Cold War

An-22 – The Largest Turboprop Aircraft in the World

The An-22 is the largest turboprop aircraft in the world today. It is an aircraft of immense proportions, with a total of 60,000 horsepower, the ability to carry huge loads like ballistic missiles or other aircraft, and travel huge distances.

This incredible aircraft has its roots in the 1950s, and has continued in service ever since.


Creating the World’s Largest Turboprop Aircraft

In the 1950s the Soviet Union developed the An-12, a 110 ft (33 meter) long transport aircraft that had a payload capacity of 20 tons. Even though this was an impressive aircraft for the time, the Soviets wanted something even bigger, something that could carry the new 36-ton T-54 tank, along with its crew and supplies.

In 1958, a design for such an aircraft was drawn up by the Antonov Design Bureau. Designated An-20, it was a large aircraft with a projected cargo payload of up to 40 tons, and enough room for 170 troops.

Power for this was to come from two Kuznetsov NK-12s, one in each wing. These monstrous turboprop engines are the same type used by the famous Tu-95 “Bear”, and are the most powerful turboprop engines ever made with 15,000 shp.

Tu-95 engines running.
The huge Kuznetsov NK-12 engines on the Tu-95. Their propellers are 5.8 meters in diameter. Image by Fedor Leukhin CC BY-SA 2.0.

However, the project was soon dropped in favour of a much larger machine.

This aircraft was scaled up from the An-20, now needing to be able to carry 50 tons over a distance of 3,500 km. NK-12 engines were used again, but this time, four were needed. Antonov had a design drawn up in 1960.

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Many Soviet industries were interested in this aircraft – the ability to haul so much weight over the vast distances of the USSR was, naturally, very appealing.

An-12 in flight.
Antonov’s new aircraft would be much, much larger than their An-12. Image by Papas Dos CC BY 2.0.

The Ministry of Defense wanted it to transport intercontinental ballistic missiles between launch sites. The Army wanted it to transport tanks, trucks, supplies, engineering and whatever else they could fit inside.

Civilian industries wanted to use it to carry large pieces of equipment or machine components to remote areas across the Soviet Union.

Antonov certainly had their hands full – they went around measuring and logging a wide variety of potential pieces of cargo, from tanks to civilian tractors, to ensure the aircraft could serve such a variety of customers.

Mil V-12 helicopter.
The largest helicopter ever built, the Mil V-12, was built to support the An-22’s ballistic missile-carrying mission. Image by Alan Wilson CC BY-SA 2.0.

But getting to places like Siberia was one thing, landing was another. Many landing strips were poorly prepared, and so it would need a rugged landing-gear system to survive. The design, known as “Product 100”, used a similar landing gear arrangement to the smaller An-12, with the main gear being stored in bulges on either side of the fuselage.

A large number of low-pressure tyres would hold the weight of this massive machine, even on rough ground. This layout also had the added benefit of bringing the fuselage closer to the ground to better facilitate loading and offloading.

In 1961 a full-scale mock-up was built – this allowed its designers to ram it full with various different objects to test its cargo carrying abilities.

An-22 Wood Mock-up.
Wooden mock-up of the An-22.

The design was approved, and work on a prototype was started. The aircraft now received the designation An-22 “Antey”, after the Greek mythological figure Antaeus (ironically, he was known for his strength when in contact with the ground).

Construction of the prototype was completed by January 1964, and undertook its first flight in February 1965 – just 5 years after the project began.

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Taking off from Kyiv in Ukraine, the 165-ton aircraft made a successful first flight and sufficiently impressed those involved.

An-22 first prototype on runway tarmac.
The first An-22 prototype.

The Soviets were extremely proud of the An-22, which had the distinction of being the largest aircraft in the at the time. They were so proud that, just three months after its first flight, they took it to the 1965 Paris International Air Show to unveil it to the world.

The aircraft did not perform a flying display, but it wowed spectators and western nations. After this, it was given the reporting name “Cock” by NATO.

After returning from the show the An-22 resumed testing. Once this was completed, the aircraft entered serial production in November 1965.

An-22 prototype next to An-2.
The first An-22 prototype, next to an An-2 biplane.

Design of the An-22

Upon its introduction, the An-22 was the largest transport aircraft in the world. Even today, it remains the largest turboprop ever built.

It follows a relatively standard layout for large cargo aircraft.

It has a circular-shaped fuselage 6 meters in diameter and pressurized throughout – although the cargo area is pressurized to a lower pressure than the cockpit/crew decks. The two areas are separated by a bulkhead.

Antonov 22 with two engines on.
The An-22 is circular, joined on both sides by the landing gear bulges. Image by CC BY 4.0.

The crew area is separated into two decks; the lower deck contains the navigator’s cabin, while the upper deck contains the cockpit. Behind that is a cabin that sits 21 people.

Cargo is loaded and unloaded through a ramp at the rear of the hold. At most, the hold can carry an incredible 80 tons payload. This is more than a M1A2 Abrams, or five BMP-1s. There is also room for up to 290 passengers.

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A dedicated passenger variant was proposed, which would have been capable of carrying over 700 passengers, but it was never perused.

Inside the An-22's cargo hold.
The An-22’s cavernous cargo hold. Image by Anagoria CC BY 3.0

At the rear is the An-22’s distinctive tail, which has two vertical stabilisers and rudders. The designers took this approach because there were fears that with a single huge tail fin, the amount of torque applied to the airframe during rudder action or side-winds may cause it to break off.

The wings sit above the cargo hold and measure 211 ft (64.4 meters) across. The fuselage is 190 ft (58 meters) long, and the height to the top of the tail is 41 ft (12.5 meters).

Powering this huge beast is four NK-12 turboprops, each one of which produces 15,000 shp. These are essentially the same engines used on the Tu-95 “Bear”, but are actually fitted with even larger propellers (5.8 meter AV-60 props on the Tu-95, compared to 6.2 meter AV-90s on the An-22).

An-22's cockpit.
The An-22’s cockpit. Image by Aleksandr Markin CC BY-SA 2.0.

The propellers are contrarotating, which helps to reduce the rotational torque produced by engines of such power.

The whole aircraft weighs in at a staggering 250 tons (550,000 lbs) when fully loaded, but these engines can still get it up a top speed of 450 mph (740 km/h).

All this weight sits on 14 large wheels, fitted with low-pressure high-profile tyres to allow for landings on poor quality runway surfaces. The wheels sit in pairs on three struts per side, and one in the nose. Each strut can be lowered or raised individually, and this gives mechanics the ability to replace whole wheels or service the landing gear without jacking the aircraft up.

The aircraft's central structural framework.
The central structural frame of the An-22, to which the major components are attached.

The An-22’s Service

The An-22 entered service in 1967, initially equipping the 5th Squadron of the 229th Military Transport Aviation Regiment, based in Ivanovo, Russia. Their enormous size meant they were soon in use transporting heavy loads.

They were used to move equipment and components (like 30-ton power plant units) for the oil industry in 1969.

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The following year An-22s carried 250 tons of cargo across the Atlantic Ocean to Peru to help deliver humanitarian aid to the nation after it was hit by a brutal earthquake.

Komatsu dump truck emerges from the Antonov.
Komatsu dump truck offloading.

But during these missions, the USSR experienced its first An-22 loss. One An-22, registration CCCP-09303, was suddenly lost during a flight between Iceland and Canada. No distress signals were sent, but the aircraft could not be located, even by NATO and Soviet search efforts.

Some wreckage was eventually found, but the exact cause of the loss is unknown. Another was lost in India just a few months later, but this was attributed to propeller disintegration, due to improper manufacturing standards. It is thought that this may have also been the cause of the loss near Iceland.

Krug SAM launcher vehicles are offloaded from an An-22.
Krug anti-aircraft vehicles are offloaded from an An-22.

Throughout their early years of service, Antonov employees accompanied the aircraft to ensure all was running smoothly. Reportedly, in one case in 1975, an An-22’s front landing gear failed to deploy. Antonov assisted the crew in finding a solution.

That solution? Cut a hole in a cabin wall and manually drain the release cylinder of hydraulic fluid. After that, the wheel lowered down under its own weight.

Antonov armor air drop.
Armored vehicle airdropped out of an An-22.

An-22s were also notable in delivering cargo to Soviet forces during their invasion of Afghanistan in the 1980s, and helping in the Chernobyl disaster control efforts. In the 1990s they were used for the movement of troops and refugees after the collapse of the Soviet Union.

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68 An-22s were built in total between 1965 and 1976. Today, just four remain in service; one with Ukraine, and three with Russia. Sadly, the Ukrainian example appears to have been damaged during the Russian invasion of the country.