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Aviation History
1954
1954 - 0967.PDF
9 April 1954 435 C. J. Fox and Sons (Aviation), Ltd., 117 Victoria Street, London, S.W.l, market "Met-L-Chek," a quick and inexpensive method of locating metal- surface defects which is widely used in engine inspection. The procedure is the coating of the suspected pan with two non-toxic fluids, bottles of which can be carried round in the pocket. Funditor, Ltd., 3 Woodbridge Street, London, E.C.I, manufacture "Sand- jet" marking machines, which are used for marking parts in glass, cera mics, Nimonic and the hardest steels. Even on delicate blading this is a standard marking technique. B. F. Goodrich Chemical Co., Rose Building, Cleveland, Ohio (Aero. Divn., Akron, Ohio), manufacture all kinds of rubber ware, including Hycar rubber products, and Electric Rubber—a heated sheet available down to one-twentieth inch thick ness. The company's Industrial Products Division has also developed Pyrolock, a sprayed-on, quick-drying, heat-resistant coating for such items as rocket motor combustion chamber liners. A one-sixteenth-inch coat, which adheres well and resists cor rosion, temporarily protects against temperatures higher than the melting point of the metal; a typical figure is 4i sec on steel with a gas tem perature of 5,000 deg F. CJarringtons, Ltd., Bromsgrove, Worcs, and Darlaston, Staffs, are manufacturers of forged blades for gas turbines, in stainless steels, nickel alloys, aluminium alloys, al-bronzes and titanium alloys. Especi ally for this work, the company has recently opened a precision forging shop with a larger production capa city than any other similar estab lishment in Europe. General Electric Co., Schenectady 5, New York, are marketing a wide range of air-turbine driven acces sories running on compressor-bleed air. Another line of development concerns electronic turbojet control systems; originally using thermionic valves in pressurized cases, tempera ture considerations have caused a switch to magnetic amplifiers, which appear to be satisfactory. Joseph Gillott and Sons, Victoria Works, Graham Street, Birmingham 1, make precision pressings and are also noted for die steels with excep tional life, used for die blocks at Bristol for Proteus compressor blades. Graviner Manufacturing Co., Ltd., Colnbrook, Bucks, last autumn announced the perfection of "Fire-wire," a continuous resetting fire de tector which combines light weight, with extreme sensitivity, robustness and stability in operation. Breakage of the wire loop still leaves each semi-circuit working, and no ampli fying valves are needed. Specified for T.C.A. Viscounts, Firewire_ is A.R.B. approved and has technical approval from the M.o.S. H. M. Robson, Ltd., Fordhouses, Wolverhampton, Staffs, have adver tised their carburettors in this jour nal for over 40 years. They are now in volume production of a mass of fuel metering and injection _ equip ment, engine-test devices, ignition controls, supercharger gear-changers and similar equipment. Unfortu nately, little can be disclosed about their research, beyond the bald fact that they are at work on fuel systems for gas turbines, ramjets and rocket motors. Hale, Hamilton and Co., Ltd., Frays Mill Works, Cowley Road, Uxbridge, Middx, specialize in fluid-control equipment, particularly pressure-re ducing valves. Some of the more recent patterns can be used with either liquids or gases at pressures up to 6,000 p.s.i. Hamilton Standard Division of United Aircraft Corporation, Wind sor Locks, Connecticut, originally formed to design and manufacture airscrews, have now branched out into the realms of air-turbine drives, refrigeration systems, pneumatic engine starters, fuel systems and other fields. Their new research A typical Heenan and Froude control panel; this one is governing an Avon cell at the Rolls-Royce establishment at East Rogerton, Scotland, where East Kilbride Avons are run. three or four variations are often necessary in each of several parts of the engine. Mechanical loads are of little concern in this work, and in any case much of the performance testing is not arduous, for most of the time is spent in examining cruising or high-altitude conditions at about one-eighth full power. Temperatures will be recorded by thermocouples in many parts of the engine, some being scattered in the compressor airflow, others embedded in the metal of casings or blades; the blade thermocouples are cemented into drillings, and high-speed slip rings lead out the electrical signals, just as is done in strain-gauging. Sheet-metal temperatures may be recorded by the use of special temperature- sensitive paints which are selected according to the range of temperatures expected, and applied to the part of the engine to be examined. A paint may, for example, pass through two or three distinctive shades within the range 920 to 990 deg K, remaining the final colour even after the engine has cooled. Also, a series of different colours on one component—e.g., a combustion chamber, give valuable evidence as to temperatures reached in various areas. With this technique, the engine is run for about a quarter of an hour, just long enough to stabilize the temperatures, without the risk of carboning or scouring the paint off. Airflow is measured by N.P.L.-type nozzles, pitot traverse combs, cascade rigs, mercury manometers or, for high pressures, bourdon gauges. Some of the results are then sent to the calculating department so that the complex aerodynamic behaviour of the engine can be worked out. The General Electric Company at Lynn, in America, send these results through a direct teletype link to a battery of I.B.M. calculators many miles away in Ohio, and they get the answers back before the engine has cooled. All this time the engineers know what the engine ought to do from their knowledge of the compressor, combustion and turbine efficiencies and compression ratio, which together indicate a certain design thrust equal to, or greater than, that required by the contract. At no point in testing is it possible to say "we're there"; the aim is to get as near to the design performance as possible—and, since the established engine companies are no mean hands at the game, they can usually get very close indeed quite quickly. Performance testing may continue for some two years with everyone involved furiously busy the whole time. Total running time should be about 1,000 hours on each engine, including several quite lengthy runs. Total running time is a fair index of progress of the engine, although it should be carefully interpreted if a misleading conclusion is not to be drawn. Acceleration, shut-down, starting, thrust and general behaviour of the engine and fuel system will all be thoroughly examined, but some things cannot be done on the ground at the present time. It is, for example, impossible for most companies to simulate true high-speed flight conditions, either at sea level or at high altitude. The high-altitude case is ruled out by the impracticability of exhausting the engine into a low pressure atmosphere, while the high-speed at sea level case, which imposes the greatest load of all, demands ram pressure supplies which are unobtainable without proper flight testing. Flight testing is also the only means of checking the behaviour of the engine under acceleration and gyroscopic loads. One notable exception to these restrictions is the Swedish firm of Flygmotor, who enjoy a unique supply of compressed air which enables them to carry out test cell runs at full ram pressure as well as full-scale compressor testing with virtually no restrictions. In rock or clay 280ft below their experimental station they have blasted out large underground chambers which can be charged with compressed air at 120
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