The Mil Mi-24 (NATO reporting name: "Hind") is a large helicopter gunship and low-capacity troop transport produced by Mil Moscow Helicopter Plant and operated from 1976 by the Soviet Air Force, its successors, and over thirty other nations.
In NATO circles the export versions, Mi-25 and Mi-35, are simply denoted with a letter suffix as "Hind D" and "Hind E" respectively. Soviet pilots called the aircraft "letayushiy tank" or "flying tank". Another common nickname is "Krokodil" (Crocodile) — due to the helicopter's camouflage and fuselage shape.
During the early 1960s it became apparent to the 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 missions and transport infantry. 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 at which 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 strategists of the armed forces, he was opposed by a number of the 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 panels opinions were mixed, supporters of the project eventually held sway, and a request for proposals for the design of a battlefield support helicopter was issued.
Mil engineers prepared two basic designs, a 7 ton single engine design and a 10.5 ton twin engine design both based around the 1,700 hp Izotov TV3-177A turboshaft. Later three complete mockups were produced along with five mockups of just the cockpit area to allow the positions of the pilot and the weapon station operator 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 mockup of the design was reviewed and approved in February 1969. Flight tests with a prototype began on 15 September 1969 with a tethered hover, 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 aircrafts tendency to Dutch roll at speeds in excess of 200 km/h. A number of other design changes were made until the production version Mi-24A (izdeliye 245) entered production in 1970 and obtaining its IOC in 1971. It was officially accepted into the state arsenal in 1972.
The core of the aircraft was taken from the Mil Mi-8 (NATO reporting name "Hip"), two top mounted turboshaft engines driving a mid-mounted 17.3 m five-blade main rotor and a three blade tail rotor. The engine positions give the aircraft its distinctive double air intake. The original versions have an angular greenhouse-style cockpit. Versions D and above include a characteristic tandem cockpit with a "double bubble" canopy. Other components of the airframe came from the Mi-14 "Haze". Weapon hardpoints are provided by two short mid-mounted wings (which also provide lift), each offering three stations. The load-out mix is mission dependent; they can be tasked with close air support, anti-tank operations, or aerial combat. The body is heavily armored and the titanium rotor blades can resist impacts from .50 caliber (12.7 mm) rounds. The cockpit is overpressurized to protect the crew in NBC conditions. The craft uses a retractable tricycle undercarriage. As a combination gunship and troop transport, the Mi-24 has no direct NATO counterpart.
While some have compared the UH-1 "Huey" as NATO's direct counterpart to the Mi-24, the helicopter that created the concept of a troop carrying gunship, this is not true. While UH-1 helicopters were used in Vietnam to ferry troops, and were used as gunships, they were not able to do both at the same time. For a UH-1 to be a gunship, the entire passenger area of the helicopter would be stripped to accommodate extra fuel and ammunition, making it useless for troop carrying. The Mi-24 can do both at the same time, and this was greatly exploited by airborne units of the Soviet Army during the 1980-1989 Soviet invasion of Afghanistan. Wikipedia
