The Albatross.
This is a successful and much used German type, made at Johannisthal, near Berlin; about two hundred of these machines were made in 1913. The German Government have a great number of Albatross biplanes and monoplanes (Taube), and also several Albatross waterplanes. There appear to be four improved Albatross types for this year, two of them biplanes, one waterplane, and one monoplane (Taube), all with Mercèdes 100 h.p. motors, capable of attaining a maximum speed of 65 to 68 m.p.h. The biplane types are just over 26 feet in length, while the waterplane and monoplane average 29¼ feet.
The Germans have not favoured rotary engines and have almost exclusively adopted those with stationary cylinders, but an exception has been made in the case of the Sommer arrow-shaped biplane.
Another feature of German machines is that they are all, with one exception, double seated, the extra swiftly dashing scouting monoplane does not seem to appeal to the German. We find, however, one exception to the rule: the Argo type of monoplane is a one-seated machine. It has a span of 9 metres, surface of 15 square metres, and speed of 130 kilometres per hour.
A feature of aviation in Germany during the last few years of peace has been the night flights. For these, they have made special provision in the shape of aërial lighthouses, scattered all over the country. Some of these are electrically lighted, others by acetylene; some are “Morse” fires; some are fixed, others revolve, and the nature of the light has a distinct meaning, such as “near is a high tower to be avoided,” and so on. Germany is alone amongst the nations in her appreciation of the necessity of aërial lighthouses.
Round Berlin there are six such stations at, respectively: Nauen, Döberitz, Tegel, Reinickendorf, Linderberg, and Johannisthal; and there are also aërial lighthouses at the following places:—Königsberg, Posen, Liegnitz, Dresden, Belgern, Eilvese, Gotha, Weimar, Schleissheim, Strasbourg, Grosser-Feldberg, Berncastel-Cues, Metz, and Bonn.
Besides building aircraft on the lighter-than-air principle, Germany has not been idle in their use during the last few years of peace. She has German military flying schools, seventeen in number. They are as follows, arranged alphabetically:—Darmstadt, Döberitz, Freiburg, Germersheim, Graudenz, Hannover, Güterbog, Köln (Cologne), Königsberg, Metz, München-Oberschleissheim, München-Oberwiesenfeld, Posen, Saarbrücken, Schneidemühl, Strasbourg, and Zeithain.
There are three naval flying schools, at Kiel, Danzig, and Wilhelmshaven, and about three dozen seaplanes, mainly biplanes—Rumpler, Albatross, Curtiss, etc.
There are also in Germany no less than eighty-eight civilian aëronautical bodies, many of whom possess flying grounds, and there must be at least between thirty and forty of these private flying grounds, in addition to those of the military schools.
M. Raoul Volens, in his lucid articles, has pointed out how Germany, who was in 1911 so much behind France, has been able to produce by 1914 an equipment that rivals hers. He points out that in the Imperial manœuvres of 1911 it was with difficulty that Germany could produce eight aëroplanes; in 1912 she produced eight squadrons; at the end of that year 230 certificates had been granted to pilots by the German Aëro Club; in 1913 the number was 600; in 1912 the number of flying machine manufacturing firms was twenty; there were fifty in 1913. The number of flights made in Germany in 1911 was 7,489; in 1912, 17,651; in 1913 it was 36,817.
In 1911, the total duration of flights was 821 hours 41 minutes; in 1912, 1,966 hours 3 minutes; in 1913, 4,096 hours 48 minutes.
The progress made appears to have been largely due to the efforts of the German National Aërial League, which collected 7,234,506 marks, to be spent on aëronautical development in a few months’ time. The Council of the League made a very practical plan for acquiring a large number of pilots, and at the same time developing the most efficient class of machine possible. They left the training of the pilots to the manufacturers, giving them grants for each qualified pilot they had trained.
They also adopted the plan of giving premiums to pilots who accomplished certain practical flights of the nature of what would be required in war. For instance, if a pilot flew for an hour without a drop, he received 1,000 marks; if he made the flight outside an aërodrome, and was accompanied by a passenger, he received an additional prize of 500 marks; for a flight of over six hours, a monthly sum of 2,000 marks was given to a pilot who flew the longest distance without descending for as long as he held the record.
Regarding the development of aëronautics in Germany, it is interesting to note that just before the present war broke out two world records, those of height and duration of flight, were won by Germans; up to this year they had been held by France. These were the last victories of peace! On July 14th last Herr Oelerich rose from Leipzig-Lindenthal at 3.45 in the morning on a D.F.W. biplane, military type, furnished with a Mercèdes motor of 100 h.p., and attained an altitude of 8,150 metres.
On July 10th last, Rheinold Boehm rose from the Johannisthal Aërodrome at 5.54 a.m. on an Albatross biplane of military type, furnished with a Mercèdes motor of 75 h.p. He flew round about Berlin. During the night-time the aërial lighthouses indicated to him his whereabouts. He did not touch the earth till 6.12 p.m., having been in the air for twenty-four hours and twelve minutes. It is curious to note in what regular progress the records of duration had been won this year. On February 4th the German Langer flew continuously for 14 hours 7 minutes. On February 7th the German Langer had flown for 16 hours 20 minutes. On April 8th the Frenchman Poulet had flown for 16 hours 28 minutes. On June 22nd and 23rd the German Basser wrested the record away from Poulet, and accomplished 18 hours 12 minutes. Then the German Landmann on June 27th and 28th beat his countryman with the record of 21 hours 50 minutes. Then came the final exploit of Boehm, which has been recorded above.
CHAPTER IX
THE FIRST USE OF THE AËROPLANE IN WAR—TRIPOLI—THE BALKANS
Manœuvres in peace were the first practical test of the value of aëroplanes in war. The French proved their efficiency in their manœuvres in Picardy as long ago as 1910. The result of their use was a surprise for the military authorities themselves. Before the test it had been considered that an observer in an airship which could hover over the lines of the enemy or over a fortification would have a good chance of being able to bring back to headquarters useful details of what they had seen; but it had been thought by many military experts that the aëroplanist from his forced, rapid movement would not be able to form a mental picture of what actually passed his eyes, that if the retina had recorded the fleeting image on the brain, there would be confusion. The success of the aviator was an example of the truism that experience often does not coincide with preconceived opinion, for the reason that some unknown factor exists, and is only brought to light by the special circumstances of the case. Of all people, the aviator is one who constantly practises sharpness and concentration of sense; his eye and brain have a perpetual habit of harmonious and close-bound working; time to him has an enhanced value; none, like he, has ever learnt the exigencies of the minutes. His whole system becomes acclimatised to the constant maintenance of the equilibrium of his powers, for he has realised that for any negligence he will pay the death penalty. Is it wonder then that the glance of the practised aviator over the far-stretching regions beneath him becomes super-sight? So is it that the best aërial observer is often one who combines in himself the varied occupation of engineer, pilot, and scout, and who in his swift machine, arrow-like, darts above the enemy.
In the case of the military machines at the French manœuvres above mentioned, the work of pilot and observer was often divided; and it was found that the observer generally required some familiarity with flight before acquiring the requisite sharpness of vision.
Generally speaking, in the manœuvres, the information brought back was clear, defined, decisive. The intelligence brought back by cavalry scouts has sometimes been a puzzle to the generals in command—hints suggesting to them probabilities, perhaps, rather than accumulated certainties. But the air scouts brought such definite statements as these: “Have seen infantry hidden in a wood,” “A squadron with machine guns are marching towards ——,” “Seen a company digging trenches at ——,” “The enemy are in full retreat,” etc.
The value of the new arm was manifest in this country in the very first manœuvres in which aëroplanes were used; by its use the plans made were all rapidly discovered and rendered useless! Plans made on the old principle of fighting in the dark, each side ignorant of the operations of the other, fell through once and for all; and it became recognised that the coming of the aëroplane meant the revolution of the methods of conducting war.
But if from the experience of manœuvres the value of aëroplane reconnaissance was patent to expert military authority, the public generally did not realise the value of the new arm until it had been tried in something beyond mimic warfare. This occurred in the Italian war operations in Tripoli. In this war the need of reconnaissance was great; operations had to be carried on in a difficult country, and with an enemy that adopted “tricky” forms of warfare. To Italy belongs the credit of being the first nation to put aëroplanes to the test in war, both for reconnaissance and offensive purposes. The types of aëroplanes used in this war were chiefly Blériot and Nieuport monoplanes; one Etrich monoplane was also included.
Very valuable information was acquired on several occasions by the air scouts, who flew over wide tracts of desert, marking the position of Turks and Arabs, and ascertaining their movements preparatory to making attacks on Italian positions. The aëroplanes were fired upon by the enemy, and sometimes the wings of an aëroplane were riddled by shot without resulting accident, proving that the riddling of the wings, so long as sufficient supporting surface remains, is not the greatest evil to be feared. On one occasion Lieutenant Rossi, while making a reconnaissance, nearly fell into the hands of the Arabs. The motor suddenly stopped, and his machine was rapidly falling; the motor, however, recovered just in time for the aviator to remain in the air, and he was able to return to Tripoli.
Regarding the offensive use of aëroplanes in this war, it was related that Lieutenant Gavotti threw from his machine upon an Arab camp a bomb made of picrate of potash; he was at the time 700 feet above the oasis of Aïn-zara, when he discovered beneath two masses of Arabs, numbering each about 1,500 men. He took out the bomb from a bag at his side with one hand, while with the other he manœuvred the machine, and as he passed over a group of Arabs he dropped the bomb. He could follow its course for a moment or two while he was passing over the bright green verdure of the oasis, but it was speedily lost to sight, while the noise of the motor prevented his hearing the explosion below. He saw, however, a cloud of smoke and the Arabs flying in all directions. This was the first instance on record of bomb throwing from aircraft. Gavotti was himself of opinion that in bomb throwing the operation should be carried out with the aid of two aëroplanes; the one in advance should throw the bomb, the one following observe the result. The one in advance would have to fly at a lower level so as to drop the bomb; the observer following would fly much higher. The dropping of the bomb in this case produced excellent moral effects. When, on a later occasion, the aviators revisited the same spot, there was no trace of Arab encampments. On another occasion Captain Moizo threw two bombs into the Turkish camp near Aïn-zara, which also had the effect of putting the Turks to flight.
A troublesome feature of flight over sandy deserts is found to be the intrusion of sand into the valves and bearings of the engines; but if aëroplanes can be armoured against shot, doubtless a sufficiently light and effective means of protecting the engines against sand can be devised.
Use of aëroplanes was also made in the Balkan war; and it may be noted that before that war broke out Germans went to instruct the Turks in bomb throwing from aircraft. Bulgaria had a hastily formed aviation corps, and it showed itself useful.
It is, however, in the present European war that the large-scale use of aëroplanes is being daily more and more manifested.
CHAPTER X
THE NEW ARM IN ARMAGEDDON
The question has been often asked why we were so long in this country in grasping the necessity of keeping pace with other countries by having a national flying corps? In an introductory chapter I have stated that a want of public interest was the cause of British dilatoriness in aëronautical matters; but there was also another very potent reason—a meteorological one. From the weather point of view, the conditions for practising flight in this country cannot be compared with those obtaining on the Continent. Our insular position affords an uncertainty of wind force that in the earlier days of the aëroplane would have been fatal to progress had the pioneers chosen this isle for their experiments. Even while the aëroplanes were only calm-weather machines, and even when they first essayed flight in moderate winds, there was an undoubted instinct in the minds of an eminently practical nation that the loss of life consequent upon a systematic military use would be hardly justifiable. So the nation waited for a certain stage of progress in flying machines before launching them into the winds and gusts for serious military work. When they were first used in this country, the nature of our climate proved exceedingly disastrous and swelled the casualty lists of peace. Those who have survived have had a hard and exceptionally strenuous training in the ways of the air, ever having had to be on the alert against the ever-present threatening blasts which tend to upset the stability of flying machines. But is it not the exceptionally hard training that the military aviators in this country have had to undergo that has produced the exceedingly able and successful Flying Corps that is struggling for King and country in the present campaign? It has been seen how they have been commended in the first report of Sir John French. Their efforts have also met with the greatest appreciation of the French. General Joffre in his report specially dwelt on the regular and valuable reconnaissance of the British Royal Flying Corps. In Sir John French’s report, dated September 11th, the following passage appears:—
Quite one of the features of the campaign, on our side, has been the success attained by the Royal Flying Corps. In regard to the collection of information it is impossible either to award too much praise to our aviators for the way they have carried out their duties or to overestimate the value of the intelligence collected, more especially during the recent advance.
In due course certain examples of what has been effected may be specified, and the far-reaching nature of the results fully explained, but that time has not yet arrived. That the services of our Flying Corps, which has really been on trial, are fully appreciated by our Allies is shown by the following message from the Commander-in-Chief of the French armies, received on the night of September 9th by Field-Marshal Sir John French:—
“Please express most particularly to Marshal French my thanks for services rendered on every day by the English Flying Corps. The precision, exactitude, and regularity of the news brought in by its members are evidence of their perfect organisation, and also of the perfect training of pilots and observers.”
To give a rough idea of the amount of work carried out, it is sufficient to mention that, during a period of twenty days up to September 10th, a daily average of more than nine reconnaissance flights of over 100 miles each has been maintained.
The constant object of our aviators has been to effect the accurate location of the enemy’s forces, and incidentally—since the operations cover so large an area—of our own units. Nevertheless, the tactics adopted for dealing with hostile aircraft are to attack them instantly with one or more British machines. This has been so far successful that in five cases German pilots or observers have been shot in the air and their machines brought to the ground.
As a consequence, the British Flying Corps has succeeded in establishing an individual ascendancy which is as serviceable to us as it is damaging to the enemy. How far it is due to this cause it is not possible at present to ascertain definitely, but the fact remains that the enemy have recently become much less enterprising in their flights. Something in the direction of the mastery of the air has already been gained.
The Royal Flying Corps has already won the distinction of the Legion d’Honneur.
The principal uses of the new arm in war may be said to be:—
1. Reconnaissance.
2. Directing and correcting artillery fire.
3. Offensive operations.
4. Rapid despatch carrying to a distance.
5. Distributing handbills to cities.
6. Photography.
7. Locating submarines, mines, etc.
1. Reconnaissance.
As a particular example of the value of reconnaissance in the present war one may well refer to that mentioned in Sir John French’s first report. He says, “When the news of the retirement of the French and the heavy German threatening on my front reached me, I endeavoured to confirm it by aëroplane reconnaissance, and as a result of this I determined to effect a retirement to the Maubeuge position at daybreak on the 24th.”
It is undoubtedly expedient to train aërial observers to make reconnaissance at high altitudes. This has been the method employed by Great Britain and France. During the present war we hear of the British and French machines flying at 6,000 feet, where they are fairly safe from gun-fire. The Germans often appear to fly considerably lower. This probably accounts for the loss of so many German machines from gun-fire. It has been stated that at the time of writing British aviators have already brought down seventeen machines. But there have been instances of the aëroplanes of the Allies also making reconnaissance at lower levels. One very remarkable case of an aviator persisting in his reconnoitring task in spite of the fire of the enemy has been reported in the daily papers. The French aviator, M. Poiret, who is in the Russian service, said that
during the recent Russian-German fighting he reconnoitered over the enemy’s positions, with a captain of the General Staff as observer, at a height of 1,200 metres. He was for twenty minutes under rifle and shell fire. Ten bullets and two fragments of shell hit his aëroplane. Nevertheless, he retained his control of the machine. The captain was shot through the heel, the bullet coming out of his calf, notwithstanding which he continued taking notes. The aëroplane returned safely.
In making reconnaissance over the enemy’s lines it is well for the aviator to be practised in the art of making vol-planés. On more than one occasion in the present war the engine has failed while the aviator has been flying over the enemy. A well-directed vol-plané has brought him down within friendly soil. This gliding by means of gravity without the motor working in times of peace may have been thought to be a foolhardy practice, merely done for the sake of sensation. But the sensation of a few years back is the necessity of to-day! The vol-plané has become one of the most useful features of aëroplaning. A machine that is fitted with wireless telegraphy equipment undoubtedly possesses a great advantage for reconnoitring. It is especially useful when a heavy attack on an enemy is in progress. By its means a continuous stream of intelligence can be supplied to headquarters. The French have been particularly active in the development of wireless messages from aëroplanes, and have devised extremely portable forms of apparatus. It will be of great interest to hear accurate information in regard to their practical use in the present war.
Aëroplane reconnaissance in naval operations is almost equally as important as its use on land. This will be one of the principal uses of the hydroplane, which can either travel on the surface of water or rise in the air. In the present war two seaplanes were recorded as scouting near Antivari on September 8th, 1914. It is also said that the Germans gave information to the Heligoland forts by biplanes concerning the fight in Heligoland Bight.
2. Directing and correcting artillery fire.
Very many reports of the use of the aëroplane in this respect have come to hand during the present war. The Germans appear to be very keen on this particular use. Stories told by wounded soldiers graphically describe how with the appearance of the enemy’s aëroplane there comes accurate and deadly fire. The Germans appear to have several simple and ingenious means of indicating the instructions of the aërial observer in this respect. An interesting contribution to our knowledge has been supplied by Bombardier Smith, who was wounded by a bomb dropped from a German aëroplane. Writing to the Times he describes how the Germans have special bombs for range-finding.
Those bombs have proved a great success in the war, as they find the enemy’s ranges very accurately. The bomb when dropped leaves a thick, black, smoky line to enable their gunners to take the exact range. We were in a good position but suffered loss. The enemy could not find us until the aëroplane came on the scene. Then we had it rather hot. The gunners had to leave the guns, but later saved them all after being reinforced by other guns.
Another method the Germans adopt is to drop a silver ball. Almost as the ball drops from the range-finding aëroplane, the shrapnel shell bursts over the lines of the opponent.
They also sometimes pull up and down a little disc suspended beneath the aëroplane. A still further variety of signalling is accomplished by the use of lamps that are visible in daylight. Almost every method of signalling can be used for the purpose, such as flag signalling; wireless signals are no doubt especially effective.
I will quote from a recent article by Mr. F. W. Lanchester in “Engineering” as to the German use of the aëroplane in this respect:—
The value of aëroplane work will be relatively greater the longer the range; in fact, it may in future be found possible to employ heavy artillery of long range under conditions in which without the help of the aëroplane it would be comparatively useless. As an illustration, there is nothing to-day to prevent a long-range battery, well served by its aëroplanes, from effectively shelling an enemy without knowing in the least the character of its objective—i.e., whether an infantry force or position, a body of cavalry, or the enemy’s guns. In the present war the aëroplane appears to have been utilised by the German army, as a matter of regular routine, as an auxiliary to the artillery in the manner indicated. It has been reported again and again that the appearance of an aëroplane overhead has been the immediate prelude to the bursting of shrapnel, frequently the very first shell being so accurately placed as to indicate that the method of signalling, and, in fact, the whole performance, must have been well thought out and equally well rehearsed.
3. Offensive operations.
This use might be well subdivided into legitimate and illegitimate offensive operations. There has been, unfortunately, ample example of the use of both airships and aëroplanes for purposes that are illegitimate and barbaric in the present war. To use the advantage of travelling in the air at altitudes for the purpose of the wanton destruction of harmless citizens, and, further, to destroy in cities the amassed wealth of art that only centuries, not years, produce, is an unrighteous use of the science of aërial navigation. Before the war it was condemned by the Hague Convention. Since, it has met with the denouncement of all civilised nations—save the one that has perpetrated the outrages. In the case of the aëroplane raid made into Germany by our own British naval airmen, one party of aviators went to Cologne to try to attack the airship halls there. The city was enveloped with an opaque fog, and it was hopeless to try to locate the position of the airship sheds. Though the British aviators circled over the town for an hour and a half they refrained from discharging any bombs, rather than run the risk of destroying civilian life or property. An example, indeed, of the legitimate offensive use of the aëroplane was the attempt to destroy or put out of action the very kind of aircraft which had been so wantonly used over Paris, Antwerp, Ostend, and other cities.
Perhaps the most important offensive use of the aëroplane is for fighting airship and aëroplane. Mention has already been made about the deadly character of the aëroplane when it encounters an airship. When it meets an aëroplane the chances are more evenly balanced. Success will depend chiefly upon the speed of the respective aëroplanes, their climbing power, their armouring, and the guns with which they are armed. Speed and climbing power are perhaps the greatest protective factors. Several stories have already been told of the pursuit of German aëroplanes by those of the Allies. The climbing power of the machines of the latter has often been the cause of victory. It is the well-directed shot from above to which the airman is exposed that has ended the career of airman and machine.
At the beginning of the present chapter it was pointed out that the British and French aëroplanes generally fly at about 6,000 feet, which is a height fairly safe from gun-fire. While speaking of the offensive work of aëroplanes, a few more words about the attack on them by gun-fire may not be out of place. As Mr. Lanchester has pointed out, an aëroplane is liable to attack by rifle, machine-gun, and shell fire. Ordinary field artillery fire can be put out of the question in the use of so rapidly moving a target as an aëroplane in flight. He has estimated that an aëroplane is absolutely safe from rifle or small-bore machine-gun fire at 7,000 feet, and it would be difficult to hit it a thousand feet lower.
Not only would the velocity become so reduced as to render a “hit” capable of but little mischief, but the time of flight of the bullet, rising vertically to this altitude, would be about eight or nine seconds, and the distance moved by the aëroplane 1,000 feet, more or less. Therefore, it would be necessary to fire into quite a different part of the heavens from that in which the aëroplane was seen.
The vertical range of aircraft artillery is much higher. In the case of a one-pounder having the same velocity the range would be over 12,000 feet; but it is a question of luck whether the aëroplane would be hit. The great difficulty is the angle of “lead” which must be given to allow for the velocity of flight.
This angle is only constant so long as the velocity of the projectile is constant, assuming (as fairly represents the conditions) the flight speed not to vary; at extreme heights the velocity of the projectile has fallen so low that a very slight error in range-finding will be fatal to accuracy.
In regard to aëroplane artillery, Mr. W. F. Reid has collected some interesting details of the guns that Krupp has devised for the purpose of hitting aëroplanes.
The 7.5 cm. gun of this firm has seats for five men and storage for sixty-two shells. It is mounted on a car which weighs 4,300 kilos., the weight of the gun alone being 1,065 kilos. Each projectile weighs 5.5 kilos. (12 lb. 2 oz.), and the horizontal range is given as 9 km. The vertical range is 6,300 metres.
A lighter gun of 6.5 cm. gauge weighs, with car, 875 kilos., the gun weighing 352 kilos. Each projectile weighs 4 kilos. (8 lb. 13 oz.), and the extreme horizontal range is stated to be 8,650 metres (9,450 yards). The height of fire obtainable is 5,700 metres (18,700 feet). The initial velocity of the projectile is 620 metres (2,034 feet) per second. A coiled spring balances the weight of the gun when pointed above the horizontal.
For naval purposes Krupp has constructed a 10.5 cm. gun weighing 3,000 kilos, with carriage. The projectile weighs 18 kilos. (40 lb.). The muzzle velocity is 2,100 feet per second, and the shells discharge a train of smoke to facilitate aiming.
Ehrhardt, in Düsseldorf, has also built a special gun for use against aërial craft. Its bore is 5 cm., and its barrel is 30 calibres long, while the length of the Krupp barrels is 35 calibres. The weight of the Ehrhardt gun alone is 400 kilos.; with car, ammunition, and five men the weight is 3,200 kilos.
With regard to the difficult subject of armouring aëroplanes, I should like again to quote from Mr. Lanchester:—
It is manifestly not possible for an aëroplane to perform all the duties required of it in connection with tactical operations at high altitude[B], and whenever it descends below 5,000 feet or thereabouts, it is liable to attack from beneath; in fact, at such moderate altitudes it must be considered as being under fire—mainly from machine-gun and rifle—the whole time it is over or within range of the enemy’s lines. Protection from the rifle bullet may be obtained in either of two ways: the most vital portions of the machine, including the motor, the pilot, and gunner, can only be effectively protected by armour-plate; the remainder of the machine, including the wing members, the tail members, and portions of the fuselage not protected by armour, also the controls, struts, and the propeller, can be so constructed as to be transparent to rifle fire—that is to say, all these parts should be so designed that bullets will pass through without doing more than local injury and without serious effect on the strength or flying power of the machine as a whole; in certain cases components will require to be duplicated in order to realise this intention. It is important to understand clearly that any intermediate course is fatal. Either the bullet must be definitely resisted and stopped, or it must be let through with the least possible resistance; it is for the designer to decide in respect of each component which policy he will adopt. The thickness of the armour required will depend very much upon the minimum altitude at which, in the presence of the enemy, it is desired to fly; also upon the particular type of rifle and ammunition brought to bear. There is a great deal of difference in penetrative power, for example, between the round-nosed and pointed bullets used in an otherwise identical cartridge.
[B] For military purposes we may take the term “high altitude” as defined by the effective vertical range of small-arm fire, in other words, as denoting an altitude of 5,000 feet or 6,000 feet or more.
If it were not for the consideration of the weight of armour, there is no doubt that an altitude of about 1,000 feet would be found very well suited for most of the ordinary tactical duties of the aëroplane. At such an altitude, however, the thickness of steel plate necessary becomes too serious an item for the present-day machine, even allowing for the very excellent and highly efficient bullet-proof-treated steel that is now available; at the altitude in question, the minimum thickness that will stop a 0.303 Mark VI. round-nosed bullet is 3 mm. (⅛ in.), but, if attacked by the modern pointed-nose Mauser, nothing short of 5 mm. or 6 mm. is of avail. If we compromise somewhat in the matter of altitude and prescribe 2,000 feet as the minimum height for which protection is to be given, the figures become 2 mm. (about 145 W. gauge) for the 0.303 round-nosed bullet, and for the pointed Mauser 3 mm. or slightly over; at present it is not expected that it will pay to armour a machine for the duties in question more heavily; thus we may take 2,000 feet as representing the lower altitude limit of ordinary military flying.... On this question of armour it cannot be too strongly insisted upon that anything less than the necessary thickness definitely to stop the projectile is worse than useless; a “mushroomed” bullet, possibly accompanied by a few detached fragments of steel, is infinitely more disagreeable and dangerous than a bullet that has not been upset.
An aëroplane armoured in all its vitals with 3 mm. steel, and otherwise designed on the lines indicated, flying at not less than 2,000 feet altitude, will be extremely difficult to bring down; so much so, that unless its exposed structural members be literally riddled and shattered by rifle and machine-gun, or unless a gun of larger calibre be brought to bear, it will be virtually impossible to effect its capture by gun-fire alone.
4. Rapid despatch carrying to a distance.
Considering the advantages of the swift monoplane for carrying despatches from one commander to another, it would seem that in time it must oust the despatch rider.
There is no obstacle to the despatch rider. The difficulties and delays of hills, woods, and rivers melt away before his ever onward course. The despatch rider on horseback may have to face the sudden appearance of the enemy, but if the aëroplane despatch carrier does, he has only to rise up out of his range of fire, and, still undisturbed, he can make his way towards his destination. There must surely already be many instances of the use of the new arm in this way in the present war. It has been reported that the Germans used aëroplanes to send messages to recall German troops stationed in the village of Coutrai to reinforce those at Charleroi.
5. Distributing handbills to cities.
This is a use which has not been much taken into account until the present war. It appears, however, one that is destined to become very general in war. It has been already used either to excite terror or encouragement amongst the population of a city either already besieged or threatened with speedy investment. It has been stated that when Liége was besieged the French aviators distributed circulars over the city to the effect that the citizens should keep up their courage, as help would soon be forthcoming. When the Germans were approaching Paris the German aviators distributed pamphlets urging the surrender of the Parisian capital. Reports also came to hand that French aviators flew over Alsace and Lorraine with pamphlets to describe the violation by Germany of the neutrality of Belgium and Luxemburg!
6. Photography.
The value of aëroplanes for this work in war is self-evident, and various means for securing good photographs from flying machines have been devised. Some years ago the public was made familiar with photographs at great altitudes in the air by the beautiful specimens taken by the late Rev. J. Bacon and the late Mr. Percival Spencer from the cars of their balloons. Since then Mr. G. Brewer has become an adept in the art of aërial photography. The clearness of detail in these photographs gives sufficient evidence as to the value of aërial photography in war.
Satisfactory photographs from balloons have been taken from as great a height as 10,000 feet. The success of aërial photography, however, depends upon the amount of haze upon the earth, which veils the plate from the actinic power of the reflected light. In taking aërial photographs from aëroplanes, owing to meteorological conditions it may often be necessary in war to take the photographs from lower and more perilous positions. The value of the photographs will, however, often be worth the risk, as very complete aërial surveys of war regions can be made from a series of photographs.
For taking photographs from aëroplanes special and in some cases automatic cameras have been designed.
The Germans use a camera fitted with a special Telephoto lens.
In an apparatus of British make, designed by Mr. Baker, the camera is suspended beneath the aëroplane. The airman presses one button to make an exposure, another when he wishes to change the plate.
7. Locating submarines, mines, etc.
In the present war ample evidence has been given of the deadly work that submarines, torpedoes, and mines can perform. Some years ago the late Rev. J. Bacon carried out experiments from balloons to show that when the surface of the sea is viewed from an altitude the observer has a vision which penetrates to some depth below the surface. At the time the great advantage of such surveys in naval war-time was pointed out.
Such aërial surveys form an important use for both the smaller types of airships, aëroplanes, and hydroplanes. When more records come to hand than it is now possible to obtain in regard to naval doings in the present war it will be interesting to observe the amount of actual work that has been done in detecting submarines and the other hidden dangers in the sea.
CHAPTER XI
PRESENT DEFICIENCIES AND FUTURE POSSIBILITIES OF THE MILITARY AËROPLANE
In the portion of this handbook which especially dealt with airships, certain advantages possessed by them over aëroplanes were noted; several of their disadvantages were also a matter of comment. It was hinted that in the future it might be possible to impart to aëroplanes also those very advantages of which the airship can still certainly make boast. Should this be done by engineering skill—and it is well within the limits of reasonable possibility—then it would seem that the lighter-than-air machine must entirely yield its claim as an adjunct of war to the heavier-than-air principle. The free balloon “mounting heavenwards,” as Carlyle said, “so beautifully, so unguidably,” is now merely a past reminiscence, and even so, too, will be the mammoth motor-impelled gas envelopes. When the din of war ceases, the still greater perfection of the aëroplane should be the object of the attention of British engineering skill. The endowment of the aëroplane with certain qualities in which it is still deficient appears to be merely a matter of engineering detail based on principles that have been already elucidated.
Since the brothers Wright made their epoch motor flights which gave to man the attribute of the bird, so long his envy, progress in flight records has been largely made in the attempt to win a money prize. In one sense the pilot has progressed at a faster rate than has the evolution of the machine. He has accomplished heights, durations, and distances on machines in which the margin of safety is indeed small. It might be well if the next series of prizes should be devoted to the further development of the machine itself—prizes which would, in their turn, stimulate the genius of the aëronautical engineer.
Four essential points in the future development of flying machines are:—
1. Variable speed.
2. Immediate rising into the air.
3. Hovering in the air.
4. Stability.
1. Variable speed.
The aërial machine that cannot vary its speed, so as to be able to go fast, at moderate pace, or quite slow, must from one point of view be in a crude state of development. Yet aëroplanes are as yet in this stage of growth.
More than one plan has been suggested for endowing the aëroplane with the power of variable speed, which would make its use in war still greater. One of these plans is the extension and reducing at will of the sustaining surfaces, so that for high speeds the practical minimum of surface may be utilised, for low speeds the practical maximum. A machine to produce this result has been already planned by Mr. C. F. Webb. It was described at a meeting of the Aëronautical Society of Great Britain in 1906. At the time of the reading of the paper the world was hardly ready to realise the importance of considering this problem; at the present moment all military aëronautical experts agree as to the advisability of the production of a variable speed flying machine, though they shirk the complexity of structure the variable speed machine would seem to necessitate. In Mr. Webb’s design is a form of aëro-surface which, by special adaptation, can vary its area in accordance with the requirements of, and in proportion to, the constants, speed, and weight, and thus automatically adapt itself to the requirements of the varying speed of the wind. In this machine the two wings are situated on each side of the car in such a way that the centre of support of each is some distance above the centre of the mass of the machine. Each wing is fan-curved from front to rear, with the outermost segment longer than the innermost. The fan wings are opened or contracted by a hand-lever arrangement, and besides the hand levers there is an automatic pendulum mechanism which regulates their area to the requirements of the wind. Whether or no the inventor’s exact arrangements may prove on trial to be successful is a matter on which decisive opinion cannot be given; but the principle of expanding and diminishing surface is thoroughly sound, and is worthy of lavish expenditure and experiment. Other ways of attaining variable speed machines have been suggested, though the method of a variable surface would seem likely to carry the regulation of speed to a greater nicety than do the other plans. One of these projects is to alter the angle of the incidence of the planes while the machine is in flight; the angle would have to be steep for slow speed, and gradually flatten for increase of speed.
2. Immediate rising into the air.
It is undoubtedly a disadvantage of the aëroplane that it has to run on the ground on wheels to get the initial velocity necessary for flight. In some of the earlier military experiments with aëroplanes the machines were made to run over ploughed fields, for it was recognised that machines which could only rise when running on smooth ground would be useless for military work. But one can imagine that it may often be expedient in military operations for machines to rise from land so unequal that with the present method flight would be impossible.
The perfect military aëroplane should be able to rise in the air at any time and from any place. The application of horizontal lifting screws beneath the flying machine would make this a possibility, though it would be necessary to have two of such screws revolving in opposite directions. It is indeed curious that so little has been done in the way of such experiments. It will be said that each added screw means engine multiplication and complication; but these difficulties are details of engineering that are not unsolvable.
In the case of such large aëroplanes as the Russian type that has been described, it would seem specially feasible to attach the lifting screws.
3. Hovering in the air.
One great advantage of the lifting screws would be that by their use the machines could hover in the air. Now, when the vertical screw is stopped, the aëroplane must fall to earth unless the aviator makes the “vol-plané.” This necessity brings into strong relief the present imperfection of the flying machine. When horizontal screws are attached to a flying machine we really have the essential feature of sustentation, and the existence of the ordinary supporting surface becomes superfluous. The flying machine has, in fact, become of the “Hélicoptère” type, though doubtless for some time the supporting surface will be retained as a means of additional security; in time it may vanish altogether, and support as well as progression depend upon revolving screws.
4. Stability.
It has been stated that the properly constructed airship is stable when in the air; it has not got to fear the more treacherous side gust which over and over again has brought the aëroplane to earth, and coupled its name with tragedy. The vexed problem of the stability and equilibrium of aëroplanes is the most important that has yet to be solved; until this is done it is not likely the airship will completely disappear as an instrument of war. In speaking of the remarkable exploits of Pégoud, it was said that they were an object-lesson on the materiality of the air, and we have yet to learn how to use this materiality to the best advantage, so as to afford us continual stability. Until the problem is solved, man cannot be said to have brought himself to the level of the soaring bird; the latter, indeed, makes good use of the very attributes of the wind which at present tend to upset the aëroplanist—the vertical component of the wind, its internal work, i.e., its gustiness; its non-uniformity, i.e., its different velocities at different levels. Every light, therefore, that can be thrown experimentally or mathematically on the difficult subject of equilibrium and stability should be eagerly sought.
Professor G. H. Bryan’s mathematical researches are indeed epoch-making, and their study by the aëronautical engineer should be prolific of practical result. He does much to elucidate points of the problem of stability that before had been imperfectly grasped. For instance, take the case of his remarks as to distinction between equilibrium and stability.
We say that the motion of a flying machine is steady when the resultant velocity is constant in direction and magnitude, and when the angle of the machine to the horizontal is constant. If this motion is slightly disturbed the machine may either return after a time to the original motion, or it may take up a new and altogether different mode of motion. In the first case, the steady motion is said to be stable, and in the second unstable.
It is evidently necessary for steady motion of any kind that there should be equilibrium—i.e., that there should be no forces acting on the machine (apart from accidental disturbances) which tend to vary the motion, and hence it follows that the number of modes of steady motion of which a machine is capable is, in general, limited, and that when an unstable, steady motion is disturbed, the new mode of motion taken up is entirely different from the old.
It is necessary to distinguish carefully between equilibrium and stability, as the two are very often confused together. Equilibrium is necessary to secure the existence of a mode of steady motion, but is not sufficient to ensure the stability of the motion. The question of the stability of a rigid body moving under the action of any forces has been solved by Routh. In order to apply his results to the stability of flying machines, it is necessary to know the moment of inertia of the machine about its centre of gravity, the resistance of the air on the supporting surfaces as a function of the velocity and angle of incidence, and also the point of application of this force—i.e., the centre of pressure for different angles of incidence. If these are known for the surfaces constituting any machine, then the problem of its stability for small oscillations can be completely solved. Unfortunately, our knowledge of these points is very unsatisfactory. Several valuable series of experiments have been made to determine the resistance on planes, but there is still some doubt as to the position of the centre of pressure at small angles of incidence, especially for oblong planes, and very little indeed is known as to the movement of the centre of pressure on concave surfaces. Until experiments are made on this point it will be impossible to solve the problem of stability for machines supported on concave surfaces.
The subject of the stability of aëroplanes falls under two heads:—
1. Automatic stability.
2. Inherent stability.
Attempts have been made to produce the first by the aid of moving gyroscopes and pendulums without much success, and Professor Bryan has pointed out, apart from the fact that movable parts are likely to get out of order, they also increase the degree of the friction of the machine, thus further adding to the number of conditions that have to be satisfied for stability.
It would seem, therefore, that the desideratum is inherent stability. Professor Bryan considers that there is hope of attaining longitudinal and lateral stability by the use of exhaustive mathematical researches; these will result in the fixing of independent auxiliary surfaces in aëroplanes in such happy positions as will secure stability in all conditions of atmosphere. Or it may well be that through some unlooked-for observation or simple experiment the answer will come. In the shape of the aëroplane surfaces alone may be the solution of the problem. But if the aëroplane be still an imperfect instrument, it is sufficiently developed to be already one of the greatest factors of modern warfare.
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