At the very end of the thirties, the French naval forces ordered the development of a promising helicopter that could be used for reconnaissance, patrolling and countering submarines. In the early forties, such a machine could have entered service - but the war began, and the Gyroplane G.20 was left without a future.
The birth of the project
In 1938, the famous aircraft manufacturer Syndicat d'Etudes de Gyroplane left its co-founder and technical director René Doran. He soon founded his own firm Société Française du Gyroplane (SFG or Gyroplane), in which he planned to continue working on promising designs.
In the same year the company "Zhiroplan" received the first state order. The Navy wanted a helicopter suitable for use in naval aviation. With its help, it was planned to carry out patrolling and reconnaissance, transport commanders and documents, as well as search and destroy enemy submarines. The car was supposed to have high flight characteristics, as well as carry machine-gun and bomb armament. The new project received the designation Gyroplane G.20. In a number of sources, he is also called Dorand G. II - by the name of the chief designer.
R. Doran decided to use some of the ideas and solutions previously tested in his previous job. In particular, it was planned to use a carrier system with two coaxial propellers. In addition, new interesting solutions were proposed regarding the design of the airframe, power plant, weapons, etc.
As the development progressed, some of the main ideas of the project were revised. So, at the final stages, the customer and the developer abandoned weapons, and also reduced the crew. Such measures led to a serious simplification of the design, but the converted gyroplane helicopter could now only conduct reconnaissance and carry small loads.
Design features
Helicopter G.20 / G. II received a cigar-shaped fuselage, made on the basis of a metal frame. The nose part received plexiglass glazing of the maximum possible area, and the other elements of the fuselage were covered with sheet aluminum. There was a V-shaped tail with linen sheathing. In the bow of the vehicle was a tandem cockpit. The central compartment housed the rotor gearbox and the power plant. In the first version of the project, there was a compartment for bomb weapons under it.
The power plant consisted of two Renault 6Q-04 piston engines with a capacity of 240 hp each. They were placed behind the axis of the screws and connected by a gearbox of a special design. The latter combined the torque of two motors and divided it between two counter-rotating screws. In the event of a breakdown of one of the engines, the gearbox automatically switched to operating and ensured the continuation of the flight.
The first version of the G.20 project used the original bushing design of the carrier system. Instead of an axis and other devices, a high pipe of large diameter was used - it was proposed to place a shooter with a machine gun in it. Outside on this tube were the bearings of two screws with a drive. With the further development of the project, the pipe was replaced with a simple axis of a smaller diameter.
Two three-blade propellers were placed 650 mm apart. The screws had different diameters - 15.4 m at the top and 13 m at the bottom. Due to the difference in size, it was planned to exclude the overlap of the blades when they move vertically. The blades were proposed to be made of an aluminum-magnesium alloy. A design was developed with a box spar forming a nose and a trailing edge attached to it.
The main landing gear was located behind the cockpit. In flight, they retracted by turning back into the niches of the fuselage. A caster wheel was located under the tail boom.
Initially, the crew of the G.20 was supposed to include three people. The pilot and gunner were in the cockpit. The second shooter was placed inside the screw hub. Access to all workplaces was provided through the side hatch. Subsequently, the crew was reduced to two people in the cockpit.
The combat version of the helicopter could carry air or depth charges of small and medium calibers. The compartment for them was located on the bottom, directly under the carrier system. For self-defense, 1-2 machine guns were provided, in the cockpit and on the bushing. It is curious that the initial arrangement of weapons made it possible to provide free shelling of almost the entire upper hemisphere.
The fuselage length of the new helicopter exceeded 11 m, the height was 3.1 m. The empty weight reached 1.4 tons, and the normal take-off weight was 2.5 tons. The maximum take-off weight was 500 kg more. According to calculations, the "ziroplane" was supposed to develop a maximum speed of up to 250 km / h (cruising 165 km / h). The ceiling is 5 km, the flight range is 800 km.
Protracted construction
The G.20 project of the second version, without weapons, was ready by the beginning of 1940, and soon the Gyroplane company began construction of a prototype. The assembly was carried out at the plant in the city of Getary (dep. Atlantic Pyrenees, New Aquitaine). The construction was not completed until the German attack in May, and the finished structures, along with the backlog, had to be evacuated to the town of Chambery (dep. Savoie). After that, R. Doran gave way to the head of the construction to Marcel Wüllerm.
The fall of France and subsequent events seriously hit both the Gyroplane G.20 project and the entire aircraft industry. Construction slowed down dramatically and almost stopped. In 1942, German troops occupied the remaining regions of France, and the unfinished helicopter became their trophy. The invaders were not interested in this machine, but did not prohibit further work. However, the main problem now was not prohibitions, but the lack of orders, funding and required resources.
For lack of prospects
For several years, the future of the "girplane" remained in question. The hope for a full-fledged resumption of work appeared only in 1944-45. However, even after the liberation of France, construction could not pick up pace for a long time. Economic and production difficulties were again evident.
The first prototype helicopter was completed only in 1947 - seven years after the start of construction. The finished car was tested on the ground and demonstrated to representatives of the recreated French army. The military showed limited interest. They were attracted by the unusual architecture and exterior of the car, rather high design characteristics, retractable chassis and other features. However, the order for the continuation of the work was not issued.
After the completion of construction, the G.20 had to undergo testing and fine-tuning, which took money and time. At the same time, the result of the project was not obvious. At the same time, quite successful helicopters have already been created abroad, which could be purchased right now. As a result, the French armed forces decided not to finance further work on their own "giroplane" and to adopt foreign equipment.
SFG did not have all the necessary resources and therefore could not conduct the tests on its own. Moreover, due to financial problems, she could not even find a test pilot. As a result, by the end of 1947, all work on the Gyroplane / Dorand G.20 / G. II was canceled due to the lack of any prospects.
R. Doran and his colleagues did not give up and did not leave the industry, and SFG continued the design work. Soon she took part in the creation of the Bréguet G.11E and G.111 helicopters - in these projects they used some of the ideas borrowed from the G.20 to a limited extent. However, these helicopters did not make it to the series, but now for technical reasons.
