How the War Has Modified the Aeroplane
The Passing of the Military Monoplane, and the
Development of the Battle-Biplane
By Ladislas d'Orcy
[Scientific American; September 4, 1915]
A recent dispatch from Paris stated that the Director of Military Aeronautics of France had decided to discontinue henceforth the purchase of monoplanes, their place to be filled entirely by fast tractor biplanes. Furthermore, such monoplanes that still are in flying condition shall be used only for training military pupils and shall see no more active service at the front.
This decision, which practically spells the death knell of the monoplane as a military instrument, has not come altogether unexpectedly. Since the beginning of the Great War a number of military airmen openly expressed their opinion about the small value of the monoplane for warfare. The principal arguments that were set forth in this connection were: 1. The monoplane's limited carrying capacity. 2. Its limited range of vision. 3. Its low range of speed.
The first argument was probably the least important, for monoplanes were used in France exclusively for gun spotting and tactical reconnaissance, for which a fuel supply of three or four hours was found to be perfectly sufficient.
Indeed, if we expect Garros' Morane-Saulnier single-seater, in which that celebrated airman succeeded in winging single-handedly several German machines, there is no instance where a monoplane was used in the French army for offensive purposes. The second argument, limited range of vision, was a matter of much more concern. Indeed, for detecting batteries and giving their correct range, as also for minor tactical reconnaissances, a fair visual range was a primordial requirement, which, it was difficult to attain with the monoplane on account of the pilot's position back of the wings which put the observer's seat squarely amidst the wings and precluded a detailed inspection of the ground below.
Realizing this defect of the standard monoplane, the French Director of Military Aeronautics first tried to obviate it by discarding in January last the whole lot of monoplanes that were in commission—Blériot, Deperdussin, Nieuport and K. E. P.—and having them replaced by Morane-Saulnier "parasols," i. e., monoplanes on which the wings are placed above the fuselage, at about the same height as the top plane of a tractor biplane. Although this type of machine proved highly satisfactory as far as range of vision was concerned, its aerodynamic qualities were pronounced to be far below those of the ordinary type of monoplane, and this chiefly owing to the low center of gravity resulting from the altered position of the wings. This was especially noticeable when such machines were banked, which often resulted in a side slip; a striking example of this assertion is furnished by the accident that resulted in the death of Marc Pourpe, one of the most brilliant airmen of the Morane-Saulnier staff, who met his death near Rheims over the German lines through a side slip caused by a sharp turn.
But it was the third argument, low speed range, that probably caused the final decision—discarding entirely the monoplane in the French army. The default proved indeed a very serious one. Low speed range, i. e., a small range between the flying and the landing speed of an aeroplane makes the latter practically worthless for military work of any description on account of the rough ground that makes up most of the so-called aeroplane bases near the front. For alighting on such a ground low speed is indispensable, unless every landing is to result in a partial distraction of the machine.
To attain the requisite of high speed range aeroplane constructors had to turn to the small tractor biplane, called Tabloid, which Sopwith in England was the first to develop. This type of machine possesses all the advantages of the monoplane without incorporating any of its drawbacks.
The Tabloid is just as handy and fast—if not more so—and almost as light as the monoplane, but its range of vision and its speed range are considerably better. A greater visual range is generally attained by "staggering" the planes, which consists in placing the top plane somewhat ahead of the bottom plane, and also in some instances by cutting away part of the bottom plane, where it joins the fuselage. The Germans, however, attain the same results through another means, i. e., the planes are "raked," or swept back from the rectilinear so as to form an arrow head—a system that incidentally secures their machines a considerable inherent stability.
As to high-speed range, this is effected on the Tabloids by a disposition simple enough, but which it is impossible to incorporate in monoplanes; it consists in giving the top plane a large incidence (up to 5 degrees) and setting the bottom plane at a very small angle (one or two degrees only). This system works then as follows: for attaining the maximum speed the airman decreases the angle of his top plane so as to cut down the head resistance to a minimum, and by doing this he has obviously flattened out his bottom plane to 0 or even to a negative incidence; while for landing, when the minimum speed is required, he "stalls" the machine in order to produce the largest angle of attack and thereby the greatest head resistance, and in this case both planes will act as a brake, the incidence of the plane being set to about four degrees. Obviously the same condition exists at the moment when the machine takes the air, only in this case the great angle of attack is used for lifting at low speed.
Thus the Tabloid biplane solves all the problems that for so long have proven the stumbling block in monoplane construction. It is, therefore, not astonishing at all that the most noted monoplane constructors of France are now all adopting the Tabloid. Thus the Nieuport Tabloid has already been adopted by the French Aviation Service, while experiments with similar machines are being conducted by the Blériot, Deperdussin and Morane-Saulnier works.
Such is the radical development of the aeroplane on account of the Great War. How far this forcible change in the constitution of France's aerial fleet affects this nation's aeroplane industry can readily be gathered from the fact that at the outbreak of the war three fifths of the 749 aeroplanes belonging to the French army were monoplanes, the gradual weeding out of which resulted in their being replaced by Morane-Saulnier "parasols." Now the latest decree of the French Aviation Service practically puts on the scrap heap over three hundred machines not more than six months old, which will have to be replaced by an equal number of Tabloids, and this means for the French aeroplane industry an order of $1,500,000 for the development of a new type of machine—a sum which, no doubt, will be instrumental in further advancing the science of aeronautics.
In Germany conditions have been very similar to those above described. At the beginning of the war the Fatherland possessed between 700 and 800 monoplanes called Tauben (Doves), a name that comes from the pigeon-shaped wings of these machines. Having chiefly in view facility of construction the German Air Service, with its characteristic thoroughness, had since 1912 practically standardized this type by issuing orders that all the army monoplanes must be of the Dove type. Later it was decided to build the monoplanes of steel, and the government hastened forward the construction of steel Doves by all the factories that had produced successful monoplanes. These were the Albatross, the Jeannin, the Luftfahrzeug (L. F. G.) and the Rumpler Works of Berlin-Johannistal, the Wagon Works of Gotha, the Deutsche Flugzeug Werke of Leipzig (D. F. W.), and Kondor Works of Essen.
Thanks to their pigeon-shaped wings, the Doves possess considerable inherent stability, which makes them particularly desirable for military work; their chief drawback is the heaviness resulting from the all-steel construction and the relatively heavy water-cooled engine employed. This disadvantage makes the operation of the Doves a very delicate one when near the ground, and necessitates a starting and landing place of considerable area, a requirement which it is difficult to conciliate with operations in the field. Furthermore, the Doves are badly designed for dropping bombs—a work they were supposed to perform—as both pilot and observer can only see ahead and not directly below; finally, on account of the tractor air-screw it was found impossible to arm Doves with a gun firing ahead, which is the logical position of armament for the attack of enemy aircraft—for this was another task the Doves were intrusted with.
When all these drawbacks, in addition to those mentioned in connection with French monoplanes, became apparent, the German Air Service decided in its turn to discard the famous Doves and to replace them by tractor biplanes, of which only about 100 were in commission at the outbreak of the war. Like the Doves, these machines were standardized into a uniform type, called Pfeilflieger (arrow-flyer), which means that their planes were "raked" so as to form an arrow-head. They were built by the following firms: A. B. G., Ago, Albatross, Aviatik, D. F. W., Buler, L. F. G., L. V. G. and Otto. Now most of these firms build in addition to their standard biplanes, machines of a reduced type, which strongly resemble the Tabloids described above and are called Falken (falcons). Just like the Allies, the Germans use these machines for gun-spotting and tactical reconnaissances. Thus the Great War has practically united the contending tendencies of the French and the Germans by eliminating both the flimsy monoplane and the heavy Dove, and making both adopt the highly efficient tractor biplane, which, by the way, is a decidedly British, product.
Perhaps the biggest surprise brought about by the Great War has been the notable success attending the use of the aeroplane for offensive operations, either for attacking enemy scouts or for bombing army depots, railway junctions, ammunition and aircraft plants et simili. This was made possible by the gradual development of two novel types of machines, the fighting scout and the bombardier. When the war began, no European government had yet made up its mind as to which type of aeroplane was particularly suited for these purposes; many military experts even held the opinion that owing to its limited carrying capacity and the sensitive gun platform afforded, the aeroplane would not prove at all practical for this task. It is true, both the French and the German governments were at that time conducting experiments in order to ascertain the value of armor plating and the exactitude of bomb dropping devices, and endeavored to solve the tangled problem of providing the aeroplane with a proper gun platform. But these experiments were merely sporadic attempts at solving the problem of the battle aeroplane.
The first few months of the war radically upset all preconceived opinions about the value and the possibilities of the aeroplane. It was rapidly becoming evident that all the warring nations were lacking a type of aeroplane that would both scout and clear the skies of the enemy scouts, for both sides were carrying out reconnaissances without meeting serious opposition in the air, the watchword being generally to get back information and decline battle. When this deficiency was realized, the various aeronautical services hastened to remedy it by arming their large aeroplanes with machine guns, while pilots of fast scouts were equipped with automatics and carbines. This improvised armament soon proved inadequate for the set purpose, although a number of aerial duels ended with the defeat and retreat, or even with the destruction of one of the antagonists. But here it should be noted that destruction, when brought about, was generally caused by the setting on fire of the fuel tank or by disabling the pilot, but only very seldom by destroying a vital organ of the machine, against which rifle and even machine gun fire proved singularly inefficient.
In this game British and French airmen generally had the better of their foes, the British chiefly owing to their light and fast tractors which would easily out-fly and out-fight the heavy and sluggish Tauben of the Germans, while the French proved superior on account of their pusher biplanes armed with a machine gun firing ahead, which the Teutons could oppose only with tractors firing broadsides and astern. Their difference in armament soon manifested itself as a great drawback for the Germans who, being unable to make frontal attacks, were also too sluggish to out-fly their foes, while it greatly accounted for the aerial ascendency, both moral and material, attained by the French in the latter period of the war, for it is an old axiom that weapons of offense impart the spirit of offense, whereas the latter is impossible without the former.
These fighting scouts of the French were, in the first four months of the war the 80 horse-power Gnôme driven Farman and Voisin pusher biplanes, which carry a crew of two (pilot and gunner) and have a cruising radius of four hours when fully equipped. The armament consists of an air-cooled Hotchkiss machine gun firing 500 rounds per minute. The Voisin pusher carried originally an armored belt around the nacelle; this was subsequently removed in order to reduce the total weight and obtain thereby a quicker getaway and more climbing ability.
How successful these fighting aeroplanes have proven in clearing the skies of enemy scouts is borne out by a record compiled by a well-known aeronautical writer now serving with the French Aviation Corps, regarding the number of German machines and their crews destroyed or captured during the first four months of the war. This record reads as follows:
Eighty percent of these craft were accounted for by French and Belgian pushers of the types above described, while the rest were winged by British tractors and French monoplanes through rifle fire. While this record is an eloquent testimonial of the efficiency of French fighting aeroplanes during the first few months of the war, a considerable change in aerial operations occurred as soon as the Germans began to use the powerful 150 horsepower Benz and Rapp motored tractors, which had been either held in reserve or building at the outbreak of the war. Whereas the 80 horse-power Farman and Voisin pushers have a speed of about 65 miles per hour, this proved insufficient for rounding up the very fast new German tractors mounting machine guns which began to show above the Allies' lines in November last. Against these the French pushers found themselves in a dangerous state of inferiority; while the Germans had the greater climbing speed, the Frenchmen were both too slow to overtake them and too slow to run away when attacked by superior numbers.
Nevertheless these defects were soon afterward remedied in the new machines the French Aviation Corps put into commission in 1915, in which more speed and life were incorporated. These machines, the 140 horse-power Renault-motored Farman and the 135 horse-power Salmson-motored Voisin pushers, have since proven to be at least the equals of their Teutonic antagonists; for being very fast and having a large cruising radius, they are enabled to carry out long distance reconnaissances into German territory, in the course of which they can easily account for the enemy aeroplanes that should want to stop their progress.
The 135 horse-power Voisin pusher is a particularly interesting type of fighting craft in that it can easily be converted into a bombardier. When used as a fighting unit the machine is fitted with a machine gun that is mounted on a tripod fixed between the seats of the pilot and the gunner; thanks to this arrangement the gunner, who works the gun standing with his back against the cellule, is both afforded a fairly comfortable position in action and a very wide arc of fire, both laterally and vertically.
When employed as a bombardier, the machine gun's place is taken by a bomb dropping device that was invented by Col. Espitallier of the French Army Engineers. How well this device works is shown by the destruction wrought at Carlsruhe, where 130 bombs were dropped, killing eighty-nine people and wrecking the Grand Ducal palace, a railway station and an arms factory. In fact, every important French air raid into Germany is to the credit of Voisin bombing squadrons (Freiburg, Muellheim, Leopoldshoehe, Ludwigshafen, Carlsruhe, Colmar); these raids are generally carried out in concert by bombing and fighting aeroplanes, the latter being given the task of tackling the enemy aircraft while the bombardiers discharge their bombs.
The bombs employed by the French Air are of three types: the largest one weighs 220 pounds, but is used only very seldom; the two current types being the 22-pound bomb of 90-millimeter caliber and the 92-pound bomb of 155-millimeter caliber. The latter is a five and one half feet long and is fitted with stabilizing fins that make it look like a torpedo.
While this materiél of fighting craft has given an excellent account of itself whenever it was employed, the French Air Service did not stop to consider it as embodying ideal features and has urged aeroplane manufacturers to produce a still more powerful fighting craft, so powerful, indeed, that it would knock out anything else aloft. The specifications called for a fast-climbing machine of large cruising radius that would carry a small quick-firer and be armor-plated. While tremendous odds confronted the realization of this programme, one French aircraft manufacturer has now succeeded in producing a type of machine that well responds to the given requirements.
This machine, an all-steel pusher biplane, is driven by a 200 horse-power engine that develops a top speed of 85 miles per hour; it carries a crew of four and mounts a 6-pounder throwing a high explosive projectile. A light armor belt fitted around the nacelle protects both the crew and the engine against rifle fire from a very close range. This machine, the first one that really deserves the name of battle aeroplane, marks an enormous advance over the former types of fighting aircraft employed by the French, which mounted only a machine gun. Being very fast and a quick climber it can easily overtake any other fighting aeroplane and promptly destroy it with its 6-pounder, whose shells, filled with a high explosive, are obviously much more effective than the steel capped bullets thrown by a machine gun. On the other hand this battle aeroplane seems to be practically invulnerable against the speed scouts developing 100 miles per hour, whose pilots are equipped only with automatics, against which the armor-clad nacelle affords sufficient protection, while the 15 miles difference in speed is more than counterbalanced by superior armament.
While the French Air Service was thus developing fighting aeroplanes which could be converted into bombardiers and was bent upon conciliating specialization with standardization, Germany found herself in a peculiar position on account of a principle carried too far.
Since 1912 all her military aeroplanes had been standardized, with a view of forming homogeneous squadrons into two types, both tractors: the Taube monoplane and the Arrow type biplane, which were expected to effect all the services the French had specialized different machines for: scouting, fighting, bombing, and gun-spotting; on the other hand the construction of pushers was persistently discouraged. The result of this somewhat excessive zeal in favor of standardization was, that while it proved excellent in view of facility of construction and the building up of large stocks of spare parts, it precluded adaptability to the quick and often radical changes war created in the design of military aeroplanes.
When this mistake was realized by the German Air Service, the Great War was in full swing and much valuable time had been lost before initial errors could be remedied. But even then Germany only reluctantly admitted the superiority of the pusher as a fighting machine; it is true two or three companies are now building exact copies of the Farman and Voisin pushers that have fallen within the German lines, but most Teutonic aeroplane manufacturers are still clinging to the type of standard tractors they have been building since 1912, although they have lately been fitted with much more powerful engines (150-200 horse-power Argus, Benz, Rapp, and Mercedes) than heretofore. The new machines generally mount two machine guns, one in front just behind the pilot and the other aft on the fuselage, the pilot sitting between the two gunners. They climb exceedingly well; indeed the only French aeroplane that has so far been able to out-climb them is the Morane-Saulnier "avion de chasse," a single-seater monoplane armed with a machine gun which is fitted with a timing device, and permits firing into the propeller.
Although little is known about the present activity of German aircraft plants, certain signs indicate that large machines fitted with independent power plants are also in course of construction in the Kaiser's empire. The first intimation regarding this fact was given by the official eyewitness with the British army in France in a report describing a combat of a British airman with a huge German biplane that had a double fuselage, two engines and a pair of propellers, and which was fast enough to circle around the Briton.
Following this report comes now the news that Germany is shortly going to put in the air a fighting triplane, which is expected to overcome anything else that flies. The new machine, it is said, will have three planes and be powerful enough to carry twenty men, four machine guns and an aircraft gun of 47 millimeters. It will be equipped with eight Maybach engines of 180 horsepower each, such as are used to propel the Zeppelin airships, the engines being coupled together in pairs, each couple driving one set of propellers. The revolver gun will be mounted in an armored turret, while the entire underbody of the machine will be armor-plated and shaped like an inverted roof in order to avoid anti-aircraft projectiles from below.
All the steering, with the exception of changes of altitude, will be executed with the aid of the engines; turns will be effected by inclining the propellers. Two engines will be sufficient to propel the machine in the air and an extraordinary speed is expected when all the engines will be running.
While France and Germany are draining every one of their aircraft plants to the utmost in order to make them produce as large a number of battle aeroplanes as is materially feasible—for which the number of pilots available comes foremost into consideration—the other aerial powers are not remaining idle either. Italy, following closely the lead of other aerial powers, has lately developed an original type of fighting scout that is the invention of Signer Caproni, the well-known aircraft manufacturer. This machine presents an interesting solution of the large aeroplane in that it combines the pusher and tractor types and can easily be converted into a sea-going craft. There are two fuselages, placed side by side between the planes, each complete with its engine and tractor screw, and a central nacelle that houses a third engine driving a pusher screw. The power plant consists of three 150 horse-power Isotta-Fraschini engines. The nacelle projects well forward in front of the tractor screws and affords thereby a wide arc of fire to the aircraft gun that is mounted on its bow. The useful load carried by this machine amounts to one ton, which is made up by a crew of two (pilot and gunner), fuel tanks for eight hours flight, a 25-millimeter aircraft gun and ammunition.
As can be seen by the appended table, the development of the battle aeroplane is by no means limited to one or two countries only; in fact, an aerial construction race seems to have just started among the Great Powers, each endeavoring to build the most powerful 'big-lift-and-speed' aeroplane. Although this movement is still in an embryonic state, it is easy to picture what proportions it will take in the near future, when the aeroplane will have become a real battle-cruiser of the air.
TABLE SHOWING ARMAMENT, SPEED AND CRUISING RADIUS OF THE FIVE PRINCIPAL EUROPEAN FIGHTING AEROPLANES. (NO DATA ABE AVAILABLE REGARDING THE THICKNESS OF ARMOR BELT CARRIED.)
CRUSING RADIUS (HRS)
© J. Fred MacDonald, 2013
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THE HEADLONG FURY
A Novel of World War One
By J. Fred MacDonald