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Aviation History
1949
1949 - 0385.PDF
MARCH 3RD, 1949 FLIGHT 251 article is considerable. It is, however, undesirable that defective castings should be allowed to pass through to the final machining stages: not only would this be a waste of material but also a waste of machining capacity. Thus, the official requirement that all cast components which could possibly lead to failure of an engine must be radio- graphed after casting, although a safety precaution, does have a useful economic effect as well. Inspection by radiography is no npw thing^at ParkJSi^e, Coventry, for a small (i^kV) Philips set Jjas been'in abn- stant use there for about ten years and has given yeoman service. This equipment can achieve penetration of about 1^ to 2in of mild steel and Is thus quite capable of dealing with small units such.as, for example, Mamba stator blades. Recently, however, a somewhat larger apparatus by Siemens Schukert (Great Britain), Utd., has been installed, and this, at 220 kV and 15 mA, oilers a penetration capacity up to 3m of «mild steel, and ts thus capable of handling both larger, a^d'/or denser units. For a given power, the penetration of X-rays is depen- dent upon the density of the object to be viewed. Changes can be rung to a certain extent between the cardinal fac- A radiograph showing micro-porosity in cast stator blades for the compressor of a Mamba turbo-prop. All these blades were rejected. tors, but typical values may be stated as exemplifying the performance, viz.: at 100 kV and 10 mA the exposure time to penetrate 100 mm of aluminium at 50 cm focal length is 50 sec. To penetrate the same thickness of ordinary cast iron in the same time, and under the same relevant conditions, the requirement would be for 500 kV. On the other hand, using 100 kV, the effective penetration limit for the same exposure time would be 20 mm. As may be seen from the photographs, the set has a work- manlike appearance and gives an impression of being appo- site more to the hospital than to the engineering laboratory. The radiographic laboratory in which both the sets are now housed is pleasantly spacious and was appropriately constructed for its purpose with integral protection. Actually, the degree of X-ray scatter is very slight, and the likelihood of serious effects would arise only if the equipment were ignorantly misused: even in this even- tuality, however, the protective construction of the labora- tory would offer adequate safety measures. Measuring 2iftx 27ftXgft the laboratory has 19m walls with a fin internal cavity filled with barium plaster, the room surfaces of the walls also being rendered with a further fin of barium plaster. The floor is of concrete, treated with a bitumastic compound, whilst the ceiling is of plaster board and glass: as there is nothing above the laboratory, the lack of screen- ing protection in the roof structure is not critical. There are steel and wooden doors serving the laboratory and all are internally lined with a ^in-thick sheathing of lead. * Control Gear Adjoining the laboratory, and as part of the same build- ing block, are the control room and dark room. Control of the apparatus is vested in a console with push-button selectors and indicator scales for A.C. volts and D.C. milli- amperes. There is also the main switchgear and an auto- matic exposure-time clock and switchgear. On this latter is pre-set the required exposure time and, as soon as the set is switched on the clock is energized; when the required exposure is complete the clock automatically switches off the equipment and re-sets itself. Unexposed negatives—ioinxi2in and i2inXi5in are the standard sizes—are placed in special envelopes, on one side of which are printed rectangular divisions. An enve- lope is placed on the lead viewing table and the units to be tested are laid in the divided areas on the envelope adjacent to small lead numerals which, opaque to X-rays, show up as identification on the negative. Whilst one batch is being viewed, the preceding batch is being developed. This process takes about 45 minutes to an hour and it is quite possible to view, develop, fix and assess 300 to 400 units in a normal working-day period of six hours. This is, however, dependent on unit size, but the normal average is, for example, to view about 55 Mamba stator blades in a single batch, whilst Python stator blades are viewed in batches of approximately 25. DEATH OF NEVILLE STACK TDELATIVES and friends were shocked to learn of the death -tv Of T. Neville Stack, A.F.C., near Karachi on February 22nd in what appear to have been tragic circumstances. We are by no means satisfied that the information available at the time of going to press tells the whole story. His family in England knew that he was on . ^, the point of a nervous breakdown, and that he was refused permission to be taken away lor treatment and rest, but other circum- stances are still not fully clear. He was buried with full military honours. Six K.A.F. officers carried the coffin and an escort was formed by 20 other ranks. Thomas Neville Stack was a familiar figure in aviation circles both at home and abroad, and was one of the real old-timers. He transferred from the Army to the R.F.C. in 1917, and on leaving the Services became chief instructor to the old L. and P. com- pany. He rejoined the R.A.F. in 1921 and served in Iraq. On demobilization in 1925 he became chief instructor to the Lancashire Aero Club and in 1926-27 he and Bernard Leete made the first flight from England to India in two D.H. Moths. In the years which followed, Stack made several notable flights and served with Aircraft Disposals Co., Ltd., National living Services, Airwork, Hillman, and British Airways. In the second, world war he was for a time chief test pilot to the Austin company and later joined the Fleet Air Arm. Lt. Cdr. T. Neville Stack, R.N.V.R. He commanded No. 742 Squadron in Southern India, formed to link up the scattered Naval air stations and establishments. The squadron did splendid work while flying Swordfish, and was later equipped with Expediters. At the time of his death Stack was manager of Orient Airways. Neville Stack was always very good company. He was never happier than when singing a song and strumming on his banjo. Often he would render his own verse and music, and his old 742 Squadron was immortalized in his little book "The Saga ~£ '742'." for which he wrote the verses and composed manyof of the tunes. With his passing a coloiirful personality has gonefrom British aviation. PLIOFILM IN PRODUCTION PLIOFILM, a rubber-base transparent film material forpackaging, is now being produced in this country by the Goodyear Tyre and Rubber Co., Ltd., whose new factory at Wolverhampton was formally opened on Friday of last week by Lord Ammon, deputizing for Sir Stafford Cripps. The material was used for the protection of aircraft engines, instru- ments and spares during the war on all fronts from the arctic to the tropics, and was claimed to effect a saving of 75 hours formerly spent in greasing and degreasing on each engine. Six standard gauges of Pliofilm are produced, 100 (o.ooiin), 120 (o.ooi2in), 140 (o.ooi4in), 170 (o.0017m), 200 (o.oo2in), and 250 (o.0025111). It is stated to be air-, moisture and liquid-proof, resistant to puncture, tear= and abrasions and easily sealed by heat.
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