Il-52 Long-range bomber
Despite the fact that thousands of articles and monographs have been published on the history of KB Ilyushin, monumental works by N.D.Talikov and Yu.A.Egorov have been published, none of them even mention the Il-52 aircraft, a strategic bomber of the “flying wing” type ". According to K. Udalov, who published material on the Aviko Press resource, the reason is that S.V. Ilyushin did not receive, and the project was worked out in draft, so to speak, “in reserve”.
This aircraft remains very poorly attested. Chernikov simply mentions it in passing, though providing a single piece of line art illustrating a flying wing. There are a handful of other reports on this project, but upon close examination they are all basically the same text and illustrations, all of which are evidently of recent vintage. What is actual history, and what is post-Soviet fantasy, remains obscure.
Chernikov reports that in 1954, while working on the IL-54 plane, the OKB began to study the possibility of creating more advanced models of front-line and long-range bomber aircraft. These works, finding themselves in the same “dead end”, did not manage to go beyond the framework of design estimates and aerodynamic studies of models in TsAGI. However, attention is drawn to the new technical ideas inherent in these developments that have not previously been encountered in the construction of IL-brand aircraft. The surviving materials on the failed Il-50, Il-52 and Il-56 bombers give a complete picture of their potential flight and, unfortunately, missed combat capabilities. In 1956, as in many other design bureaus, there was a radical change in the subject of work of the design bureau S.V.Ilyushin, switched to the creation of cruise missiles.
The idea of the all-wing or habitable wing airplane is not new, but has occupied the attention of aeronautical engineers for since at least 1911. In the USSR since 1922, Boris Cheranovsky engaged in the design and construction of gliders and light aircraft of the "flying wing" type, notably the BEACH-8 "Triangle" experimental glider Cheranovsky built in 1929. In 1930-1940, the aircraft designer Nikitin developed a light torpedo bomber — a Planer Spetsial'nogo Naznachenaya (Glider for Special Purposes) PSN-1 and PSN-2 of the “flying wing” type in two versions: a manned training sighting and unmanned anti-shipping missile with full automation.
The structure can be utilized with no fuselage (which contributes nothing to lift but which does add to the weight), the saving in weight can be devoted to some combination of payload and range. The eliminated structures contribute in a large degree to drag, not only that due directly to their aerodynamic forms, but also an additional drag due to interference between the airflows caused those due to the sustaining airfoils. All of these advantages had been apparent for years, and had been highly publicized, as had been the accompanying problems necessary to be overcome before these advantages can be realized.
Attempts dating back to at least 1931 have been made to provide "flying wing" aircraft which have largely failed because of the difficulty in obtaining sufficient pitch stability. This longstanding pursuit for viable advantageous flying wing designs is testament to the non-obvious nature of the field. While many assume aerodynamics is a completely characterized technical field, citing deterministic analytical computational fluid dynamics (CFD) simulation tools, the reality is something less certain. Wind tunnel and flight testing remain important aspects of new aircraft design for this reason.
In the United States, Northrop began the development of a long-range flying-wing strategic bomber in 1941 when the Army Air Force ordered two prototypes of the XB-35. The XB-35 was designed with four engines to drive contra-rotating pusher propellers and was expected to be less expensive and more efficient than bombers such as the B-29 and the Convair B-36, which was then under development. Construction of the full-scale aircraft was commenced in January, 1943, and it was completed and wheeled out for engine running, etc., in April 1046. The XB-35 suffered a series of propulsion problems and was finally canceled and replaced by a version powered by eight jet engines, designated the YB-49.
The Northrop YB-49 Flying Wing was a jet-powered flying wing bomber with a maiden flight of October 21, 1947. Throughout its history, the YB-49 design had stability difficulties and a series of accidents, which eventually led to the termination of the program. At Muroc Air Force Base, CA, in 1948, Air Force Major Daniel Forbes, co-pilot Captain Glenn Edwards, and the entire crew were killed while test flying a YB-49. In descending from an altitude of 40,000 feet, the wing panels were given off, and the aircraft disintegrated. Muroc AFB was renamed Edwards AFB in December of 1949 in honor of the co-pilot who was a native of California.
The history of the creation of high-speed long-range bomber (RBM) began in the late 1940s. The end of Great Patriotic War was marked by the appearance of nuclear weapons, which were first used by the US Air Force in the war with Japan. A new type of weapon required the creation of reliable delivery vehicles. Therefore, immediately after the war, large-scale research and development efforts were launched in the USA and Great Britain to create medium and heavy strategic bombers.
In the USA, Convair and Boeing designed and built the YB-60 and B-52 aircraft, which had an intercontinental flight range. Preference was given to the B-52 aircraft and from August 1954 he began to enter the arsenal of the airborne wings. Earlier on a competitive basis, medium-sized strategic bombers Conver HV-46, Boeing HV-47 and Martin HV-48 were built. The B-47 turned out to be the best, and already in March 1950 its mass production began.
Despite the lightning speed with which it was launched into mass production, the Tu-4 was just a transitional type of bomber, since its flight characteristics, such as speed and range, as well as the mass of combat load no longer satisfy the Soviet military leadership.
In the conditions of rapid development and improvement of jet fighter aircraft, piston bombers could not successfully overcome the powerful air defense of a potential enemy, which, incidentally, was confirmed during the war in Korea in 1950–53, when the B-29 and B-50 planes in air battles with MiG-15 fighters, they suffered significant losses and were forced to switch to military operations at night.
The creation of a heavy bomber at that time was a very difficult technical task. The transition from piston aircraft with takeoff masses of the order of 40–50 tons and flight speeds of 500–600 km / h to jet technology with masses of 150–200 tons and transonic speeds required a large amount of aerodynamic research, scientific studies on strength and aeroelasticity, and the creation of completely new designs, materials and equipment.
A difficult problem was the creation of a powerful turbojet engine (turbojet engine) - the first turbojet engines only appeared, had low thrust and resource, large specific fuel consumption, low reliability. In addition, there was no consensus among domestic aviation specialists at that time about the possibility of creating an airplane with a turbojet engine with an intercontinental flight range.
Some of them believed that it was impossible to create such an aircraft in a short time. Somehow, during a conversation with the Minister of Aviation Industry M.V. Khrunichev, I.V. Stalin asked if it was possible to create an intercontinental bomber based on the Tu-16 aircraft, adding two more engines and increasing its size and weight? To which a negative answer was received. Then he decided to talk personally with A.N. Tupolev.
To a similar question from the leader, Tupolev said that with existing engines it would not be possible to get a large range. Then Stalin said that another designer undertakes to create such a machine. For this, all conditions will be created for him. This designer was Myasischev.
Sergey Vladimirovich knew about this conversation with Stalin from Khrunichev himself, since he had good relations with him. Ilyushin instructed the general types department to work out the first sketches of the strategic bomber.Unambiguously, like A.N.Tupolev, S.V.Ilyushin would not have undertaken such work if Stalin had addressed him with a similar question.
However, being a man with a long-range sight, Ilyushin instructs the general types department to make the first estimates of the appearance of a strategic bomber. At the same time having no task and government regulations, this was done absolutely on their own initiative. With no TK, no Government decrees with tight deadlines hung over the heads of the designers - absolute creativity.
The result was a unique machine - a flying wing bomber. The flying wing idea had emerged in the 1930s which anticipates the elimination of all surfaces that are not generating lift in order to minimize wetted area with a simultaneous increase of airlifting area, thus increasing the lift capacity, as well as minimizing aerodynamic drag and fuel consumption of aircraft.
Modern aircraft are of tube-and-wing design. Conventional aircraft generally utilize a wing for lifting the aircraft and a fuselage having a horizontal stabilizer and elevator for controlling the pitch of the aircraft and a vertical stabilizer and rudder for controlling theyaw of the aircraft. Roll control of the aircraft is normally effected by ailerons mounted along the outer rear edges of the wing. The center of gravity of the aircraft is normally located forward of the center of lift, thereby generating a pitch-down moment. To counteract this pitch-down moment, the horizontal stabilizer and elevator produce a downward force to generate an equal pitch-up moment.
However, a major shortcoming of the tube-and-wing design makes it technically difficult to build even bigger aircraft. That is, load of a tube-and-wing aircraft is concentrated in the middle portion of its wing. In order to carry the load, the wing must transfer its lift to its middle portion. This causes high level of stress over the wing structure. The stress becomes even greater for aircraft with heavy payload and makes the tube-and-wing design structurally inefficient for aircraft with substantial payload.
Tailess flying wing aircraft have only a single integral airlifting body, which is simultaneously producing aerodynamic lift while longitudinally stabilizing itself in different flight conditions. This is an extremely ambitious goal from the flight mechanics perspective due to the fact that the above is achieved by natural fliers with the change of surface area and position of wings in all three planes, while additionally having a tailplane with the changeable area and position thereof for pitch control in various flight conditions.
The integral rigid airlifting body of tailess flying wing aircraft can not meet several simultaneous and contradictory requirements including natural dynamic and static stability when the airlifting body is designed with efficient aft camber airfoils that have air pressure center shifted in aft direction while having inability to deploy trailing edge devices for extra lift production at low sped during take-off and landing due to high negative pitch momentum. Tailess flying wing aircraft are having the position of their neutral point approximately at around 25% of mean geometric chord of integral airlifting body. The gravity center of natural dynamically stable aircraft needs to be positioned in longitudinal direction in front of neutral point. This consequently requires the integral airlifting body to be defined with low efficient reflex airfoils that have air pressure center shifted in front of 25% of airfoil chord to satisfy the static stability of aircraft in cruising conditions when trailing edge devices for aerodynamic lift regulation being in the neutral position.
The low aerodynamic efficiency of such aircraft is especially pronounced at high subsonic and transonic speeds. If the integral airlifting body of a tailess flying wing aircraft was designed with efficient aft camber airfoils, the aircraft gravity center would need to be shifted in aft direction behind the neutral point in order to satisfy the static stability of aircraft when trailing edge devices for aerodynamic lift regulation being in their neutral position, thus such aircraft being naturally dynamically unstable.
Aspect ratio is a measure of how long and slender a wing is from tip to tip. The Aspect Ratio of a wing is defined to be the square of the span divided by the wing area and is given the symbol AR. High aspect ratio wings have long spans (like high performance gliders). Wings exhibit increase in aerodynamic efficiency with increasing aspect ratio. This resulted in high aspect-ratio flying wing configurations being proposed for high-altitude, long endurance missions. High aspect ratio flying wing configurations have been seen to exhibit significant coupling between flight dynamic and aeroelastic modes. If this coupling is not accounted for during analysis and design, instabilities arising from these may be overlooked and may lead to loss of control during flight.
Of course, before that the Soviets had, for example, the project of I.V.Chetverikov, but the IL-52, even now, after 60 years, looks surprisingly elegant and modern. Even the Il-54, created and tested later, was a typical example of the design of a jet bomber of the mid-late 50s, while the Il-52 carried all the features of modern machines of the 1980-90s.
In 2013, Russian media reproted that the Russian Air Force had selected a subsonic Tupolev flying wing proposal as the basis for its PAK-DA long-range bomber program. The choice ended a long campaign by deputy prime minister Dmitry Rogozin to develop a hypersonic aircraft, which appears to have been abandoned as technically incompatible with the air force's insistence on extended-range performance and stealth characteristics.
|180 ft (55 m)|
|Length||90 ft (27 m)|
|Height||20 ft (6 m)|
|Empty Weight||75,000 lbs (34,000 kg)|
|Loaded Weight||78,000 lbs (35,000 kg)|
|Wing Loading||45 lbs/ft2 (220 kg/m2)|
|Wing Area||1,725 ft2 (160 m2)|
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