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Tu-104 Camel - Design

The strategy chosen when making this aircraft - "strategy of minimal technical risk (basic aircraft was TU-16 bomber) which allowed to make a quite effective and reliable aircraft within short time period. The first drafts of new jetliner coded Tu-2AM-3-200 appeared during the development of Tu-16 bomber. In the summer of 1954 the Soviet government ordered the development of a new aircraft named Tu-104 with AM-3M turbojets. The future aircraft had to be able to carry 50 passengers and 1000 kg of cargo to a range of 3500 km at speeds close to 1000 km/h.

The design bureau tried to exploit tested technology of Tu-16 design for the creation of commercial liner. This changed the layout of the aircraft: instead of a midplane, the aircraft became a low-level plan, respectively, the centroplane and the nacelles were redesigned. The flight deck layouts, wings and stabilizers, gear struts and navigation equipment the Tu-104 obtained from "Badger". From the serial Tu-16 were used detachable parts of the wing, engine wing compartments, chassis, horizontal tail, vertical tail and gondola chassis. Although this approach shortened the developmental cycle, it failed to contribute much to the commercial efficiency.

The fuselage was totally new in design and thorough attention was paid to the large pressurized cabin. For the Tu-104 was designed a wider fuselage (3.5 meters instead of 2.9 meters in the Tu-16). Tu-104 had an airtight cabin from the toe of the fuselage to the compartment of the tail unit. It was necessary to develop from scratch such things as air conditioning units, electrical appliances for cooking and heating food, lighting salons, radiating passenger cabins.

During the creation of Tu-104, special attention was paid to ensuring high reliability of the aircraft structure, as well as increasing life time of the airframe and especially of pressurized cabin. Bearing in mind the challenges faced by the British with "Comet", airframe of Tu-104 for the first time in the Soviet practice was cycled in TsAGIs new purpose-built water-tank, within the framework of Tu-104 creation program. These tests had revealed weaknesses in the design, thus, the redesign was performed to ensure its durability was enough.

At the same time, a search for the most rational layouts of passenger cabins, galley and domestic compartments was being performed for the aircraft. Comfortable passenger seats and shadow-free lighting were being developed; interiors color palette and materials for upholstery of chairs and partitions were being chosen. The interior of the aircraft was being designed with the idea that a sense of comfort and security can be achieved by creating a "home environment" in the airplane ("House-cabin" idea).

Hence, the interior was a little bit overfilled with elements of traditional imperial style and both the total space and individual parts didnt resemble a unity; shapes and design of wagon architecture were used as well as gold and walnut finish. All these interior features existed only on the first prototype. Later, in batch production, the interior of the passenger compartment became more "democratic", approaching the international standards of the period.

Passenger aircraft specificity has necessitated the development of new units of air conditioning systems, electrical units for food cooking and warming up, new lighting, radio installation of passenger cabins, etc. All that was, to a large extent, just being mastered by our aviation industry, that had been working for many years mainly for the mass military contracts. In addition to it, increased requirements on reliability were imposed on the previously developed systems and units. Some new units, mainly for domestic service, have been designed in the Tupolev Design Bureau, because the specialized bureaus refused to deal with the subject, having no experience of designing specific units of passenger aircraft.

The Tu-104B is a low-wing aircraft with a conventional tall arrangement and a wing incorporating pronounced sweepback. The transparent nose adopted from the bomber version of the aircraft is clearly visible in the photograph. The two engines that power the Tu-104 are located in nacelles that are faired into the wing roots. This arrangement is somewhat similar to that employed on the Comet; however, the nacelles are larger and the circular inlets extend forward of the leading edge of the wing, as contrasted with the leading-edge inlets on the Comet. The two main landing-gear struts are fitted with four-wheel bogies and retract rearward into pods on the wing. The aircraft has a seating capacity of 100 passengers arranged in a 5-abreast configuration.

The sweepback angle of the aspect ratio 6.5 wing is 40 from the root to about the midsemispan position and is 37.5 from there to the tip. Each wing has two large fences located in the streamwise position on the top surface of each wing. One of these is at the position where the sweep angle changes, and the other is farther outboard. These fences help control the boundary layer and, hence, improve the stalling characteristics of the wing. Lateral control is provided by conventional ailerons that are operated manually; manual longitudinal control is also used. The rudder is actuated hydraulically. The wings are equipped with trailing-edge Fowler-type flaps and have no leading-edge devices. A Fowler flap is without the small segment between the wing and the main portion of the flap.

The Tu-104B is powered by two Mikulin turbojet engines of 21 385 pounds thrust each. The engines are equipped with thrust reversers, although some of the early models did not have this equipment. These early aircraft employed two braking parachutes to assist in stopping the aircraft on landing. Insofar as can be determined, no other commercial transport aircraft (except early versions of the Tupolev Tu-134) has utilized braking chutes as a routine operational procedure. The gross weight of the aircraft is 167 551 pounds, which is somewhat heavier than that of the piston-engine transports at the end of the era in which these aircraft dominated the world's airlines. With the large turbojet engines, the thrust-to-weight ratio of the aircraft, 0.26, is nearly as high as any of the large transports whose characteristics are given in table VII. The wing loading of 84.8 pounds per square foot is relatively low compared with more modern designs; however, comparison of the data given in table VII for different aircraft indicates that the combination of low wing loading and relatively simple high-lift devices on the Soviet aircraft give stalling speeds comparable to those of more modern high performance jet transports.

The range of 1500 miles for the Tu-104 aircraft with maximum payload places it in the short-range category. The cost-economical and maximum cruising speeds are 497 and 590 miles per hour, respectively; these speeds correspond to Mach numbers of 0.75 at 35 000 feet and 0.85 at 25 000 feet.

The Tu-104 was built in a number of versions, and some were still in use on domestic routes inside the Soviet Union in the mid-1980s. Production of the aircraft ended after 250 units were constructed.

Both the DeHavilland Comet and the Tupolev Tu-104 were pioneers in a new and exciting concept of air transportation, and both have a well-deserved place in the history of aeronautical development. In many respects, however, the design of these aircraft reflected the philosophy of contemporary propeller-driven aircraft. For example, the low wing loadings, unsophisticated high-lift devices, and simple control systems are typical of high-performance propeller-driven transports. The high wing loadings and powerful high-lift devices permited cruising at near maximum values of the lift-drag ratio, but at the same time retaining satisfactory stalling speeds.

The engine location on the Comet and the Tu-104 are no longer used on modern jet transports and must be considered obsolete for this type of aircraft. The advantages and disadvantages of mounting the engines in the wing roots are discussed above in the description of the Comet. This aircraft, as well as the Tu-104, employed turbojet engines of relatively small diameter. The beginnings of the high-bypass-ratio turbofan engine with its large diameter fan poses an additional problem with the wing-root engine location because of the difficulty of integrating the large engine into the wing root.




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