# Aircraft in Warfare (1916)/Chapter 4

CHAPTER IV.
(September 25th, 1914).
LOW ALTITUDE FLYING. THE AEROPLANE IN A COMBATANT CAPACITY. THE MACHINE GUN IN THE SERVICE OF THE AERONAUTICAL ARM. THE FUTURE OF THE FIGHTING MACHINE.
§ 13.Low- Altitude Flying. Our interest in the subject of low-altitude flying from the military point of view is entirely prospective; there are certain advantages to be derived from low-altitude flying that are not at once apparent; the disadvantages are too obvious to need mention.
It has often been noticed by the writer, and it is probably a matter of common observation, that an aeroplane, however visible it may be with the sky as background, is readily lost to sight and becomes exceedingly difficult to pick out when backed by a hill or a mountain-side. This is the case with a machine finished "bright;" when machines are given protective colouring, as is now customary, the difficulty of detecting their presence when below the sky-line will be far greater. Thus, so long as an aeroplane approaches any position at medium or high altitude, it may be clearly seen at some few miles distance, and measures will be taken to give it an appropriate reception; whereas a machine making its approach at low altitude would frequently be able to take the enemy quite by surprise. Beyond this it has been found that, except for reconnaissance, high altitude is not altogether advantageous. ​A certain amount of harm may be done by bomb-dropping, machine-gun fire, the raining of steel darts, etc.; but an aeroplane at a height cannot take an intimate and decisive part in a fray, as, for an example, cavalry charging, or infantry with the bayonet. It might prove of enormous and overwhelming value if at any critical moment, or at any critical point, it were possible to let loose a few squadrons of aeroplanes each mounting one or more machine guns, to bring short-range concentrated fire to bear, or alternatively to make an attack by the aid of bombs or hand-grenades. The scene that would ensue, for example, on a congested line of retreat would be indescribable: horses thrown into hopeless confusion or stampeded, mechanical transport lorries holed in a dozen or more vital points, water-jackets or radiators damaged, cylinders pierced, etc., gun teams wiped out, infantry decimated; in brief, chaos over endless miles of high road.
§ 14. Armour for Low-Altitude and Point Blank Range. The question arises whether it is possible for the aeroplane to fly at a sufficiently low altitude to act effectively in the manner indicated without exposing itself to immediate destruction. The matter is entirely a question of armour; the unarmoured portions of the machine, which derive their immunity from their transparency to rifle-fire, are no worse off at point-blank range than at 2000 ft, or 3000 ft, altitude. Taking the altitude as 500 ft. (a reasonable maximum for the effective execution of the duties contemplated), the thickness of armour necessary is approximately $^5$⁄$_{32}$ in. (4 mm.) for the British service Mark VI. ammunition, or slightly over ¼ in, in the case of the pointed Mauser bullet, the latter thickness representing a weight of 10 lb, per sq. ft. It is evident that the problem of giving complete protection to the motor, pilot, and gunner will become a ​problem of some difficulty; probably in the present state of the constructor's art the protection would need to be somewhat "scamped," and a certain amount of risk admitted. Whatever economies are effected in armour^ the main principle must not be lost sight of—i.e., the thickness must not be tampered with; armour too thin for its duty is worse than canvas or brown paper.
Once the altitude has been brought down to 500 ft.—that is to say, if and when it is recognised as advantageous and found possible to utilise such low altitudes in aeroplane tactics—it becomes a question whether it will not be found to pay to "go the whole hog" and fly at the very lowest altitude possible. It may be at once admitted that all the dangers of flying, qua flying, will be thereby increased, but danger of the degree in question is a matter of little or no consideration in actual warfare. Briefly, the immediate suggestion is that if low-altitude flying is systematically to be undertaken, it should be conducted quite low—dangerously low, according ta ordinary standards. At an altitude of 500 ft, an aeroplane still makes a very clear mark against the sky, visible from a considerable distance. By following the contour of the ground, never rising more than 100 ft, or 200 ft., unless to clear an obstacle not otherwise to be avoided, an attack will be made with comparative suddenness, and the machine will be gone out of sight almost before there has been time to bring a gun to bear. Even when under fire it will have a certain tactical advantage in the fact that it will be attacking a line parallel to which it is flying—it need never miss its target—whereas it itself offers the worst kind of mark to the enemy, combining small size, high speed, disconcertingly short ​range, in addition to which it is, in effect, a disappearing target. If one is tempted to be over-influenced by the obvious danger of such tactics, it is well to recall the exploits carried out as a matter of ordinary experience by cavalry under fire, without the advantage of armoured protection, while presenting a target (man and horse) something like 20&nbsq. ft, in area, and with a speed contemptibly small in comparison with that of flight. It is only necessary clearly to admit that in this form of fighting we may have to reckon with serious losses of men and machines, not occasional losses, as at present, but rather such as can be expressed as a percentage of the force engaged.
The further reduction of altitude now under discussion means that rifle-fire must be faced literally at muzzle velocity, and corresponding provision made in the thickness of the armour. For the pointed Mauser bullet, representing the maximum requirement of to-day, the thickness of plate needed is scarcely less than ⅜ in., and the weight 13 lb, or 14 lb, per sq. ft. Evidently the question of weight of armour will become a difficulty of a most serious character, and no pretence can be made to give complete protection; the area must be cut down to an absolute minimum.
§ 15. The Machine-Gun in the Service of the Aeronautical Arm. Rapidity of fire to the aeronautical gunner is a matter of first importance; the time during which he has the enemy under fire is necessarily brief, and in that time he must do the maximum injury possible; consequently amongst present existing weapons we may regard the machine-gun as without rival. The degree of accuracy attainable in firing with a machine-gun from an aeroplane depends primarily upon the weapon and the man, as in every other kind of shooting, but in addition the steadiness of the aeroplane ​is an important factor, this being mainly dependent upon the wind and weather. Under favourable conditions an expert shot using the Lewis gun has delivered the whole contents of a magazine (of 47 cartridges capacity) into an area 10 ft, by 60 ft, from an altitude of 600 ft, at a range of 1,000 yards. Making allowance for this expert handling of the weapon, as being superior to the average ability available under service conditions, there can be no doubt as to the deadly efficiency of a gun of the Lewis type as an aeroplane armament. The author has himself witnessed a performance very little inferior to the above in weather that could by no means be considered ideal. Apart from many detail points of merit, the Lewis gun for aeroplane service, has many advantages; firstly, on account of its self-contained magazine, which, by the abolition of the cartridge-belt, etc., permits of the gun being trained freely in any direction from vertically upwards to vertically downwards; secondly, its light weight, which also allows of its use as a shoulder-arm; and, thirdly, the adoption of direct air cooling in place of the usual water-jacket.
Assuming the proved accuracy of the Lewis gun as the criterion of machine-gun fire, it is evident that an estimate of the effectiveness of low-altitude aeroplane attack becomes little more than a matter of simple arithmetic. We may take, for example, the problem to be that of executing a counter-attack upon infantry, themselves attacking a position in open order, the counter-attack to be delivered against the foremost line, lying prone at two or three paces interval. We are justified in assuming that the magazines will be emptied over an area defined as a belt of 10 ft, or 12 ft, width, in which, therefore, there is one man to approximately 100 sq. ft, of ground under fire. Now the area of target ​offered by a man prone is approximately 5 sq. ft., so that, as an average, one bullet in twenty will find its mark. This represents a man knocked out for every 10 oz, of lead expended, which must be regarded as extremely economical, in view of the fact, that it is usually supposed to take a hundredweight of lead to kill one man, say 30 lb, or 40 lb, for every man put out of action.
§ 16. Points in Favour of Extreme Low-Altitude. In any such work as the foregoing, the question of lowness of altitude is of vital importance. Since no attempt to aim at an individual mark is contemplated, there is no disadvantage from the point of view of the gunner in flying quite low. His target may appear as blurred as the side of a railway cutting viewed from the window of an express train, but so long as he "delivers the goods" within the belt of ground intended, his average hits will not be detrimentally affected. If he is shot at by the infantry line he is attacking, or by a supporting line (usually 300 yards, more or less, in the rear), every man attacking him breaks his cover, and becomes a prominent mark for the defending infantry force. Beyond this, the aeroplane carries armour and presents a comparatively small vulnerable target. The advantage of extreme low-altitude flying in the present connection lies in the fact that it is, in effect, a perfect defence against attack by long-range fire. No matter what developments may be made in air-defence artillery—even if means should be found to render an 18-pounder as handy as a sportsman's shot-gun—if the attacking aeroplane fly low enough, the enemy cannot bring long-range fire to bear without bringing his own infantry lines under fire at the same time.
§ 17. The Future of the Fighting Type of Aeroplane. A reservation has already been made to the ​effect that low-altitude flying —i.e. under 2,000 ft.—as affecting the service use of the aeroplane, lies mainly with the future; the design of the machine for this class of work will require the most careful study on the lines already indicated, the essential point being immunity to attack by small-arm fire. In obtaining such immunity sacrifice of some kind will have to be made. Whether it be in the armour-plating of vitals, or in the provision of redundant members or material, a great deal of otherwise unnecessary weight must needs be carried which ultimately reduces the carrying power in other directions. This means eventually either a reduction in the speed or a positive all-round increase in the size and weight of the machine. Granted that all initial difficulties be overcome, the advent of the armed and armoured low-altitude machine will initiate a new phase of aeroplane tactics, and one that cannot fail to have a far-reaching effect on the other Arms of the Service. The difficulties of cavalry operations will be increased incalculably; a body of cavalry, unless protected by a covering force of aeroplanes, will find itself continually open to attack, both by short-range machine-gun fire and by bombs and hand-grenades: in addition to this the demoralising effect of numbers of high-powered aeroplanes flying overhead, perhaps within 200 ft, or so, will be by no means a negligible factor. Up to the present the cavalry have been the Arm of greatest mobility, and nearly all cavalry operations on a large scale are fundamentally based upon, and rendered possible by, that fact. Once the aeroplane has taken its place in the actual fighting arena, this condition is definitely a thing of the past, and, so long as daylight lasts at least, any cavalry-force not itself accompanied, or supported, by its own aeroplane auxiliary will find its every movement dogged by the hostile aeroplane, and its every operation baulked by counter-attack from above.
Plate V.
Test of "bullet-proof" steel plate, 3 m.m. thick. Range 300 yards. Service Rifle. Mark VI. Ammunition.
​Caught in the open, its only defence will be in dispersion over the widest possible front or area, otherwise it must take to the woods or whatever other cover is available. Further, it will be impossible for it to undertake a dismounted action, for the led horses (the bugbear of dismounted cavalry) will be either stampeded or destroyed, and its existence as an effective unit will be at an end.
§ 18. As Affecting the Cavalry Arm. It must not be supposed, however fully the present anticipations of the development of the aeroplane as a fighting machine may be realised, that the value of cavalry is at an end; this is not the author's view. It is probable that in the early stages of a battle, or of a campaign, the cavalry Arm will cease to play the important role that at present is, and has hitherto been, assigned to it, and that the pushing out of advance posts and reconnaissance will devolve more and more on the armed and armoured motor-car and aeroplane. However this may be, there will still remain country in which cavalry can be advantageously employed, country in which cover (woods, forests, etc.) is plentiful, where mounted men are secure from aerial observation and attack, and where a mounted force is virtually the only means by aid of which the terrain can be effectively reconnoitred.
Thus, also, in wooded country, in the reconnaissance that accompanies or precedes an army on the march, it would seem probable that the aeroplane and cavalry will be used in conjuction, the more distant work being accomplished by the aeroplane, whose presence would also ensure the protection of the cavalry from hostile aircraft. The detail work, including the holding of bridges and advance positions of importance, also the location of and dealing with any patrols or other bodies of the enemy that may be encountered, will be accomplished by the cavalry. The obvious disadvantage of the ​use of the aeroplane for reconnoitring is that it informs the enemy of the advance or presence of a hostile force. Where this fact is of weight, the protecting flight or squadron of aeroplanes would be best handled as a supporting force, with perhaps one machine at high altitude to maintain contact, the duties of this latter machine being to keep in touch and transmit information to the divisional or army corps command, and to call for the supporting aeroplane force should occasion require. Exactly how the combination of the two Arms (aircraft and cavalry) will be controlled and handled it is impossible, without actual experience, to lay down. The main point is that in the new Arm we have a force altogether transcending the cavalry in mobility and range of observation, and which before long will become an actual fighting force of no mean importance, and these facts cannot fail to be revolutionary in their ultimate influence on the rôle and employment of the cavalry Arm.
* ↑ A term used by boat-builders to denote a varnished boat—not painted.
* ↑ In nearly all cases the objective of attack will be a line of some kind; thus it may be a convoy or column in retreat; alternatively, if the attack be on an entrenched position or on the attacking force, the line formation is again in evidence; the pilot's instructions in every case would be to fly directly over or parallel to the line to be attacked.
* ↑ Compare Appendix.