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Aviation History
1955
1955 - 1285.PDF
FLIGHT, 2 September 1955 399 ACCESSORY DEVELOPMENTS de Hayilland cold-air unit. EACH year it is our custom toreview in this issue new develop-ments by the British companies responsible for the more complex types of airborne accessory—such items as air- conditioning equipment, power systems and control devices. Never before, even during World War 2, has such work occupied so large a section of in- dustry, for a modern fighter or trans- port absorbs hundreds of such units, worth many thousands of pounds. Every item has to work efficiently, precisely and reliably, notwithstanding the fact that it may get very hot, very cold, or be shaken violently; furthermore, everything has to fit into the smallest possible space while remaining easily accessible for servicing or replacement. Many components have to be specially tailored for a particular installation, and the number of people involved in de- veloping and producing such equipment actually exceeds that employed in the manufacture of airframes. No fewer than 287 "accessory companies" are this year exhibiting at the S.B.A.C. Show. This is a record number, and it reflects the healthy state of our great industry. Nearly all the items described on the following pages will be available for inspection at Farnborough; further pro- gress reports, together with accounts of electronic, radio and radar develop- ments, will appear in subsequent issues. Addresses of firms mentioned below will be found in the address section on pp. 424-428 of this issue. B.T.H. liquid-fuel (i.p.n.) turbine starter. The Airscrew Company and Jicwood, Ltd. Development and production is proceeding upon all kinds of fans, the majority being in wood, although the company are also delivering fans for special purposes in which the material is of even lower density. Both axial and centrifugal patterns are in production for aircraft ventilation purposes, and the company also make fans for wind tunnels (as well as complete low-speed tunnels) and for demonstration tunnels for instruc- tional or test purposes. Automotive Products Co., Ltd.. To the well-known range of Lockheed-Ayery flexible pipes and self-sealing couplings have been added several new lines. One of these is known as the Type 15 hose, and is suitable for use with high-temperature fuels and synthetic lubricating fluids. Another type of hose has been specifically designed for use in high ambient tempera- tures, and constitutes a new range of fire- resisting equipment. Self-sealing-coupling developments in- clude the super-high-pressure coupling, suitable for all aircraft fluids and capable of accepting pressures as high as 5,000 lb/sq in. Bore sizes range from £in to |in at present. Another improvement is a quick-acting coupling, without a screwed union, joined by sliding sleeves or a spring- loaded bayonet union. When broken, the fixed portion of the coupling can be her- metically sealed by a blanking cap. Belling and Lee, Ltd. Specially developed for 30-V circuits, the L.I330 fuse is being manufactured in ratings from 35 to 275 amp for direct bus-bar mounting. This fuse-link is already widely used in the U.S.A. and is expected soon to be in service on the Viscount and other British aircraft. The familiar general-purpose fuse-link L.1O55 is now being manufactured by an entirely new technique, which bonds caps, glass and filament into one unit, caps being so securely held that they cannot be twisted off without fracturing the glass. Heavier ratings in this range for low- voltage applications are now made with strip-type elements which will withstand considerable vibration. British Messier, Ltd. One of the most recent undercarriages to be designed by this company is that for the forthcoming Bristol 191 anti-submarine helicopter. The installation comprises four fuselage-frame members each mounting a vertically held oleo-pneumatic shock absorber. The wheel fork is of the usual castoring type, but it incorporates a special hydraulic lock to prevent this action when the parking brake is on. Another hydraulic lock is incor- porated which prevents the leg from tele- scoping beyond the static equilibrium posi- tion when the helicopter is parked on a vertically accelerating surface (such as the deck of a carrier). A new hydraulic pump is the model 4839, a high-speed, lightweight unit which can be driven either electrically or by an air turbine. The operation is by swash- plate and plunger, and a small centrifugal pump is included which pre-pressurizes the incoming fluid to 40 lb/sq in. By mis action, the pump is primed and the de- livery pressure raised to 4,000 lb/sq in. The shaft input can be at up to 10,000 r.p.m., this speed resulting in an output of 15 cu in/sec. A third new development is a nose-flap actuator for a large, near-sonic aircraft. Very rapid flap actuation is required, and an accumulator supplements the normal power supplied to the jack, which is itself very large. The British Thomson-Houston Co., Ltd. Major new development by B.T.H. is a monofuel starter. In its earliest form this system required electrical power, not only to provide heat for ignition but to pump the fuel (iso-propyl nitrate) and to pres- surize the unit to initiate combustion. In the new B.T.H. starter, a fuel injector re- sembling a small liquid-fuel cartridge is incorporated, holding just sufficient fuel for one start, restrained by a spring-loaded piston. The start is initiated by a small cartridge, mounted remote from the starter in an accessible position, which provides both heat and pressure and, acting on the piston against the spring, forces fuel into the combustion space. Engagement between the starter coup- ling and the engine is gentle, being made before full power or torque is developed; further, as only enough fuel for one start is available at any time, any failure leads to safe conditions. The total electric cur- rent required does not exceed one ampere; B.T.H. also calculate the system as being some 30 per cent lighter than other similar equipment. It is going into production for the Sapphire-powered Javelin. High-energy ignition units, operated off the normal 24-V D.C supply, have been designed for various gas turbines. They are suitable for operation at altitudes up to 55,OOOft and between temperature limits of - 50 to 100 deg C; special units are now also being developed for ambients of 150 deg C. Other developments con- tinue in the field of electric motors, rang-. ing from large units for flying-control systems to very small induction motors used in radar servo-control circuits and in small blower units. de Havilland Propellers, Ltd. A new airscrew already in service is a two-bladed Hydromatic, constant-speed, feathering unit for the Heron. Previously the Heron was fitted with the well-known non- feathering bracket-type airscrew, and the new unit is offered as an alternative. It has a fibre-glass spinner and fluid de-icing, and involves a weight penalty of less than 25 1b. Considerable development has also been completed upon cold-air units for cabin air circuits. Under Hamilton Stan- dard licence, de Havilland Propellers have in production cold-air units suitable for the most advanced types of civil and mili- tary aircraft. Used in conjunction with a heat exchanger, these units can reduce the temperature of compressor-bleed air by more than 300 deg C; two of the standard sizes have deliveries of 30 and 80 lb of refrigerated a'r per minute. This company are one of the leaders in the development of guided weapons, but little of this work can yet be made public.
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