Flight, February 1926

THE “K.1" MONOPLANE
A Commercial Machine Constructed in Soviet Russia

   WE have of late been able to give readers of FLIGHT certain information regarding aviation in Soviet Russia, from which it will have been apparent that this country is fully aware of the importance of aviation - both commercial and military. Indeed, Soviet Russia is making a bold bid for a foremost position in the world of aeronautics.
   So far, Russia has done but little as regards the design and construction - although mention should be made of the successful Russian designer, Sikorsky, who constructed, some time ago, the forerunners of the Giant multi-engined aeroplane, and who is now producing aircraft in America.
   Recently, however, we learn that Soviet Russia has been giving more attention to the construction side of aeronautics, and that factories have been established where aircraft are being - or have been - constructed. We are able this week, through the courtesy of the Soviet Aircraft journal "Samolet," to give a brief description of one of these Russian-built aeroplanes - the "K.1."
   The "K.1" is a tractor high-wing monoplane of the enclosed cabin or limousine type, similar to the Dornier “Komet" monoplanes, which are employed on certain of the Russian air lines. It was originally constructed in one of the Soviet factories in 1920, under the very difficult conditions obtaining at that time. It was not until five years later, however, that the completed machine made its appearance as a commercial aeroplane under the title of R.W.Z.6. - K.1. K. A. Kalinin, who was a pilot himself in 1916, and who is now at the head of the Bureau of Construction, was responsible for the design of this machine.
   An interesting point regarding the construction of the K.1 is the use of steel tubes, which had been in stock in connection with the Voisin machines previously used in Russia, but since abandoned. These tubes were, of course, first tested in the laboratories and were found to be satisfactory for the purpose, and have been employed throughout in the construction of the fuselage, under-carriage and rudder. The wings and tail surfaces, however, are of wood construction. "Samolet" refers to the fact that M. Kalinin was helped considerably in the production of this machine by the workmen, who showed great interest and enthusiasm in its design.
   As will be seen from the accompanying illustrations, the fuselage of the "K.1" is of deep rectangular cross-section, with enclosed cabin, provided with a door and windows, for the passengers, located immediately beneath the wings, and with an enclosed cockpit for the pilot located high up in the fuselage at the leading edge of the wings.
   Communication is provided between the pilot's and passengers' compartments by means of a door. The covering of the fuselage from the engine to the rear of the cabin is sheet aluminium, while the remaining portion of the fuselage is fabric-covered.
   The engine, complete with accessories, is mounted on a special frame, which is attached to the fuselage by four bolts, and it is possible to remove this frame and replace it by another frame with a spare engine installed in about half-an-hour. Or, if desired, an engine of different make can be fitted. For instance, at present a 170 h.p. Salmson engine is fitted, but provision has been made in the design for replacing this engine by one of entirely different make, such as the 185 h.p. B.M.W., for which engine a special engine frame is employed, but which is attached to the fuselage by the same four bolts.
   The wings of the "K.1" form another feature, for M. Kalinin has adopted the elliptical plan form, which, although presenting certain difficulties from the production point of view, possesses good aerodynamical qualities. The wing section employed is the Prandtl No. 436.
   The wings, which are set at a dihedral angle of 6°, are built up in three sections, a centre panel mounted on the top of the fuselage, and two outer panels bolted to the former. Bracing is by two pairs of steel struts streamlined by aluminium fairings extending from the lower longerons of the fuselage up to the wings. The strut attachments to the latter are faired by neat aluminium boxes.
   An elliptical plan form is also employed for the horizontal tail plane and divided elevator, but the section is symmetrical. A small triangular vertical fin, to which is hinged a balanced rudder, is mounted above the horizontal tail plane. The angle of incidence of the tail plane, it should be noted, can be adjusted to meet variations of load. Wings and tail surfaces are fabric covered. Lateral balance is obtained by means of ailerons, which, it will be observed, are not particularly large.
   A conventional V-type undercarriage, with V-inter-strut bracing, is employed, the struts being steel tubes with streamline aluminium fairings. A special airscrew, designed by M. Kalinin and constructed in the R.W.Z.6 factory, is fitted.
   If required, the "K.1" can be adapted for hospital work, the cabin being altered to accommodate three berths, stretchers and other hospital appliances. Its adaptability is thus particularly suitable for the conditions in Russia.
   The "K.1" - which is the first machine employing steel tube construction to be produced in Russia - was completed in July, 1925, and on the 26th of that month made its first trial flight, piloted by the work's chief pilot, Kossinsky, with satisfactory results. In September the first flight with passengers was made to Moskva, via Charkov. The 430 kms. (266-6 miles) to Charkov was accomplished in 2 hrs. 45 mins. at an average speed of 156 k.p.h. (96-7 m.p.h.), and the 390 kms. (242 miles) to Orel in 2 hrs. 55 mins. The remaining 380 kms. (235-6 miles) to Moskva, against a strong headwind, took, also, 2 hrs. 55 mins. This was in the nature of its official trial, and after further various trials under a special commission, it was found to answer all requirements, and was therefore passed on for service on the civilian air lines.
   The principal characteristics of the "K.1" are :-
   Span 16-76 m. (55 ft. 0 ins.).
   Chord 3-50 m. (11 ft. 5 ins.).
   O.A. length 10-72 m. (35 ft. 2 ins.).
   Wing area 40 sq. m. (430-4 sq. ft.).
   Weight laden (approx.) 2,000 kgs. (4,400 lbs.).
   Wing loading 49-3 kgs. m2 (10-1 lbs./sq. ft.).
   Power loading 12-3 kgs./h.p. (27 lbs./h.p.).
   Speed range 60-160 k.p.h. (37-99 m.p.h.).
   Climb in 12 mins. 1.000 m. (3,280 ft.).
   Ceiling 3,000 m. (9,840 ft.).
   Gliding angle 1 in 9-2.
   Pull-up in landing 100-120m. (328-373 ft.).