Technical data
Type RK, LIG-7
Function Experimental
Wing position Retracted Extended
Year 1937
Crew 2
Engines 1*100hp M-11
Length 7.34m
Wingspan 11.3m
Wing area 16.56m2 23.85m2
Empty weight 667kg
Loaded weight 897kg
Wing Load (kg/m2) 54.2 37.6
Power load (kg/hp) 9.0
Speed at 0m 150km/h 144km/h
Landing Speed 100km/h 75km/h
Landing Roll 210m 12sec 110m 9sec
Takeoff Roll 250m 14sec 135m 9sec
Range 400km 370km
Flight Endurance 3.0h
Ceiling 2900m n/a
1000m 7.5min n/a
2000m 19.5min n/a
Fuel+Oil 70kg

RK, LIG-7 by G.I.Bakshaev

24k b/w drawing "History of aircraft construction in the USSR", Vol.2 p.117

This was one of the weirdiest aircraft ever to be flown. Otherwise conventional two-seat low wing monoplane with a 100hp M-11 engine, it was technology demonstrator for telescoping wing (so RK designation).

RK used a thin wing with a high-aspect ratio was to be used for cruising flight. For take-off and landing six broad-chord wing sections would be extended from each side of the fuselage to 2/3 of the wingspan. Each section was 500mm wide, 40mm was consumed by necessary overlap of sections. Sections were made of plywood, with support rib on inboard side and light frame on the outboard side. Telescoping wing was retracted and extracted by steel wire, driven manually from the cockpit. In flight all retractable sections were completely hidden inside the fuselage.

Outer wing sections (1/3 of span), carrying ailerons, were not covered with broad sections.

RK was finished and flown in 1937. All elements functioned properly. Moreover, in-flight wing retraction (20 to 30sec) and extraction (30 to 40sec) was easier to perform than while on land. Designers took into account wing load effects properly, what is not so trivial. Right/left symmetry was perfect. No handling peculiarities observed during in-flight wing extraction and retraction.

Effect on takeoff/landing characteristic was impressive (see table), technology was tested and proved to be reliable. Of course on small and slow aircraft (when the wing contributes only 20% of total drag) positive impact on performance was not as significant as it could be on high speed combat planes.

In 1938 G.I.Bakshaev came up with proposal for record setting high-speed aircraft with M-105 engine. This project got governmental support. Later same year G.I.Bakshaev received a Governmental Order to built single-seat fighter utilizing RK technology and present it for trials in 1940. But this is a different story...

RK-I push-pull

  • "History of aircraft construction in the USSR", Vol.2 p.116-118;
  • RK, Bakshaev

  • Created January 25, 1996
    Modified October 29, 1998;
    Back to
    Main Gate