Y-7 / Y-14
Development of the An-24 began in 1960 in response to an Aeroflot requirement for a cheap and simple transport to replace the Li-2 (licensed DC-3), Il-2, and Il-14 aircraft. Two prototypes flew in September 1962, and the An-24 Coke first entered service in 1962. The production version turned out to be a reliable aircraft - An-24 was shown to be able to maintain an altitude of 3000 m with full payload and only one working engine. The An-24RT transport aircraft features an additional RU-19-300 jet engine.
The wings are high-mounted and equally tapered from the engines to the blunt tips. Two turboprops are mounted in pods beneath the wings, which extend beyond the wings' leading and trailing edges. The fuselage is long and slender with an upswept rear section and a solid, rounded nose featuring a stepped cockpit. The fin is back-tapered with a blunt tip and angular fairing. Flats are high-mounted on the body, back-tapered with blunt tips, and have a positive slant.
The development of this aircraft widely used in the regional airlines and abroad started in 1956, when the long-range Tu-104 and IL-18 went in service. The Aeroflot and AF Li-2, IL-12i and IL-14 did not meet the requirements in terms of load lifting capacities and were obsolete, so the urgent need appeared in the speed gas-turbine aircraft for local lines and for military needs. There existed no serial engines for that type aircraft and the assignments were set for the O.K. Antonov Design Bureau (airframe) and the A.T. Ivtchenko Design Bureau (engine).
The first An-24 piloted by test pilot G.I. Lysenko made its maiden flight on October 20, 1959. The aircraft was very successful as the Ivtchenko engines had optimum power, weight and service life parameters. The An-24 was used as the basis for the An-24T transport version followed by the An-26 and An-32, "Toros" ice reconnaissance aircraft, the An-30 for airphotography and others. A.N. Tupolev told about the An-24: "This aircraft demonstrated its high capabilities and is an up-to-date sample of this type of aircraft."
The Irkutsk factory manufactured the An-24T military transport version with a cargo door in the tail fuselage, overhead-track hoist and airdrop equipment. The An-24T serial production started within a year. It was also facilitated thanks to the organisational restructuring when the narrow-specialisation sub-assembly was introduced which later on, proved to be effective, when the IAIA manufactured the MiG-23UB and the Su-27UB). The IAIA had to master the production of glue-and-welded panels for the nacelles. The technique of the E. O. Paton's Research Institute was improved and adapted to be used in aircraft manufacturing industry. Some issues were solved thanks to the experience of the Factory test pilots, V.S. Prantskyavitchus, E.N. Tcheltsov, V.N. Trubnikov, G,M. Kurkai and others, who tested the An-24Ts.
In 1962, the passenger An-24 started operation on the local lines and soon it became one of the most numerous Aeroflot aircraft. The An-24 was in service with the Air Forces of USSR, Bulgaria, Bangladesh, Vietnam, Hungary, East Germany, Iraq, the Congo, Cuba, Laos, Mongolia, Poland, Romania, Somali, Sudan, Czechoslovakia and South Yemen.
The aircraft was developed in mid-sixties. It is equipped with RU-19A300 auxiliary power plant of 800 kgf-thrust mounted in the RH turboprop nacelle. This engine improves the aircraft takeoff performance. An-24 "Coke" is configured as a cantilever monoplane with high-mounted wing equipped with extended-span Fouler flaps. The double-slotted flaps are externally fitted at the engine nacelle and single-slotted flaps are installed at the root wing. The tail unit has a traditional design, in a serial aircraft it is completed with a ventral fin; the fuselage is of a semi-monocoque type. The hydraulically-retractable three-strut landing gear has double wheels at each strut, steerable and rotatable nose wheels, providing the pressure inside tires to be adjusted on the ground.
An-24B aircraft is equipped with AI-24 2nd series engines; and An-24RV aircraft is equipped with AI-24T engines with variable pitch propeller. From the seventies both An-24B and An-24RV are equipped with two anti-spin ventral fins. The performed tests and aircraft operation later on revealed that it is featured with a good stability and easy controllability, capable to continue one engine inoperative takeoff. The landing gear construction and mechanical design ensures its extension by gravity or by ram air even if any system fails. The aircraft is provided with reliable wing and tail unit anti-icing systems.
An-24 aircraft is a metal-made monoplane with high-mounted wings. It is fitted with in-flight retractable three-strut landing gear with a nose wheel. The main landing gear struts are installed in the engines' nacelles and are retracted against ram air into special under-engine compartments. The nose wheel is installed at the fuselage front end and is retracted into compartment under the cockpit. The nose strut is a pedal-controlled unit that significantly improves the aircraft mobility on the ground. The landing gear wheels with low-pressure tires allow landing soaked unpaved aerodromes.
The adhesive bonded joints were for the first time applied for An-24 in the practice of world aircraft construction. More than 67% of rivet joints were replaced with adhesive-bonded joints that resulted in the increased structure fatigue, considerable labor performance saving and production cost reduction.
The aircraft wing consists of center-section, two middle sections and two cantilever sections. The wing middle sections are fitted with double-slotted flaps, while the centre-section is fitted with single-slotted flaps. Each aileron root is fitted with a trimmer and balance tab. The centre-section chamber incorporates four soft fuel tanks; the middle section chambers are made as pressurized fuel integral tanks. The aircraft is equipped with two AI-24 jet-prop engines.
The aircraft is equipped with communication aids and all facilities required for day and night flights in adverse meteorological conditions any season of the year. The aircraft altitude equipment produces and maintains the pressure and air temperature to the extent required for the crew and passengers normal vital activity when flying at high altitudes. In icing conditions the wing leading edge, tail unit and engines' air intakes cowlings are heated with hot air taken off the engine compressors. The propellers, cockpit windshields, pitots, batteries containers are provided with electrical heating. If required, An-24 can be easily converted either to a cargo-passenger or cargo version.
An-24 aircraft stands among the best world examples of aircraft for its reliability and operating life. An-24 airframe time between overhauls is 6,000 flight hours and total depreciation overhaul period makes up 30,000 flight hours. The engine TBO is 3,000 hours.
The Russian production run stopped in 1978 after, totally, 1100 aircraft of this type were produced (the Irkutsk factory manufactured 164 An-24Ts out of these within 1967 through 1971).
Xian Yunshuji Y-7 / Y-14
The Xian Yunshuji Y-7 is a reverse-engineered Chinese version of the Antonov An-26. Y-7, Y-7H, Y-7H-500 Chinese modifications are known.
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