During the early 1960s, it became apparent to Soviet designer Mikhail Leont’yevich Mil that the trend towards ever-increasing battlefield mobility would result in the creation of flying infantry fighting vehicles, which could be used to perform both fire support and infantry transport missions. The first expression of this concept was a mock-up unveiled in 1966 in the experimental shop of the Ministry of Aircraft’s factory number 329 where Mil was head designer. The mock-up designated V-24 was based on another project, the V-22 utility helicopter, which itself never flew. The V-24 was similar in layout and configuration to the UH-1A Huey, with a central infantry compartment that could hold eight troops sitting back to back, and a set of small wings positioned to the top rear of the passenger cabin, capable of holding up to six missiles or rockets, with a twin-barreled GSh-23L cannon fixed to the landing skid.
Mil proposed the design to the heads of the Soviet armed forces, and while he had the support of a number of strategists in the armed forces, he was opposed by several more senior members of the armed forces who believed that conventional weapons were a better use of resources. Despite the opposition, Mil managed to persuade the defence minister’s first deputy, Marshal Andrey A. Grechko, to convene an expert panel to look into the matter. While the panel’s opinions were mixed, supporters of the project eventually held sway, and a request for design proposals for a battlefield support helicopter was issued. The development of gunships and attack helicopters by the US Army during the Vietnam War convinced the Soviets of the advantages of armed helicopter ground support doctrine. This had a positive influence on moving forward with the development of the Mi-24.
Mil Mi-24 HIND A
Mil engineers prepared two basic designs: a 7-ton single-engine design and a 10.5-ton twin-engine design, both based on the 1,700 hp Izotov TV3-177A turboshaft. Later, three complete mock-ups were produced, along with five cockpit mock-ups to allow the pilot and weapon station operator positions to be fine-tuned.
The Kamov bureau suggested an army version of their Ka-25 Hormone ASW helicopter as a low-cost option. This was considered but later dropped in favor of the new Mil twin-engine design. A number of changes were made at the insistence of the military, including the replacement of the 23 mm cannon with a rapid-fire heavy machine gun mounted in a chin turret, and the use of the then-under development 9K114 Shturm (AT-6 Spiral) anti-tank missile.
A directive was issued on 6 May 1968 to proceed with development of the twin-engine design. Work proceeded under Mil until his death in 1970. Detailed design work began in August 1968 under the codename Yellow 24. A full scale mock-up of the design was reviewed and approved in February 1969. Flight tests with a prototype began on 15 September 1969 with a tethered hover, and four days later the first free flight was conducted. A second prototype was built, followed by a test batch of ten helicopters.
Acceptance testing for the design began in June 1970, continuing for 18 months. Changes made in the design addressed structural strength and fatigue problems, and reduced vibration levels. Also, a 12-degree anhedral was introduced to the wings to address the aircraft’s tendency to Dutch roll at speeds in excess of 200 km/h, and the Falanga missile pylons were moved from the fuselage to the wingtips. This gave the helicopter its characteristic wings. The tail rotor was moved from the right to the left side of the tail, and the rotation direction reversed. The tail rotor now rotated up on the side towards the front of the aircraft, into the downwash of the rotor, which increased the efficiency of the tail rotor. A number of other design changes were made until the production version Mi-24A (izdeliye 245) entered production in 1970, obtaining its IOC in 1971. It was officially accepted into the state arsenal in 1972.
Russia has developed the Mi-28 Havoc and Ka-50 attack helicopters, which are smaller and more maneuverable and do not have the large cabin for carrying troops. The Russian Navy however has no plans to retire their small number of Mi-24s. As for the Russian air force the service is severely short of funds, the “krokodil” will serve for many years to come.