SPL (Hydro-1) by I.V.Chetverikov

General Information
Type SPL, Hydro-1
Function Specialized amphibian
Year 1934
Crew 2...3
Type M-11
Power 100hp
Length 7.4m
Height ?m
Wingspan 9.6m
Wing area 13.4m2
Weights and loads
Empty 592kg
Loaded (normal) 800kg
Loaded (overload) 879kg
Wing load (normal) 59.7
Wing load (overload) 65.7
Power load (normal) 8.0
Power load (overload) 8.8
at 0m 186km/h
at 2500m 183km/h
Landing 85km/h
Landing 14sec
Takeoff 12sec
Practical 400km
Flight Endurance 2h
Ceiling 5400m
1000m 3.9min
2000m 8.7min
3000m 15.3min
4000m 25.5min
5000m 50.0min
Fuel+Oil 60+10kg
Gidro-1 in civil markings
66k color photo of Gidro-1 from 'Hydroplane for Submarine' by V.Kondratiev

The idea of aircraft cooperation with submarine on remote naval theaters developed in few directions:

Third option was explored in Great Britain (late 20's), but aircraft turned to be oversized for contemporary and projected submarines. In addition, British plane had poor seaworthiness. Soviet designers, in addition, had to rely mostly on the wood and steel tube rather than light alloys.

In 1931 I.V.Chetverikov made a bold effort to overcome the problem by making aircraft fit in a 7.5m long 'hangar' tube (diameter 2.5m). Strict demands were applied to aircraft flight readiness and storage time - 3 to 5 minutes. Those demands could not be fulfilled for no cost. Tail surfaces area was small and its lever arm was quite short, resulting in insufficient stability. Limited engine power demanded to hide crew in deep cockpit to keep airdynamic good and to lower the gravity center. View field for the observer was quite limited. Aircraft carried neither armor, armament or bomb load, and had no provisions for catapult launch.

First prototype (OSGA-101) had no provision for wing folding, but used as a test platform of the aircraft layout. The SPL was finished in December 1934. It was almost identical to the predecessor, but was slightly smaller.

SPL on Moscow river, Townend ring removed
13k b/w SPL during trials on Moscow River (WWW.AVIATION.RU)

Tail stabilizer was made as a biplane box to provide sufficient surface area within restricted size. Wings could be folded backwards without disconnecting the control wires. Sliding rear engine struts allowed to 'sink' the engine assembly into the tail boom free space - also without disconnecting any controls.

In the beginning of trials SPL was flown with light aluminum Townend ring on the engine, which was later removed without much harm to performance. Trial program was fulfilled on August 29, 1935.

SPL is folded, ready for container
13k b/w SPL 'folded' drawing ('Hydroplane for Submarine' by V.Kondratiev)

SPL could be prepared for flight in 4...5min and 'packed' into watertight container in 3...4min. As demanded, container size was 7.45mx2.5m diameter. Despite all demands were fulfilled, it was clear that tiny aircraft provides no 'room' for development and as military plane will be obsolete in short time. It was renamed 'Gidro-1' (Hydro-1) and received Aeroflot markings.

In 1936 Gidro-1 was demonstrated at Milan International Airshow.

Small aircraft had a record ceiling for its class - 5400m. Pilot A.V.Krzhizhevskij (who performed trial program on the SPL) established two other records on this plane:

  • September 21, 1937: speed 170.2km/h on 100km route
  • October 7, 1937: range 480km
  • SPL aircraft, early trials period
    SPL (22k b/w) as seen at many sources including "History of aircraft construction in the USSR", Vol.1 p.528


  • "History of aircraft construction in the USSR", Vol.1 p.341-342;
  • ....

  • Created February 25, 2000 Back to
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