A second prototype followed, almost identical to the Lebed XI but slightly smaller. This was the Lebed XII, again with the Salmson engine. Test-flown by Capt. Sleptzov on December 28th, 1915, it was reported to be superior in most respects to the German original, and an order was placed for 225 machines, Lebedev’s chief designer, Shkulnik, and his executive, Ribokov, receiving high praise for their work. The first batch of Lebed XIIs was handed over to the War Ministry on August 4th, 1916, and from the Komendantski airfield at Petrograd a pilot named Michailov put one of the machines through its paces, reporting an overall rate of climb of 200 ft/min., and a ceiling of 10,000 ft.
   Officially approved for operational flying, this group of first production machines were sent to the Front, but unfortunately the qualities of the prototype were missing from them, and it was discovered that they had a failing similar to that of the German LVG biplanes: a badly positioned centre of gravity, also some wing-flexing, both of which combined to cause a pilot to lose control in a dive or a steep turn. These disturbing factors were made worse when a bomb-load was in position on the four underwing racks. The observer too had the unenviable choice of being gassed by exhaust fumes inside his cockpit or of being frozen by the icy slipstream when standing up to operate his pillar-mounted Colt machine-gun. A contribution towards the many fatal crashes of the XII was that the angle of incidence of the upper wing was positive, the lower negative!
   Various modifications were made without marked success, and the Lebed XIIs, together with the Voisins and Morane-Saulnier Ls, were withdrawn from active service in the summer of 1916. The frequent reports from front-line units of the faults of the XII went unheeded, and the Advisory Committee of National Defence ordered the Air Service Administration to acquire the type in quantity. There could have been only two reasons for this action; the shortage of aircraft known to exist at that time, or corruption, prevalent in some offices of the Russian Empire. In the event, it may have been a little of both!
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   In 1917, the Lebed XII was modified in an attempt to improve its performance. The 150 h.p. Salmson engine was replaced by a Hispano-Suiza of similar power but smaller frontal area, considerably altering the machine’s appearance. The installation of a liquid-cooled power unit also required the addition of radiators, which were positioned on the sides of the fuselage. Some airframe modifications slightly altered the overall dimensions, but the net result of all this work was not encouraging, for the XIIbis did not show any great improvement over the original.

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   For all this, the Russians, like their contemporaries in other countries, were often frustrated in their attempts to build successful flying machines by the lack of a lightweight and efficient power unit. No better example of this fact exists than the machine built by Mozhaiski in the period 1882 to 1884. Alexander Fyodorovitch Mozhaiski was a Russian naval officer, and a student of aerodynamics, having an income quite adequate for his needs. Firmly convinced that it was possible to build a machine to confirm the aerodynamic theories he had studied, Mozhaiski started with calculations, then applied the results to flying models and kites. One of the latter was of very large size, and a contemporary report states that the designer was towed into the air as its pilot, by a team of horses harnessed to a long rope! Eventually, Mozhaiski finalised the design of a full-sized man-carrying aeroplane, and, presumably because he was a serving officer, had then to submit his design to the members of a special commission, set up to examine the project. By good fortune, one of the commission members was the great Russian chemist, Professor Dmitri Ivanovich Mendeleyev, himself deeply interested in aeronautical problems, and he gave Mozhaiski considerable support and advice to such effect that the project was approved and construction commenced in 1882. The machine, a monoplane, was of considerable size, with a wing span of about forty feet, a long, slender fuselage and tail control surfaces, while the wing itself had a very broad chord, square-cut tips, and was wire-braced from above and below the fuselage. The undercarriage consisted of two pairs of wheels in tandem. Somewhat limited by his lift and weight calculations, Mozhaiski managed to acquire a pair of British lightweight steam engines, of 10 and 20 h.p. respectively, mounting the 10 h.p. engine in the nose of his machine to drive a forward propeller, and the 20 h.p. engine amidships to drive two propellers which rotated in slots cut into the wing, the drive transmission of the latter being by chain. Both engines exhausted into a vertical funnel amidships. In 1884, after a series of tests and engine runs, the machine was positioned at the top of a launching ramp, with a man named Golubev at the controls. The engines were started, and the machine descended the ramp, gathering speed and leaving the ground for a few feet at the bottom before touching down on even keel. Its weight of nearly one ton had proved too much for the power available. What might have been accomplished with more efficient engines is only conjecture, but Mozhaiski’s aeroplane certainly deserves its place in aviation history.

In November, 1915, W. Zalewski, a young Polish aircraft designer, together with V. F. Saveliev, a head mechanic, submitted a design for a quadruplane to the Commander in Chief of the Air Service, the project being designated as the S.Z. Quadruplane No. 1. Official approval was given, and construction of the machine authorised to commence at the 2nd Aircraft Park, Smolensk, where both men were stationed as members of the Air Service. The machine was intended as a small-scale prototype of a much larger multi-winged bomber, for Saveliev, who had worked at Russo-Baltic on the Sikorski giant aircraft, was convinced that future large aircraft should have five or even six wings. The S.Z. No. 1 emerged at the beginning of April, 1916, as a two-seater, with an 80 h.p. Gnome engine. The wings were of diminishing span, from the upper of 27 ft. 11 in. to the lower of 18 ft. 1 in., the latter having raised tips, all being supported by long interplane and centre-section struts and wire-braced. The fuselage, tail surfaces and undercarriage were conventional in appearance. The commander of a reconnaissance squadron, Col. Jungmeister, was nominated as test pilot, and in this capacity carried out taxi-ing trials on April 23rd, 1916. In the event, these trials provided the first flight, for the S.Z. No. 1 had so much lift that Jungmeister unexpectedly found himself airborne, and decided to carry on! With a top speed of 72 m.p.h. the machine proved to have exceptional manoeuvrability, and Jungmeister requested that it should be released for duty with his unit, but Zalewski insisted upon modifications to improve performance still further. These consisted of redesigned wings of slightly greater span and area, installation of a Gnome Monosoupape 100 h.p. engine, and armament for the observer in the front cockpit by means of a light machine-gun mounted to fire above the propeller. Test flights confirmed the wisdom of the alterations, for the speed was now 82 m.p.h. and the machine was capable of out-turning even the agile Nieuport single-seaters.
   The S.Z. No. 1 joined the strength of the 4th Squadron, 4th Wing of the Imperial Air Service, based in the Baranovitche region, in early November, 1916, and became the personal mount of the Commander, Col. Jungmeister. Unfortunately, its operational career was short, for after a few sorties a forced landing due to engine failure occurred, and the resultant damage was never repaired owing to the start of the Revolution. The political upheaval also prevented completion of a three-seater 200 h.p. Army reconnaissance bomber quadruplane, developed from the S.Z. No. 1 and under construction at the Central Experimental Aerodrome at Cherson, on the Black Sea. A detailed design study for a giant quadruplane bomber with four 200 h.p. engines was abandoned for the same reason.
   Although there was little obvious difference between the original S.Z. No. 1 quadruplane and the machine in its modified form, the latter was often referred to as the S.Z. No. 2, and to further complicate the issue Zalewski later re-designated these two forms as ‘W.Z. III’ and ‘W.Z. IV’ (Wladyslaw Zalewski), having taken into account some earlier designs. The incompleted three-seater bomber became ‘W.Z. V’.

As already mentioned, the ‘Russki Vityaz’ was lost by mid-air collision in the 1913 military trials, but Sikorski had its successor under construction at the time, utilising the test results and knowledge gained to build the largest machine of all, which he named after a tenth-century hero of Russian folklore. The ‘Ilya Muromets’ had a wingspan of no less than 113 ft. and was 67 ft. in length, with a loaded weight of about 4 3/4 tons, power being provided, as before, by four of the well-tried 100 h.p. Argus water-cooled engines driving tractor propellers. Although similar in layout to the earlier machines, the ‘Ilya Muromets’ had a much shortened front fuselage with the crew cabin only just protruding over the wing leading edge, and for initial test-flying the outboard engines were mounted higher than the inboards. The wings were not staggered and ailerons with an increased chord at their extremities were fitted to the upper wing only, while the considerable overhang of the wingtip extensions had bracing in the form of outwardly-splayed interplane struts. The undercarriage consisted of two pairs of wheels with a secondary precaution of twin skids extending well in front of the axles and fuselage nose, each skid stiffened by a strut rising upwards and backwards to form an apex with the leading centre-section struts under the top wing. The entire airframe was of wood, wire-braced and fabric covered. An unusual feature of the machine took the form of two auxiliary lifting surfaces, fitted aft of the wings. The cabin of the ‘Ilya Muromets’ was spacious and well-equipped, including a dining room and pantry, toilet, dynamo lighting, and heating piped from the engine exhausts via an external air intake. Passengers with an adventurous turn of mind could obtain some very fresh air by visiting the promenade deck, complete with safety rail, on top of the fuselage!
   On December 11th, 1913, the ‘Ilya Muromets’ became airborne for the first time, flying from the snow-covered Komendantski airfield on the outskirts of St. Petersburg, a ski undercarriage having been fitted in place of the wheels. Trouble developed immediately, for the lift generated by the auxiliary lifting surfaces had been seriously underestimated, and the great machine reared up, stalled and crashed, smashing the port wings. Fortunately, the speed at impact was low, and after five days of repair the flight trials were resumed, this time minus 345 sq. ft. of auxiliary lift!
   Under-powered, laterally unstable and requiring a pilot of some skill and not a little physical development, the ‘Ilya Muromets’, or ‘I.M.’ as it was becoming known, had exceptional load-carrying capabilities, proved by Sikorski himself on February 12th, 1914, when he inched the huge aircraft to just under 1,000 ft., carrying fifteen passengers and his dog ‘Shkalik‘ a total payload of nearly 3,000 lb. - on 400 h.p. Sikorski made another flight soon after this epic, with eight passengers, when he cruised from Komendantski to Gatchina, Tsarskoe Selo, and return, at a height of 3,280 ft., remaining airborne for 2 hr. 6 min. Imperial recognition followed, for Tsar Nicholas II inspected the ‘I.M.’ at a Krasnoye Selo military parade, being no doubt pleased to note the Imperial Eagle motif gracing the front of the crew cabin. Impressed by the machine’s obvious war potential, the Tsar ordered it to be produced in numbers for the Imperial Russian Air Service, the Central Board of the General Staff immediately drafting an order for 10 to be constructed by Russo-Baltic, delivery to be made by March, 1915. This order had been anticipated, and work on a production prototype, the ‘I.M.’ Type A, was already well advanced, but by this time the tension between Germany and the ‘Entente Cordiale’ had increased, cutting off the supply of German aero-engines and spare parts, and Sikorski was forced to fit French Salmson engines to the ‘I.M.’ Type A. These radial engines developed 150 h.p. but did not have the reliability of the Argus, the latter having such a reputation that ‘second-hand’ units were often fitted in preference to the new French engines. Nevertheless, the ‘I.M.’ Type A made a remarkable flight on June 18th, 1914, when it remained airborne for 6 hr. 33 min. with seven persons on board. The original prototype was re-engined with Argus power units as stocks permitted, flying with two 132 h.p. engines outboard and two 140 h.p. units inboard on June 17th, 1914, when it made a long sortie to Kiev from its St. Petersburg base, returning on the 29th of that month. As a result of this outstanding flight, the machine was re-named ‘ Kievski ’.

The first months of the war brought trouble for the ‘Ilya Muromets’ bombers. The General Staff regarded these machines highly, as did the Tsar himself, and this led to a further order for 32 of the huge aircraft, Russo-Baltic receiving an advance of over 3 million gold roubles for expansion of production facilities. The first three ‘I.M.s’ had been sent to the North-Western Front on August 26th, 1914, for operational trials, but nine weeks later the second order was cancelled, a report stating that the ‘I.M.’ was unsuitable for further development for military use. It is highly probable that the initial burst of enthusiasm did not take into account the inevitable teething troubles of the aircraft and the fact that its pilots needed special training to handle it.
   In December the Supreme Command of the Russian Armed Forces received a cable: ‘The I.M. aeroplanes are unfit for military purposes. Do not send them to the Front. Do not order more of them. Cancel existing order.’ As a result of this cable, the balance of the first order for ten machines was indeed cancelled. To Sikorski and Russo-Baltic this was a bombshell, and the Chairman of R.B.V.Z., the retired Lieutenant-Commander M. V. Shidlovski, hurried to the Secretary of the War Ministry with a bitter protest, to such effect that the Commander-in-Chief, Grand Duke Nikolai Nikolayevich, consented to a series of operational tests of the ‘I.M.’ to decide its fate.
   The R.B.V.Z. proposed the formation of all available machines as one squadron, and the supervision by themselves of maintenance, and of ground crew and aircrew training. This recommendation was accepted, and the responsibility of the scheme laid firmly at the feet of Shidlovski, who was given command, returning to active service with the rank of Major-General. Officially formed on December 10th, 1914, this unit became known as the E.V.K., Eskadra Vozdushnykh Korablei, or 'Flying Ship Squadron' a sly reference to its Commander’s former service in the Navy! Equipped with the first three machines, the squadron soon felt the benefit of Shidlovski’s outstanding ability as an organiser, and within a short time it possessed its own workshops, school, photographic report section and many other facilities. Efficient bombsights were developed and equipment modified and improved, Shidlovski later claiming, with some justification, that ‘The bombing of the “I.M.s” is vertical artillery fire, and we reached 60 to 90 per cent of hits ’.
   By the end of 1914 three ‘I.M.s’ were in service. The third machine was fitted with four Argus engines, as in the prototype, but its wingspan had been slightly reduced and the cabin nose made more pointed. This version was classified as Type B, and only four of these were built. It is reported that the Argus engines of the prototype were later fitted to at least four other machines, and that these four power units amassed a total of over 700 flying hours during a period of some two and a half years.
   ‘The Flying Ship Squadron’, operating from Yablonna, near Warsaw, ensured the continued existence of their machines by very effective bombing and reconnaissance sorties, which, early in 1915, evoked a report by General Odeshilidse in glowing terms, serving to underline the decision to reinstate the second production order.

At the beginning of 1915 the first Sikorski S.16 two-seater biplane scout emerged from the Russo-Baltic Works, designed to fill a requirement for an ‘Ilya Muromets’ escort fighter, although the bombers were soon to prove quite capable of looking after themselves. The S.16 was a small machine, having a wingspan of only 27 ft. 6 in., and unusual in that both pilot and observer were seated one behind the other in a single cockpit. The specification had called for a 90-110 h.p. Le Rhone rotary engine, but since these power units were in short supply and the S.16 was somewhat experimental, the 80 h.p. Gnome engine had to be installed, and once again an excellent Sikorski design suffered the effects of underpowering. Two more examples were completed in March, 1915, and delivered for trials to the bomber squadron where the pilots received them with enthusiasm, no doubt pleased to fly an aircraft which did not require large amounts of muscular effort.
   In September a Government contract was signed with the R.B.V.Z. for eighteen S.16 aircraft, the first being delivered in December and seven more at the beginning of 1916. Unfortunately, by this time, the S.16 was outclassed by the German Fokker D.II and D.III, and following a highly critical report made by a member of the Russian Parliament, further production was halted. Alternatively fitted with a 100 h.p. engine and with the Russian-manufactured 60 h.p. Kalep engine, the S.16 was interesting in many respects - its propeller was designed by Professor Zhukovski, the most important point being that it provided one of the world’s first examples of an aircraft armed with a machine gun synchronised to fire through the propeller disc, the synchronising gear having been designed by Lavrov, an ‘Ilya Muromets’ pilot and engineer. Other Russians were working on this type of device, notably Smyslov for the Dux Works and Lt.-Cdr. V. V. Dybovski, the latter collaborating with Warrant Officer F. W. Scarff to produce an efficient gear used on early Sopwith 1 1/2 Strutter aircraft.
   It should be mentioned that the Lavrov gear was far from perfect, suffering numerous failures when in use, this presumably being the reason for some S.16s having a Lewis gun on an upper wing mounting in addition to the fixed gun with Lavrov gear. Among the S.16s produced, several structural differences were apparent, some machines having ailerons on upper and lower wings and a raked fin and rudder, others with ailerons on the upper wing only and a fin and rudder of curved profile. One machine was equipped with floats, and in winter conditions a ski undercarriage was generally fitted, as with other Russian aircraft. The S.16 had a good performance for its time, with a service ceiling of 10,000 ft. and a maximum speed of 73 m.p.h., but no record can be found of operational use, and although one or two S.16s may have been used at the Front, its probable role was that of a trainer and general-purpose aircraft. An armoured version of the S.16, the S.17, powered by a 150 h.p. Sunbeam engine and intended for ground attack duties, did not proceed beyond the prototype stage.