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Aviation History
1953
1953 - 1256.PDF
412 FLIGHT September 18, 1953 "Wit** f FARNBOROUGH'S FULL WEEK Messier was the main and nose undercarriage for an aircraft whose identity must, for the time being, remain secret. The main unit was illustrated and commented upon in our September 4th issue. It carries a very-high-pressure tyre and the geometry suggests that it will be housed within a swept wing. The nose gear is short and neat and, during retraction, the hydraulic steering jack turns the leg so that the wheel lies flat in the nose of the aircraft. It can now be said that the massive Goodyear wave-type wheel exhibited was the pattern employed on the Valiant B.2. The fact that four such units are fitted to each of the new bomber's bogies underlines the very great increase in weight of this aircraft, in comparison with the earlier Mk 1 Valiant. The wave-type wheel was developed to permit forging in magnesium alloy, although the Valiant unit shown was cast. That particular attention has been paid to ease of servicing is shown by the fact that the brake discs—system pressure is 900 lb/sq in—can be examined in situ; the whole design, in fact, facilitates inspection without the need for any dismantling. A three-spot brake unit goes with each wheel, and the tyre size is 43in. The whole unit is of Goodyear (Wallasey) design and manufacture. Smaller units of the same family are expected to save B.E.A. £1,000 a year, fitted to the Pionair-Leopard freighters. The same airline expects to save a similar sum when the Viscount fleet is re-equippd with Rotol rebated-blade airscrews. The new blade is a solid duralumin forging, the leading edge of which is rebated over the inner two-thirds radius. This cut-away portion is filled with an electric heating element consisting of woven glass and wire fabric, with an outer covering of black neoprene rubber. The whole is cemented down and ground flush, and is said to have no measurable effect on performance. Compared with the blades originally used, the new pattern is easier to service and repair. Rotol also showed the synchronizing equipment already flying in the Comet 2 and soon to be fitted to Viscounts. Flying safety will gain by the adoption of such devices as the Ferranti air-stream direction detector. The sensing head of this equipment consists of a short tube—visible in the illustration below —whose area of 0.0091 sq ft can cause no real performance- loss, even on supersonic fighters. From narrow slots, parallel to the tube axis and 90 deg apart, ram air pressure is led to a chamber, where the pipes from the slots act on opposite sides of a paddle. The paddle shaft is geared down to drive the shaft upon which the sensing probe is mounted until the slots are symmetrically disposed with regard to the local airflow, the two ram pressures then being equal. Movement of the paddle shaft is recorded on an angle-of- attack meter, with a 20 deg range. From the demonstration rig we saw—driven by an air stream moving at no more than 60ft/sec —the accuracy and response appeared all that could be desired, the brochure figures being "within one-tenth of a degree" and "five c.p.s. at 200 knots I.A.S." The probe can be fitted to measure either angle of attack or yaw according to which way ___-^_^__ it is mounted. It can be applied to any aircraft, once initial calibration has been carried out. New Kelvin and Hughes products shown included two types of stall-warning device, the need for which is be coming daily more ap parent. One pattern, de- The Ferranti air-stream direction detector (left) and Kelvin and Hughes precision tachometer with synchroscope. From the left: Servo motor Type A for the Sperry Mk 11 Auto pilot; Flight Refuel ling Mk 11 "in line" refuelling valve, weighing 28 oz. and claimed to be the lightest and most compact valve of its kind; and the very practical Short ana logue computor. veloped and patented by G. F. Bethwaite, a lecturer in the Depart ment of Flight at Cranfield, consists of a small metal plate mounted above the wing at about 90 per cent chord—where no icing should be met. The plate is hinged to rock about a spanwise axis, and is normally held forward by a spring. Ram air pressure, however, holds the plate against the spring in flight until—as the stall ap proaches— decreased ram and me onset of flow reversal allows the spring to pull the plate forward so closing an electric circuit. Spring tension can be adjusted to cause operation at any desired speed, 1.1 Vs being typical. The second instrument is the Youngman detector, in which two capsules are respectively connected to underwing static pressure and full ram pressure. As the stall is neared, the static pressure becomes proportionately greater, although bom pressures fall away together. When the static pressure reaches a value fixed for a given aircraft—perhaps 60 per cent of ram pressure—an electric contact is closed by the relative capsule movement. Both the Kelvin and Hughes systems can be used in conjunction with stick-shakers, horns, or any other type of warning. Briefly referred to in our pages last week was the Boulton Paul variable gear and datum change mechanism. This permits un- worried piloting over a wide speed range without overloading the airframe, the control-surface deflection caused by full travel of the pilot's controls being progressively reduced as indicated airspeed is increased. This is accomplished—very simply, in principle—by placing two control rods roughly at right angles to each other, and constraining the pivot between them to move along a guiding ramp. When the ramp is at 45 deg to both rods, the longitudinal motion of both rods is the same, but rotation of the ramp varies the gear ratio as the tangent of the ramp angle. The limitation so placed on high-speed control-surface move ment can lead to difficulties in that all the available move ment in one direction may already be taken up to trim the aircraft. Accordingly a separate trimming mechanism is incorporated in the control run, so leaving the pilot with the full movement per mitted by the gear ratio in use. Electric trimming is provided, with a fast and accurate movement. The datum shift can also be used with powered controls in place of spring bias, with con sequent improvement in the "feel."
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