Editing Mikoyan-Gurevich MiG-19 (section)

==Design and development==
In 1950 the Mikoyan-Gurevich (MiG) design bureau (also known as [[OKB]]-155) began work on a new fighter aircraft, intended to have a greater range than the existing [[MiG-15]] and [[MiG-17]] aircraft, and capable of reaching [[supersonic]] speeds in level flight. MiG chose to use two of the new [[Mikulin AM-5]] axial jet engines (a scaled-down version of the [[Mikulin AM-3]] that powered the [[Tupolev Tu-16]] bomber) for its new fighter.<ref name="melp180">Belyakov and Marmain 1994, p. 180.</ref><ref name="WoF9p124">Gordon ''Wings of Fame'' 1997, p. 124.</ref> As a test bed for the new engine, OKB-155 was authorised on 20 April 1951 to convert one of the prototype MiG-17s, replacing the single [[Klimov VK-1]] engine with two {{convert|19.60|kN|lbf|abbr=on}} AM-5s (later replaced by {{convert|21.08|kN|lbf|abbr=on}} AM-5As), with the testbed, designated SM-1 (or I-340), flying late in 1951.<ref name="melp180"/><ref>{{cite book |last1=Belyakov |first1=R.A. |last2=Marmain |first2=J. |title=MiG 1939-1989 |date=1991 |publisher=Editions Larivière |location=Paris |isbn=2-907051-00-8 |page=137}}</ref> While the SM-1 was a useful testbed,<ref name="WoF9p124"/> its performance was less than expected, and first resulted in an [[afterburner]] being designed for the AM-5, resulting in the AM-5F (reaching {{convert|26.45|kN|lbf|abbr=on}} with afterburner).<ref name="melp180-1">Belyakov and Marmain 1994, pp. 180–181.</ref>

While the SM-1 was a test bed, the SM-2 (or I-360) was intended as the required supersonic escort fighter, with work authorised on 10 August 1951. The SM-2 was a twin-engined, mid-winged aircraft. Its thin wings, which had been designed at TsAGI, the Soviet [[Central Aerohydrodynamic Institute]], for supersonic flight were swept back at an angle of 55 degrees and had a single [[wing fence]] on each side. Unusually, a [[T-tail]] was fitted. Armament was two [[Nudelman N-37]] 37-mm cannon located in the leading edge of the aircraft's wings, near the wing roots - the guns had been moved compared to those in the MiG-15 and -17 to avoid ingestion of gun blast gases causing surging of the aircraft's engines.<ref name="WoF9p124"/> The first SM-2, the SM-2/1 was sent to the ''[[Letno-Issledovatel'skiy Institut]]'' (en:flight research institute) (LII) in April 1952 for testing, and was flown for the first time on 24 May 1952, with test pilot G. A. Sedov at the aircraft's controls.<ref name="WoF9p124"/><ref name="melp208">Belyakov and Marmain 1994, p. 208.</ref> With the AM-5A engines without an afterburner the SM-2 could not exceed the speed of sound in level flight. To solve this, AM-5F engines with afterburners were substituted.<ref name="melp208"/> While the new engines improved performance, the aircraft was found to have handling problems, particularly at high [[angle-of-attack|angles of attack]], where the aircraft was prone to spinning. To solve these problems the aircraft's horizontal tail was lowered, with other changes including moving the aircraft's airbrakes and deepening the wing fences, with the modifications causing the aircraft to be redesignated SM-2A and then SM-2B.<ref name="melp208,0">Belyakov and Marmain 1994, pp. 208, 210.</ref><ref name="gunp195">Gunston 1995, p. 195.</ref>

The AM-5F still generated inadequate thrust and so the Mikulin engine design bureau developed a new engine to replace it, the AM-9B (later  re-designed the [[Tumansky RD-9]]), rated at {{convert|25.5|kN|lbf|abbr=on}} dry and {{convert|31.87|kN|lbf|abbr=on}} with afterburner.<ref name="WoF9p124"/> When fitted with the new engines, the SM-2B became the SM-9, first flying in this form on 5 January 1954. The SM-9's performance impressed the Soviet authorities, and it was ordered into production as the MiG-19 on 17 February 1954, despite the fact that factory testing had only just started.<ref name="melp212-5">Belyakov and Marmain 1994, pp. 212–213, 215.</ref><ref name="gunp196-7">Gunston 1995, pp. 196–197.</ref><ref name="WoF9p125">Gordon ''Wings of Fame'' 1997, p. 125.</ref>

The rush to get the MiG-19 into service resulted in initial production aircraft having a number of serious problems. The type suffered a number of in-flight explosions, eventually traced to poor insulation between the aircraft's engines and fuel tanks in the rear fuselage - overheating of these tanks could cause fuel explosions. This was eventually partly solved by fitting a metal heat shield between the engines and the tanks.<ref name="WoF9p129">Gordon ''Wings of Fame'' 1997, p. 129.</ref> The aircraft's [[Elevator (aeronautics)|elevators]] proved ineffective at supersonic speeds, and an all-moving [[Stabilator|slab tail]] was tested by the second and third SM-9 prototypes, and later included in the major production type, the MiG-19S, which also featured an improved armament.<ref name="WoF9p127,0">Gordon ''Wings of Fame'' 1997, pp. 127, 130.</ref>

At the same time that the daylight escort fighter was developed from the SM-2 and SM-9 into the MiG-19 and MiG-19S, work went on in parallel to design and build a radar-equipped all-weather fighter, with the first prototype SM-7/1 flying for the first time on 28 August 1954. This prototype had a similar airframe to the first SM-9, including the conventional fixed horizontal tail, with the second and third SM-7s introducing similar changes to those tested on the SM-9 prototypes, including the slab tail.<ref name="WoF9p134-5">Gordon ''Wings of Fame'' 1997, pp. 134–135.</ref> The all weather fighter entered production as the MiG-19P in 1955. Major differences from the MiG-19S included RP-1 ''Izumrud'' radar in the aircraft's nose, with small radomes in the centre and on the top lip of the air intake and an armament of two cannon in the aircraft's wing roots.<ref name="WoF9p134-5"/> From 1957, production of all weather fighters switched to the missile equipped MiG-19PM, with an armament of four [[K-5 (missile)|K-5M]] air-to-air missiles, with the cannon removed.<ref name="WoF9p137-8"/>

In 1955, following American introduction of high-altitude [[espionage balloon|reconnaissance balloons]] and overflights by British [[English Electric Canberra|Canberra]] aircraft, which could not be intercepted by existing aircraft, together with intelligence reports of the development of the [[Lockheed U-2]] with an even greater ceiling, development began on a specialist high-altitude version of the MiG-19, the MiG-19SV, which entered limited production. This had more powerful engines and was lightened, with seatback armour and one of the guns removed, while flap settings were adjusted to give greater lift at higher altitudes and a new [[pressure suit]] was introduced. These changes increased the aircraft's ceiling from {{convert|17500|m|ft|abbr=on}} to {{convert|18500|m|ft|abbr=on}}.<ref name="WoF9p132-3"/><ref name="melp225-7">Belyakov and Marmain 1994, pp. 225–227.</ref><ref name="gunp197-8">Gunston 1995, pp. 197–198.</ref> The prototype MiG-19SV was further modified (as the MiG-19SVK) with increased wingspan, giving a ceiling of {{convert|19100|m|ft|abbr=on}}, but this was still inadequate to deal with the U-2, and effort was switched to adding rocket boosters.<ref name="WoF9p33"/>