Why history's biggest helicopter was never more than a prototype

Was it a rare case of quality over quantity? Or was it simply a design that was too big to be realistic? The Mil V-12 never made it past the prototype stage and we want to know why... 

In July 1968, the world’s biggest helicopter made its first successful flight. It had attempted such a feat just over a year earlier, but with unsuccessful consequences. The Soviet-built mega machine was the result of a desperate attempt to hide weaponry sites from the West during the Cold war – from the United States in particular.

It had become clear by the late 1950s that the United States had begun to discover the locations of the Soviet’s Inter Continental Ballistic Missiles (ICBMs) through their use of U-2 spy planes conducting high altitude reconnaissance flights over the Soviet Union. Prior to the idea to design the Mil V-12, the only way to move heavy first generation nuclear missiles had been using rail links. This posed a problem: not only did they have to build railway lines to the remote launch sites in which they wanted to house ICBMs, but when they did so it was only a matter of following the railway lines on the reconnaissance photos for the United States spy planes. This simply wouldn’t do, which meant that the Soviets had to come up with a way to transport their weaponry to the secluded launch sites without leaving a trace of evidence. On top of this, whatever they came up with had to be big and powerful enough to lift the extremely large and heavy weapons they were dealing with. Enter the Mil V-12.

The idea for the Mil V-12 was cooked up when it was realised that the world’s current biggest helicopter wasn’t big enough for the job. Helicopters were at the top of the Soviet’s list of ideal machinery: they were fast and could hover above or land in dangerous, remote terrains – which was the type of hidden environment that was best for the ICBM launch sites.

At the time, the world’s biggest helicopter also happened to be Soviet-built. The Mil MI-6 was the worlds largest and fastest helicopter and was produced in seriously large quantities. However, for their plan to work, the Soviet’s would need an aircraft with at least twice the lifting power of the Mil MI-6. Design and engineering studies began in 1959, but the development was not formally approved until 1962. First ideas regarding the design of a new aircraft entertained the idea of simply sizing the Mil M-6 up for it to be capable of carrying the missile in the fuselage. However, to do this would involve developing an entirely new engine that could produce a lot more power, something that the Soviets didn’t have the time for. After various considerations, the solution to the problem seemed to be to arrange the engines and rotors transversely on a set of wings. The resulting machine looked half-helicopter-half-aeroplane. However, it saved time by allowing them to reuse the MI-6’s engines and gearboxes entirely whilst doubling the power.

Construction of the first prototype of the Mil V-12 began in 1965. The resulting aircraft was 37m long and over nine meters in height. By comparison, the rival Mil M-10 that entered service in 1962 was 33m long and its height was just under eight meters. The first test flight of the V-12 in 1967 was unsuccessful due to oscillations caused by control problems, resulting in the aircraft crashing. Just a year later, the helicopter tried again and this time was successful. However, the Soviet Air Force refused to accept the V-12 into state acceptance trials. Despite the fact that the helicopter held eight world records (some of which are still held today), the rapidly changing strategic situation meant that the need to hide nuclear missiles was irrelevant. Spy satellites had been developed by this time, as well as smaller, more mobile ICBMs that could be transported and hidden far more easily. On top of this, the Soviet Air Force claimed that now the V-12 was no longer needed for its intended use, there was just no need for such a large and complex helicopter. As a result, the development of the helicopter was cancelled in 1974 and was never produced commercially. Many consider the cancellation of the project a great shame, with a great deal of aviation enthusiasts holding a place in their heart for the Mil V-12 despite its cancellation after just two prototypes.