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Aviation History
1952
1952 - 1148.PDF
PIKA JINDIVIK The Jindivik—pilotless version of the Pika. Later production aircraft will feature a needle nose, a smaller but more powerful Viper turbojet and simplified airframe structure. Further Details of Australia's Turbojet Piloted and Pilotless Aircraft A FTER consultation with the Australian Department of /% Supply and Development early in 1948 the Ministry of Supply issued specification E.7/43 for a pilotless target aircraft for use in conjunction with the development of guided missiles. The responsibility for the design and construction of the aircraft was vested in the Government Aircraft Factory at Fishermen's Bend, Melbourne; design work began in the summer of 1948. To cut down development time, a piloted version was first built. This aircraft—originally known as "Project C," but now given the name "Pika" (an aboriginal word meaning "flier")— enabled a direct human check to be made on both general flight characteristics and on the functioning of the control equipment. This aircraft, which first flew in October, 1949, differs from the unmanned machine in several major features. Provision of a cockpit with all essential services implied the use of side intakes for the Armstrong Siddeley Adder turbojet. The two ducts blend behind the cockpit and pass through the annular fuel tank before reaching the engine. In addition, an under carriage is fitted—with main wheels of but 13m diameter— retracted by a fixed-capacity 2,000 lb/sq in pneumatic system capable of providing four cycles per charge. As Pika data became available, the unmanned aircraft was rapidly developed; originally "Project B," it now bears the name "Jindivik"—an aboriginal spear-thrower. The Jindivik wing uses N.A.C.A. 64 section with a constant T/C ratio of 10 per cent; the small span (19ft) permits a minimum number of panels to be used. Each wing employs a one-piece skin reaching back to 50 per cent chord on both top and bottom surfaces; there are no chordwise joints. Direct shear is carried by the two spars at 30 and 70 per cent chord, while bending and torsional loads are taken in the 14 s.w.g. skin reinforced by vee-section stringers. The small number of nose and intermediate ribs are light pressings. The ailerons and flaps are of the plain circular-nosed type with sealed gap; in addition, Vampire dive-brakes are incorporated, while the wing root sweep-back at the leading edge is stated to be an anti-stall feature. Construction of tai' follows that of the wing; plain circular-nosed metal control surfaces are used, with small unshielded mass-balance horns. N.A.C.A. 64 section is also employed for the tailplane, the T/C ratio of which is 8 per cent. The fuselage is divided into three detachable sections. Details of the remote-control equipment cannot be given, but it broadly consists of a radio receiver, signal analysers, an autopilot and a telemeter. A transponder is also carried to provide a large return radar signal and thus increase the range over which the aircraft can be "seen" on the radar screen. As surmised in Flight of January 25th, 1952, the radio receiving aerials are housed in the fin leading-edge. Accu-nulators and autopilot gyro-units are accommodated in the nose section; production aircraft will have a conical nose carrying the pitot heads. Radio and telemeter equipment is carried in a removable crate in the centre fuselage; abaft this crate is a bay to be used for housing special target equipment, while yet further aft is the lightweight bag-type fuel tank, through which the engine intake duct passes. At the centre fuselage the wing is picked up by two bolts at the front spar and two shear-pins at the rear. The engine—a Viper in the production aircraft—is carried on trunnions in the rear fuselage and below it are two small fuel tanks, while servo motors for rudder and elevators are mounted under the tailpipe. Air is tapped from the engine compressor, led through a reducing valve and used to pressurize the fuel system; the fuel is pumped from the rear-fuselage tanks i>ia the main tank to the engine. "The landing skid is held in the retracted position in the centre fuselage by a copper shear-pin, with all air exhausted from the shock-absorber strut (ground handling and take-off are performed with a tricycle trolley). The "wheels down" signal admits air from a bottle to the charging connection on the strut; this both shears the locking pin and extends the strut fully. Skid and flapi are interconnected to move up and down in harmony when the aircraft has landed on bumpy ground, so preventing flap damage and also reducing any tendency to bounce. Fuselage and wing-tip bumpers are provided, together with a tail parachute. The take-off trolley releases the Jindivik at a predetermined speed, when the arms supporting the aircraft collapse—with spring assistance—and the rear wheels of the trolley are braked; the trolley nosewheel is monitored by directional gyro to cure an early directional instability. Future development will largely concern the Jindivik 2, which is to be powered with the Viper, the thrust of which is some 1,600 lb, or over 50 per cent more thrust than that of the Adder. The airframe is being suitably modified to permit higher speeds and the structure is being still further simplified. Production of the type will take place at the Finsbury, S.A., works of Chrysler (Australia), Ltd. DIMENSIONING COMPRESSOR BLADES IN me past, considerable delay has sometimes been caused in the manufacture of gas-turbine axial-compressor blades owing to lack of any uniform method of dimensioning. Compressor blades exhibit some of the most irregular shapes met in the whole air craft industry : the blading of a single engine type may be made up of perhaps a dozen different patterns, each with its own profile, length, thickness, twist, lean and surface finish. All these factors are now included in a standardized method for blade-dimensioning evolved by the engine standardization panel of the S.B.A.C. The standard specifies the minimum information which must be included on each blade drawing, together with the relevant tolerance and the measuring methods to be adopted. This should make for a great reduction in the time formerly spent by forging firms, engine manufacturers and their sub contractors and the A.I.D. in translating drawings into their own terms. When it is realized that current gas turbines require about 2,500 compressor blades each—irrespective of spares—the importance of eliminating bottlenecks becomes apparent.
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