Mikoyan-Gurevich MiG-23
The Mikoyan-Gurevich MiG-23 is a single-engined, supersonic, variable-geometry fighter aircraft, designed by the Mikoyan-Gurevich design bureau in the Soviet Union. It is a third-generation jet fighter, alongside similar Soviet aircraft such as the Su-17 "Fitter". It was the first Soviet fighter to field a look-down/shoot-down radar, the RP-23 Sapfir, and one of the first to be armed with beyond-visual-range missiles. Production started in 1969 and reached large numbers with over 5,000 aircraft built, making it the most produced variable-sweep wing aircraft in history. The MiG-23 remains in limited service with some export customers.
The basic design was also used as the basis for the Mikoyan MiG-27, a dedicated ground-attack variant. Among many minor changes, the MiG-27 replaced the MiG-23's nose-mounted radar system with an optical panel holding a laser designator and a TV camera.
Development
The MiG-23's predecessor, the MiG-21, was fast and agile, but limited in its operational capabilities by its primitive radar, short range, and limited weapons load. Work began on a replacement for the MiG-21 in the early 1960s. The new aircraft was required to have better performance and range than the MiG-21, while carrying more capable avionics and weapons including beyond-visual-range missiles. A major design consideration was take-off and landing performance. The Soviet Air Force demanded the new aircraft have a much shorter take-off run. Low-level speed and handling was also to be improved over the MiG-21. Manoeuvrability was not an urgent requirement. This led Mikoyan to consider two options: lift jets, to provide an additional lift component; and variable-geometry wings, which had been developed by TsAGI for both "clean-sheet" aircraft designs and adaptations of existing designs.The first option, for an aircraft fitted with lift jets, resulted in the "23-01", also known as the MiG-23PD, was a tailed delta of similar layout to the smaller MiG-21 but with two lift jets in the fuselage. This first flew on 3 April 1967, but it soon became apparent that this configuration was unsatisfactory, as the lift jets became useless dead weight once airborne. Work on the second strand of development was carried out in parallel by a team led by A.A Andreyev, with MiG directed to build a variable-geometry prototype, the "23-11" in 1965.
The 23-11 featured variable-geometry wings which could be set to angles of 16, 45 and 72 degrees, and it was clearly more promising. The maiden flight of 23–11 took place on 10 June 1967, flown by the famous MiG test pilot Aleksandr Vasilyevich Fedotov. Six more flight prototypes and two static-test prototypes were prepared for further flight and system testing. All featured the Tumansky R-27-300 turbojet engine with a thrust of 77 kN. The order to start series production of the MiG-23 was given in December 1967. The first production "MiG-23S" took to the air on 21 May 1969, with Fedotov at the controls.
The General Dynamics F-111 and McDonnell Douglas F-4 Phantom II were the main Western influences on the MiG-23. The Soviets, however, wanted a much lighter, single-engined fighter to maximize agility. Both the F-111 and the MiG-23 were designed as fighters, but the heavy weight and inherent stability of the F-111 turned it into a long-range interdictor and kept it out of the fighter role. The MiG-23's designers kept the MiG-23 light and agile enough to dogfight with enemy fighters.
Design
Armament
The armament carried by the MiG-23 changed as new models underwent development. The initial production variant, the MiG-23S, was fitted with the S-21 fire control system borrowed from the MiG-21S/SM. Based on the RP-22SM Sapfir-21 radar with an ASP-PFD-21 lead computing gunsight, it could carry only four R-3/K-13 air-to-air missiles in addition to a Gryazev-Shipunov GSh-23L autocannon. In the ground-attack role, the MiG-23S could carry two Kh-23 radio guidance air-to-surface missiles, two to four UB-16 rocket pods with S-5 rockets, S-24 rockets or up to of various bomb types. The MiG-23 Edition 1971, equipped with the Sapfir-23L radar and TP-23 infrared search and track, could fire the new BVR R-23 missile, although only the R-23R SARH variant. However, the Sapfir-23L was considered unreliable and lacked look-down/shoot-down capability.The MiG-23M, the definitive first-generation variant of the fighter, was equipped with the improved Sapfir-23D look-down/shoot-down radar and could carry a pair of R-23 missiles and a pair of R-60 missiles. Starting with aircraft number 3201, the APU-60-2 double-rail launcher was introduced, allowing the MiG-23M to carry eight R-60 missiles. The MiG-23 could carry up to in bombs and rockets, and from aircraft number 3701 onward it could fire the Kh-23 and Kh-23M air-to-surface missiles. Lastly, all VVS MiG-23Ms had the ability to mount a single nuclear bomb via a special adapter under the fuselage, either the 10-kiloton RN-24 or the 30-kiloton RN-40.
In the second-generation MiG-23ML, a new SUV-2ML weapons system allowed the aircraft to carry both types of R-23 missiles simultaneously. The typical loadout was an R-23R on the starboard wing pylon and an R-23T on the port wing pylon. Besides other ordnance, the MiG-23ML could also carry two UPK-23-250 23 mm gun pods on the underwing pylons. Starting in 1981, the MiG-23MLA could carry the improved Vympel R-24R/T missiles. The final fighter variant, the MiG-23MLD, could also carry the improved R-24R/T missiles in addition to a pair of B8M1 20-round rocket pods firing S-8 rockets, the Kh-23/Kh-23M air-to-surface missile, or a single RN-24 or RN-40 nuclear bomb. The MiG-23MLD's maximum bomb load was, with a standard loadout comprising four FAB-500 general-purpose bombs or ZAB-500 napalm bombs. Other configurations included sixteen FAB-100 GP bombs carried on four ejector racks, four FAB-250 GP bombs, or two RBK-500 cluster bombs.
Cockpit
The MiG-23 cockpit was considered an improvement over previous Soviet fighters as it was more ergonomic in its layout. However the pilot still had a high workload, having to manipulate switches and monitor gauges, compared to more modern aircraft with HOTAS controls. The instrument panel featured a white stripe to serve as a visual aid for centering the control column during an out-of-control situation. To prevent the pilot from exceeding a 17° angle of attack, the control column incorporated a "knuckle rapper" which would strike the pilot's knuckles as the limit was approached.Cockpit visibility was also somewhat poor in the MiG-23, although the view straight ahead was superior compared to the MiG-21. In particular, visibility was poor looking to the rear, partially due to the ejection seat which wrapped around the pilot's head, requiring the pilot to lean forward to look to the side or behind. To assist with looking directly behind the pilot, the cockpit was fitted with a mirror or 'periscope' embedded in the middle rail of the canopy, similar to the one on the MiG-17. With an infinity focus, the periscope provided a clear view of behind the plane, but did not have a wide field of view.
The MiG-23's ejection seat, the KM-1, was built with extreme altitude and speed in mind: leg stirrups, shoulder harness, pelvic D-ring, and a 3-parachute system. Engaging the ejection seat could take a long time, as the pilots had to place their feet in the stirrups, let go of the control column, grab the two trigger handles, squeeze and lift them. The first parachute, the size of a large handkerchief, was deployed out of a telescoping rod which would pop out of the top back of the seat as it started to clear the windscreen windbreak area. It was supposed to help rotate the seat into the windblast and stabilize into a flight path that would take it above and behind the vertical stabilizer. As the first chute and rod separated from the seat, a larger drogue parachute deployed to slow down the seat, allowing the deployment of the main parachute. If engaged at low altitudes, the seat included a barometric element that allowed the drogue chute to separate more quickly. One deficiency of the KM-1 was that it was not a zero-zero ejection seat – it required a minimum speed of 90 knots.
Starting with the MiG-23 Edition 1971, the MiG-23 replaced the head-down radar scope with an ASP-23D gunsight/head-up display onto which data from the radar was displayed. This was updated in the MiG-23MLA with the ASP-17ML gunsight/HUD. Because information from the radar had to fit on the combining glass of the HUD, the amount of space that could be scanned was limited to a relatively thin slice. This required that the fighter be flown very close to the target's altitude and well ahead of it to be picked up, necessitating good ground-controlled interception instructions. Israeli pilots who flew captured versions of the MiG-23 found it relatively easy to use.
Control surfaces
The MiG-23 was among the first Soviet aircraft to feature variable-geometry wings. These were hydraulically controlled by means of a small lever set beneath the throttle in the cockpit. There were three main sweep angles that were set by the pilot for different levels of flying. The first, with the wings fully spread at 16°, was used when cruising at or below Mach 0.7 or when taking off and landing. Putting the wings at mid-spread of 45° was used for basic fighter maneuvering, as well as cruising at high speeds or making low-altitude intercepts. Moving the wings to fully swept at 72° was reserved for making high-altitude intercepts or high-speed dashes at low altitudes.The wings were not fitted with ailerons but used spoilers to control rolling when the wings were at 16° and 45° angles. In addition to the spoilers, the wings were fitted with trailing edge flaps and leading edge slats to try to give the fighter a short take-off and landing performance. Although there was a gauge in the cockpit showing the position of the wings, when they were in motion, and the Mach limit for each position, there was none to indicate what was the optimum wing position for the prevailing flight condition.
Two tailerons controlled pitch and roll, in the latter case working in conjunction with wing control surfaces when the wings were not fully swept back. In addition to a large vertical stabilizer, the MiG-23 had a ventral fin to improve directional stability at high speeds. During take-off and landing, the fin hinged sideways when the landing gear was extended to prevent it striking the ground.
Starting with the Edition 1971 model, the MiG-23's wings had their surface area increased by 20%, necessitating the positions be changed to 18°, 47° 40', and 74° 40'. A dogtooth extension was added but the leading-edge slats were removed to simplify manufacturing. However this proved to exacerbate the MiG-23's stability issues at high AoA and made take-off and landings more difficult. The definitive Edition 3 wing design, introduced with the MiG-23M, retained the dimensions of the Edition 2 but added back in the leading-edge slats.
A strengthening of the wing pivot in the MiG-23MLD allowed the addition of a fourth wing sweep position of 33°, which was intended to reduce turn radius and allow for rapid deceleration during dogfights. However, with the wings at the 33° position, the MiG-23MLD was much more difficult to handle and suffered from poor acceleration. Moving the wings to this position was primarily reserved for experienced MiG-23 pilots, while combat manuals continued to emphasize the 45° position.