In the 80-s the MIG-OKB (Mikoyan Design Bureau) started the development of the combat airplane which was given the designation "Aircraft 23-11". On 22 May 1967 the prototype known as "aircraft 23-11/1" was taken for trials in Lll (Flight Experimental Institute) at Zhukowsky and a few days later, on 26 May made its maiden flight with the MIG-OKB's chief test pilot A. Fedotov at the controls. In 1969 the aircraft entered the full-scale production designated as MIG-23s, Since then they had been continually imroved and subsequently several modifications emerged: MIG-23M, -MF, -MS and so on-Needless to say that each of MIG-23 modifications deserves a special consideration, but the present article will be concerned with late production aircraft of this family: MIG-23ML, -P and -MLD.

   Efforts to improve the aircraft characteristics had been made along diversity of avenues: creation of more economic power plant, aircraft firepower increase, improvement of radioelectronic equipment. These effort made jointly by several design teams had a success. In 1976 a new MIG-23 version designated as "Aircraft 23-12" (Products) had been built up. Changes introduced to the power plant, airborne equipment and armement made it possible to consider them as a major step toward the creation of a up-to-date fighter demonstrating extensive capabilities. The R29-300 engine (Product 55) which powered the previous modification (MIG-23M} had been abandoened in favour of the R35-300 one (Product 77) developed at Hatchaturov Design Burean. The early series of this engine were rated at 8550 Kg under the maximum operational mode and 12700-1300 Kg with a controllable afterburming. The installation of a more economic engine allowed to remove the fuselage fuel tank N4 (It was located between frames 28 and 32 just ahead of the stabiliser). Nevertheless, the total fuel capacity of 550 Kg with three external PTB-800 tanks of 800 I each permitted to increase the aircraft's ferry range to 2820 km. Since the weight savings had been almost of 1250 Kg as compared with MIG-23M variant the new modification received the designation MIG-23ML (L - legkij, i.e. light), NATO reporting name "Flogger-B".

   The MIG-23ML was equipped with automatic control system SAU-23AM, "Polyot-21-23" navigation and flight control complex comprising "RSBN-6S" - short-range radionavigatlon system, "IKV" inertial navigation system (a gyroscopic system enabling a very precise definition of the aircraft's lateral position and its coordinates) and air signals system allowing to establish with a high degree of accuracy the flight altitude and speed. The "Polyot" complex could operate separately and is conjunction with the "SAU-23AM" system. Such a set of navigation and flight control equipment made it possible to minimize errors in the aircraft's flying and its vectoring on to the target. This enabled to reduce the aircraft's stay in enemy defendant airspace, to simplify aiming processes and weapons use, to reduce fuel consumption in target searching. The "23-12" version was provided with RP-23ML sighting system which comprised the "Saphire-23ML" fire-control radar (search range up to 80 km and tracking range 50 km), the TP-23M infra-red radar (search range 35 km) enabling to hit targets against the background of the earth's surface and the ASP-17ML air gun sight. In comparison with an earlier version (MIG-23M) the MIG-23ML's characteristics had been improved through the use of the SRO-2M mode limitation system. It simplified the aircraft handling at high angles of attack which allowed the pilot to use the machine performances to best advantage (e.g. in air combat maneuvering with 360° banked turns and great toad factors). The MIG-23MB had been manufactured in full-scale production at Moscow "Znamya Truda" (Banner of Labor) factory until 1981 for Soviet Air Force and 1985 for exports.

   The MlG-23MLs, when being taken at aircraft repair factories were constantly Improved after which they were designated as "MIG-23MLD" (D-dorabotannyj, i.e. "improved"), NATO reporting name "Flogger K". The refinements were concerned primarily with the fuselage structure and were intended for improving the aircraft stability in conducting high angle-of-attack maneuvers. For instance, vortex generators had been installed at the juncture of the Pilot-static tube boom and the fuselage. The generators were made in the form of two plates which in flight gave rise to air vortices behind them. At high angles-of-attack (for MIG-23 they constitute 17-20° and over) when the aircraft's stability Is adversely affected the nose begins to yaw. Such a trouble in its turn may result in stalling and uncontrollable spin entering. But the vortices produced by plates vortex generators) prevent the development of such events. Similar arrangements were later tested in F-18s and SU-27s.

   Another updating consisted in a saw-cut out completed at wing root which also created a powerful vortex but in contrast with an above-mentioned improvement it was responsible for a general wing and fuselage flow. Further developments In airborne equipment led to the emergence of the SOS-3-4 automatic angle-of-attack and wing sweepback limitation system (sistema ogranitchenya signalov - signals limitation system). In accordance with the aircraft's lateral altitude, flight speed and altitude the system drooped the leading-edge. This improvement made it possible to delay the aerodynamic stall from the upperwing surface and therewith to get better the fighter's maneuverability, i.e. to gain its handling at great load factors and high angles of attack. The leading-edges were drooped a! up to 900 km/h (M<0,9) and at angle-of-attack being more then 10°. The system was to operate in the wing-sweep angle range between 16° and 33°. At high speeds, when the wing had the maximum sweep (72°) the leading-edges returned to their original position. Such restrictions on the speed and sweep angle had been made with regard to the experience gained in local conflicts. Following the course of hostilities in Afghanistan late production aircraft were provided with:
- more sophisticated SPO-15L irradiation warning equipment supporting a more accurate finding of the air enemy's attack direction and subsequently offering good opportunities in carrying out appropriate anti-missile maneuvers;
- BVP-50-60 chaff/flare dispenser (radar-reflective dipols cause chaff dutters on enemy's radar screens;
- SPS-141 active jamming radar which affects the operation of enemy's radio aids;
- wind sweep angle warning indicator "16 degrees";
- IFF system "Parol" ("password") created after It V. Belenko defeated In a "MIG-25" to Japan. The system is designed in such a way that codes change automatically and therewith even a regiment navigator responsible for installation of new codes does not know what they will be after computer-aided processing. If one makes any attempt to read codes from "Parol" system storage the latter will be automatically deleted. So, the enemy can not copy the system and penetrate the defendent airspace without being identified as intruder.

   Additionly to MIG-23ML, MLD modifications the middle 70s saw a new interceptor to emerge which was intended to replace SU-9s considered as out-dated, When developing the new interceptor (aircraft 23-14, Product 6) the MIG-23 Mi-was chosen as a basic airframe. Since the changes concerned essentially the equipment the interceptor had been tested in a very short time. In 1978-79 the Interceptors began to go into service with air defense regiments under the designation "MIG-23P" ("P" perehvatchick, i.e. Interceptor), NATO reporting name "Flogger G". The MIG-23P airframe srtucture was similar to that of its counterpart MIG-23ML since it was manufactured at Moscow maschine-building factory "Znamya Truda- and even rolled off the same assembly line. But differences in assigned task (the principal one consisting in the interaction with the national air defense system) determined the choice of the equipment that MIG-23PS had to be provided with which in its turn, caused the partial relocation of some service hatches.

   The MIG-23PS were equipped with:
- ASP-23PM gun sight;
- SAU-23PM automatic control system;
- "Saphire-23P" radar;
Apparatus enabling the Interceptor to be vectored automatically on to its target following the signals provided by automated command guidance system. The interceptor inhereted the MIG-23ML's armament but it was not fully utilized in fighter units. The aircraft were not used in training flights for air-to-ground role, therefore they were not fitted with weapons carriers intended for the use of guided missiles, rockets and bomb armament. !n 1989 after the Soviet government's decision concerned with tactical nuclear forces limitation, the possibility to use the inerceptor for air-to-ground role has been practically reduced to zero. The point is that in accordance with this decision most of the MIG-23s and all MIG-23PE have lost their special bombing equipment and "Delta" system which enabled the utilization of X-23 (Product 68) air-to-surface missiles the necessary arrangements being performed immediately in fighter units. Nowadays, several dozens of MIG-23P interceptor versions differing to only a small extant in equipment remain operational.

   In 80s late production MIG-23P interceptors (sometimes they are reported as MIG-23MLA began to go into service being equipped with:
- ASP-17 gun sight;
- TP-26 infa-red radar (seach range up to 60 Km);
- "Saphire-23MLA" radar presenting 170 kg of weiht savings as compared with previous radars;
- digital system for checking and controlling optimized flight path, aiming mode selection and weaponry use moment in conjunction with a ground-based guidance station or a director airplane (e.g. MIG-31)
- late production KM- 1M ejection seat unlike earlier grey-coloured modifications its colour is black).

   The fighter's armament system comprised R-24 missile. Later it has been completed by R-73 omnidirectional missile. Thus, having a service ceiling of 18500 m the interceptor could engage targets at flight levels ranging from 40 to 24000 m. The article is continued with the descripption of aircraft's structure features and maintenance procedures. The concluding part deals with colour shemas of aircraft versions under consideration.