The research program for vertical and short take-off and landing was launched in the mid-fifties at the initiative of the military department. The army command, taking into account the experience of using military transport aircraft and helicopters, wished to receive in the future equipment that has positive features of both classes aviation technicians. It was decided to start work in a promising direction with a variety of studies. Later it was planned to build several experimental aircraft to test ideas in practice. As a result, by the end of the decade, three cars were lifted into the air, one of which was created by Fairchild Aircraft.
General view of the aircraft Fairchild VZ-5, the rear wing sections are omitted. Photo Diseno-art.com
The project of a promising aircraft with improved take-off and landing characteristics was given the brand name Model M-224. In addition, the military gave their own designation to the military - VZ-5. Later, the unofficial name Fledgling appeared. For several reasons, the name assigned to the project by the customer is more known among aviation specialists and amateurs.
To reduce the required take-off and landing distance, it was possible to use different technologies and techniques. In the project of the Fairchild company it was proposed to apply the so-called. airflow deflection. With the help of special devices, the aircraft carrying plane had to change its configuration, which allowed it to change the direction of air movement with noticeable positive consequences for the general characteristics. Such a system made it possible to significantly increase the lift force of the wing and, as a result, reduce the requirements for the landing area or take-off.
From the point of view of the overall layout, the prospective VZ-5 aircraft was supposed to be a lightweight vehicle with a high-lying rectangular wing, one engine and four propellers, as well as a tail fin of a T-shaped design. At the same time, the main objectives of the project forced its authors to introduce into the design of the aircraft a number of original components and assemblies necessary both to increase the required characteristics and to eliminate the expected shortcomings.
Early version of the appearance of the car. Figure Wikimedia Commons
One of the tasks of the Model M-224 project was to maximize the ease of the machine and simplify its design. Because of this, she received a fairly simple fuselage, equipped with the minimum necessary set of devices. At the same time, there was a need to use non-standard layout solutions and some non-traditional units. So, it was the fuselage that had to accommodate the only engine of the aircraft, which was connected to a relatively complex transmission.
The project VZ-5 used fuselage simplified design, based on a metal frame. Almost the entire nose of the fuselage was given under the cockpit, which gave the car a distinctive appearance. There was a sloping curved canopy of the lantern, protecting the pilot from the oncoming flow. Under the visor there was a small metal fairing associated with vertical sides of a small height. Behind the cabin, the height of the boards increased significantly, reaching the wing mount. The tail of the fuselage was made in the form of a tapered design with a sloping bottom. The absence of large aggregates has reduced the width of the tail boom. On it were placed the keel and the stabilizer of the T-shaped structure, reinforced with two struts.
Tests of the model in a wind tunnel. Images from the chronicle
For the new aircraft was developed wing of unusual design. It was proposed to fasten the front fixed wing assembly of a relatively small width to the fuselage. On its lower surface were placed four gears of propellers, covered with small-sized fairings. The shaft of the screws was located at a small angle to the wing chord, because of which the gearboxes were fixed on the trapezoidal pylon frames. To cool moving parts, there was an air intake window on the bottom of the gear housing. The fixed part of the wing was equipped with wing-combs, which eliminated the incorrect flow of air flow. For greater rigidity, the fixed part of the wing had struts.
Behind to the fixed part of the wing was pivotally fastened the second section, which had the ability to swing on a hinge. On its trailing edge were fastenings for flaps and ailerons, which were proposed for use in order to control the aircraft in horizontal flight. For flight “on an airplane”, the VZ-5 Fledgling unit had to place the wing moving sections horizontally: a wing of great width and small elongation was formed, equipped with two flaps and a pair of ailerons. Vertical or shortened take-off should have been carried out with the movable sections lowered down. On the moving parts of the wing accounted for about two-thirds of the chord. Because of this, in particular, fully rotated sections reached the level of the bottom of the fuselage.
Airplane in position for shortened / vertical take-off. Photo Diseno-art.com
In the central part of the fuselage fit the only engine of the aircraft. The basis of the power plant was a General Electric YT58-GE-2 turbo-shaft helicopter engine with 1032 horsepower. Before the engine in the fuselage was a large window of the air intake, the exhaust was discharged through a pipe on the left side. Next to the engine, there was a gearbox, necessary for distributing torque to the drive shafts of the propellers. The rotation of the screws was carried out with the help of two main shafts, passing along the wing, and several devices that bring the power to the four wing gearboxes. The plane received four three-blade propeller of large diameter. The bored disks of the screws almost completely blocked the frontal projection of the wing.
One of the objectives of the Fairchild VZ-5 project was to reduce takeoff and landing speed, which, however, required the use of non-standard control systems. During horizontal flight, pitch and yaw control was proposed to be carried out using standard rudders on the tail unit. Standard ailerons with a large area were used for roll control. During the flight at low speed, which reduced the efficiency of aerodynamic control surfaces, it was proposed to use other means.
At the rear of the keel, on the same level as the stabilizer, an additional gearbox was placed, mechanically connected to the main gearbox. This device was completed with two four-blade screws of small diameter. By connecting tail screws to work, the pilot could influence the pitch of the machine. Low speed roll control could be done by changing the thrust of the screws. An increase in the thrust of one pair of propellers led to an increased blowing of the wing with increasing lift and following this departure into a turn.
The prototype is taken to the runway. Photo Diseno-art.com
Aircraft VZ-5 "Chick" received the original "multifunctional" chassis. Tubular elements of non-removable main struts were attached to the fuselage and the fixed part of the wing. Another rigid rack was in the nose. The small size and weight of the aircraft made it possible to equip all three racks with identical small diameter wheels. In the rear fuselage, under the rudder, it was proposed to install a small crutch. Standing on three wheels, the plane had the ability to perform normal or short takeoff. When relying on the main pillars and the tail crutch, the angle of attack of the wing increased, which could give a certain increase in lift on take-off. Thus, the pilot could choose the position of the equipment corresponding to the task.
As required from the outset, the experimental aircraft was not too large and light. The length of the vehicle was 10,26 m, the wingspan was 9,98 m, the height (when using the wheel landing gear) was 5,13 m. The total area of the wing reached 17,74 sq.m. The empty aircraft weighed just over 1,53 t. The take-off weight in the configuration for vertical take-off and landing was determined by the 1,8 t. According to calculations, the maximum flight speed was to reach 184 miles per hour (about 295 km / h). The planned flight range is unknown, but a small amount of fuel tanks did not allow to obtain high values of this parameter.
The development of the Fairchild VZ-5 Fledgling project was completed in the middle of 1959. After this, Fairchild specialists and NASA employees began building a large-scale mockup and blowing it in a wind tunnel. The model of the aircraft was checked on all the required flight modes at different flow velocities and various wing configurations. Also on the layout checked the efficiency of tail tail rotors. In the course of all the necessary research, scientists and designers collected the required amount of information, which allowed to draw final conclusions about the prospects of the project. Moreover, the final research report had a great influence on the further course of work.
Wing transferred to the configuration for horizontal flight. Photo Diseno-art.com
Research at Langley led to disappointing conclusions. It turned out that the proposed design of a promising aircraft cannot be used in practice due to the presence of a number of serious problems. The layout of the aircraft behaved unstably throughout the entire speed range, which was associated with an unsuccessful layout. The center of gravity of the machine was on 64% of the chord of the front fixed section of the wing, and this made the aircraft unstable in pitch. To correct such a problem, it was necessary to move the center of gravity a long distance ahead. Without changing the existing design, such an effect could be obtained by installing an 700-pound (317,5 kg) load near the cockpit.
With all these shortcomings, the proposed wing (in terms of full-size aircraft) should have created a lifting force at the level of 4 thousand pounds - a little more than the take-off weight in the calculated configuration for vertical takeoff. The proposed three-section wing with the developed mechanization of a large area was distinguished by high efficiency. Nevertheless, the high characteristics of the wing, combined with the instability of the aircraft could lead to the most unpleasant consequences. Thus, in its current form, the Fairchild VZ-5 aircraft was not of interest from the point of view of practical application.
The wing sections are omitted. Photo Diseno-art.com
Almost simultaneously with the assembly of a scale model for testing in a wind tunnel, the construction of a full-fledged prototype started. The prototype build ended in the fall of 1959 of the year. The first flight was planned to be carried out only after the end of comprehensive tests of the model. The date of the first flight of the experienced VZ-5 was selected on November 18. However, the findings of scientists who checked the model of the aircraft provided to them, forced the project developer to reconsider their plans. Now it was proposed to carry out ground and tethered flight tests of the “Chick”, the results of which were intended to make a final decision.
At the end of 1959, Fairchild Aircraft experts conducted the necessary tests in which the movement of the prototype was limited to a special cable system. Such equipment allowed us to limit the movement of the aircraft and eliminate possible accidents. As it turned out, the cables are fully justified. During the tests “on a leash” experienced aircraft VZ-5 Fledgling confirmed the findings made during the tests at NASA. He showed unacceptably low stability in take-off mode, which did not allow to go to free flight.
View of the rear wing. Photo Diseno-art.com
After confirming the findings of the test, the aircraft manufacturers decided to abandon the further development of the pilot project. According to the findings of scientists, the project needed major changes that were considered inexpedient. The new version of the project VZ-5 has not been developed, improved prototype technology was not built. The prototype, which never took off without insurance, was written off. Fairchild Aircraft was forced to abandon further work on vertical or short take-off and landing aircraft using the principles of air deflection.
Unlike the development of Ryan Aeronautical, the experimental aircraft from Fairchild could not fly free. Nevertheless, checks of its scale model and full-fledged prototype allowed collecting a solid amount of data on the behavior of such equipment in the air. Analysis of the information obtained allowed us to determine which features of the VZ-5 aircraft should not be used in new projects because of the risk of obtaining negative results. All this information was later used in the development of new experimental aircraft.
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