Mikoyan-Gurevich MiG-21

The Mikoyan-Gurevich MiG-21 (Russian: Микоян и Гуревич МиГ-21; NATO reporting name: Fishbed) is a supersonic jet fighter and interceptor aircraft, designed by the Mikoyan-Gurevich Design Bureau in the Soviet Union. Its nicknames include: "Balalaika", because its planform resembles the stringed musical instrument of the same name; "Ołówek", Polish for "pencil", due to the shape of its fuselage, and "Én Bạc", meaning "silver swallow", in Vietnamese.

Approximately 60 countries across four continents have flown the MiG-21, and it still serves many nations seven decades after its maiden flight. It set aviation records, becoming the most-produced supersonic jet aircraft in aviation history, the most-produced combat aircraft since the Korean War and, previously, the longest production run of any combat aircraft.

The MiG-21 jet fighter was a continuation of Soviet jet fighters, starting with the subsonic MiG-15 and MiG-17, and the supersonic MiG-19. A number of experimental Mach 2 Soviet designs were based on nose intakes with either swept-back wings, such as the Sukhoi Su-7, or tailed deltas, of which the MiG-21 would be the most successful.

Development of what would become the MiG-21 began in the early 1950s when Mikoyan OKB finished a preliminary design study for a prototype designated Ye-1 in 1954. This project was very quickly reworked when it was determined that the planned engine was underpowered; the redesign led to the second prototype, the Ye-2. Both these and other early prototypes featured swept wings. The first prototype with the delta wings found on production variants was the Ye-4. It made its maiden flight on 16 June 1955 and its first public appearance during the Soviet Aviation Day display at Moscow's Tushino airfield in July 1956.

In the West, due to the lack of available information, early details of the MiG-21 often were confused with those of similar Soviet fighters of the era. In one instance, Jane's All the World's Aircraft 1960–1961 listed the "Fishbed" as a Sukhoi design and used an illustration of the Su-9 'Fishpot'.

The MiG-21 was the first successful Soviet aircraft combining fighter and interceptor characteristics in a single aircraft. It was a lightweight fighter, achieving Mach 2 with a relatively low-powered afterburning turbojet, and is thus comparable to the American Lockheed F-104 Starfighter and Northrop F-5 Freedom Fighter and the French Dassault Mirage III. Its basic layout was used for numerous other Soviet designs; delta-winged aircraft included the Su-9 interceptor and fast Ye-150 prototype from the MiG bureau, while the successful mass-produced frontline fighter Su-7 and Mikoyan's I-75 experimental interceptor combined a similar fuselage shape with swept-back wings. However, the characteristic layout with the shock cone and front air intake did not see widespread use outside the USSR and ultimately proved to have limited development potential, mainly due to the small available space for the radar.

Like many aircraft designed as interceptors, the MiG-21 had a short range. This was exacerbated by the poor placement of the internal fuel tanks ahead of the centre of gravity. As the internal fuel was consumed, the center of gravity would shift rearward beyond acceptable parameters. This had the effect of making the plane statically unstable to the point of being difficult to control, resulting in an endurance of only 45 minutes in clean condition. This can be somewhat countered by carrying fuel in external tanks closer to the center of gravity. The Chinese variants somewhat improved the internal fuel tank layout (as did the second generation of Soviet variants), and also carried significantly larger external fuel tanks to counter this issue. Additionally, when more than half the fuel was used up, violent maneuvers prevented fuel from flowing into the engine, thereby causing it to shut down in flight. This increased the risk of tank implosions (MiG-21 had tanks pressurized with air from the engine's compressor), a problem inherited from the MiG-15, MiG-17 and MiG-19. The short endurance and low fuel capacity of the MiG-21F, PF, PFM, S/SM and M/MF variants—though each had a somewhat greater fuel capacity than its predecessor—led to the development of the MT and SMT variants. These had an increased range of 250 km (155 mi) compared to the MiG-21SM, but at the cost of worsening all other performance figures, such as a lower service ceiling and slower time to altitude.

The delta wing, while excellent for a fast-climbing interceptor, meant any form of turning combat led to a rapid loss of speed. However, the light loading of the aircraft could mean that a climb rate of 235 m/s (46,250 ft/min) was possible with a combat-loaded MiG-21bis, not far short of the performance of the later F-16A. MiG-21's Tumansky R-25 jet engine's specialty was the addition of a second fuel pump in the afterburning stage. Activating the ЧР (rus. "чрезвычайный режим" - emergency mode)(Emergency Power Rating, EPR in India) booster feature allows the engine to develop 97.4 kilonewtons (21,896 lbf) of thrust under 2,000 meters (6,600 ft) of altitude. The rpm of the engine would increase by 2.5% and the compression ratio would thus increase, with a rise in exhaust temperature. The limit of operation is 2 minutes for both practice and actual wartime use, as further use causes the engine to overheat. The fuel consumption increased by 50% over the rate in full afterburner. Use of this temporary power gave the MiG-21bis slightly better than 1:1 thrust-to-weight ratio and a climbing rate of 254 meters/second, equalling the F-16's nominal capabilities in a close-quarters dogfight. The use of WEP thrust was limited to 2 minutes to reduce stress on the engines' 750 (250+250+250) flight hours lifetime since every second of super-afterburner counted as several minutes of regular power run due to extreme thermal stress. With WEP on, the MiG-21bis's R-25 engine produced a huge 10–12 meter long blowtorch exhaust, with six or seven brightly glowing rhomboid shock diamonds visible inside the exhaust. The Russians gave the emergency power setting its "diamond regime" name, which was never popularly used in India. Given a skilled pilot and capable missiles, it could give a good account of itself against contemporary fighters. Its G-limits were increased from +7Gs in initial variants to +8.5Gs in the latest variants. It was replaced by the newer variable-geometry MiG-23 and MiG-27 for ground support duties. However, not until the MiG-29 would the Soviet Union ultimately replace the MiG-21 as a maneuvering dogfighter to counter new American air superiority types.