CHAPTER XII.
(November 20th, 1914).
THE NAVAL AIR-SCOUT. THE FLYING-BOAT TYPE. THE DOUBLE FLOAT TYPE. THE OCEAN-GOING FLOATING BASE OR PONTOON SHIP.
§ 77. The Duties of Naval Reconnaissance. The work of scouting, or reconnaissance, will undoubtedly be the first and most important duty of aircraft in the service of the Navy. Whether it be in connection with the work of coast defence, in giving timely warning of the approach of hostile vessels of war, or in searching out and reporting the whereabouts of an enemy's battle fleet, in locating the enemy's commerce-destroyers on the high seas, or in directing gun-fire during a bombardment or a fleet action, the employment of aircraft cannot fail to be of signal value.
So far as coastal work is concerned, there appears to be no present difficulty in effectually patrolling the whole of the home waters to a distance of some 200 or 300 miles from our shores, other than the want of the necessary machines and the requisite organisation—that is to say, there is no difficulty of a technical or engineering character. To some extent, as touching more especially points of strategic importance, aircraft are already occupied in this duty; the extension of the system is mainly a matter of increase in materiel and personnel. Unfortunately the demand and pressure for increase are felt in all branches of the aeronautical services, and it cannot but take some considerable time to build additional machines, apart from the time which must be expended in the training of the personnel and in accumulating the experience necessary to determine what types and establishment are really necessary.
§ 78. Type of Aircraft as imposed by Extraneous Conditions. In connection with the work of reconnaissance in home waters, where the "base" is a station situated on or in the region of a coast-line, it is well understood that the length and extent of the coast-line is a matter of considerable importance. If, on the one hand, the base be situated on a small island or promontory in the vicinity of hostile or neutral country, a dirigible or other similar low-velocity machine is clearly unsuitable. In the event of a high wind it would frequently be impossible for it to return to its base; tersely, it would be blown away. If, on the other hand, the base be situated on a long stretch of coast-line (such as the East Coast of Great Britain) with a number of well-placed stations, the risk is comparatively small; since, unless the wind is directly off shore (or nearly so) it will always be possible to make some other "port" than that of origin; the chance of its being lost will be remote.
When the operations in contemplation are far removed from home, beyond the radius of action of aeroplanes operating from a coast station or from friendly territory, we find ourselves confronted with difficulties of a kind for which there is no parallel in land operations. As pointed out in the preceding chapter, two solutions are possible. Either the machine must be capable of alighting on, and rising from, the water, and of riding in safety on the surface of the sea or ocean under ordinary weather conditions, and so be able to accompany and act as an auxiliary to a warship or squadron at sea; or some kind of sea-going pontoon vessel must be devised from which machines can be launched and on whose deck they may alight. Both these schemes are evidently practicable, and each has its advantages and difficulties.
§ 79. Advantages of Flying-Boat Type. For the former scheme the most suitable type of machine would appear to be the "flying boat"—that is to say, the type in which the flotation, when riding at anchor, is derived from a hull of boat shape and of seaworthy design, with the usual "hydroplane" stepped bottom to give the necessary lift to cause the craft to rise on the water and skim whilst acquiring the speed necessary for flight. It is by no means certain that this single hull or boat will oust the double float at present more generally adopted, but for the larger naval aircraft, weighing probably upwards of two or three tons, the single boat may be reasonably expected to prove the more seaworthy, especially in heavy weather. In discussing the question recently[1] the author made the suggestion that, for the sea-going aeroplane (such as now under discussion), it may be found advantageous to make arrangements for the abandonment of the flight organs, and to provide a marine propeller, so that in case of emergency the hull may be navigated as an ordinary motor-boat. The flying boat will thus, it is anticipated, be found the most convenient type of machine to act as sea-going air-scout to the cruiser or battleship. It is a type which may be so designed as to be readily stripped and carried in davits, the flight organs being fitted, and the boat otherwise made ready for air service, when required. For the commerce-raider, or the cruiser or cruiser squadron detailed for the destruction of the hostile commerce-raider, an air-scout capable of being carried in this manner would prove of the greatest value. In really bad weather it would not perhaps be possible to launch or fly a machine of this type; but so far as present experience _-_Plate_X.png)
FLOATS 1912 TYPE. AS FITTED TO H.R.E.3.
Compare Plate IX.
goes, it is impossible to fly any aeroplane which has to rise from the water under such conditions. However, if it should prove possible to fly, as an average, on but half the total days in the year, the extended range of vision obtained (even by such limited use of the air scout) would frequently prove of decisive value. In the case, for example, of the recent pursuit of the Emden and Königsberg, if our cruisers had been able to sweep a belt of some 200 or 300 miles in width (instead of about one-tenth of that amount), the result might have been achieved in far less time. A cruiser, well served by its air scouts, in pursuit of an enemy (if not fast enough or strong enough to give battle), would be able, having located the enemy, to warn merchantmen of their danger and at the same time to call for the requisite reinforcements. It would also be no longer possible for an enemy cruiser to secure concealment amongst the islands of an archipelago or in a river mouth or estuary.
§ 80. Points in Favour of the Double- Float. For the duties of bomb and torpedo air-craft, discussed in detail in the preceding chapter, the boat type of machine is ill-suited; the conditions are such as would indicate the two-float type as necessary. The latter admits of the bomb-magazine or torpedo-cradle being arranged centrally beneath the fuselage, from which position, by suitable release mechanism, the missile or torpedo can be readily let fall. It is doubtful, on the other hand, whether the two-float type will prove as convenient to handle aboard a vessel not especially fitted out for its reception, and it is further doubtful whether it will prove as seaworthy when compelled to depend on its own resources. However, there are authorities who are disposed even to give it preference on the latter count, and certainly for the smaller craft there is something to be said in favour of the fact that, so long as the floats are intact and uninjured, the machine is virtually unsinkable—it cannot be swamped, as is the case with the boat-type.
A serious disadvantage under which the sea-going aeroplane at present labours, whether it be of the single boat or double-float type, is that its speed is essentially limited by the fact that it has to alight and take off from the water, and this involves designing to a comparatively low minimum flight velocity. Whilst not necessarily limiting the mean or maximum in like degree it tends in that direction.
§ 81. The Ocean-Going Aeroplane Pontoon Base or Pontoon Ship. Passing now to the alternative scheme—the aeroplane pontoon-ship, we find opened up possibilities of quite a different kind. We are no longer concerned of necessity with the limitations imposed by rising from or alighting on water, and the vessel will be expressly designed to suit the aeroplane service, instead of the aeroplane requiring to adapt itself to the vessel. Any land type of machine could be used from the pontoon-ship, but by preference floats would be fitted, and so far as practicable, machines would be rendered amphibious. Whilst it is evidently desirable that all machines in the service of the Navy should be able to rise from the sea, the conditions are evidently altered when an immersion is to be regarded as an accident rather than as part of the regular routine. For the primary function of the aeronautical arm in the Navy, whether it be scouting, or attack on the submarine, or torpedo work, there is no outstanding advantage in the employment of machines in great numbers.
For the latter duty (when the machine for this class of work has been developed), it may be found desirable to attack by squadrons or flights rather than by individual machines. But even this is doubtful, since the advantage gained by simultaneous attack from different points of the compass, as preventing the enemy from concentrating his fire on any one machine, may be more than outweighed by the greater risk of the impending attack being detected and reported by the enemy's air service or torpedo craft. When, however, we have to consider the demands which will be made on the naval air-service for the performance of its secondary function, in addition to the occasions when it will be required to act in connection with land operations, it is evident that provision must be made for transporting and handling machines in large numbers, and this, so far as can be made practicable, irrespective of ordinarily bad weather conditions, and independently of any land station or base. It is here that the need for the floating base or pontoon-ship will be felt.
We may anticipate that, apart from such mechanical detail as alighting gear, relative petrol capacity, etc., the requirements of the naval and military machines for the destruction of hostile aircraft will not differ greatly. Bach will rely mainly on the gun in some shape or form for its power of offence, and will depend upon its speed to force the enemy into engagement. Both types will be sent into action in the greatest numerical strength that circumstances permit, or as limited by the number that can be handled or manoeuvred without undue danger to themselves, in order to bring the heaviest fire concentration upon the enemy, and to take full advantage of the n-square law. To this end the whole subject of formation flying will need to be studied exhaustively and practised assiduously both in time of peace and in time of war. For the time being, however, we are concerned with the question of the floating base—whose object is to render it possible to mobilise an air fleet, as contemplated (complete with repair depot and supplies of every kind) at any point required, in the shortest possible space of time.
§ 82. Conditions to be fulfilled. The conditions which it is desirable that the air-service pontoon-ship shall fill are, briefly, as follow:—
(1) To act as storage and transport for a fleet of at least three squadrons, say fifty or sixty machines, complete with spares, fuel and oil supplies, and personnel, together with all guns, ammunition, bombs, torpedoes, etc., necessary for complete equipment.
(2) To carry a workshop fully equipped, together with the necessary mechanical staff to deal with repairs, etc., such as are reasonably required to maintain the said air fleet in fighting order.
(3) To provide an upper deck of sufficient area to act as an "alighting ground" completely free from obstruction—i.e., there may be no masts, funnels, ventilators, cranes, searchlight platform, or wireless apparatus such as would form a permanent projection above the flying-deck level. The conditions as to deck area, etc., must be such as to give ample room for alighting or getting off to a pilot of ordinary skill.
(4) It must have a speed exceeding 20 knots in order that it may be able to accompany a battle fleet at sea, or to render it able to save itself by flight from an enemy battle squadron.
(5) It must have a gun armament of sufficient power to protect it from attack by the light fast cruisers of the enemy.
(6) It must be of comparatively shallow draught, as light as is consistent with its sea-going qualities and other requirements, in order that it may be able to act in rivers, harbours, or estuary regions in support of land operations, and incidentally to enable it to evade pursuit and destruction by war vessels of heavy draught and gun power (such as the battle-cruiser) by taking refuge in shoal water.
§ 83. The Pontoon-Ship, Specification. The above list of requirements indicate at once that the pontoon vessel will need to be a ship of very large size, comparable to that of a first-class battleship, at least as ta length and beam. Beyond this, taking the requirements in order, there appears to be nothing really difficult or impossible of fulfilment. Thus, conditions (1) and (2) could be met without difficulty by a specially-designed vessel of a few thousand tons displacement. Condition (3) is more exacting, and requires that the vessel should be of the maximum beam admissible—say 90 ft.—with a water-line of not less than 500 ft.; also the need for doing away with funnels probably means that the internal-combustion engine will have to be considered as the means of propulsion. This, for the horse-power required—about 15,000 indicated—is rather beyond anything yet attempted; however, it can be by no means deemed impossible. The conditions could be met by employing six propeller-shafts, each driven by a Diesel unit of 2,500 indicated horse-power; this is not regarded as by any means beyond the limits of commercially sound engineering. The present day uses of the masts of a warship are mainly for signalling (by wireless and otherwise), to serve to carry searchlight and lookout platforms, and as an anchorage for jib-cranes. All these various requirements will need to be met without hampering the flying-deck with any permanent obstructions. Thus it is well understood that the "aerial" for a wireless installation may be arranged horizontally; in the present case it could be carried on spar outriggers, some 10 ft, or 15 ft, away from the gunwale, being shipped and unshipped as needed. Searchlights could, without difficulty, be mounted on telescopic pillars dropping flush into the deck, operated by hydraulic power or other means, and taking but a few seconds to raise or lower; cranes also can be provided in such form as to be rigged only when needed. Altogether there is nothing in these detail requirements likely to prove of insuperable difficulty. Condition (5) would be adequately met by a powerful broadside armament of 6-in. guns, in addition, perhaps, to guns of heavier calibre mounted in a single turret astern, all arranged below the level of the flying-deck. With a ship of the size contemplated there should be no difficulty in providing a sufficient weight of armament for the purpose specified. The gun-deck would be the main upper structural deck of the vessel, with only the comparatively light flying-deck above it.
§ 84. Advantage of Pontoon-Ship as Aeroplane Base. The pontoon-ship as an aeroplane base possesses certain and obvious disadvantages; an area for alighting such as is presented by the deck of a ship, although it may be, say, 90 ft. beam by 400 ft. or more in length, is none too large under really bad conditions of weather for even a skilled pilot, especially if the vessel be rolling in a heavy seaway. Without doubt, under extreme conditions operations will become frankly impossible; but, under similar conditions, it will be also impossible to employ a machine designed to rise from the water. The conditions in the case of the pontoon-ship, however, are not really so unfavourable as might be thought; the vessel can always be brought head to wind, when the relative velocity of the machine on alighting will be reduced by the velocity of the wind; it may also be still further reduced by maintaining the vessel under power; these two effects in combination, assuming the wind to be 40 miles per hour and the vessel at full speed, will result in a machine, flying through the air at 60 miles per hour, taking the deck without any relative motion whatever — a most favourable state of things, permitting it to be instantly secured and made fast. Beyond this, under the said condition — i.e. head to wind — it is only in the exceptional case of a heavy cross sea that the rolling could be serious, and with the modern methods of steadying sea-going vessels (gyroscopes and ballast-tanks) it would require a quite exceptional state of weather to keep the air fleet imprisoned. There is one constructional point worthy of mention; the flying-deck will require to "run-out" at the bows of the ship in easy lines, to avoid setting up eddies or dead regions, such as might affect the stability or buoyancy of machines landing or leaving the deck; to some extent it may be found necessary to extend this precaution to where deck joins gunwale abeam.
It is also worthy of note that the proposed pontoon-ship, being of comparatively light draught and great beam, will possess naturally the type of stability of a raft rather than that of an ordinary ocean-going vessel, and will thus tend in a seaway to follow the changing slope and motion of the long ocean waves. Now this slope and motion, as is well known, are so co-ordinated that the normal to the wave slope is always the apparent plumb, and so it may even turn out that the flying-machine, on taking the deck of a vessel studied as a raft rather than as a ship, will (even when the motion is severe) have no tendency either to side-slip overboard or turn turtle.
The same conditions which are favourable to alighting, as from the point of view of relative motion, are also favourable to the machine when getting away. Thus, with a 40-mile-per-hour wind and a vessel at full speed, head to wind (as already assumed), a machine will be able to leave the deck with a relative motion of only some 10 or 20 miles per hour and a flight velocity of 70 or 80 miles per hour. Taking all the possibilities of the situation into account, it is probable that the machines to operate from a pontoon will, on the whole, be constructed as faster fliers than those designed for rising from the water, and to that extent at least will be better fitted for combatant duties.
_-_Plate_XI.png)
R.A.F. TYPE R.E.1 (1912) FOLDED FOR TRANSPORT OR STORAGE.
- ↑ James Forrest Lecture. Institution of Civil Engineers, 1914.