Antonov Design Bureau - The Big, the Heavy and the Bold. Part 2
By Amith Babu
A formation of U.S. Air Force Fairchild C-119 Flying Boxcar transport planes of the 403rd Troop Carrier Wing over Korea, on 1 October 1952.Photo © USAF - U.S. DefenseImageryDesignated DT-5/8 (Desahntno-Trahnsportnyy Samolyot - assault transport aircraft) the Antonov OKB lead by A. Ye. Belolipetskiy initiated the design of a new transport of similar capability to that of the Fairchild C-119; to transport and drop troops, cargo and light vehicles. The main focus of the design was around a large rear cargo ramp and it would be the first aircraft of soviet design with a rear cargo ramp. The design consisted of a high-mounted wing with a rectangular fuselage and a large unpressurized hold, glazed nose with a chin radar dome, twin nose wheels and a main gear of eight wheels in fairings alongside the fuselage, which left more internal space for cargo. The most complex part of the design was the most important one, the tail. In order to give clearance for cargo operations, the tail was upswept with a manned 23mm turret and most importantly, a ramp.
In December of the following year, the Soviet Council of Ministers issued directive No.2922-1251 to OKB-153, calling for them to develop a twin-turboprop transport aircraft derived from the DT-5/8. Given the in-house designation "Izdeliye-P" (Izdeliye - article or product), the team started by coming up with a new technique for strength calculations, which was followed by the construction of a 1:10 model accurate to the last rivet. Research and experimentation on this model progressed into two 1:5 models, further detailed and complex testing was done by suspending the 3 models underneath an AN-2F. After much calculation and testing, a full-scale model Izdeliye-P was built for final evaluation. This model featured a Kuznetsov TV-2 Turboprop engine on the left wing and a turbojet engine on the right wing. Turbojets would however not meet the range requirements and were dismissed.
The Kuznetsov TV-2 Turboprop engines were not perfect either: - they were still under development and there were no concrete performance figures. The TV-2 engine was based off the Junkers Jumo 022 contra-rotating turbo-prop engine which was designed in 1944, during the Second World War by Junkers, but cancelled in favour of the jet engine. In 1947, the Soviet Commission gained an interest in turbo prop engines and with the assistance of former deported Junker engineers, would work on reproducing the engine with the Kuznetsov Design Bureau (OKB-276). Further developments of this engine are still in use today including both the world's fastest propeller-driven aircraft, the Tupolev Tu-114 airliner and unsurprisingly the world's biggest turbo-prop powered aircraft, the Antonov An-22(more on this later). A passenger variant "Izdeliye N" was also drawn up from the same design with a pressurised circular section cabin carrying up to 57 passengers and removal of military hardware, a model for this aircraft was also in the works.
In the summer of 1955 (during development of the An-8 prototype), Khrushchev made his first visit to the Antonov Design Bureau and was thoroughly familiarized with the development of the An-8. Khrushchev was happy with Antonov, his young design team and the progress they were making. Khrushchev showed particular interest in "Izdeliye-N", the passenger version, of which a full-scale wood model was constructed and presented. Khrushchev enquired about the western counterparts to the "Izdeliye-N" and was made aware that its counterparts had four engines. Hearing this, Khrushchev suggested that Antonov's new aircraft should also have 4 engines. Being handed an opportunity, Antonov didn't waste any time informing the First Secretary of his notion of a four-engine passenger aircraft, but it would be designed in such a way that a military transport aircraft could be made from the same design with ease. It would be 1 project but would result into 2 aircraft. This methodology meant design and production preparations would be significantly quicker and cheaper and since the aircraft would be designed with military requirements, it would be incredibly rugged and could operate in conditions that other airliners couldn't, such as unequipped or rough fields. This also meant an increased network for airlines, especially peripheral airlines which served rural areas.
Oleg Antonov's proposal was ingenious and one that could not be taken lightly and so just a few months later, on the 30th of November 1955, the USSR Council of Ministers passed Enactment No.1956-1055 on Antonov's proposal and just 9 days later, the Ministry of Aviation Industry would approve development of the aircraft. The Antonov OKB started work on the new aircraft right away, designating the airliner "Izdeliye-U" (U-Universal) and the transport "Izdeliye-T" (T-transport). Even with the new project on its hands, progress with the "Izdeliye-P" was unaffected and on the 11th of February 1956, the prototype now officially named An-8, made its first flight at the hands of Captain Yakov I. Vernikov. During State Acceptance trials, it became clear that the An-8 had some major drawbacks; the TV-2 engines showed poor high-altitude performance and hit developments issues which later led to its discontinuation, the aircraft was unstable and performed poorly in spins and easily entered self-induced oscillations. There were also minor structural weaknesses and the controls left more to be desired. In conclusion the An-8 was not recommended for production.
To rectify these problems, the design team made adjustments to the aircraft design which included; an increased area on vertical and horizontal tail for improved stability, reinforced structural integrity for strength and anti-spin strakes on the upper rear fuselage sides. As for the engines, the OKB-478 Ivchenko AI-20D turboprop engines produced in Ukraine were chosen instead, mainly due to pressure from Ukrainian authorities who wanted the plane to be as Ukrainian as possible and they had the added benefit of reducing the empty weight by three tonnes. One major drawback was that they only delivered 85% of the power. The final test flight with the modified design took place on October 30th, 1957, after which the aircraft was approved for serial production.
Despite the Antonov Bureau's recent relocation and modification of a factory in Kyiv, Ukraine, the An-8 was serially produced in State Factory Number 84 in Tashkent, now the capital of Uzbekistan. The exact reasons for this are unclear, but new and improved manufacturing processes were the likely possibility. Furthermore, the Lisunov Li-2 (Soviet license-built Douglas DC-3), which the An-8 was hoping to replace, was also produced in Tashkent. The production An-8s starting rolling out in late 1958 and had rear doors with manual set up twin ramps instead of a rear ramp, bombsight for dropping flares, cargo pressurization, de-icing systems, fuel vents and increased rudder range of movement. Its lack of power would ultimately lead to a short production run of just 3 years with 151 aircraft built. The An-8 was flown by a crew of 6 (Pilot, Co-pilot, Navigator, Flight engineer, Tail gunner, Radio/radar operator,) and could carry 48 people or 11 tonnes of freight with a cruising speed of 480 km/h (260 kn) and a range of 2,780 km (1,500 Nm)
Although manufactured in low numbers, the An-8 saw an extensive life with the Soviet Air Forces, especially in special forces and reconnaissance roles as well as some commercial service with cargo carriers around the globe which included Aeroflot. Antonov would withdraw the An-8s Airworthiness Certificate in 2004.
Izdeliye-U - Replacing a plane yet to be built
The new design was completed in just 11 months following Khrushchev's visit and on the 30th of November 1956, the USSR Council of Ministers issued Order No.1956-1055 on the creation of both Izdeliye-U and Izdeliye-T starting official construction of both aircraft. The 2 aircraft shared the same general layout with the An-8 and used upgraded models of the Ivchenko AI-20 engines for the same political reasons as the An-8, the main differences being increased dimensions, drooped outer wings, 2 more engines and a circular pressurised fuselage.
An-10 operated by Aeroflot. Photo © Konstantin Y. Kosminkov via Wikimedia Commons
Retired An-10 in Aeroflot colours, a high majority of the An-10s produced were operated by Aeroflot. Notice the lack of endplates on the tailplane of this An-10.Photo © Dmitry Avdeev via Wikimedia Commons.
Over its life, the An-10; held an impressive record of more than 35 million passengers and 1.2 million tons of cargo flown. It was awarded a Diploma and Gold Medal at the Brussels World Fair in July 1958, landed a record 7 times on Ice platforms in the Artic and set a speed record on a closed circuit in April 1961. The An-10 became Aeroflot's most cost-effective machine and was used extensively until May 1972 when an An-10A descending for landing separated from its wings and crashed, killing all 121 aboard (8 crew and 113 passengers).
The investigation attributed the crash to fatigue cracking of the wing centre section stringers, which was also detected on many of the remaining aircraft. Aeroflot withdrew operations of the An-10 on the 27th August 1972 and permanently grounded regular passenger service in 1973, 25 remaining airworthy aircraft were transferred and continued to fly with the Soviet Air Forces and governmental services until they outlived their airframes in 1974. Soviet authorities censored the An-10 from Soviet aviation history and all remaining airframes were either scrapped or were lucky enough to be turned into a monument. An-10 monuments could be found throughout the Soviet Union in the form of children's cinemas, cafés and even a slots machine hall. Unfortunately, over time many of these monuments were vandalised or eroded away and would eventually be scrapped too. A last-ditch effort to preserve An-10s failed, resulting in just 1 aircraft being preserved at the Central Air Force Museum in Moscow.
An-12 - The Soviet Hercules
Although given less priority, development of the AN-12 was not far behind and the first of its 2 prototypes flew on 16 December 1957, yet again with Captain Yakov I. Vernikov at the controls. As the An-12 was a military version of the An-10, its two prototypes were essentially production prototypes. The key exterior differences between the two aircraft were the manned tail turret and cargo door. Internally however it had more resemblance to the An-8 due to its added military hardware.
The An-12 featured a crew of six (Pilot, Co-pilot, Flight engineer, Radio/radar operator, Navigator and Tail gunner) contained in a pressurised and armoured flight deck. Just after the flight deck lies another pressurized compartment for loading crews or the crews of vehicles being carried. The tail gunner was cocooned in a pressurised and armoured compartment featuring a ventral escape hatch, dual 23mm cannons and a ranging system. The cargo deck was unpressurized as it unnecessarily increased weight and complexity, but was highly equipped with ventilation, oxygen and heating systems, tie-down points, cargo ramps, cargo winches, two 2300 kg capacity monorail hoists and even removable cargo conveyors. All this meant the An-12 was highly optimizable for any role it was needed for (even as a bomber) since it had a bombsight just like the An-8. The rear cargo doors were in the same configuration as the An-8 too. It had 3 doors, one top door which opened out and upwards and 2 lower doors which opened inwards flushing with the sides and additionally an extendable leg that stopped the plane from tipping backwards. For vehicles, there were two ramps that had to be set up manually. The advantage of this was that vehicles could reverse into the cargo hold, easing loading and offloading of cargo but at the cost of slowing loading and offloading of vehicles.
Truck offloading cargo through the rear door of an An-12. Photo © Iskander Ziatdinov via Wikimedia Commons
Looking at its size and capability, the An-12 was erringly similar to the Lockheed C-130 Hercules with very minute differences between the 2 in terms of capability and size; the An-12 could carry 1 ton more than the C-130, but was slightly faster, smaller and lighter. Because of this, the An-12 was sometimes referred as the Soviet C130.
he AN-12 played a very important role in the formation of the Airborne Forces of the USSR, China, India and many other countries and became the backbone and lifeline for these air forces for decades. Soviet production ended in 1972, but the An-12 still flies today with both civil and military operators. A good number are still being used by the Russian Air Force today even after the fall of the USSR.
In recognition for the creation of the An-12, Oleg Antonov and his four assistants were awarded the honorary Lenin Prize in 1962 and the aircraft itself set 39 speed and altitude world records with the Soviet State Air Force Research Institute.
Honourable mention
An-14
The An-14. Photo Antonov.com
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