to the type of engines, and whether or not the propellers were geared down. But again it was a help if the Asdic operator could get a count. The most valuable method of all was to plot the enemy's advance, the rate at which he was closing you. To do that you needed ranges. The periscope had a device whereby you could make two images of the target and separate them one above the other. You then balanced the water-line of one image on the mastheads of the other and you could then read off on a scale the number of minutes of are subtended by the masthead height of the target. If you knew the masthead height and had balanced the images right--which was nearly impossible to do without showing rather a lot of periscope--you could then calculate the range. But you did not actually know the masthead height, you had to judge it--or some might say guess it. If the target was hugging the shore you could plot him along the coastline as he passed various salient features--if there were salient features, that is--and if he were close enough to them for you to judge when he passed them. Finally the rate of change of bearing, either by taking bearings at set intervals, or just by eye. In the end, after checking up on the speed in every possible way, you used your seaman's eye and with experience this was not a bad range finder. When we were going to surface for a gun action, I always gave the range to be set on the sights as judged by eye, after a quick mental sum to allow for the relative movements between starting to surface and getting off the first round; it was seldom appreciably out. The professional should know his trade. If you had got the enemy course and speed right--you had your attack team to help you in computing it from your estimations--you knew what angle to aim ahead; that angle could then be set on the periscope. There was a bearing ring where the periscope passed through the pressure hull and you could read on it the bearing from dead ahead, on which the periscope was pointing. The actual sight was a graticule, or line down the centre of the periscope lens. There was nothing to stop the enemy altering speed during the attack, though he seldom did; but he could also, and regularly did when zigging, alter course. Zig-zagging is a recognised and quite effective method of confusing submarine attack, and is regularly practised by shipping in war. You could never be certain of your estimations of course and speed until you fired. These estimations were only a minor part of the whole business, though they were running through your head all the time. The trouble was to manoeuvre your boat to be in the right position, at the right range, pointing in the right direction at the right time. You had to do all this without using much power on your propellers, which could give you away to the escorts, if the target was screened; with a minimum use of the periscope to take your observations; and without asking too much of the First Lieutenant and planesmen by turning the boat about too violently, making it difficult to keep depth accurately. In a seaway you might also have to plan to avoid driving the boat on certain courses where the sea would make depth control difficult. The target was always going a lot faster than you and to a large degree your position was dictated by her movements. If she were sighted in such a position that she was going to pass a long way off, all you could do was to run in as fast as the circumstances-escort vessels and aircraft--permitted, and get off your shot from as near as you could get. Then you just had to trust that you had made a good estimation of enemy course and speed, and that the torpedoes were feeling co-operative. It would probably mean that you would have to fire from outside the screen, the torpedo tracks would probably be seen by the escorts and the target could be warned to alter course so as to avoid your torpedoes. There was no particular skill in this sort of attack; if you got a hit you were duly grateful and it gave no satisfaction to your professional pride--there was too much luck in it. It was also more dangerous, strangely enough; in the same way big game hunters who take long chancy shots at dangerous game seldom survive. It needs some nerve to stalk within a few yards of a vicious quarry; there was some strain on the nerves in taking your boat through the screen; but if you did it, you were safer. You let off your shots on the side of the escorts where they were not looking out; your noises and those of the torpedoes, were mixed up with the noises of the target. Above all you were fairly certain of making a kill and that is always upsetting for the opposition.

Gun Attack The British boats used guns a lot in their stalking of small Japanese-manned and or controlled ships in the Far East - mainly to the west of Singapore - from 1943 to 1945. Daylight hours were usually passed as periscope depth and a practice was perfected of not surfacing until the very last moment and then opening fire immediately. The drill was exciting and several of the crew who did not usually see action were able to lend a hand even if only in the ammunition chain. Into the 1970s, with the last few remaining gun-fitted submarines, like the Auriga and the Andrew, of the A Class, these drills were still carried out and gave considerable excitement to the crews on a dull day. On sighting a suitable target through the periscope, 'Stand By Gun Action' was ordered and the crew raced to diving stations while the magazine hatch was wrenched off, leaving a large manhole in the centre of the passageway. The Gunlayer and Trainer inspected the target through the periscope while the captain estimated range, angle-on-the-bow and target speed in the usual way so that range and deflection could be set on the control room transmitter or passed directly to the sight-setter. With the boat still at Periscope depth, the captain gave the executive order 'Salvoes shoot' followed by 'Man the gun tower'. (The British 'S' and 'T' Classes had gun towers - in 'U' Class submarines, which had no separate gun-tower, the gun's crew had to climb up the conning-tower hatch, with the captain and lookouts. At 'Stand by to surface', the gunlayer removed both safety pins that secured the upper guntower hatch and reported 'Tower manned, pins out'. The First Lieutenant (XO) bled HP air into the boat until three or four inches above normal pressure. The motors were put into Half Ahead Group Up (about 7 knots) for the hydroplanes to have maximum effect, and the captain ordered 'Surface' and all the tanks were blown. When, despite the hydroplanes, the boat could no longer be held down against the rapidly increasing buoyancy and when the depth gauge was passing the 20-foot mark, the XO would blow a whistle. The gunlayer released the last hatch clip; the planesman put the plane hard a-rise; the hatch, still under water but very close to the surface now, flung itself open with the pressure from inside and the gun's crew followed, jet-propelled, as the air rushed out around them. The first shell was away before the boat had settled on the surface. The first round cleaned the gun; the second was the one to watch for, and by that time an officer on the bridge would take over spotting corrections. The U Class (2" or 3" gun) (the above two pictures) was fairly unprotected from the elements. The S Class (either 3" or 4" gun) had a fixed gun position, with or without shield, while the T Class (4" gun) had a movable turret (See Thrasher, left).  Most of the bigger and older boats, like the Porpoise class and the River and R Classes, had a 4" gun, usually with a screen built around it. A new gun was ordered in 1942, the Mk.XXIII Quick Firing 4", but only the A Class, 1945 onwards, actually received them.