All the World's Rotorcraft
Part I |
Part II |
Part III |
Part IV |
Part V
1. It all began with an autogyro
On August 24, 1907, in France, a four-rotor helicopter designed by the Breguet brothers and Professor C. Richet became airborne for the first time. In November same year a tandem twin-rotor helicopter designed by Paul Cornu climbed to a low altitude. In 1914 E.Mooford's helicopter made its first low-level flight in Great Britain, and in 1922, in the USA, a helicopter designed by the Russian emigrant Professor George de Bothezat succeded in lifting as many as four persons into the air. In May 1924 a French helicopter designed by Etienne Oemichen completed a 1-km circuit. It should be noted that early helicopters designed outside Russia had a complex multi-rotor layout and, as a result, an unreliable design coupled with unsatisfactory stability and handling characteristics. Lightweight and high-strength aviation materials began to become available in the late '20s. Their introduction made it possible to design and manufacture rotors of the required dimensions with improved aerodynamics producing sufficient thrust to lift a helicopter into the air. This enabled designers to abandon the cumbersome and complex multi-rotor layouts in favour of the simpler and more reliable single-rotor and co-axial (contra-rotating) configurations. The development of new lightweight engines with improved power-to-weight ratios and specific fuel consumption, as well as gearboxes for torque transmission from high-speed engines to the main rotor and the introduction of the swashplate, brought closer the era of practical application of helicopters. In the '30s and '40s, know-how in the field of helicopter design was accumulated both in the Soviet Union and abroad; this knowledge became a springboard for a transition to a new level in rotorcraft design. While helicopter designers were busy researching, autogyros came on the scene, filling the resulting void. The idea of the autogyro with an autorotating rotor which does not lose speed in the event of an in-flight engine failure came to the Spanish engineer Juan de la Cierva who was to gain fame as an aircraft designer. The properties of the autogyro place it in an intermediate position between the aeroplane and the helicopter. Given the level of theoretical knowledge and the technologies available by then, it was easier to build a safe and sufficiently reliable autogyro than a helicopter. The main rotor autorotating under the influence of the incoming flow did not require a complex power train, as in the case of the helicopter. The use of articulated rotor blades hinged to the rotor head ensured enhanced dynamic strength of the rotor and gave the autogyro adequate stability in flight. In the event of engine failure the rotor continued to autorotate, enabling the aircraft to make an emergency landing with a short run. J. de la Cierva built several autogyros. The C-4 autogyro with articulated blades was the first to make a successful short-duration flight in January 1923. The best-known autogyro is the C-30 of 1934 which was produced in quantity in Great Britain. Cierva's autogyros were built under licence in France, Germany, Japan and the USA. During that period autogyros with articulated rotors were designed in our country, too. The first of these was the KASKR-1 built by the enthusiast designers N.I.Kamov and N.K.Skrzhinsky. It made its maiden flight on September 25, 1929 at the hands of I.V.Mikheyev, with its designer N.I.Kamov in the rear cockpit. The design of the aircraft resembled the well-known Cierva C-8 autogyro. Shortly afterwards the young designers built an improved model, the KASKR-2 (1930) based on the KASKR-1. NII VVS (Air Force Scientific and Research Institute) specialists participated in the evaluation of the autogyros' performance. Between 1929 and 1931 the autogyros made 79 test flights. Among the members of the KASKR group was - as a probationist - M.L.Mil', then a student of the Novocherkassk Polytechnical Institute. In 1930 a specialised autogyro design group was formed within the framework of the Experimental division of TsAGI (the Central Aero- and Hydrodynamics Institute) - to be precise, in the SOK (Special Designs Section). N.I.Kamov began working in this group in 1931. In 1933 the SOK was transformed into a Special Designs Division (OOK), within which three brigades were formed for the development and construction of autogyros. The brigades were headed by N.I.Kamov, V.A.Kuznetsov and N.K.Skrzhinsky. The aerodynamics brigade was led by M.L.Mil'. Successful autogyro development in the USSR had a positive effect in speeding up the work of the helicopter group of the Experimental Hydrodynamics Division of TsAGI. This group headed by B.N.Yur'yev was engaged in the construction and testing of the first Soviet experimental helicopter designated TsAGI 1-EA. This single-rotor helicopter with a rigid main rotor was developed under the leadership of A.M.Cheryomukhin, who also became its first pilot. In 1932 at a small TsAGI airfield near Ukhtomskaya railway station of the Kazan' railway in the Moscow region, Cheryomukhin reached an altitude of 605m. Incidentally, the official helicopter altitude record achieved by the Italian D'Ascanio helicopter stood at that time at just 18 meters. Autogyro testing was performed at the same location. In honour of the test flight of the TsAGI 1-EA helicopter and in memory of its pilot A.M.Cheryomukhin (who eventually became Doctor of Technical Sciences) a memorial sign in the shape of a rotor blade and a silhouette of a helicopter climbing in a spiral has been erected on the territory of the former airfield in Ukhtomskaya (currently the territory of the Kamov company). Information about our country's autogyros and the USSR's first helicopter is presented in the permanent display and in the archives of the Kamov company's "People's Museum". The TsAGI 1-EA paved the way for the TsAGI 3-EA and TsAGI 5-EA experimental helicopters. These were followed in 1938 by a compound rotary-wing machine featuring a transverse layout with a wing, two tractor propellers at wingtips and one main rotor. The helicopter, which was allocated the designation TsAGI 11-EA, was designed by I.P.Bratukhin. The "Omega" helicopter built in 1940 by the Bratukhin OKB became the first nationally-designed helicopter suitable for quantity production. It had a transverse twin-rotor layout with fully-articulated rotors. Later models included the "Omega-II", G-3, G-4, B-5, B-9, B-10 and B-11 helicopters. The Bratukhin OKB was closed down in 1951 because it failed to solve the complex problems associated with the dynamics of the rotor system of the transverse-layout helicopter. Progress in the work on helicopters within TsAGI, in turn, had a noticeable influence on the achievements in autogyro design. The A-7 autogyro successfully passed its State acceptance trials in 1937 thanks to the scientific, experimental and methodological experience amassed in TsAGI and required for the development and testing of rotary-wing aircraft, and also thanks to the perseverance and talent of its designer. In the beginning of 1940 aircraft factory No 290, the first to be tasked with autogyro production, was established on the base of the facilities of the Podosinki airfield near Ukhtomskaya railway station. N.I.Kamov, the man behind the idea, was appointed the factory's chief designer and director, while M.L.Mil' became his deputy. Factory No 290 also produced the military version of the A-7 autogyro, designated A-7-3a and intended for reconnaissance and artillery spotting. A unit equipped with these autogyros operated within the framework of the 24th Army near the town of Yel'nya during the initial period of the Great Patriotic War. The autogyro had a crew of two - a pilot and a gunner. The armament comprised three 7.62-mm machine-guns, bombs and RS-82 unguided rockets. The A-7-3a was powered by a 480hp engine and had impressive performance: take-off weight was 2300kg, maximum payload 800kg, top speed 218km/h, endurance 4 hours and service ceiling 4700m. In comparison, J. de la Cierva's C-40 autogyro built in 1938 was powered by a 175hp engine, had take-off weight of 885kg, maximum payload of 272kg and top speed of 193km/h. Regrettably, the war caused the production of autogyros to be terminated. The construction by N.I.Kamov of a prototype AK autogyro with "jump-start" capability was discontinued in 1943. By that moment its creator possessed sufficient knowledge and experience to design the lifting system: main rotor blades with tubular steel spars, a rotor head with articulated blade attachment, automatic damping of the flapping movement of the blades, a system for controlling rotor thrust etc. The autogyro possessed adequate stability and controllability in flight. M.L.Mil' and V.A.Kuznetsov took part in the design work. As Mil' put it, there was just one step to be made from the AK autogyro to a helicopter; all that remained was to design the main gearbox for transmitting torque from the engine to the main rotor. After the end of the war, countries with a highly developed aircraft industry, including the USSR, gave their preference to the helicopter capable of hovering flight, of moving slowly in any direction and of vertical take-off and landing. Hence the autogyro was forgotten for many years. However, it is notable that it is the pioneers of autogyro construction in our country - N.I.Kamov, N.K.Skrzhinsky, M.L.Mil', V.A.Kuznetsov et al - who soon became the key figures in the field of helicopter construction.
From "OKB Kamov. 50 years" by G.I.Kuznetsov
The great Russian scientist in helicopter aerodynamics,
the founder of soviet helicopter production
Designer, pilot and scientist in fixed-wing
and rotary-wing aviation
The first soviet helicopter designer