Mikoyan-Gurevich E-8 "MiG-23" - Design
The layout scheme of the traditional MiG had the air intake in the nose, power plant behind the cockpit in the tail, and the radar arranged in the central cone. This scheme was optimal from the point of view of aerodynamics, especially for the first jet MiGs. However, when more powerful radars were required, there was clearly not enough space for their placement in the cone of the air intake. In addition, at speeds M> 2.5, aerodynamic heating was already beginning to affect, and the air intake channels located inside the fuselage became centers of completely unnecessary heating. The solution could be only one: remove the air intake from the nose of the fuselage. Of the many layouts, those were chosen where the air intakes were placed either at the bottom of the fuselage or on the sides.
The outward appearance of the Ye-8 differed substantially from the standard look of the MiG-21, on the basis of which it was constructed. It featured canard foreplanes and a redesigned rear of the fuselage to accomodate new engine. There were a number of other features that were different from MiG-21PF - from new ejection seat and canopy to modified rudder and new fin under the rear part of the fuselage. The R-21F engine developed by N Metskhvarishvili, was rated at 4500kg and 7000kg with afterburning. A variable-incidence canard spanning 2.60m was fitted - this having been earlier tested by a Ye-6T - and it was proposed to install Sapfir 21 radar to accompany an armament of two K-13 AAMs.
All preceding aircraft of the MiG firm had a central, frontal air intake, but on this one it was located below, under the cockpit. The nose portion of the fuselage was faired, and was intended for the placement of a radar with a large-diameter antenna. There was still no radar, true, on the first experimental Ye-8/l and then on the second Ye-8/2. The installation of the new 8-23 intercept system, which included the Safir-23 radar and the R-3S air-to-air missiles, and later the R-23T, was planned. There was still no radar suitable for installation on the aircraft by the time of building of the first flight of the Ye-S, and the weight equivalents of it were thus installed in its place. The monitoring and recording apparatus and the telemetry unit were also accommodated in the nose portion along with the weight equivalents.
One of the chief features of the aircraft, simultaneously with the new and progressive aerodynamic configuration, was the new, experimental R21F-300 engine with enhanced thrust. It was somewhat larger than its series predecessor, the R11F2S-300 on the MiG-21PF aircraft, in overall dimensions and weight. Its thrust with afterburners increased from 5,740 to 7,200 kgf. The degree of thrust augmentation for the new engine was quite high and reached 55 percent. The R21F-300 was designed and built at the motor-building OKB headed at the time by Chief Designer I. Metskhvarishvili. Many aviation designers placed great hopes on this twin-rotor engine -- which were not, unfortunately, later justified.
The R21F-300 engine - due to the culprit of all ills - a six-speed compressor - turned out to be unviable. Designers were forced to reduce the pressure of the steps, increasing their number. Engines of the P27-300 and P29-300 family, which used the main two-shaft scheme from their progenitor P11-300, had a thrust on the afterburner of 10,200 kgf and 12,500 kgf. These were the main engines for the MiG-23 fighter.
Small winglet side stabilizers were mounted along the sides of the nose portion of the fuselage. The wing, landing gear and empennage of this aircraft did not differ from the same elements ofthe MiG-2IPF design. The forward landing-gear strut, true, was somewhat altered in appearance -- it had a breakaway strut. There was one more feature that struck the eye -- a large fence (supplementary fin) was placed under the tail section of the fuselage. The fence was turned 90° when the landing gear was down, and it was opened after takeoff, significantly increasing directional stability in flight. The lowering and retraction of the fence was interlocked with the retraction and lowering of the landing gear. This very design was used several years later on the MiG-23 aircraft.
The winglet in the nose portion of the fuselage had no control system at all, and was located in a wind-vane position in subsonic mode. When the aircraft reached Mach 1 the winglet was mechanically fixed in a neutral position relative to the axis of the aircraft. This altered the position of the focal point and reduced the reserves of longitudinal stability, which were excessive at supersonic speeds. The possibility of sustaining much larger G-forces at supersonic speeds was provided thereby. The Ye-8 aircraft actually could have become a fighter for maneuvering aerial battle as early as the beginning of the 1960s, such as the MiG-29 and the American F-16. The air intalke, located under the fuselage, was executed in a flat, dual-stream mode with a vertical three-position wedge with electrical / hydraulic control. A recess for lowering the forward landing-gear strut was located between the panels of the wedge.
There was another innovation on the Ye-8, albeit invisible from the outside -- all of the fuel tanks in the fuselage were no longer rubber bag (insert) tanks, as on all the various modifications of the MiG-21. They were tanks of the design that later became widespread on all subsequent MiGs without exception. The Ye-8 could hold in all 3,200 liters of kerosene, in five fuselage tank compartments and four wing tanks (as on the MiG-21). The Ye-8, like the Ye-7, had a system for boundary-layer ejection from the flaps when landing. It had not been activated on either the Ye-8/l or the Ye-8/2, however.
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