Sviatogor, V.A.Slesarev

I
t was the largest aircraft built in Russia before the revolution. Heroic effort of designer and his team resulted in failure - but it played considerable role in large aircraft development all over the world.
Construction started in 1913 (4-5 years before similar attempts were undertaken in Germany). It was a wooden biplane with fabric covered fuselage and wings. Two enormous 6m diameter pusher propellers (300-400rpm, supposed to be more effective on takeoff) were installed between the wings. To provide arc for such a propellers landing gear was also quite enormous: four wheels of 2m (rear) and 1.5m (front). Despite the size, wheels were light and aerodynamically clean - as well as the whole landing gear.
The 'key' idea (and the wrong one!) was to place engines inside the fuselage to provide in-flight access. This advantage was overshadowed by complicity of transmission, specially for such a powerful engines. Finally, those transmissions caused fatal complications for the project.
Pilot and observer occupied nose section of the fuselage. Fuel tanks were located inside the fuselage close to the center of gravity. Unusual for the historic period (and advanced!) feature was 'normal' location of the center of gravity - on 35% of wing chord. This allowed to unload the tailplane (~20m2) whole tail structure, saving some weight.
Suggested armament included high-rate cannon in the nose and other.
Project was studied by several 'commissions', resulting in positive recommendation. But there were no financing before the outbreak of the war, when wealthy landlord E.M.Malynskij (member of the All-Russian Airclub) offered his support (100.000 roubles!). Contract was signed with V.A.Lebedev enterprise, and full-speed assembly started in December 1914.
War with Germany put a cross on 300hp Mersedes engines. V.A.Slesarev tried to restore some taken from shot down Zeppelin, but those were unrepairable. He was forced to look for other options - and choose French 220hp Renault engines. They arrived only in January 1916...
At the time not only E.M.Malynskij's 100.000 roubles were gone, but also 65.000 of personal V.A.Slesarev's money. Too optimistic weight estimations by V.A.Slesarev resulted in 1500kg overweight of the construction. Another expert board, including N.E.Zhukovsky, A.A.Arhangelsky, V.P.Vetchinkin and G.I.Lukianov provided detailed expertise of the project, produced another positive conclusion - despite all problems and weaker engines, aircraft should fly at 114km/h.
Despite luck of money construction continued (probably designer found some loan).
In March 1916 tests started with transmission problems. Several techniques were tried, among them only belts did not fail at first try. In November during taxi trials (takeoff was not achieved) aircraft hit a drainage. Rear half of landing gear and right propeller were damaged. Once damage was fixed, transmission belts started to give up.
Colleagues suggested to V.A.Slesarev to move engines from the fuselage and get rid of faulty transmissions. But he refused, insisting that in this case aircraft will lose its individuality. The result was lose of interest in 'Sviatogor'. Project stalled...
After Slesarev's death in 1921, engineer E.N.Sivalnev suggested to re-initiate the project but with normal engine location. Two years of paperwork resulted in nothing, and in 1923 'Sviatogor' was dismantled.
'Sviatogor's airframe was more advanced than contemporary 'Ilya Mouromets'. It was the aircraft that could have much longer service career. But whole assortment of problems - technical, personal and others - resulted in failure.
References :
  • "History of aircraft construction in the USSR" by V.B.Shavrov, Vol.1 p.82
  • Technical data
    Type 'Sviatogor'
    Function Experimental
    Year 1916
    Crew 3-?
    Engines 2*300hp 'Mersedes' (project)

    2*220hp Renault (used)
    Length 21.0m
    Wingspan 36.0m
    Wing area 180m2m2
    Empty weight (project) ~3200kg
    Loaded weight (project) 6500kg
    Wing load 36.1kg/m2
    Power load 10.8kg/hp
    Speed (project) 100+km/h
    Flight duration (project) ~30h
    Ceiling (project) 2500m
    Modified October 10, 1997
    by Alexandre Savine;
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