General Information
Type OSGA-101
Function Experimental amphibian
Year 1934
Crew 2
Type M-11
Power 100hp
Length 7.6m
Wingspan 9.6m
Wing area 17.0m2
Weights and loads
Empty 630kg
Loaded 880kg
Wing Load (kg/m2) 52
Power load (kg/hp) 8.8
Maximum at 0m 170km/h
Cruise 130km/h
Landing 75km/h
Landing 16sec
Takeoff 14sec
Practical 400km
Flight Endurance 3h
Ceiling 3500m
Fuel=oil 60+10kg
OSGA-101 side view
67k b/w drawing, derived from illustration to 'Modelist-Konstructor' articles, available at Base-13

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.

As a result, the amphibian was much closer to sport planes than to military aircraft. Intended to participate in trials of the 'Cheluskin' icebreaker as an shipborn flying boat, OSGA-101 had no provision for wing folding (half-wings were detachable , 6 bolt locks each) demanded for use on the submarine. Segmented ailerons were large and covered almost full wing span. Inboard sections of the ailerons served also as a flaps.

The hull shape with high bows was very successful, allowing operation of small plane even in stormy weather. Tail section was just an uncovered wire-braced steel tube frame. Tailplane and rudder had thin-wall steel tube frame with fabric cover. The M-11 engine with the U-2 type propeller was installed on hight struts above the wing. This was dictated by necessity to protect the powerplant from water. Angular Townend ring was wielded from the thin stainless steel to reduce engine drag.

As mentioned, OSGA-101 was planned for 'Cheluskin' icebreaker navigation. Team had only eight months to design, build and test the aircraft - and failed. Ill-fated ship left for its first and last Polar Navigation carrying V.B.Shavrov's Sha-2.

OSGA-101 was ready in Spring 1934 and flown by N.Kastanaev on Moscow River. During trials Townend ring was removed - it made no advantages at relatively low aircraft speed. Articulated wing tapering resulted in insufficient stability at large attack angles due to flow instability. This effect was not well understood. Effort to cure instability by increase the wing dihedral to 5° did not help, but large and effective ailerons allowed to keep aircraft straight during landing.

Trials of the prototype confirmed all expectations of the designer. Now all efforts could be concentrated on the folding SPL sibling. Construction of this aircraft was going almost neck-in-neck with the OSGA.

As an experimental plane of mid-30's, OSGA-101 was painted all-silver and carried no insignia.

SPL, Gidro-1
  • "History of aircraft construction in the USSR", Vol.1 p.527;
  • 'Flying boats of I.V.Chetverikov' by L.Egenburg;
  • 'Hydroplane for Submarine' by V.Kondratiev
  • OSGA-101

  • Created February 10, 2000 Back to
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