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Mi-24

The Mil Mi-24 is a large helicopter gunship and attack helicopter and low-capacity troop transport with room for 8 passengers. It is produced by Mil Moscow Helicopter Plant and operated since 1972 by the Soviet Air Force, its successors, and by over thirty other nations.

In NATO circles, the export versions, Mi-25 and Mi-35, are denoted with a letter suffix as "Hind D" and "Hind E" respectively. Soviet pilots called the aircraft "flying tank", or летающий танк. More common unofficial nicknames were "Crocodile" due to the helicopter's camouflage scheme and "Glass" because of the flat glass plates which surround the cockpit of the Mi-24.

 

Development

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 and 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, 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, which had a positive influence on moving forward with the development of the Mi-24.

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 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, 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. 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 initial operating capability in 1971 and was officially accepted into the state arsenal in 1972.

In 1972, following completion of the Mi-24, development began on a unique attack helicopter with transport capability. The new design had a reduced transport capability (3 troops instead of 8) and was called the Mi-28, and that of the Ka-50 attack helicopter, which is smaller and more maneuverable and does not have the large cabin for carrying troops. In October 2007, the Russian Air Force announced it would replace its 250 Mi-24 helicopter gunships with 300 more modern Mi-28s and possibly Ka-50s by 2015.

 

Design

The core of the aircraft was derived 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 configuration gave the aircraft its distinctive double air intake. Original versions have an angular greenhouse-style cockpit; Model D and later have a characteristic tandem cockpit with a "double bubble" canopy. Other airframe components came from the Mi-14 "Haze". Two mid-mounted stub wings provide weapon hardpoints, each offering three stations, in addition to providing lift. The load-out mix is mission dependent; Mi-24s can be tasked with close air support, anti-tank operations, or aerial combat.

The body is heavily armored and can resist impacts from .50 caliber (12.7 mm) rounds from all angles, including the titanium rotor blades.[citation needed] The cockpit is protected by ballistic-resistant windscreens and a titanium-armored tub. The cockpit and crew compartment are overpressurized to protect the crew in NBC conditions.

Considerable attention was given to making the Mi-24 fast. The airframe was streamlined, and fitted with retractable tricycle undercarriage landing gear to reduce drag. The wings provide considerable lift at high speed, up to a quarter of total lift. The main rotor was tilted 2.5° to the right from the fuselage to counteract dissymmetry of lift at high speed and provide a more stable firing platform. The landing gear was also tilted to the left so the rotor would still be level when the aircraft was on the ground, making the rest of the airframe tilt to the left. The tail was also asymmetrical to give a side force at speed, thus unloading the tail rotor.

A modified Mi-24B, named A-10, was used in several speed and time to climb world record attempts. The helicopter had been modified to reduce weight as much as possible, and among the measures used was to remove the stub wings. The speed record over a closed 1000 km course set on 13 August 1975 of 332.65 km/h still stands, as does many of the female specific records set by the all female crew of Galina Rastorgoueva and Ludmila Polyanskaia. On 21 September 1978 the A-10 set the absolute speed record for helicopters with 368.4 km/h over a 15/25 km course. The record stood until 1986 when it was broken by the current record holder, a modified Westland Lynx.

 

General characteristics

Crew: 2–3: pilot, weapons system officer and technician (optional)

Capacity: 8 troops or 4 stretchers

Length: 17.5 m (57 ft 4 in)

Rotor diameter: 17.3 m (56 ft 7 in)

Wingspan: 6.5 m (21 ft 3 in)

Height: 6.5 m (21 ft 3 in)

Disc area: 235 m² (2,530 ft²)

Empty weight: 8,500 kg (18,740 lb)

Max. takeoff weight: 12,000 kg (26,500 lb)

Powerplant: 2 × Isotov TV3-117 turbines, 1,600 kW (2,200 hp) each

 

Performance

Maximum speed: 335 km/h (208 mph)

Range: 450 km (280 miles)

Service ceiling: 4,500 m (14,750 ft)

Armament

 

 Possible armament configuration on Mi-24W

 

 Yakushev-Borzov YakB-12.7 machine gun

Internal guns

flexible 12.7 mm Yakushev-Borzov Yak-B Gatling gun on most variants. Maximum of 1,470 rounds of ammunition.

fixed twin-barrel GSh-30K on the Mi-24P. 750 rounds of ammunition.

flexible twin-barrel GSh-23L on the Mi-24VP and Mi-24VM. 450 rounds of ammunition.

PKT passenger compartment window mounted machine guns

External stores

Total payload is 1,500 kg of external stores.

Inner hardpoints can carry at least 500 kg

Outer hardpoints can carry up to 250 kg

Wing-tip pylons can only carry the 9M17 Phalanga (in the Mi-24A-D) or the 9K114 Shturm complex (in the Mi-24V-F).

Bomb-load

Bombs within weight range (presumably ZAB, FAB, RBK, ODAB etc.), Up to 500 kg.

MBD multiple ejector racks (presumably MBD-4 with 4xFAB-100)

KGMU2V submunition/mine dispenser pods

First-generation armament (standard production Mi-24D)

GUV-8700 gunpod (with a 12.7 mm Yak-B + 2x7.62 mm GShG-7.62 mm combination or one 30 mm AGS-17)

UB-32 S-5 rocket launchers

S-24 240 mm rocket

9M17 Phalanga (a pair on each wingtip pylon)

Second-generation armament (Mi-24V, Mi-24P and most upgraded Mi-24D)

UPK-23-250 gunpod carrying the GSh-23L

B-8V20 a lightweight long tubed helicopter version of the S-8 rocket launcher

9K114 Shturm in pairs on the outer and wingtip pylons