AKL-201407 AviaCollection / AviaKollektsia series 07/2014: Antonov An-26 Curl Soviet Turboprop Civilian and Military Transport Aircraft. Photos, schemes, colour pictures. 32 pages, soft cover, text in Russian.

CREATING OF AICRAFT
In the early 1960s in the USSR, both military and civilian specialists were concerned about the same problem: the lack of a modern transport aircraft with a carrying capacity of 4-6 tons. The An-8 and An-12 were too large, and the Il-12T, Il-12D and Il-14T had limited transportation and landing capabilities due to the lack of a ramp (they were loaded via side cargo hatches).
In the late 1950s and early 1960s. The main efforts of Soviet designers focused on the creation of heavy transport aircraft. This was explained by the growing "appetites" of the military leadership, supported by the corresponding concepts of warfare and, as a consequence, the development of the armed forces. The emphasis was on the transportation of bulky heavy loads over long distances. Antonov Design Bureau was working on the An-20 and VT-22 projects, Beriev - Be-16 and Be-18, Ilyushin - Il-60, Myasishchev - project "26", and the Tupolev tried to adapt the Tu-114 for these purposes, working over its transport modification "114TS".
In addition, in the middle and second half of the 1960s. Antonovites actively worked on the further development of the An-12 concept - the An-40 airplane, and the Beria and Myasishevsky workers - on the Be-32UVP and M-12 light vehicles, respectively. But none of these projects solved the problem of creating a transport aircraft of the required carrying capacity ...
TRANSITION STAGE
To save time and money, we decided to go the well-trodden path - to create a military version of a passenger aircraft, as it was possible to do earlier with the IL-12 and IL-14. The An-24, which took off for the first time on October 20, 1959, was best suited for this role. Its use as a transporter was immediately provided for in a decree of the Council of Ministers of December 18, 1957. According to it, Antonov Design Bureau was instructed to proceed with the design of a 44-seat passenger aircraft with two AI theater -24, as well as work on its military transport option.
After the successful completion of the main stage of testing, the third prototype An-24 (No. 00-03) was converted into a military transport vehicle, designated An-24T, by the autumn of 1961. They dismantled passenger seats, reinforced the plywood floor of the now cargo, rather than passenger, cabin, and installed folding seats along the sides. On the starboard side in the rear part they made another door, a cargo one. The aircraft could carry 37 soldiers with weapons, 33 paratroopers, 24 wounded on a stretcher and three seated, accompanied by two paramedics or cargo weighing up to 4000 kg. For landing, it was equipped with a portable landing system PDSP-2, and at the workplace of the navigator, an AIP-32 sight was installed.
Tests of the An-24T began on September 4, 1961. By this time, the plane had received a completely gray color and military side number “83”, which was applied to the bow. Until January 3, 1962, 36 flights were performed on the An-24T to test the discharge of people and goods through both doors. In late May - early June 1962, according to the program of additional factory tests, they made another 22 flights to test special equipment.
From September 17, 1962 to July 12, 1963, the An-24T passed joint state tests on the basis of the branch of the Civil Aviation Research Institute of the Air Force in Chkalovskaya. The leading pilot was appointed Lieutenant Colonel V.S. Eliseeva, and the lead engineer - Major V.A. Anisimova. In their conclusion, military testers indicated that the An-24T almost completely meets the requirements of the Air Force and can be put into service.
However, the headquarters of the Military Transport Aviation believed that they needed another aircraft. On the An-24T there were no means of mechanizing the release of goods, the cargo hatch was small, and the dimensions of the cargo compartment did not allow the transport of light military equipment. Insufficient floor strength of the cargo compartment and a short flight range (distillation was 1900 km) were noted. They made a number of other comments. It is clear that, despite the positive conclusions of the testers, the main thing was the opinion of the customer.
Antonov Design Bureau proposed to strengthen the cargo floor, which allowed to increase the mass of the cargo up to 5000 kg, to equip the cargo hatch at the bottom in the rear part of the aircraft, and to install additional tanks in the wing that increase the ferry range to 2900 km. Solution for implementing everything this was enshrined in a decision of the MAP leadership of February 13, 1965. For the practical implementation of the idea, one serial An-24 (No. 06-02) was allocated. After the conversion, the aircraft was supposed to receive a new designation - the An-34, but subsequently it did not take root, and it remained the An-24T. The maximum take-off weight was, like that of the passenger An-24, - 21 tons.
A cargo hatch with dimensions of 1.4x2.72 m was placed in the lower part of the fuselage in the area of frames 33 - 40, behind it were installed two ventral crests. A P-149 conveyor was mounted in the cargo compartment, a flow separator at its rear, and a loading device on the ceiling. The number of soldiers transported increased from 37 to 38, the wounded - from 27 to 37, but the number of paratroopers decreased from 33 to 30.
To assess the effectiveness of the improvements, as well as to verify the safety of the aircraft leaving the paratroopers through the new cargo hatch from December 7, 1965 to February 12, 1966 in Kiev and Fergana, the crew headed by the leading test pilot Yu.N. Ketov were test days. Their results were recognized as successful, which allowed from June 16 to November 10, 1966 to conduct state tests of the modernized aircraft. In this case, the crews of A.S. Timofeeva and I.Ya. Markov from the Civil Aviation Research Institute of the Air Force completed 73 flights. The result was the conclusion that the An-24T in a new look corresponds to the TTZ. The only significant disadvantage was considered to be an insufficient flight range of 2565 km instead of the required 2900. This and a number of less significant comments had to be eliminated before the serial production of the aircraft at the factory number 39 in Irkutsk, the decision on which the MAP made on July 29, 1965. In 1966 they released the first two serial An-24Ts, the next year, 34 vehicles rose into the sky. In total, 103 aircraft of this modification were built in 1966 - 1971.