Convertible Nord 500 Cadet (France)

5
At the end of the fifties of the last century, the first experienced tiltrotor with rotary annular channels of propellers first flew into the air. The first projects in this area were developed by the United States industry. At the same time, other countries have shown their interest in this type of aircraft. So, in the mid-sixties, the French convertiplane Nord 500 Cadet was put to the test.

The Nord 500 project was developed by Nord Aviation as an initiative. The purpose of these works was the creation of a light aircraft, capable of rising vertically into the air and moving on to horizontal flight. It was proposed to obtain similar characteristics using the Tiltduct scheme - the rotors were to be located inside the oscillating annular channels. With the help of such a machine, it was supposed to study various features of convertoplanes and later use the knowledge gained in new projects. If the Nord 500 project was successful, the development of aircraft of similar design suitable for full practical operation could begin.



Convertible Nord 500 Cadet (France)
Layout of the convertiplane Nord 500 during one of the exhibitions. Photo Airwar.ru


The development of a pilot project, which received the official designation Nord 500 or N500, as well as the name Cadet (“Cadet”), was launched in the early sixties. Over the next few years, French aircraft manufacturers carried out various studies and tests in wind tunnels, which were necessary to determine the most successful appearance of an aircraft. The formation of the overall scheme of the convertoplan was completed by the year 1965, when the first layout was built.

By this time, the developers decided on the main features of the design, and in the future the overall architecture of the aircraft did not change. At the same time, at the next stages of development, some minor changes were made to it, due to the need to install new systems and devices. Such improvements to some extent affected the appearance of the aircraft, but almost did not affect the basic technical characteristics.

In the middle of 1965, the first demo mock-up of a convertible glider was shown at the aerospace exhibition in Le Bourget. A full-fledged prototype of the new machine was built only in the spring of 1967 of the year. The first prototype was designed for ground testing on a special stand and on a leash. The company-developer did not plan to send this car in free flight. In the same year, a prototype for ground tests was shown at the Paris exhibition. Shortly thereafter, a second prototype was brought out of the assembly shop, which was to participate in the flight test program.


Scheme of the car. Figure Airwar.ru


According to available data, taking into account ground checks and tethered flights, the designers of Nord Aviation drew certain conclusions, after which the existing N500 project was finalized. As a result, the second prototype was noticeably different in its design from the first, although it was built according to the same scheme. It should be noted that both prototypes, for obvious reasons, also seriously differed from the first layout presented earlier.

The convertible Cadet was supposed to be an exclusively experimental machine, which to a certain extent reduced the requirements for it. There was the possibility of reducing the size and weight of the structure, and in addition, the experimental machine should not bear any payload. As a result, the aircraft had to get the minimum necessary set of onboard equipment, which to some extent reduced the complexity of the project.

An airframe of the original design was developed, which is a high-wing monoplane with a small elongation. The power set of the airframe was proposed to be made of metal. The sheeting also used metal sheets, but some elements of the structure, such as radar fairing, should have been made of plastic.


The prototype is on trial. Photo Klassiker-der-luftfahrt.de


The aircraft Nord 500 received a streamlined fuselage of variable cross-section. Its nose, which contained the cockpit, had a shape close to the drop-like one and differed in a reduced width. Behind the cockpit, the fuselage passed into the tail boom of great width and low height. In this part of the machine, assembly assemblies of the center section were provided. The tail boom served as the basis for the tail fin as a keel and stabilizer. Handlebars of height and direction were absent. The layout of the fuselage was simple. A large nasal volume was given under the location of the pilot and the necessary equipment, directly behind him were the main elements of the transmission, and a significant part of the tail boom contained the engines.

Immediately behind the cockpit in the upper part of the airframe was attached a trapezoidal wing of small span. The wing was raised above the lantern to a sufficiently large height, and an air intake was provided in the center of its leading edge to cool some transmission devices. Only the root of the wing was fixed on the fuselage with a span of 2,05 m. A console of similar width was made rotatable and could swing in a vertical plane. The movable element of the wing served as the basis for mounting the annular screw channel.

They decided to equip the convertible with two propellers of a variable pitch of a five-blade design. The screw had a diameter of 1,5 m and was placed inside an annular channel with an inner diameter of 1,58 m. The shaft of the screw and the associated gearbox were placed in a drop-shaped nacelle connected to the channel with several racks. The annular channel of the screw had profiled walls with a maximum thickness of 250 mm. Due to its shape, a channel in horizontal flight could create lift, complementing the main wing. Together with the reduced wing of the wing, the annular channel could rotate around a horizontal axis. To control the position of the channels used electric drives.


The machine is ready for vertical takeoff. Photo Maquettes-missiles.blogspot.fr


The experimental machine was supposed to use unusual control systems that are uniform for all flight modes. In the back section of the annular channel, two pairs of V-shaped planes of polygonal shape were placed. The rear edge of each such device carried four aerodynamic steering. The presence on each channel of a large number of steering surfaces with their own drives made it possible to change the direction of the outflow of the flow and thereby control the flight in all modes. Already at the stage of preliminary studies, it became clear that such a system makes it possible to abandon traditional ailerons, elevators and directions.

Inside the center section and partly inside the tail boom, side by side were placed two turbo-shaft engines Allison T63-A-5A with 317 horsepower X. each. The flow of atmospheric air was carried out through the intake devices in the upper surface of the center section, the release of reactive gases through the nozzles at the top of the tail boom of the beam. The engines were connected to the main gearbox, which provided the transmission of torque to the longitudinal shafts of the wing. The latter reached the gondolas inside the annular canals, where the screw reducers were located. The applied transmission made it possible to fly with one engine off, as well as ensure the rotation of the screws in all positions of the annular channels.

The prototype machine received a three-point chassis of simple design. Under the bottom of the nose of the fuselage was placed a rack with one small diameter wheel, in the tail - two racks with larger wheels. To increase the wheelbase, the main racks were installed at an angle and carried the wheels to the level of the axis of the annular channels.


Take off on a leash. Photo Airwar.ru


In the forward part of the fuselage was placed single pilot's cabin. The pilot had a large lamp that provided a good overview of the front hemisphere, as well as allowing to monitor the work of the screws and their channels. The lantern was divided into a fixed canopy of a large area and a folding part, with the help of which the vehicle was mounted. Helicopter-type controls were placed at the pilot’s workplace, allowing control of engine thrust and propeller pitch, as well as control of the rudder position. Also in the cockpit was a lever for controlling the position of the channels. The Nord 500 project meant using a single set of controls to operate in all possible modes.

During vertical takeoff or landing, the main control methods were to change the thrust by adjusting the engine speed or setting the required screw pitch. The roll control was carried out at the expense of a differentiated change in the thrust of the two screws. Control in the pitch channel was carried out by tilting the channels. The yaw control was imposed on the tail rudders of the canals, which were deflected as required.

In horizontal flight, it was proposed to use an asymmetrical change in the propellers of the screws as a yaw control. The pitch and roll, respectively, were varied by synchronous or differential deflection of the existing aerodynamic rudders. In transient conditions, the pilot had to use all these methods, depending on the current speed and flight altitude, as well as on the position of the annular channels.


Preparing for the flight. Photo Airwar.ru


The experimental convertoplane turned out to be quite compact. The length of the vehicle was 6,6 m, the total length was 6,1 m. The height was slightly more than 3 m. The empty car weighed only 768 kg, while the maximum take-off weight was set at 1300 kg. It was assumed that the N500 Cadet will be able to reach speeds of up to 350 km / h and show high flight characteristics comparable to modern helicopters. Particular attention was paid to the parameters of take-off and landing.

Construction of the second prototype convertible Nord 500, intended for flight tests, was completed at the very beginning of 1968. In February, the car for the first time took to the air on a leash. Having confirmed the characteristics already established in the framework of ground and tethered tests of the first prototype, the second was admitted to free flights. Such tests began with vertical takeoffs and landings, after which the opportunity arose to begin to study the operation of technology in transient conditions. As far as is known, during these checks the experienced "Cadet" showed itself well and confirmed the calculated characteristics.

In 1969, the experienced convertoplane was transferred to the research organization Office National d'Etudes et de Recherches Aérospatiales (ONERA) for new checks. This time the experimental machine was supposed to be tested in wind tunnels, imitating various flight modes. Special attention in these studies was paid to the work of propellers and their interaction with annular channels. Inspections in wind tunnels once again confirmed the high performance and viability of the original idea. In addition, certain advantages of the convertoplane over helicopters with similar characteristics were established. One of the advantages of the experimental machine was less noise produced by propellers when creating the same lifting force.


During the test. Photo Maquettes-missiles.blogspot.fr


Even before the completion of testing of experimental equipment, French aircraft manufacturers began to make plans concerning the future of the original development. The specialists of Nord Aviation offered several options for advanced technology, using the main achievements of the N500 project. Moreover, some such projects could be a direct development of the existing one.

Army planned to offer a slightly modified Nord 500, suitable for solving some applied problems. So, by changing the fuselage and adding a compartment for photographic equipment, the tiltrotor could be made an easy reconnaissance aircraft. Similarly, it was possible to create a light transport or ambulance. Further development N500 could be a civilian passenger modification. In this case, it was necessary to use the new fuselage with a five-seater cabin and a thin tail boom, carrying the plumage in the form of an inverted V.

Subsequently, convertilanes of the Nord 501 family could rise into the air. The basic model of this family was supposed to make a shock aircraft vertical takeoff. When developing its appearance, the developers of the company planned to use the experience of building and using American AH-1 combat helicopters, which, among other things, should have an impact on the appearance of the car. The combat tiltrotor was supposed to carry a machine gun turret and various rocket-bomb weapons on the wing pylons.

On the basis of the combat N501, it was possible to create a civilian passenger modification. When using the main components and assemblies of the military machine, it was possible to create an eight-person convertiplane. It was also possible to develop a transport modification with a payload of the order of 5 t. If there was an appropriate request from the military, Nord Aviation could modify the Nord 501 civil project and make an exclusively military transport on its basis.


The possible appearance of combat tiltrotor N501. Picture by Youroker.livejournal.com


Such proposals were in fact the direct development of the existing Nord 500 Cadet project and made it possible to solve the assigned tasks by using ready-made components or without the need to create a large number of new ones. At the same time, the concepts of other tiltroject-tiltdacts were proposed, which were distinguished by their large size of equipment and enhanced characteristics. For example, already at the end of the sixties - before the start of the “Cadet” flight tests - the Nord Aviation company began to show the Nord Rocade convertoplane at the exhibitions. Such a machine, according to calculations, could carry 10 tons of cargo or 40 passengers at speeds up to 540 km / h.

In 1970, Nord Aviation was merged with Sud Aviation into a larger organization called Société nationale d'industrie aérospatiale. Later it was renamed Aérospatiale. As a result, for some time the Cadet project carried a new name Aérospatiale N500.

A variety of tests promising technology on the ground, in the air and in wind tunnels continued until 1971 year. Experienced technology has shown itself well and confirmed the possibility of practical use of movable propellers installed inside the annular channels. With extensive experience in testing and operating the first convertoplane, the company-developer could proceed to the creation of new models of such equipment. Upon receipt of the order from the army or any civilian structure, the designers could start creating projects based on previously proposed concepts.


Layout of the transport vehicle Nord Rocade. Photo by Youroker.livejournal.com


However, this did not happen. In the current form of the convertoplan Nord 500, it was planned to offer the army as a light scout. However, by the beginning of the seventies, several light helicopters with similar characteristics had been created by the French and foreign industries. Experimental N500 exceeded them only in maximum speed, while other parameters of different types of equipment were on the same level. At the same time, helicopters were easier to manufacture and operate, and also differed in lower cost. In such conditions, the military could hardly prefer convertiplane to helicopters.

The lack of real interest on the part of potential customers, as well as the presence on the market of more successful samples of less daring designs, led to a halt in work. In 1971, the testing of experienced Nord 500 was completed, and the project was soon closed due to lack of prospects. Cancellation of further work on the basic project put an end to all the options for its development previously proposed. All N501, Nord Rocade family projects, etc. went to the archive. The further development of convertoplanes with turning channels was considered inexpedient. No longer needed prototypes went for disassembly.

Showing interest in promising options aviation high-tech equipment, the French company Nord Aviation tried to create its own tiltrotor with rotors placed inside the rotary ring channels. At the same time, the project was created on an initiative basis, which to some extent determined its future fate. The situation with the absence of customers at the design stage did not change further, due to which the original aircraft could not get out of the test stage. The Nord 500 Cadet project was the first and last attempt by the French aviation industry to create and bring to operation a tiltrotor of this class.


On the materials of the sites:
https://vertipedia.vtol.org/
http://airwar.ru/
http://aviastar.org/
http://diseno-art.com/
http:// klassiker-der-luftfahrt.de/
http://youroker.livejournal.com/
https://maquettes-missiles.blogspot.fr/
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5 comments
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  1. +1
    April 11 2017 00: 07
    One of the advantages of the experimental machine was the lower noise produced by the propellers when creating the same lifting force.

    Was it worth it to make such a garden for such a “plus”?
    France: The country is overpopulated to the limit, it is difficult to find a freely growing tree, wherever a runway is needed. Then why in France convertiplanes? Maybe for their colonies? So they seem to be gone. Under such specific conditions, it is difficult to ensure, necessary in such cases, the economic feasibility of developing and building such aircraft in general.
    1. +1
      April 11 2017 07: 18
      Quote: venaya
      Under such specific conditions, it is difficult to ensure, necessary in such cases, the economic feasibility of developing and building such aircraft in general.

      Even provided
      Quote: venaya
      The country is overpopulated to the limit, it is difficult to find a freely growing tree, wherever a runway is needed.

      can't business strategists consider the supply of such equipment for export? Look narrowly! )) Remember the story with Concord.
      Well, and the fact that it turned out not only unpretentious, but even I would say a too-overdone complicated technique - a “creative search” may not lead into such jungle if there is no strictly defined development strategy in the right direction wassat
  2. +1
    April 11 2017 11: 10
    A screw in a ring is more efficient than just a screw and quieter. But for some reason, they rejected this idea.
    1. +1
      April 11 2017 12: 44
      Quote: Zaurbek
      A screw in a ring is more efficient than just a screw and quieter. But on osprey for some reason this idea was abandoned

      ))) The reason is only this
      http://www.svvaul.ru/538-prakticheskaya-aerodinam
      ika
  3. +1
    27 December 2017 20: 22
    + + + + + + + + + +

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