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An-72 COALER

The An-72 Coaler is designed as a short takeoff and landing aircraft which can operate from unprepared airfields. The An-72 originated as An-32, but was later fitted with jet engines. The first prototype flew on December 22, 1977, and the aircraft entered service in 1979. The name An-74 was extended to the entire family of commercial airplanes, and the An-72 remained for military service.

The wings are high-mounted and back-tapered with blunt tips and a negative slant. Two turbofans are mounted in long pods mounted on top of the wings. Round air intakes extend from the front of the wings' leading edges. The engines were placed on the leading edge of the wings to increase lift for STOL capability, with the jet exhausts blowing over titanium panels on the upper surface. The engine position also gives good Foreign Object Damage (FOD) protection. The fuselage is circular with round, solid nose, upswept rear section, and a flush cockpit. The rear fuselage has a hinged loading ramp with a rear fairing that slides backwards and up to clear the opening. Up to 7.5 tons can be airdropped, and there are folding side seats for 42 paratroops or 52 passengers. The swept-back, untapered fin features back-tapered flats high-mounted on the fin forming a T.

The An-72P is a maritime patrol variant with bulged observation windows, liferaft provision, cameras as well as offensive armament, including underwing rocket pods, a podded cannon on the undercarriage sponson and bombs that can be mounted in the rear fuselage and dropped through the open rear ramp.

The idea of the aircraft, which does not require special airfields, is so old as very history of aviation. Designers repeatedly attempted to realize it, with more or smaller success trying to create the aircraft, which combines sufficiently high flight characteristics with the small landing speed. One of the most known and successful aircraft of such type was the German Arado Ar-242, intended for the transportation of loads on the unprepared areas. In its construction were combined well the equipped by effective flaps wing, powerful motors and special chassis, whose device ensured the aircraft high passability.

Preliminary studies on the aircraft of short takeoff and landing ([KVP]) were begun in OKB of Oleg Konstantinovich Antonov in Kiev in 1972. The firm, which specializes in the creation of the transport aircraft of military and civil designation, had large work experience in this direction. Wide reputation obtained such aircraft, as An-26 and An-32, that raised to 5 tons, An-8 and An-12 middle class, heavy An-22 Antey, on which was established a number of the records of load capacity. Design project leader, was the initiator of the works on the aircraft, which uses a nontraditional method of increasing the lift. Speaking about the expediency of this solution, O.K.Antonov descriptively described to colleagues as "the powerful flow of gases, which at a high speed escapes from propulsion nozzle, will pass above the wing, creating additional lift". This method is based on, so called, Coanda effect, patented in 1932 and bearing the name of the author - Rumanian on the origin, who was being occupied in France by works in the region of physics and aerodynamics.

In the initial development stage of new aircraft was conducted in the initiative-taking order OKB themselves to of necessity consume the being isolated from the budget money (otherwise saved means they were withdrawn, and financing for the following year respectively it was reduced). The initiative-taking proposal, advanced by Antonov OKB, met the support of the main staff VVS, interested in the creation of the light transport aircraft, suitable for the transportation of the troops and technology in the front area and the supply of the dispersal airfields of combat aircraft. Together the representatives for OKB, administration of orders VVS and Ministry of Aircraft Industry [MAP] affirmed the requirements for the aircraft.

The technical proposal of OKB provided for the design of the front transport aircraft of class An-26, by load capacity to 5 tons, with the characteristics [KVP]. Aircraft had to have the small sizes (on the conditions of basing and masking), high rate of climb and strength for guaranteeing the take-off on the poorly trained areas. After agreement and assertion of by the MAP, the theme of a light frontal transport aircraft was included in the job schedule of OKB. In the routine the joint resolution of the CC CPSU and Council of Ministers of USSR began financing the creation of "the aircraft of 200" (under this cipher it figured in the design documentation; An-22 it bore the designation of "the aircraft of 100" , and projected "Ruslan" the aircraft of 400"). Chief designer along the aircraft was appointed Ya.G.[Orlova].

The basic features were determined sufficiently unambiguously: the special support of reaching [KVP] was done to the use of the Coanda effect. Confidence in the prospect of the selected diagram was so strong, that the alternative assembly versions practically were not examined. The theoretical calculations were confirmed rather well by the experimental testings of model in wind tunnel of aircraft in the wind tunnels. A lift increment was sufficiently significant and in some regimes it reached 20%.

Essential for the fate of project was, first of all, the presence of the suitable engine - turbofan D-36 with the thrust in the takeoff conditions 6500 kg. - although O.K.Antonov was a convinced adherent of economical turboprop engines, precisely TRDD (turbofan engine) with the high bypass ratio made it possible to realize the Coanda effect in practice. The D-36, created in OKB Progress of V.A.Lotareva, ensured a sufficient air flow rate, and that is especially valuable, plume exhaust of the gases directed for the blowout of the wing (let us recall that the duralumin alloys (basic construction material in the aviation) lose strength at 150C. The D-36 at first was intended for the aircraft An-60 (not built), it was well developed and has already been used on the passenger aircraft Yak-42. In the efficiency it approached the best western models, and modular construction and high resource simplified its operation. Series production D -36 was fixed at the Zaporozh'ye motor-building plant.

The airplane design accepted had its deficiencies: it was explained with the scavengings that the blowout of wing causes the formation after it of the vortices, especially, in the site of joint with the fuselage, intensity and distribution of which depend on the angle of attack, flight speed and regime of the work of engines. Accordingly, the behavior of aircraft and its controllability could change in flight. Taking this into account to the tail assembly was attached T-shaped form, and along the sides of tail section were established the large crests, which decrease the harmful interference (solution, inherited from An-26/32). The stabilizer, established on to the top of keel, was located out of the zone of wing downwash, and for guaranteeing the large scale of the operating angles of attack it was executed by adjustable.

The cargo compartment of aircraft with the size of 9000x2200x2100 mm ensured the arrangement of the standard nomenclature of transportable loads, including to 32 soldiers with the armament, automobiles of the type GAZ-66 and [UAZ]-469, aircraft engines, standard containers and cargo pans. The device of ramp had the [patentovannuyu] Antonov construction: during the load and the unloading it descended to the earth, and for the discharge of loads in flight it rolled away on the guide under the fuselage. Special attention with the design of " the aircraft of 200" it was given to the construction of chassis.

At the firm they already had solid work experience in this direction - all its machines could be exploited from the unpaved airfields. According to such indices as equivalent one-wheeled load (fraction of the mass of aircraft, which falls for each of the landing gear wheels) and on passability over ground An-22 exceeded even more contemporary Il-76. However, now problem was posed somewhat otherwise - aircraft had to have the capability of takeoff and landing on areas with uneven surfaces. About 30 versions of the landing gear were examined, including as exotic as chassis on the air cushion. For evaluating its possibilities was built the unique flying platform on the base of aircraft An-14. The results of tests showed that this landing gear turned around by the complication of construction, by worsening in aerodynamics and operational fitness of aircraft. Skirt on the air cushion had small resource, it was fragile, and device itself is considered unpractical.

The beginning of production preceded numerous operational and finishing tests of pre-series model (factory serial number 0404), in course of which the aircraft was tested under the most severe conditions. In March 1986 the An-72 was drawn for rescuing of the crew of the drifting polar station CP-27. The ice floe, on which was located the station, broke up, and it was necessary to take off from the strip with a length only of 300 m. at the end of 1987. The An-74 it flew around almost entire Arctic coast of the USSR, it visited Chukot, Franz Joseph Land, also, in Yakutiya, after overcoming under the conditions of polar night the aircraft sat down on the ice airfields of polar stations CP-28 and CP-30, where for the landing to it 350 m. were sufficient.

In the following year An-72 it visited Antarctica, where besides the basic works on connection and supply of Soviet stations for it was necessary to carry out the unplanned flight to Argentina in order to deliver into the hospital of the fallen ill polar explorer. In the process of the finishing of aircraft by it they replaced auxiliary power plant TA-8 on TA-12 of larger power and established new navigation complex with more advanced RLS, under antenna of which it was necessary to increase the nose fairing (in a series they were changed and the circumscriptions of nose section).

The first series An-72 (factory serial number 0706) rose into air in December 1989. First released An-72 were directed to the Yakut force of civil aviation. In the interview in regard to this the director of the aircraft factory A.Myalitsa said: " Series output An-72 we mastered into the shortest of time". On the basis of base construction An-72, that possessed significant reserves, was planned the creation of the entire family of the aircraft of different designation: search and rescue An-72[PS] for the works at sea, base antisubmarine with the produced on the rope magnetometer, fireman and even seaplane with the fuselage- boat with the lateral loading door and the underwing floats. The ship versions were intended for the basing on the decks of aircraft carriers: transport and radar surveillance, that were being characterized by well-made wing.

Special attention was paid to the versions of the An-72 created to the order of the military, concerned with outfitting of the Soviet Air Force. The experience of Near Eastern conflicts (in particular, combat in Lebanon in the summer of 1982) convincingly proved the need of improving Soviet military equipment. Especially strong were delay in the means of electronic reconnaissance and the complexes of control and guidance. It developed in accordance with the requirements VVS Antonov OKB and in spring 1985 derived on the tests the front aviation complex of radar surveillance, observation and electroninc warfare. Into it entered the aircraft An-71 - their kind the airborne command post, intended for detecting of air and waterborne targets and guidance on them of groups of impact aircraft, and An-72[P] (the first with this name), that carried out electronic reconnaissance and setting of interferences with enemy.

With the disintegration of the Soviet Union political problems were added to the design and technological difficulties. The hasty finding of independence by the former Soviet republics and subsequent gap of economic and economic ties placed under the threat very possibility of further production of aircraft. Although the airframe and engines of aircraft are assembled in Ukraine, obtaining the completion of components and aggregates became a problem, for permission of which often it is necessary to come running to the barter (so, the obtained from Russia landing gear struts and wheel it was necessary to pay finished aircraft and spare parts for them). For Ukraine the An-72 - the only aircraft constructed at its plants - acquired the special importance.

The need for the aircraft of different designation in combination with the financial difficulties they led to the appearance of modifications of the An-72, that preserve the base construction and characterizing by only layout and equipment of cargo compartment. In their number several versions, passenger aircraft to 52 places and even presidential aircraft in the society performance. The attempts to propose An-72 on the outside market did not have special success. With the price of $12.5 million, its western competitors (in particular the BAe.146, according to their possibilities, equipment, efficiency and, to the big enough degree, to service maintenance proved to be more attractive for the potential buyers. Such customers, as Nicaragua and Afghanistan fell for the known reasons, and to the summer of 1993 the only aircraft in the West An-72 was one leased by Columbia. Around 30 An-72s and 6 An-74s were in commercial use by 1998.




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