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Aviation History
1952
1952 - 2039.PDF
FLIGHT, 25 July 1952 103 believed to be designated Mig-1 SF, the all-weather ver sion is equipped with a large A.I. scanner above the nose intake; this drawing also shows an additional con tainer under the belly. In this form, the fighter approxi mates to the F-86D (single- seat, all-weather); a two-seat development is also in ser vice, with increased span wings with rounded tips. MOT-IS ... considerable flexure. Outboard of the undercarriage there are two spars running at approximately 20 and 60 per cent chord; the rear spar continues to the fuselage in a straight line, but the front spar is angled forward at the undercarriage hinge to provide for the front wall of the wheel well; the front spar meets the fuselage at about 12 per cent chord. These spars are of light alloy, with plate webs and extruded booms forming an I-section. There is also a third spar which runs diagonally from a point on the front spar just outboard of the landing gear perpendicular to the fuselage centre-line; this is also a light-alloy I-section, but has wider booms to transmit the wing bending loads. Flaps are of the split Fowler type. Actuation is hydraulic, one cylinder in each wing operating its flap via push-pull rods and bell-cranks, the flaps running down track and roller assemblies to increase the effective wing area. The stressed-skin ailerons have internal mass balance and sealed aerodynamic balance; the use of such a pressure-differential balance allows a maximum effective control area, but limits the maximum surface movement. Aileron operation is by push-pull rods, which enter the wing at the leading edge; there is no power-boost. Early Migs had slats on the outer leading edges, but these have apparently been abandoned. On the other hand, each wing now mounts two stall fences, each some 4in high, formed by riveting together two sheets of thin aluminium; they are riveted to the upper wing surface parallel to the line of flight. Critical-frequency flutter build-up is prevented by a pair of weights of about 60 lb each which are shaped to fit inside the leading edges near the wing tips; they are permanently riveted in place. Tail construction follows that established by the wing. The very large fin employs two spars, the rear spar carrying the chief flight-loads. These loads are transmitted by a heavy steel frame which is built into the fuselage around the tailpipe at the same angle of rake as the fin rear spar. Both fin spars are I-beams with flanged lightening holes, the rear spar being of steel. Pressed light alloy ribs and stringers complete the structure, to which the skin is flush-riveted. The tailplane has but one spar—a massive steel I-section, forged and machined—running at 25 per cent chord. This carries all shear and bending loads to a steel carry-through structure in the fin; torsion is shared by the spar and the forward fin attach ment point. This forward attachment embodies a serrated plate which can be engaged with an indexing tooth in a number of positions to provide ground adjustment of tailplane incidence; there is no provision for actuation in the air. The tailplane halves are attached to each side of the fin by pivots, and are mutually connected by channel section members through which pass push- pull rods for elevator actuation. Elevators and top and bottom rudders are all light stressed-skin structures, operated by a combined torque-tube and push-pull rod assembly within the fin. The lower rudder carries a steel-plate mass balance at its lower end, while the upper rudder is balanced by a weight housed in a fairing at the top of the fin. The elevators are unconnected; the port surface bears an electrically-actuated trim tab. . , The main undercarriage legs are lever-suspension units; the air-oil shock absorber cylinders are hinged to the wing at their upper ends, the wheels being mounted on levers hinged to brackets on the lower ends of the cylinders. The units retract inwards hydraulically. the operating cylinders incorporating ball-locks tor locking the undercarriage in the down position. The up-lock is mechanical, and includes a small release cylinder to tree the legs by a small hydraulic jack. The large inner wheel doors are hinged to the wing root and are operated by their own hydraulic jacks, sequenced to the wheel-retracting system. The mainwheel tyre size is 26 x 6.6in, and the innerjubesrare made from a mixture of natural and synthetic rubber. The braise assemblies are of the two-shoe type, each shoe being actuated by its own cylinder. The nosewheel retracts forward, without rotating, to lie in the space between the inner walls of the engine air ducts. An emergency pneumatic system is provided for flap and under carriage operation, supplied from pre-charged air bottles. This is, apparently, a "single-shot" system. The RD-45 engine now used on the Mig-15 represents aD appreciable advance on the Rolls-Royce Nene of 1947, the independent work displayed affording an interesting comparison with similar developments—on the same engine—by Rolls-Royce, Pratt and Whitney, and Hispano Suiza. Materials used in the RD-45 are generally reported to be of good quality. Nimonic 80 and 75 have, apparently, been produced in Russia for the turbine blades and combustion chambers respectively. Many parts of the engine employ titanium-stabilized stainless steel, particularly around the fuel burners. The compressor is a normal-looking double-sided centrifugal unit, 28.8in diameter, with 29 machined radial vanes. Aluminium alloy is used for the compressor, and for the 17.7m diameter guide vanes on each side. The compressor is housed in a typically Nene light alloy casing, attached on each side of the diffuser by bolts. The nine combustion chamber assemblies each consist of a cast light alloy cover, a chamber of aluminium-sprayed steel and a Nimonic 75 flame tube. Improvements over the original Nene are given as the inclusion of an additional row of perforations in the primary mixing portion of the flame tube; the reinforcing of this section with welded rings; use of heavier metal gauges; and, most importantly, an increase in cross-sectional area of 15 per cent, and the use ofa new pattern of duplex burner. To accommodate the increased mass flow, the turbine blades and guide vanes are some half-inch longer and quarter-inch broader than those of the Nene, while the tailpipe area is up by about 30 per cent. Engine weight has increased to about 2,000 lb (up by 285 lb), although the overall diameter has been held at the standard 49.5m. Thrust Increase No afterburner is fitted to the standard Mig, although the rear fuselage permits a short afterburner to be installed if necessary. Water injection, however, is fitted as a standard feature. With it, the RD-45 Sives about 6,7501b thrust, the dry thrust of 6,000 lb already representing a gain of 1,000 lb over the Nene. The RD-45 burns kerosene, and has a specific fuel consumption of i.i4lb/hr/lb thrust. Engine controls are similar to those on British Nene-powered aircraft; it is interesting to note that the throttle quadrant embodies a cam-operated microswitch at the full power position, but on the aircraft examined, this was not in use. Engine accessories include dual fuel pumps, tachometer, generator, oil sump and filters, barometric fuel valve, auxiliary gear-box drive, and electric starter. The two flame igniters use H.T. plugs. Fuel is carried in one, two, or three centre-fuselage tanks, with a combined capacity of 330 gal. Most Mig-i5s have provision for underwing jettison tanks of similar shape to those used on the Mosquito, each with a capacity of about 160 U.S. gall. The main fuselage tanks house float-type gauges which actuate sliding potentiometer contacts. The standard armament of the Mig-15 is two 23 mm NS cannon below the port side of the nose and one 37 mm N cannon on the starboard side. Both guns are identical in general layout, mounting and ammunition feed. The 23 mm weapons, with their electro-pneumatic valves for controlling the charging and feed-assisting cylinders, each wf igh 87.5 lb. The overall length of these cannon is 78.25m. The ammunition is fired by a centre-fire percussion cap; the breech of the gun is locked at the moment of firing by the bolt-head being rotated one-quarter turn in curved guides in the body. Operation is by recoil and hydraulic buffers and pneumatic feed-assistance is used. Firing is controlled by an electric solenoid. Open link ammunition (which was beginning to come into use
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