OUTLINE OF THE CONTROL SYSTEM.

The Problem.

415. In high angle firing, the main general principle of pointing the guns at the enemy is exactly the same as in low angle firing, inasmuch as the guns are kept aimed at the enemy, regardless of the ship rolling or altering course, by the HIGH ANGLE DIRECTOR keeping on the aircraft and sending away electrical movements to red pointers at the elevation and training receivers at the high angle guns.

Gravity also affects the high angle shell, in the same way as it does when firing on the surface, so that the gun has to be elevated above the line of sight to the aircraft by an amount, which varies with the range and the angle of sight. (Angle of sight is the angle between the horizontal plane and a line to the aircraft.)

Besides being originally aimed at the enemy aircraft, the guns have to be aimed off for deflection. In low angle firing, when this was discussed (see paras. 300 and 301) we had to consider a ship which was moving along the surface of the sea.

In high angle firing, we have to consider an enemy aircraft, which is not only moving very much faster than a ship but is also free to move in any direction, i.e., diving, climbing, or flying on a steady course.

416. For an aircraft that is flying on a course at right angles to our line of sight, the aim-off, or deflection, is nearly all LATERAL DEFLECTION. It is ahead of the aircraft and is calculated in the High Angle Calculating Position, before being sent away electrically to the red pointers at the training receivers at the guns.

For an aircraft that is coming directly towards us, the aim-off or deflection, is nearly all VERTICAL DEFLECTION. Again it is ahead of the aircraft and it is calculated in the High Angle Calculating Position, this time being sent to the red pointers at the elevation receivers at the guns.

If an aircraft is flying on a course between the two, both vertical and lateral deflection have to be sent away to the guns.

Thus, we see that the High Angle Calculating Position in the first place calculates deflection. The method of solving this part of the problem is dealt with later on.

417. The next part of the problem is to burst the shell when it reaches the aircraft. In low angle firing broadsides were fired so that the shells would burst on impact with the enemy's hull.

In high angle firing this would be practically impossible, so high explosive shells, fitted with fuzes that will burst after a certain time, are fired and if the shell is burst as close as possible to the enemy aircraft, the fragments of shell will be sufficient to bring down the aircraft, or at least seriously damage it.

418. The fuze to be set on the nose of the shell has to be calculated an appreciable time before the shell reaches the immediate vicinity of the aircraft, this time being known as the PREDICTION INTERVAL.

PREDICTION INTERVAL DEAD TIME + TIME OF FLIGHT.

It will be seen from this, that timing is a very important factor in this problem, and the High Angle Calculating Position besides sending out the fuze to be set, also puts on a light at the guns, which tells the crew when to set that fuze and load the shell into the gun.

419. Now let us sum up the whole problem.

First of all, the high angle director elevates and trains on to the target, sending away both elevation and training through the calculating position to the red pointers at the receivers at the guns. The director keeps on the target the whole time as the ship rolls and alters course, and the guns follow.

420. In the calculating position, the deflection, both lateral and vertical, is calculated, the result being an added movement sent away to the same red pointers at the gun receivers. The guns are now "Aimed off" from the H.A. director. In the C.P. a fuze number is calculated and sent to the guns. When the load lamp at the fuze setting machine burns, the fuze that has been sent from the C.P. is set on the shell, and the shell loaded into the gun.

From the C.P. a fire buzzer is rung at regular intervals; this tells the director layer when to fire.

In the director, the layer presses his trigger whilst the buzzer is ringing and all the guns are fired electrically.

The shells now travel to the position which the C.P. has calculated as being the future position of the aircraft, and burst at the same moment as the aircraft arrives .

Principles of Deflection. Diagram 27.

421. When calculating deflections in high angle firing, it is always assumed that the aircraft is flying at a level height and constant speed.

Let us first consider that the enemy aircraft flying towards the ship is such that its future position, i.e., when the shell bursts, is directly above the gun (see Fig. I. Diagram 27).

From the Diagram, P is the present position of the aircraft.

F is the future position of the aircraft, directly above the gun, G.

422. The height of the aircraft can be measured and the time of flight (t) from G to F is also known, so that we know the average speed of the shell as it travels from G to F.

This is called AVERAGE PROJECTILE VELOCITY (a.p.v.) and the distance G F is this velocity multiplied by the time of flight (a.p.v. x t ).

The speed of the aircraft (u) is estimated by the Control Officer and if the aircraft is to travel from P to F during the time of flight (t) of the shell, the distance P F must be u x t

The deflection or aim-off must therefore be the angle P G F, which can be calculated from the ratio (u X t)/(a.p.v. X t) or u/(a.p.v.) and to hit the plane at F we must fire when it is at P, with the gun aimed off an amount equal to this angle.

423. So far we have considered the case of one aircraft coming from a certain direction, and flying so that its future position when the shell burst is directly over the gun.

If, however, we go further and imagine that the aircraft can come from any position, as long as its future position is at F directly over the gun, we find that P, the present position of the aircraft can be anywhere on a circle, whose centre is at F and whose radius is u t.

Now let us suppose that the aircraft is such that its future position F, instead of being directly overhead is at 60° from the horizontal (see Fig. II, Diagram 27).

Once again this aircraft is flying at a constant height towards the ship and can come in from any position on the circle with centre at F and radius u t.

424. If, however, we look at this circle from the gun G we notice that it now appears to be an ellipse and not a circle, as was the case when the future position F was directly overhead.

It can also be imagined that the circle becomes a thinner and thinner ellipse as F approaches the surface of the sea. If the speed of the aircraft is greater, then the circle becomes larger because u x t, which is the radius of the circle, becomes larger.

This principle, which is called the ellipse method of calculating deflection, is used in all existing long range high angle control systems.

425. In Diagram 28 will be seen a picture showing the deflection screen of an H.A.C.S. IV table. An optical system inside the table throws on to the screen the image of a circle, which is engraved on a plate. This circle can be tilted by a mechanism, according to the angle of sight and will thus show on the screen as an ellipse, whose shape will vary according to the angle of sight.

The track of an aircraft is also shown on the deflection screen by means of a wire, which is pivoted at the centre and rotated in agreement with an arrow in the Control Officer's binocular. The Control Officer, in the H.A. director, keeps this arrow along the fuselage of the aircraft and thus the correct track is sent down to the deflection screen.

426. The deflection screen operator sits facing the screen, looking at the ellipse. He has two handwheels, one either side of the screen, marked Vertical Deflection and Lateral Deflection. These are connected to wires, which can be moved across the face of the screen. The duty of the deflection screen operator is to keep these deflection wires over the intersection of the wire marking the track of the aircraft and the ellipse. By moving the deflection wires from the centre of the ellipse to the point of intersection, the deflection screen operator measures the vertical and lateral deflection of the aircraft and sends these away to the red pointers at the elevation and training receivers at the high angle guns and so gives the guns the necessary "Aim-off," both for elevation and training.

H.A.C.S.-FUZE PREDICTION.

427. In the beginning of this chapter we saw that, besides allowing for "Aim-off," a fuze had to be set on the shell, so that it would burst at the future position of the aircraft.

In order to do this, we must have some means of finding out what the range of the aircraft is going to be when the shell arrives. In H.A.C.S. this is done by " Prediction," that is to say that we measure the present range of the aircraft continually and by means of a range plot at the opposite end of the H.A. table to the deflection screen, we note the way in which that present range is altering and from this we forecast what the range will be in the future. This is done as follows:-

428. Mounted in the H.A. director is a High Angle Rangefinder. This works on the same principle as the L.A. rangefinder, inasmuch as the deflecting prism inside the instrument is moved for range but the operator moves his Working Head for height. The reason for this is fairly obvious, because if the working head were connected directly to the prism of the rangefinder, the operator would have to move the working head continually, owing to the fact that the rate of change of range of an aircraft is extremely high, owing to its speed. The rangefinder is, therefore, designed so that the operator only has to move his working head when the aircraft changes height and as long as the height is correct, the change in the angle of sight to the aircraft, as the director layer keeps on, operates a mechanism in the table, which converts this measured height into range. This moves the prism in the rangefinder and also goes to the range plot in the H.A.C.S.

429. This observed range appears in the range plot as a series of short lines, which slope across the moving paper of the plot. The "pricker" underneath the plot is operated when the rangetaker in the H.A. director presses the "cut push" with his foot.

The observed plot is liable to be irregular, especially when the rangetaker throws off and re-cuts on the aircraft or through any errors in aim on the part of the director layer, and this irregularity makes it difficult to predict the future range from its slope.

In order, therefore, to get a plot with a smooth slope, another plot is introduced on the paper, called the generated plot. This is produced by the operators on the table keeping pointers to the "mean" of the observed readings, for both

angle of sight and height. The generated plot appears in the range plot as a series of lines about twice as long as those of the observed plot.

430. A third pricker is also operated by the Radar set. The Radar aerials are mounted on the H.A. director and are pointed at the aircraft, when the layer and trainer get on. Continual ranges are taken by Radar and these appear on the range plot as a series of small holes.

The range plot operator, therefore, sees on his plot, three sloping plots (see Diagram 29).

He then, by means of a handwheel at the end of the table, moves a cursor with a length of wire attached to it, until the wire is placed in such a position that the knob on the end of the cursor is a continuation of the slope of the plots.

431. The operator aligns his cursor parallel to the slope of the generated plot and over the latest readings of the observed plot; if the Radar plot is working accurately, he uses this plot rather than the other two.

By moving his handwheel the plot operator sends away to the fuze setting receivers at the guns continual fuze numbers for the predicted future range of the aircraft. At the guns these fuzes are set when the " load " lamp lights at the receiver. The load lamp is worked automatically by the H.A. table at regular intervals, as is also the fire buzzer, which tells the director layer when to fire the broadside, whose shell are fuzed for the correct future range.

432. The fuze keeping clock is fitted in destroyers and small ships, to solve the long range high angle problem. The deflections, both vertical and lateral, which provide the necessary "Aim-off" for the guns, are produced on the same principle as in H.A.C.S., except that the deflection operator looks through a hole at the end of the clock at the ellipse, instead of watching the ellipse on a screen.

In the director is a rangefinder. This rangefinder takes ranges of the aircraft continually, when the director layer and trainer are on; in order that the rangetaker will not have to move his working head continually as the range alters, the deflecting prism in the rangefinder is moved automatically by the F.K.C. This is done by means of a "Rate Clock," which works on the same principle as the rate clock in the Admiralty Fire Control Clock, which is used for low angle firing, that is to say, when the inclination and speed of the aircraft is set on the F.K.C., the rate of change of range is calculated, which in turn, moves the deflecting prism in the rangefinder. Thus, as long as the correct settings are passed down to the F.K.C. by the Control Officer in the director, the rangetaker will find that his cut is being held the whole time.

434. Thus we get the present range of the aircraft being sent down continually to the F.K.C., the rangetaker pressing a cut push with his foot when he has la cut. At the same time Radar aerials mounted in the director are pointed at the aircraft.

Future range, however, is required in order to set the correct fuze at the gun and this is calculated by the mechanism in the F.K.C., which works out the enemy's travel during the "Dead Time" and "Time of Flight" of the shell and hence calculates the future range.

435. In the mechanism of the F.K.C. is an instrument similar to that in the H.A.C.S., called a FIRING INTERVAL CLOCK, which burns the PREDICT LAMP on the F.K.C.

The fuze number is then read off from a rotating disc at the opposite end of the clock to the deflection operator and the fuze sent to the guns via a fuze transmitter on the bulkhead in the T.S. Thus the correct fuze for the future range is passed to the fuze setting receivers at the guns. The guns are then loaded with the correctly fuzed shell; and a fire buzzer sounds in the director, telling the director layer when to fire.

THE HIGH ANGLE FIRE CONTROL TEAM. Diagram 31.

Composition of the Team and Air Defence of the Ship.

436. As in low angle firing so in high angle firing, the successful defence of the ship against hostile aircraft is brought about only by good teamwork, backed up by constant practice and an understanding by each member of the team of the difficulties and complexities of each other's jobs.

The high angle control team is as follows:-

(i) The Air Defence Officer.

437. He is the captain of the team and on him rests the responsibility of seeing that no enemy aircraft approaches without being engaged. He chooses the targets to be engaged from the air defence position at the rear end of the bridge and by means of the Air Defence Officer's Sight, indicates the approaching enemy aircraft to whichever H.A. director he wishes.

(ii) The Assistant Air Defence Officer.

438. Assists the A.D.O. and operates the A.D.O.'s sight on the other side of the air defence position.

"(ii) a. The Target Indication Officer.

He is responsible for the Air Defence of the ship in Blind Fire. He is stationed in the Aircraft Direction Room, which is part of the Action In formation Centre, and by means of the Target Indication Unit (see paragraph 446) he passes ranges and bearings of Aircraft Targets, detected by Long Range Warning Radar, to the appropriate H.A. Director and Transmitting Station."

(iii) The Long Range Warning Radar Set Operators.

439. This Radar set is designed to pick up aircraft flying either singly or in formation at long ranges. The information that it receives is passed to the Action Information Centre, and thence to the A.D.O.

440. These are very important members of the team. There are six air lookouts, three each side, who sit on special air look-out seats, fitted with binoculars, in positions either side of the Air Defence Position. Each look-out has an arc for which he is responsible. He sweeps that arc continually through his binoculars reporting as soon as he sees an aircraft. Having seen an aircraft he must keep it in his binoculars, until he receives further orders from the Air Defence Officer.

(v) The High Angle Control Officer.

441. He sits in the high angle director and having been put on to the aircraft to be engaged, by the Air Defence Officer, he gives the necessary orders to the calculating position for opening fire and subsequently spots the bursts on to the enemy aircraft.

(vi) The High Angle Director's Crew.

442. Consists first of all of the director layer and trainer, who keep on the enemy aircraft continually, the layer operating the angle of sight cut push with his foot as soon as he is on. This burns a light in the calculating position and in the air defence position and tells these positions that he is "On" the enemy aircraft. The director layer also fires the guns electrically, by means of a trigger, during the time that the fire buzzer is ringing.

The other member of the crew is the rangetaker. He gets a "cut " as soon as the director layer and trainer are on and subsequently throws off and re-cuts continually, so as to get as accurate readings as possible.

(vii) The Radar Ranging Set Operators.

443. The aerials of this set are mounted on the director and are moved when the director is laid and trained on to the target. Thus they are pointed continually at the enemy and Radar ranges are passed to the H.A.C.S. Plot, from the Radar Ranging panel operator.

(viii) The Crew in the High Angle Calculating Position.

444. The operators of the H.A. table are given the estimated course and speed of the aircraft by the Control Officer and from this information, together with the measured range and movements of the director as it follows the target, are calculated the gun elevation, training and fuze number. These are passed continually to the guns. The H.A. table also sounds the fire buzzer automatically at regular intervals. This tells the director layer when to fire.

(ix) The High Angle Guns' Crews.

445. The gunlayers and trainers must follow the movement of electrical pointers in the elevation and training receivers. It is also extremely important that the correct sequence of setting fuzes and loading the fuzed shell into the guns is carried out by the guns' crews, because each shell carries a fuze that is only correct for that particular moment. These points must never be sacrificed to achieve a higher rate of fire.

AIR DEFENCE OF THE SHIP.

446. It will then be seen that some of the members of the high angle control team are widely separated from each other, so that very good co-operation is necessary if quick and accurate fire is to be opened, especially against enemy attacks, which may come in from different directions at once and may give very little warning of their approach. The Air Defence Officer receives all the available information from the Action Information Centre, when hostile aircraft are reported, and he can then get the H.A. directors on to the best possible look-out bearings. When a formation is sighted he immediately trains his sight on to it, sending

"At night or in thick weather neither the Air Defence Officer or the H.A. Directors will be able to see the enemy Aircraft, so the responsibility for the Air Defence of the Ship rests with the Target Indication Officer. This officer is stationed in the Aircraft Direction Room situated below decks and part of the Action Information Centre. He is assisted in his task. by an instrument called the Target Indication Unit (T.I.U.), worked by four operators. This unit is linked with a Long Range Warning Radar and gives a picture of all targets within range of the set. The T.I.U. has a number of handwheels (depending on the type of ship) for transmitting Relative Bearing to the appropriate H.A. Director or Close Range Group and can also transmit range by Range Transmission Units on either side of the Radar Display.

There are also switches for controlling Call-up Gongs in the Air Defence Position and H.A. Directors, and the Check Fire Bells at the guns."

Barrage Firing.

447. So far we have only considered " predicted firing " against high level bombing attacks, when each fuze is calculated to burst at the future position of the aircraft. When the enemy aircraft dive to attack, it is necessary to fire a barrage ahead of the aircraft. This barrage is fired at a fixed range, and therefore with a fixed fuze setting such that the aircraft must fly through the barrage to complete its attack.

A.B.U. Firing.

448. An instrument called the Auto Barrage Unit is fitted in the H.A. Calculating Position for firing the guns. Its function is to measure the rate of change of range of the aircraft by Radar and, having previously been set with a barrage range, it will fire the guns at the correct moment so that the shell and aircraft arrive at the same instant.

The A.B.U. operator, by pressing a foot pedal on the instrument, will automatically fire the guns at the correct time.

The change-over switch, which decides whether the A.B.U. or the director layer will fire the guns, is in the H.A. director.

The great advantage of this form of barrage firing is that the shell is definitely fired to hit the enemy aircraft and not only to deter him from pressing home his attack.

DRILL AT HIGH ANGLE GUNS.

449. The object of the H.A. control system is to burst a shell at the aircraft's future position at the moment when the aircraft reaches it.

To achieve this, two things, apart from accurate pointer following, are necessary at the gun:-

So far as (i) is concerned, a heavy responsibility for the accuracy of the gunfire against aircraft rests on the fuze-setter (if setting fuzes by hand) or on the fuze follower when using a fuze-setting machine. In either case the fuze must be set immediately the " load " lamp lights.

A round fired with a badly set fuze is a round wasted.

It will be appreciated that so far as the second condition is concerned, this can only be achieved by the closest attention being paid to the time of the drill by the captain of the gun and the trayworker, who must not allow the gun to be loaded with an out-of-date or "stale" fuze.

When the target gets within a certain range of the ship, "barrage" procedure may be used.

Rounds with a previously ordered "barrage" fuze setting are loaded as quickly as possible, whenever the gun fires.

450. The gun may also be required to engage a target in "local barrage," in which case the gun is aimed by the gunlayer and trainer, using eyeshooting sights

In H.A. as well as L.A. fire it is important to realize that what has to be learnt by the gun's crew is the action required of them on receiving any given order and not a set sequence of orders, which may vary in action.

451-454.

NECESSITY FOR SIMPLE CONTROL.

455. Close range weapons are used against low flying or diving aircraft, moving at very high speeds at close ranges (3,000 yards and below). The time during which the enemy is within range is very short, so that it is important for the control of these weapons to be simple and if possible under the direction of one man.

The guns are in all cases designed to fire very rapidly, with a high muzzle velocity, and are capable of being swung quickly when following an aircraft or for picking up a fresh attacker.

CLOSE RANGE GUNS' CREWS.

456. The crews of the close range weapons are the "commando troops" of the ship. They have got to be tough, well disciplined, and capable of withstanding hardship. They are not protected from the weather or splinters and have got to be able to keep cool and collected, and shoot accurately in spite of all that is going on around them.

Strict discipline at close range weapons is essential, otherwise, in action you may easily become distracted, or be caught napping by a surprise attack.

457. The following are the usual faults apparent in air battles and must be guarded against:-

It is essential for all close range weapon- crews to keep a look-out. Do not rely on the Air Defence Position to see the enemy or to communicate with you, or the bridge to tell you when to open fire. You must be ready to open fire on your own at the correct target as soon as it is within range.

Close range weapons are usually to be found in the most exposed positions in the ship so that they can have the best arcs of fire. This is all the more reason why they and their ammunition must be scrupulously clean.

458. The latest method of sighting close range weapons is by using gyro gunsights. All that need be said about them in this book is that steady aiming and constant practice are essential. The other method, which is the "stand-by" method, is "Eyeshooting."

EYESHOOTING. Diagram 32.

459. "The Eyeshooting Pocket Book" (B.R. 254) contains full information regarding the principles and application of eyeshooting sights on close range weapons and should be thoroughly understood by all crews. You can buy a copy of it for a few pence, or borrow it from the Gunnery Office.

As applied to close range anti-aircraft weapons, the word " eyeshooting " simply means the method of aiming in which the aimer judges by eye and without any calculating instruments where to point his gun, in order to hit a moving target.

There is nothing difficult nor new in the principles of eyeshooting with A.A. weapons; the mode of operation is similar say, to throwing a boot at a cat running along the top of a wall. To allow for the movement of the target during the time of flight of the bullet, the gun has to be pointed ahead of the target at some position along its future path.

Foresights.

460. Looking at the eyeshooting foresight in Diagram 32, you will see that it consists of a number of equally spaced rings, one, two and sometimes three (see also Diagram 35).

In the case of all modern sights the inner ring is the 100 knot ring, the next one the 200 knot ring and the third one, if fitted, the 300 knot ring.

462. The method of using the sight is very simple. Look at the aircraft, note its direction of flight and estimate its aim-off speed. Point the gun so that the aircraft is flying towards the centre of the sight, with its nose the distance from the centre corresponding to your estimate of its aim-off speed. As the attack develops and the aim-off speed increases, bring the nose of the aircraft further and further out from the centre, always adjusting direction of aim-off to keep the aircraft flying towards the centre of the sight.

To assist you in applying direction of aim-off correctly, when the amount of aim-off is large, some sights have " radial wires " pointing towards the centre from the outer rim of the sight. These are valuable because, although wrong estimation of aim-off speed is the most common cause of missing the target, misses are due quite often to incorrectly gauging the direction of aim-off, particularly when the aim-off is large.

At weapons which may have to be used against surface craft, you will find "ticks" fitted at 10 or 20-knot intervals along the horizontal and vertical crosswires inside the 100 knot ring. These are to assist you in holding the correct point of aim after you have found it by spotting.

Backsights.

463. Most backsights are of the aperture type with rubber eyepiece. Having placed your eye correctly in the eyepiece, you can forget about the backsight and concentrate on pointing the foresight in the correct direction. You must, however, be quite certain first that you have centred your eye correctly in the eyepiece, otherwise you will introduce an error in your aim. In modern backsights there are crosswires or crossed cards to assist you to centre your eye. A glance at them just before you take aim will enable you to put your eye correctly on the line between centre of foresight and centre of backsight. Having got it central, keep it central.

In the heat of action unless you guard against it, unbeknown to yourself, you will aim without putting your eye to the backsight. This is fatal, so see that it does not happen.

464. At certain weapons "bead" backsights are fitted. The principles of eyeshooting with these sights are the same as with aperture sights but you keep your head well to the rear, so that you can see the bead, the foresight and the target all at the same time and instead of keeping your head in a fixed position, you have to move it about as necessary to take aim.

To take the correct aim with a bead backsight, the bead must be covering the nose of the aircraft, when the nose of the aircraft is where you want it in the foresight.

In the case of the Oerlikon gun, which vibrates greatly when firing, you will find that although there is a fitting for a rubber eyepiece fitted to the backsight, you have to keep your head well to the rear and use it like a bead backsight. The sight is designed to be used in this way; the rubber eyepiece should not be on the sight.

465. There are three things you must learn about enemy aircraft, viz.:-

Recognition.

466. You must be able to recognise aircraft for the following reasons:-

You should take a pride in your ability to recognise aircraft and to judge approach angle. Get hold of any cards, models, pamphlets, newspapers or magazines that you can and study them carefully. Do not try and learn too many types at once but get to know the three or four types in general use really well; then you can start adding to your collection as other types come into use. Some credence should be given to the opinions of youths in this matter; some of them have surprisingly accurate knowledge.

Estimation of Speed.

467. As you have previously read, you must know the flying speed 'of an aircraft before you can estimate the aim-off speed correctly. judging the speed of an aircraft depends almost entirely on knowing the performance of the different types and you must learn this when you are studying how to recognise aircraft.

Unless you have had very considerable experience, you will not get much assistance in judging speed from the noise of the aircraft or from looking at it, except that it obviously goes faster when diving. You can generally assume that, when attacking, your target is going at full speed but do not forget that, if diving, it will probably be going much faster than its full level flight speed.

A good rule for judging aircraft speeds at the present time is given below, although new types coming into service may not fit into this rule.

Type of Attack.

Estimation of Range.

469. You should be able to estimate the range of an enemy aircraft by eye in order that you will know when to open fire.

The estimation of range depends entirely on practice and experience, and you must get all you can. You must remember that varying weather conditions and differences in the sizes of aircraft may produce misleading effects. For example, if you are used to dealing with medium-sized aircraft, you will tend to under-estimate the range of a larger aircraft and open fire too early. Therefore, when studying recognition, you must note which are large machines and which are small ones. Very often recognition drawings and silhouette cards do not make this point clear, but you can spot it at once with the models.

The "Maximum Effective Ranges" of close range weapons are as follows:-

Note. Against approaching targets, fire should be opened when the present range is some 200 or 300 yards greater than the above figures.

Consider a fighter aircraft approaching at 300 knots. It covers a nautical mile (2,000 yards) in 12 seconds. It is within effective range of a .303 machine gun for 400 yards coming towards, and 400 yards going away, a total of 800 yards which it can travel in under five seconds. You haven't much time, have you?

THE POM-POM DIRECTOR MARK IV. Diagram 33.

471. In earlier types of Pom-Pom directors, the necessary "Aim-off" at the director and thus at the guns was done by " eyeshooting."

In the Pom-Pom Director Mark IV (see Diagram 33), the eyeshooting principle is abandoned and the target's vertical and lateral movement is measured by an instrument called the GYRO RATE UNIT. These movements are combined with the time of flight of the shell and produce vertical and lateral deflections.

The transmission from the director to the Pom-Pom is by remote power control, whereby the Pom-Pom mounting automatically follows the director.

472. The Pom-Pom director has a full crew of eight men, whose duties are as follows:-

THE 2-PDR. MARK VIII GUN ON THE MARK VII MOUNTING. Diagram 34.

473. This Multiple Pom-Pom has four barrels and is found in destroyers and cruisers.

The mounting may be fitted with or without a Pom-Pom director, and in the former case, laying and training is by remote power control. As a general rule, Pom-Pom directors are fitted in cruisers and not in destroyers.

Ammunition is supplied in belts; eight belts per gun, each belt consisting of 14 rounds, are loaded on to the feed rails. The first and last round of each belt rests on the rails and are connected to the next belt by connecting links. The remainder of the belt hangs in a bight.

Mounting fitted with Remote Power Control.

474. The motive power of mountings fitted with R.P. 50 remote power control is electric. An indicating lamp is fitted at the mounting to show that this source of supply is flowing.

When in director control, a power change-over switch at the mounting is put to DIRECTOR and the mounting will automatically follow the director and the director will fire the guns, when the firing clutch lever is put to ELECTRIC.

If it is necessary to bring the mounting back to a convenient position for loading, this is done by putting the power change over switch to LOCAL from DIRECTOR and taking over the control of the mounting with a joystick, fitted at the mounting. The mounting can also be fired by means of a local firing trigger on the joystick, when being laid and trained by the joystick.

Mounting fitted Without a Director.

475. In this case, laying and training is by hand, the gunlayer and trainer using eyeshooting sights. The guns can be fired either by "Hand" or "Electric" depending upon the position of the firing clutch lever. In "Hand" the guns are fired by turning the hand firing gear, in "Electric," pressing the local firing pistol energises a circuit, which clutches the firing motor to the firing cam and fires the guns.

The latest type of mounting fitted without a director is power-controlled by means of a joystick on the mounting.

THE 20 m.m. OERLIKON GUN. Diagram 35.

Description of Gun and Mounting.

476. The Oerlikon is an automatic gun designed for close range anti-aircraft fire, with an effective range of 1,000 yards. It is mounted on a single shoulder-controlled mounting, or on a twin power-operated mounting.

Operation of Gun.

477. The gun is operated by the pressure set up by the explosion of the round. The empty case is blown back against the breech, forcing it to the rear against the pressure of the barrel springs, which carry the moving parts forward again.

The breech is not locked at the time of discharge and the round is fired a fraction of an inch before it is fully home in the chamber, the neck of the case swelling to form a gas seal.

The barrel and casing do not recoil; the whole force of the explosion is utilised in propelling the projectile and operating the moving parts.

478. The gun is cocked by means of the cocking lanyard.

The gunlayer presses the magazine catch lever as far forward as it will go, otherwise the interlock mechanism will not be cocked. It is essential that the magazine catch lever be pushed fully forward, either by the knuckles or finger tips, as few men have sufficient arm length to push the catch lever fully forward with the palm of the hand, when behind the shoulder piece in the firing position. If the lever is not pushed right forward, the catch will not be cocked, with the result that the magazine interlock will still render the firing gear inoperative.

The loading number places a loaded magazine in position forward end first and swings the rear part of the magazine down smartly to seat it; the lever is automatically released, locking the magazine in position. The action of shipping the magazine presses down on the ends of the catch and releases the magazine interlock from engagement with the trigger gear and the gun can then be fired.

It is possible to remove an empty magazine and ship a fresh one although the magazine catch lever has not been pushed as far forward as it will go. In this event the magazine interlock gear will not have been released and the gun will not fire.

Automatic Firing.

479. With the gun cocked and a loaded magazine in position, a full round is lying in front of the breech face ready to be driven into the gun.

With the safety catch lever to FIRE, pressing the firing lever releases the breech mass, which flies forward under the action of the barrel spring, driving the live round into the chamber.

The breech mass at the instant of firing is still travelling forward. The force of the explosion, as far as the rearward direction is concerned, is then absorbed in checking this forward movement and reversing its direction, against the action of the powerful barrel springs.

On firing, the empty case is blown back against the breech face piece, forcing the moving parts of the gun to the rear, so compressing the barrel springs. (The moving parts consist of the breech, the bolt, cotter, two breech bars, and barrel spring casing, and they, being held together by the cotter, move as one part.)

480. The force of the explosion has now been overcome and the barrel springs are fully compressed and buffering of the extreme rearward movement has taken place.

As the barrel springs, assisted by the buffer springs, exert themselves, the run out commences. If the firing lever is held to FIRE, the top of the breech face piece will pick up a fresh round from the magazine during its run-out movement and the cycle of operations will be repeated until the magazine is empty.

Holding back the Breech Mass after the Last Round in the Magazine has been Fired.

481. A catch automatically holds the breech mass in its rear position after the last round in the magazine has been fired, so that when the empty magazine has been exchanged for a full one, it is not necessary to cock the gun as on the first occasion. The gun is held cocked and it is only necessary to cock the magazine catch lever and ship a fresh magazine.

482. The double shoulder piece, which is adjustable for width and is fitted at the rear end of the casing by a bayonet joint, together with the harness fastened round the body, gives adequate control of the mounting enabling a rapidly moving target to be followed with precision. Accuracy of aiming is very largely dependent on smooth footwork which requires constant practice.

Balance Spring.

483. To assist in easy elevation of the gun, a spiral counter-balance spring is provided at the left hand side of the bracket. At the front end of the cradle the gun lies in a " shoe " in which it is held fast by a securing bolt; this gun securing bolt takes the thrust of the gun when fired and care must be taken that the bolt engages properly with the underside of the gun and that it is kept greased and functioning correctly. The cradle can be secured in the horizontal or vertical position by the stops provided. If a gyro gunsight is fitted, it should always be left horizontal.

The Drum Magazine.

484. With each gun are supplied six drum magazines, each capable of holding sixty rounds, one loading stand and two ratchet levers for tensioning the magazine spring.

Every possible care must be taken to avoid damage to the magazine, otherwise failures will almost certainly result.

Before loading a magazine it should be tested for freedom of its moving parts by first ensuring that the tension indicator is showing zero, after which the ratchet collar should be lifted and the axis shaft rotated through its full travel by means of the boss on the centre of the ratchet lever handle.

If the muzzle covers provided are in use, the following precautions must be taken.

The last two rounds to be loaded into magazines are to be either practice or practice tracer rounds, so that the first round to be fired will carry away the muzzle cover and the second will do so in the event of the first round missing fire. H.E. ammunition would give a premature on hitting the cover.

Grease on Ammunition.

485. Ammunition supplied in boxes is not greased.

For the gun to function it is essential that each round should be lightly greased with Grease No. 0 before loading into the magazine. This should be done by hand and not with a brush. Oil is not to be used.

A little grease applied shortly before firing to the cartridge case visible in the mouth of the magazine helps.

To Charge a Magazine.

486. Place the magazine upon its side on the loading stand, pulling up the ratchet collars. By applying the ratchet lever with the boss on the centre of the ratchet lever engaged with the pin within the ratchet collar, and turning the spring axis, wind the feeder block to the opening of the magazine.

Insert the rounds, pushing them in with the thumb and taking particular care that the feeder block remains in contact with the first round inserted, and that none are allowed to fall forward after being inserted.

When the magazine has been charged, the ratchet collar is allowed to go down, permitting tension to be applied by the ratchet end of the lever.

Tensioning the Spring.

487. When the magazine is fully loaded with 60 rounds it should be fully tensioned by rotating the magazine lever as far as possible.

Should the magazine be partly loaded, e.g., 30 rounds, it is to be tensioned until the indicator reads 30, followed by two further clicks on the ratchet. To put tension on a magazine loaded with less than 60 rounds, it is necessary to hold the ratchet collar, while using the ratchet lever.

Care must be taken that the magazine interlock plunger is free, otherwise the breech block will not remain in the rear, i.e., cocked, position when the last round is fired from the magazine. This plunger is spring loaded and is situated at the rear of the magazine cartridge feeder.

If a magazine is loaded only to be stored, the spring is merely given a slight tensioning.

Make sure that the magazine is fully tensioned before placing it on the gun. If this is not done stoppages will result.

Should the magazine be given no tensioning at all, the rounds would be liable to fall out or become disarranged in the magazine when removing it from the loading stand.

To Release the Tension on the Spring.

488. If a magazine that has been charged and tensioned is not required for ready-use purposes, the tension is to be released to that small amount which is necessary, as described above, to prevent the rounds from becoming disarranged.

To do this:-

489. If it is desired to unload a charged and spring-loaded magazine, it should be placed on the loading stand and the rounds pushed out one by one, by hand. This relieves the pressure of the spring at the same time.

If the magazine is charged but not tensioned, it must be tensioned before unloading, so that the spring may force the rounds forward to the opening.

Caution.

490. Ammunition is greased and care must be taken to see that the grease which is in sight in a loaded magazine is not removed. This grease is necessary for the functioning of the loading arrangements.

491. The following are the routines which should be carried out with the Oerlikon gun:-

Daily.

Remove magazine. Sponge out bore, taking particular care to see that the chamber is left clean and greasy. Lubricate breech and breech block guideways in magazine opening without easing the spring.

Weekly.

Remove magazine. Ease the barrel springs and lubricate the top of the breech. Remove the shoulder piece, hand grips, the trigger cover plate and trigger casing, drain out any water in the gun body. Lubricate the trigger mechanism and reassemble. Cock the gun, ease springs again and recock.

After Firing.

Carry out a daily and weekly routine. See that the gun securing bolt at the front end of the cradle is free and grease it.

492-494.

LOOK-OUTS.

495. The safety of the ship and its success in action, to a great extent depends on look-outs. Keeping a good look-out for long periods at a time is apt to become extremely dull and tedious and will produce eyestrain. It is for this reason that the length of a look-out's trick is reduced as much as possible and, if sufficient men are available, this trick should be cut down to 20 minutes.

This period is not too long and if you are detailed as a look-out in your ship, you must realise the very essential and important task that you are performing, and keep strictly to the routine that you are taught.

Before considering the actual look-out routines that are carried out, it is essential that the look-out should have a thorough knowledge of how to use his binocular.

CARE OF BINOCULARS.

496.

HOW TO ADJUST BINOCULARS. Diagram 36.

497.

HOW TO USE BINOCULARS.

498.

TYPICAL LOOK-OUT ORGANISATION.

499. Look-outs may be divided into the following classes:-

DUTIES OF LOOK-OUTS.

(i) A.A. LOOK-OUTS. Diagram 37.

500. These are stationed near the AIR DEFENCE POSITION. They v in pairs, relieving each other every 20 minutes. Once an air look-out has sighted an aircraft, he must not take his eyes off it until the A.D.O. has found the target. The rating not closed up at the seat reads off the bearing and angle of sight.

A.A. look-outs are given definite "sectors" of 60° to search.

The STANDARD ROUTINE is as follows:-

Each period must take from 15 to 20 seconds.

The elevation of the 1st sweep is ordered by the Air Defence Officer, according to the conditions.

The SHADOWER'S ROUTINE is as follows:-

Method of Reporting.

502. On sighting an aircraft, the look-out must report:-

The look-out off trick, as soon as he hears the report "Aircraft " reads off and reports:-

He continues to do this until the A.D.O. has found the target.

(ii) SURFACE LOOKOUTS.

503.

(a) Far Look-outs.

Far look-outs are stationed aloft in clear weather. The sector for which each look-out is responsible must be swept slowly and systematically keeping the centre of the binocular field just above the horizon. The time taken for a 70 degree sector should be from half a minute to a minute, and on completion the look-outs must sweep back slowly with the naked eye, and repeat the sequence. Whilst sweeping with the naked eye, they should search for the tracks of approaching torpedoes.

(b) Near Look-outs.

Near look-outs are situated lower down usually on or near the bridge. The same procedure should be carried out as for far look-outs, but in this case keeping the horizon in the top of the binocular field.

(c) Fog Look-outs.

In times of extremely bad visibility or fog, special look-outs are placed as far forward as possible. In these circumstances it is sometimes better for the sector to be searched with the naked eye, binoculars being used only to verify a suspected object.

(iii) NIGHT LOOK-OUTS.

504. At night the eye has to deal with intensities of light over a million times weaker than those of day. Night vision requires an entirely different mechanism in the eye from that used in day vision and the process by which the eye changes over from day vision to night vision is called DARK ADAPTATION.

After the eye has been adapted to the dark for about half an hour, it is many thousand times more sensitive than it is in a well lit room. For this reason no night look-out should look at an instrument unless it has a red light in it, or strike a match or enter a lighted compartment before going on watch. If he does so it will take up to 30 minutes to get dark adapted again and he will be of no use as a look-out. This is a very important point to remember, if you are detailed as a night look-out.

How to Use Your Eyes at Night.

505. At night you will have to learn a new way of using the eye. Few people realise that when they look straight at an object on dark nights it will tend to disappear from view, whereas it will be clearly visible if they look slightly to one side, or above or below it.

Without going into the complicated details of the eye's construction, it is worth noticing that the parts of the eye that are most sensitive to dim lights, in fact, the only parts that enable you to see at night are all situated off centre.

The very centre of the eye, which is the most sensitive part of all in day time, is almost useless at night. Some people with exceptionally good eyesight can still see a little with it. But for the average person, it is night blind.

Method of Sweeping.

506. When sweeping as a night look-out, try to scan your sector by making small movements of the head and binocular, each movement followed by a pause; at each pause move your eyes to cover the field of view of your binocular. Your total sweep should be even slower than by day.

Quick movements and short pauses are better than long movements and long pauses. If you think you can see an object, look well away from it with the head and binocular, count 10, and then look back. Take a sharp look at the place where you thought you saw it, but a little to one side.

When you have completed your scan with the binocular which should take about a minute for a sector of 70 degrees, sweep back slowly over your sector with the naked eye, taking about half a minute. Pay particular attention to any part of the horizon which appears to be broken or distorted.

REPORTING.

507. Remember that it is essential to report at once anything which you see or think you see. If in doubt, report.

Reports should be made as follows:-

At night it is difficult to determine the distance, and " Near " or " Far " may be omitted from the report.

RECOGNITION.

508. It should hardly be necessary to stress the importance of look-outs being able to recognise an enemy ship or aircraft. But what is also extremely important is that they should know what to look for at night, such as a white bow wave, whether to expect to see a ship looking dark against a light sea, or light against a dark sea.

This knowledge comes with constant practice and by noticing the appearance of ships in company, the position of the moon and the state of the sea and sky.

A dull glow of light, apparently below the horizon may be reflected light on upper works or glow from a funnel. In both cases these will mean a ship comparatively close to your ship, so act quickly.

On a dark night, with breaking seas, it is particularly difficult to see approaching small craft, but they may be given away by an irregularity in the general line of waves and specially bright patches where the waves are breaking over the ship's bows.

509.

510. Full particulars regarding the whole of the gunnery organisation of ships may be found in the BR 974 "Handbook of Gunnery Organisation," and should be consulted if it is desired to go deeper into the question of organisation of any particular ship.

DEGREES OF READINESS IN WAR-TIME.

511. The general requirements to be met are as follows:-

In order to fulfil these requirements four degrees of readiness are allowed for, both in low angle and high angle armaments. The degree of readiness that is assumed by the ship depends upon the situation.

Anti-Ship Armament.

Anti-Aircraft Armament.

514. Degrees of readiness are assumed as follows:-

G

515. It is, of course, possible to be in a different degree of readiness for L.A. and H.A. For instance, in 4th degree of L.A. readiness and 3rd degree of A.A. readiness. Also if it is required to man the A.A. armament fully whilst in 4th degree of L.A. readiness, the extra men to man the A.A. guns must be trained from the L.A. armament.

Guard Ships.

516. The 1st and 2nd degrees of readiness will normally be required only when the fleet is at sea. If the operation is prolonged men will not get sufficient sleep if closed up all the time, in which case "Guard Ships" may be detailed, thus providing all ships in turn with a lower degree of readiness. The guard ship remains in the 1st degree of readiness.

This applies to the A.A. armament in harbour as well as at sea.

ALARM SIGNALS.

517. In order to give immediate warning and to get every man to his action station as quickly as possible, WARNING ALARM HOOTERS are fitted throughout the ship. These are usually worked from the bridge and consist of a series of hoots followed by the appropriate bugle call for " Action Stations," "Night Action Stations" or "Repel Aircraft."

The hooters should never be used for exercising action.

On hearing these hooters, every man in the ship, no matter what he is doing, must immediately go to his action station. If a man is already manning a gun other than his own, which is in action, he must not leave that gun until he is relieved.

If when the armament is closed up a sudden alarm is given and it is necessary to open fire quickly, the order "Alarm" is followed by a series of short rings on the fire gong. This means that the guns are to be loaded, if not already loaded, and brought to the " Ready " as quickly as possible.

FOOD AND SANITATION.

518. When closed up for long periods, it is not always possible to allow men to leave their action stations at all. For this reason, sanitary arrangements must always be available at all quarters, as well as mess traps. When possible, certain cook ratings will be fallen out to prepare food and when this is ready, action cooks, detailed from each quarter, go to the galley and fetch food for their particular gun or station. The meal is then eaten whilst closed up.

In some cases it may be possible to allow a part of the armament at a time to fall out for a short period. In this case certain mess decks will be used as action messes by each quarter in turn.

519. Spare parts of guns that can be shipped quickly are normally stored in the vicinity of the gun. The position of all spare parts must be known by the officer of quarters and the captain of the gun. "Action Boards" should be placed in the various quarters showing the storage for various spare parts. The Gunner of the ship knows the quantity and disposition of all armament stores on board.

CASUALTIES.

520. Whenever possible, when battle is imminent, men should wear clean underclothing to minimise infection of wounds and should be fully protected against flash, by wearing anti-flash clothing and overall suits. This is especially important in the tropics, where the tendency is to strip to the waist.

First aid posts are distributed about the ship and each quarter is provided with certain first aid facilities. Guns' crews must be trained so that casualties can be rapidly replaced. The guns must always be kept in action and casualties can only be taken to the first aid stations when a lull in the action allows.

521-524.

525. A ship must be seaworthy in order to fulfil her function as a fighting unit. Damage control has as its object, the preservation of the maximum offensive power of the ship.

In order to achieve this, it is first of all necessary to keep the ship afloat, secondly to keep the ship moving, thirdly to keep the ship upright, and fourthly to reduce the risk of fire and smoke to a minimum.

The damage control organisation in each ship is therefore built up with this object in view.

526. In this book no attempt is made to go deeply into the intricacies of the organisation or the operation of the various fire fighting appliances but merely to discuss quite shortly the primary basic principle of damage control, which is to keep the ship water-tight, and to touch on the ways in which you can assist in keeping the ship an efficient fighting unit.

The best way to ensure that the ship can stand up to a large amount of damage is to divide up the underwater structure into a large number of small water-tight compartments. This is, however, impossible throughout the length of the ship, because this type of sub-division is limited by the size of essential compartments, such as boiler rooms and magazines. It would also make living conditions in the ship quite impossible and it would be very difficult to get from one place in a ship to another.

527. A compromise is, therefore, reached whereby the water-tight integrity of the ship is balanced with the living conditions.

Nearly all water-tight compartments have water-tight openings in them and these openings are marked in certain ways, so that it is possible to see at once how much that opening affects the water-tightness of the ship (see Plate 21).

The risk involved by any opening being opened is shown by one of two colours, RED or BLUE. The colour is painted across the corner of the door or hatch, and in the case of a valve or other opening, a red or blue disc is painted where it can best be seen.

528. A RED opening, when open, constitutes an immediate risk to the watertight integrity, a BLUE opening a less immediate risk. Openings which have no colour on them constitute no risk to the water-tight integrity.

The obvious way then, to keep the ship as watertight as possible is to keep all the RED and BLUE openings permanently closed, both at sea and in harbour. If this was done, however, it would not be possible to get into certain compartments at all, so a letter is also put on to each door, which tells you at once what action you must take before opening it. Valves, etc., are marked in a similar way and for the same reason.

The letters are X, Y, Z or O.

There is a special marking-"ROUTINE".

529. An X on an opening means that it is very important to keep it closed as much as possible and permission must first of all be obtained from the officer of the watch or the D.C.H.Q. before it is opened.

A Y on a door or hatch means that it may be opened without permission in order to go through it but it must be closed again immediately and secured. If

A Z on an opening means that it is usually open, except at action stations or in an emergency, but RED Z doors, that is to say RED doors with a Z on them may be closed or opened by pipe, independently of other Z openings.

An O on an opening means that it is always open and only closed by special order.

ROUTINE on an opening indicates that a special routine governs its operation. The routine is posted near and must be read.

530. These colours and letters are most important and must be known thoroughly. The rules governing the operation of water-tight openings must be strictly obeyed, otherwise the whole ship's safety is imperilled.

531. Besides the above, there are other symbols which may be found on doors. These are self explanatory and are additional to the letter or "ROUTINE" marking. They are as follows:-

CLOSING DOORS.

532. When you close a door, see that the clips are put on correctly. The clip should be put on from above downwards, so that any pressure on the door will tend to jam the clip more tightly. If the clip is put on from underneath upwards, it will tend to fall off and the door will no longer be water-tight.

ABANDONING COMPARTMENTS.

533. Remember that if you are the last man to abandon a compartment you must see that the water-tight door or hatch is closed after you and that any valves into that compartment are also closed.

FIRE.

534. Fire is a menace that grows, that is to say from the smallest beginnings a fire will spread rapidly, if allowed. Therefore, the first essential when fighting a fire is speed of attack. The duty of anyone discovering a fire is to try and put it out. This can be done if the fire is small, or at least it will in all probability be possible to keep it under control.

G1

PREVENTION OF FIRE IN A SHIP.

535. Various precautions can be taken in a ship to reduce the risk of fire. The obvious things such as landing superfluous gear, draining petrol systems, etc., are done wherever possible in ships.

There are other precautions, perhaps not quite so obvious, which must also be taken. One of the chief troubles in this category is the hiding away of paint, boxes and cartons. This must always be guarded against, because it is the hidden "treasure" kept for convenience in some "caboose" which is the hardest to locate and thus the greatest menace.

536. All gear that has special stowages must be stored properly and not left to smoulder in some forgotten corner. Doors of kit lockers must be kept firmly secured. Loose clothing and paper are liable to choke pump suction.

Personal gear must be reduced to a minimum and all unnecessary electric circuits must always be switched off. Paint must not be allowed to accumulate on bulkheads. This will mean chipping the plates before they are painted, but it will be worth the time and work involved if it prevents a serious fire.

MAGAZINES.-FLOODING AND SPRAYING.

537. Magazines which contain explosives are fitted with means of flooding the compartment and with spraying the cordite charges. Full details of the rules regarding flooding and spraying may be found in the N.M. and E.R.

Flooding.

538. Flooding is done from the sea, that is to say a seacock is fitted which, when opened, allows sea water to enter. This flooding of the sea water is controlled by a FLOOD VALVE and each valve can usually be operated from three positions. One position is just outside the magazine, the others are at special flooding positions in the ship. The operating handwheels are inter-connected by shafting capable of being uncoupled if necessary. Should the shafting from one position to the flood valve become damaged, that from another can probably still be operated.

The order to flood the magazine is usually given only by the Captain or the Damage Control Officer, because once a magazine has been flooded, the gun and turret which that magazine serves is put out of action. Magazines are therefore flooded only in the case of a dangerous fire.

It takes some time to flood a magazine, about twenty minutes in a cruiser, and whenever a magazine is flooded the spray system should be turned on fully.

Spraying.

539. Magazines are sprayed with water taken from the ship's fire-mains through pipes which run along the deck head of the magazine. These pipes have a series of "roses," attached to them, which spray the water over the cordite charges.

Spray valves are fitted to control the system and these also can be operated from three positions. One is in the magazine itself, the others at the special magazine flooding positions in the ship.

540. Spraying a magazine is very effective when there is a fire in an adjacent compartment and it is necessary to keep the magazines cool. It can also be used when there is a small fire. Spraying has the great advantage that although it may be necessary to stop providing ammunition, whilst spraying is actually in progress, it does not put the gun out of action.

The order to spray can be passed by the officer of quarters or the captain of the magazine.

541. The primary positions from which the flood and spray valves are operated are divided throughout the ship into groups. That of each group comprises a locked cabinet containing the operating handwheels which is unlocked and manned by an engine room rating in action. The handwheels in the cabinet are normally pinned to prevent their being rotated. To work the valve from any of the secondary positions whilst the primary position is pinned it is necessary first to unlock the cotter and remove it from just above the wheel it is desired to operate; this enables the lower part of the shafting to be moved whilst the upper part remains stationary.

CORRECTING HEEL AND TRIM-COUNTER-FLOODING.

542. When a ship sustains underwater damage she will often take up a list. If this list is excessive, it will prevent the guns being fought effectively and, in the case of a carrier, will prevent aircraft being flown on and off: it will also affect stability.

A list (or trim) is corrected by counter-flooding selected compartments or by transferring fuel and water, or by jettisoning topweight. In cruisers and above, counter-flooding parties form part of the damage control organisation and are controlled from the D.C.H.Q.

A ship may take up considerable list without risk of overturning.

DAMAGE CONTROL COMMUNICATIONS.

543. Every man in a ship should be able to recognise and be prepared to use a damage control telephone should necessity arise. They are painted in three different colours:-

They lead direct to the nearest damage control base or headquarters, who take reports and initiate any action that may be necessary.

GENERAL.

544. Damage control is not only the business of the damage control parties but is very much the concern of all sailors whatever their rank, rating or branch. Damage control requires common sense, and, above all, a good knowledge of the ship. It is, in effect, modern seamanship.

. . . nothing to do with them. (Para 457)

COLD WEATHER.

545. When ships are required to operate in very cold weather, special precautions have to be taken to keep the armament in an efficient condition. In nearly all modern ships a special steam heating system is put in, which heats all essential machinery that would otherwise become "iced up." In addition to this electric radiators are installed whenever possible.

546. If the temperature does not fall below 28° F., at which temperature sea water freezes, no great difficulties need be expected, but at temperatures lower than this certain additional precautions must be taken:-

547. Muzzle covers should normally be kept shipped over muzzles, whenever there is a possibility of the ship encountering heavy weather. Under such conditions ice might form in the bore of the gun or the constant accumulation of water in the bore might make it dangerous to fire the guns.

Muzzle covers should be removed before firing but trials have shown that no damage is likely to be caused, if a practice shell or a shell fitted with a base fuze is fired with the muzzle cover on.

Shells fitted with nose fuzes, however, will probably be " blind," i.e., they will not burst or they may even burst prematurely if they are fired through muzzle covers. This may cause serious accidents and nose fuzed shell should not be fired through muzzle covers.

548. Every endeavour should be made to keep the muzzle covers free from ice formations by applying G.S. grease liberally to both sides of the cover.

549-554.

555. In all ships a Boarding Party is detailed, whose duties are to board any suspicious Merchant Vessels when required.

It is not possible to lay down any hard and fast rules regarding the size of the boarding party, or the equipment that they carry. These depend upon the situation at the time, but a typical boarding party in a cruiser might consist of the following:-

The remainder of the party consists of a reduced seaboat's crew.

556. In addition to the above, it may be necessary to send a Prize Crew on board the Merchant Vessel, to take her into the nearest British Port.

The Prize Crew might consist of the following:-

All Seamen, Stokers, and Royal Marines, comprising the Prize Crew would be armed with rifles, the remainder with pistols.

Normally, Ammunition, Equipment and Rifles for the Boarding Party and Prize Crew are kept in a separate store, so that they are readily accessible should they be required.

557. Whenever a suspicious ship is boarded, the armament is closed up and ready to open fire immediately. If the Merchant Ship attempts to scuttle herself, ". . . fire should be opened with the Close Range Armament on the boats to prevent them being lowered, and to render them unserviceable ".

W/T watch is always kept to listen for any transmission from the Merchant Ship, and look-outs should keep a careful look-out for any submarines.

558-559.

TYPES OF PRACTICE FIRINGS.

560. When a ship is newly commissioned her practices are simple, but they gradually become more difficult, as her efficiency and experience improve. Firings are always arranged with some definite object. It may be, as in the case of a simple firing, merely to accustom the personnel to carrying out their duties correctly while the guns are making interference by smoke and noise. In later stages some definite problem of fire control may have to be solved or investigated. The practices become much more interesting to the men taking part in them if the object is fully understood.

Sub-Calibre Firings.

561. The number of full calibre rounds available for firing from each gun during the year for practice purposes is limited. To make up for this deficiency sub-calibre guns are used. Practices with these guns give excellent experience and form a fair test for the control system and for layers and trainers. Unfortunately the loading numbers obtain very little value from them and only a few of the men are required to take part. As regards the control system, the sub-calibre practices can have the same objects as full calibre firings.

When using sub-calibre guns it is important that the guns are not brought to the "Ready", until a definite loading interval has expired after firing the previous round. These guns can be loaded very quickly and if a loading interval is not used, a false impression of the rate of fire of the parent guns will be gained.

Low Angle Full Calibre Practices.

562. There are various types of Low Angle full calibre practices, which may be carried out by ships. Each type is best suited to certain conditions only and nearly all practices have certain disadvantages when compared with firing under action conditions.

563. The main types of low angle full calibre practices that may be carried out are as follows:-

Range and Inclination Exercise.

564. These exercises are done without firing the guns and are used for practising the control team fully in Radar, rangefinding and inclinating. Ranges and courses steered are signalled during the practice between the ships taking part.

These exercises are of very great value and should be carried out as often as possible.

Long Range High Angle Practices.

565. As in low angle, so long range high angle practices have certain disadvantages. The main types of high angle full calibre firings that can be carried out are as follows:-

Dummy Aircraft Attacks.

566. If sufficient aircraft are available, realistic dummy attacks are of great value in working up the air defence organization of the ship.

Close Range Practices.

567. Close range weapons may be used against all the above Long Range targets, except throw off practices.

Balloons may be used as targets for close range weapons but are unrealistic from the point of view of speed and should only be used to work up the guns' crews.

568. There are numerous methods of training close range guns' crews. At all anti-aircraft schools, non firing practices are carried out against aircraft. These can then be analysed, immediately, so that the gunlayers and trainers can at once see the mistakes that they have made in their aim.

Dome teachers are also used for exercising close range guns' crews. In these, realistic photographs of attacking aircraft are thrown on to the inside of the roof of a dome-shaped building. The gunlayer aims a sight at the aircraft and the instructor can at once tell whether he is aiming correctly or not.

Films. Various films are distributed to all ships to instruct the close range crews in eyeshooting and tracer observation.

Portable aiming teachers. These are also distributed to ships and are very useful for elementary aiming practice.

Precautions During Firing Practices.

569. In all practice firings, when director firing is in use, a safety number is to be employed at each gun to ensure the safety of the towing ship or aircraft, or in the case of a throw-off firing, of the target ship. This rating is stationed in a position where he can observe the bearing or elevation on which the gun is trained or laid. He may be at the trainer's or the layer's telescope or have a special set of open sights, according to the mounting in use. He must also have a whistle.

Should the safety number observe that the gun is trained or laid so as to endanger the towing ship or aircraft he must blow his whistle immediately and order "Half cock" and then give orders as necessary for pointing the gun in a safe direction.

When the bearing or elevation is again safe, the safety number is to report either "Target visible" or in the case of a throw-off firing "Safe bearing." On hearing this report the O.O.Q. or Captain of the gun is personally to inspect the director receivers and then give orders as to the method of training and laying to be employed.

RECORDS AND RECORDERS.

570. In order to find out any mistakes that have been made, so that these can be put right, records are taken of all the events during the practice. These, when put together, form an analysis of the practice.

Records to be of any value must be absolutely truthful and accurate. Recording, like any other art, requires constant practice. There are various forms of records that have to be taken and these may vary for each type of practice.

Stop Watches.

571. In nearly every record that has to be kept, the time of occurrence has to be logged alongside the record of each event. It is, therefore, essential that every recorder should know how to use the stop watch issued to him for keeping the record.

All stop watches must be worn on a lanyard unless a special holder on a wrist strap is issued. There are two types of watches in general use in the Service.

572. Pattern 3. This type has a single second hand which is started and stopped by a small sliding lever on the left hand side of the winding crown. The minute and second hands are both replaced to zero by pressing down on the winding crown but this will not stop the watch.

573. Pattern 4. This type has two second hands which can be started, stopped and brought back to the zero position by pressing down on the winding crown. The lower or split second hand is also controlled by a small press button to the left of the winding crown. This button is pressed when it is required to stop the split second hand.

To use the Pattern 4 watch, fully wind with the winding crown, taking the same care and precautions as with Pattern 3. To start the watch, press down on the winding crown. To record a time, press down on the small button; this will stop the split second hand and the time can be read off. After recording the time, press on the same small button and this will cause the split second hand to flick on into line with the ordinary second hand. To stop the watch press down on the winding crown, when both hands will stop. To replace the hands to zero, press down once more on the winding crown.

Notes for Recorders.

574.

575-579.

.. no matter what he is doing .. (para 517)

NATURE AND NUMBER OF GUNS USED.

580. The nature and minimum number of guns with which a salute may be fired is laid down in the King's Regulations and Admiralty Instructions.

It is clearly to be understood that no less number of guns than therein stated is ever to be employed unless dispensation is allowed by Admiralty.

The interval of time between successive rounds of a salute is to be 5 seconds, the interval being regulated by the hands of a watch.

A useful device in keeping count of the correct number of guns is to paste a small piece of paper under the glass of a centre seconds stop watch, with the numbers 1 to 21 marked on it at the appropriate positions for the second hand. It should be observed that the ordinary numbers denoting the hour on the face of a watch cannot be used as the first gun fires at zero time. The extra figures 1 and 13 will therefore be written in line with XII hours on the watch face, the starting point of the seconds hand.

581. An equal number of guns each side of the ship is to be employed. Numbers 1 and 3 the Starboard side, Numbers 2 and 4 the Port side.

Either 1 and 2 should be used to fire the salute with 3 and 4 as "Stand by" guns or vice versa, unless the ship is lying alongside a jetty when those guns on the seaward side only should be used, keeping those to landward as "Stand by" guns.

There is some degree of risk from the debris of the discharge of an unshotted round if one is unreasonably close to, and in line with, the muzzle of the gun.

582. In addition to the gun about to fire, a "Stand by" gun, ordinarily on the same side, is to be ready to fire in case the other fails to fire. The gunlayer of the "Stand by" gun will fire without order should this occur. He is to be drilled to watch the firing gun on his own side closely, and fire his own gun the instant the failure of the other gun becomes evident.

Each saluting gun's crew consists of three men, a gunlayer, a breech worker and a loading number. The saluting battery will be in the charge of the Gunner of the ship carrying out the salute. In giving an order to a gun to fire he will be in easy distance and in sight of the gun. He will regulate the time interval and count the guns.

SINGLE SHIP PROCEDURE.

583. The normal procedure in firing a salute from a single ship is to be as follows:-

On completing the required number of guns the Gunner will order the guns to cease fire and the bugle "Cease Firing" will be sounded, followed by the "Carry on." In all cases the Gunner is to report to the Commanding Officer the number of guns fired.

Note. When using 6-pdr. or 3-pdr. guns, if a missfire occurs after re-cocking the breech is not to be opened for 15 minutes; a gun at which this happens is therefore thrown out of the salute.

FLEET PROCEDURE.

584. When firing a salute with the Fleet, the executive for the Flagship to commence the salute is given by signal, but her guns are not to be brought to the "Ready " until the executive has been received.

The first gun of each of the remaining ships is not to be brought to the "Ready" until the first gun of the Flagship has fired. They will open fire with the second gun of the Flagship, and will then fire the full salute as for a single ship.

A "Royal Salute" of 21 guns will therefore terminate in the Fleet, 1 minute and 45 seconds after the Flagship has fired her first gun.

1. It may be required to man and arm boats for services, such as the following:-

It is probable that no two situations will be alike and for this reason it is undesirable to lay down rigid instructions as to the manning and arming of boats.

The more recent introduction of the "Combined Operations" arm of the Services, with its many innovations, has tended greatly to specialise and enlarge the form of work as hitherto specified in (ii) above. No attempt can be made to deal with the aspect of "Combined Operations" which is outside the scope of this book. Nevertheless, the sporadic occasions when the administration of "Combined Operations" is not available may still arise.

2. The personnel, stores and alternative armaments shown in the following paragraphs give a guide as to how boats may be equipped. All boats built prior to 1929 are fitted and strengthened to take any of the alternative armaments shown, but those built after this date can take only the Lewis gun armament.

The Lewis gun mountings in boats should be constructed and arranged in such a manner as to facilitate the use of the weapon against close range enemy aircraft.

LAUNCHES, 45 FEET.

3. Armament .. .. 1 3-pdr. Q.F. Mark I Gun or 4 pair Lewis guns on 4 double mountings.

ALL MOTOR AND STEAMBOATS, 40 FEET AND ABOVE.

4. Armament .. 1 3-pdr. Q.F. Mark I gun or 1 Maxim or 1 pair of Lewis Guns on double mounting.

Guns and Stores.

MOTOR BOATS, 35 FEET AND 30 FEET: STEAM CUTTERS, 35 FEET AND BELOW.

5. Armament .. 1 Maxim gun or 1 pair of Lewis guns on double mounting.

Guns and Stores.

6. Armament .. 1 3-pdr. Q.F. Mark I gun or 1 Maxim or 2 pairs of Lewis guns on double mountings.

Guns and Stores.

PULLING CUTTERS, 30 FEET AND ABOVE.

7. Armament .. 1 Maxim or 1 pair of Lewis guns on double mounting.

GIGS AND WHALERS.

Ammunition and Stores.

Boat's Magazine.

9. For Boats armed with 3-pdr. Q.F., Maxim, or Lewis Guns.

10. For Boats armed with rifles only.

Note. Rocket stick and boat's rocket firing upright must be taken separately.

(58402) Wt 53357/D8707 26.961.8 60M 3/44 L&B

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