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Aviation History
1956
1956 - 1331.PDF
14 September 1956 483 Left, a Normalair liquid oxygen storage tank and converter, made under Bendix licence. Right, the Kelvin and Hughes roller blind attitude indicator. This is a significant new departure in flight instrumentation. in performance to two 70 litre gaseous-oxygen bottles. The advantages in com- pactness of installation of liquid-oxygenconverters are well known. An additional advantage of this range of equipment isthat the reservoir itself is made in stain- less steel and is therefore Lighter and hasbetter characteristics in case of structural damage causing explosion. Normalair, Ltd., showed liquid-oxygenconverters (Bendix licence) for both military and civil application includingthe military Mk 17 5 litre unit. In this case the reservoir is made of copper and,for safety in case of explosion, is fitted with a steel-cable protective corset. British Oxygen Aro showed a series ofdemand regulators including types for normal breathing, pressure breathing andalternative pressure and normal use, each having emergency flow selectors. TheNormalair equipment was combined with their standard pressure-demand regula-tor panel produced under American licence. The lightweight oxygen equip-ment designed for gliders—and used in the world championships at St. Yan—wasalso shown by Normalair. Features of an excellent panoramic display on theNormalair stand were a complete aircraft air-conditioning pressurization system(with full complement of heat exchangers, turbines, regulators and water extractors),and a miniature version of this, using the tiny, 10 lb flow turbine (this year no longera mock-up) which is intended to supply air-ventilated suits with completely tem-perature- and humidity-controlled air. Another of Normalair's latest ventures isa vapour-cycle cooling system with the necessary fans, compressors and ducting.Normalair are working hard to produce lightweight versions of all their equip-ment and a number of pressurization and discharge valves in this new category wereon view. Sir George Godfrey and Partners, Ltd.,and the Godfrey Engineering Co., Ltd., have also entered the Freon vapour-cyclecooling field, and showed their screw- type compressor pump with an air-turbinedrive. Electric drives are also available. They also exhibited a complete ventilated-suit conditioning system and the S.R.M. screw compressor which is specified forthe Vickers Vanguard pressurization system. UNDERCARRIAGES, WHEELS, TYRES & BRAKES THE oft-stated truism that "the hardestthing about flying is the ground" might be extended to add that components usedfor the shortest time often work the hardest; this is certainly the case withlanding gear, which every year is called upon to provide a little more for a littleless. There are developments this year in brake design, tubeless tyres and thespecial wheels that are needed to go with them, and some detail improvements toundercarriage legs. British Messier, Ltd., displayed on theirstand a very small undercarriage—for the Gnat—and a very large one for theBritannia. The main undercarriage for this machine is of the four-wheeled bogietype, and the nose undercarriage shown on the stand could be steered by anadjacent rocking handle. This handle controls a selector valve which admitspressure to one side of the steering motor. A control arm translates the linear motionof the motor into a rotary motion of the toggle-links (and hence to the wheels) bymeans of two sleeves which are free to rotate about the outer tube. The follow-up mechanism (which prevents excess rotation being applied) consists of a chain,fitted to the upper end of the two rotating sleeves and engaged by a sprocket attachedto the end of a universally jointed rod. This arrangement is actuated by move-ment of the rotating sleeves. The main wheel shock absorption isoleo-pneumatic, and a bogie beam at the lower end of the absorption leg carriestwo pairs of wheels in tandem. A telescopic radius rod mounted forward ofeach leg locks the undercarriage down by means of a hydraulically applied colletwhich is released when "up" is selected. Retraction is accomplished firstly by arotation jack which rotates the bogie about its pivot and then (by sequence-valve command) a retraction jack. The wheels, tyres and brakes on thisundercarriage are all manufactured by the Dunlop Rubber Co., Ltd., who arenow manufacturing a brake which is notable for the use of inorganic frictionmaterial for the brake pads. In this type of brake, a caliper is formed by the torqueplate, spacer tube and back plate. Between these components, steel segments arelocated radially in rotor spiders keyed-in to the wheel structure, and are brought intocontact with the friction pads by means of a pressure plate. Now coming into service are Dunloptubeless tyres and special non-porous wheels are being manufactured to containthe air within the tyre and wheel. Both hydraulic and pneumatic operation (usingpoppet valves) of the Maxaret anti-skid braking controls is now provided, a typicalapplication of the pneumatic unit being in the Fokker Friendship. Over a millionMaxaret-assisted landings have now been made, largely by Viscounts in America. The Ferranti EV6 gyro vertical with three Type B rate gyros grouped round it. Such a unit would feed attitude information to the roller blind instrument illustrated, above right, as well as to other aircraft systems. Goodyear Tyre and Rubber Co., Ltd.,were showing their tri-metallic brake (a photograph of which appeared in Flightof August 31) in which the moving discs are coated with a special sintered iron;and one of the tyres exhibited was of the tubeless type—this, Goodyear expect, willrapidly outplace the conventional tyre which is less satisfactory in accommo-dating heat-soak from the brake. Special non-porous wheels are being developed. The disc brake which was shown byGirling, Ltd., consists of a disc gripped by friction pads in a caliper set astridesingle or twin discs floating on axial splines. An independent emergencyoperating system is provided. A feature of this brake is that the friction-pad wearis taken up by automatic adjustment incor- porating the well-known Girling hydra-static principle. Servicing is simple and can be accomplished with a minimum ofdismantling. ENGINE ACCESSORIES —FUEL SYSTEMS THE demands of a gas turbine fuel systemnecessitate specialized equipment to pro- portion the supply from the fuel tanks, tomeasure the flow, despatch it along the pipe lines, filter it and finally deliver it tothe combustion chambers in the exact quantity required for the particular con-ditions of r.p.m., altitude and temperature prevailing. Dowty Fuel Systems, Ltd., have nowproduced an engine fuel system which is built as a one-piece unit rather than anumber of components positioned on the engine at various points and inter-con-nected by piping. An advantage of this arrangement is that the whole engine fuelsystem can be serviced from a general access point. This system, which has beendesigned for use with Dowty spill nozzles, comprises a single basic hydraulic controlincorporating an hydraulic all-speed governor. The latter operates over thewhole engine speed range, synchronizing electrical trim, temperature maximumlimit or range control, acceleration control, automatic minimum safe idling speed con-trol (at all altitudes) and a mechanical governor for emergency maximum speed.The Dowty spill system gives improved atomization with increasing altitude since,for a given circulatory flow, the quality of atomization tends to improve with reducedrates of discharge from the nozzle. Other advantages claimed for spill nozzles arethat the system is less sensitive to dirty fuel because the discharge orifices are rela-tively large and no valve gear is required
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