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Aviation History
1922
1922 - 0180.PDF
materials of an aeroplane—a matter always of life and death— demands that no method of inspection which adds or may add so much to the security of the structure as a whole can be ignored without the fullest possible investigation. Slides were then shown illustrating general radiological inspection work. The majority of these were radiographs of objects not connected with aircraft construction, although some illus-, trated well-known aeroplane components. One slide showed an aeroplane spar with internal cross-grain which was not visible externally ; others illustrated what appeared to be defects in welding elevator and aileron king posts. The most glaring example was, however, furnished by a slide showing a radiograph of a control lever in which the end of the pivoted portion was not pushed sufficiently far into the main tube, the two pins which were intended to secure the two parts to one another passing through the main tube only. A quantity of solder at the outer end was all that kept the control tube attached to its swivelling base. Had this control tube been mounted in the machine an accident would almost certainly have happened. The Discussion THE Chairman, Lieut.-Col. O'Gorman, said that some seven years ago he visited a large French aircraft factory not far from Paris, and he discovered that this establishment had a radiological research department. This was, however, of a very dangerous nature, he was told, and he was not allowed to see very much of it. Great satisfaction was expressed with the work which could be carried out, although apparently the only defect which had ever been discovered by the aid of radiological examination was a small crack in a certain component. As this crack was easily visible by ordinary inspection, the value of the installation seemed somewhat doubtful. He hoped that modern work was of more value. He then asked the audience to consider the paper open for discussion. Col. Briggs thought that, as metal construction is now coming to the fore, any means which would enable one to detect flaws was of importance, and especially for metal propellers, where there was a great deal of welding, radio logical inspection might be of considerable help. He thought that the A.I.D. might make more use of it, and wanted to know if it would be possible to have a portable plant which could be used by the A.I.D., and how much such a plant would cost. Mr. Manning said that he had watched with great interest the various slides, and noted the dark spots and light spots, but he was somewhat at a loss to interpret the radiographs, MARCH 23, 1922 and would like more information regarding the manner in which an inspector could interpret the information conveyed by the radiograph. One member of the audience, whose name we failed to catch, asked if it was usual, during inspection, to turn the specimen over for examination, so that a defect which in one view appeared as a hole might be revealed in another position as a line or crack. Mr. Kaye, of the N.P.L., stated that the A.I.D. already had an apparatus at the N.P.L., and that a certain amount of work had been carried out. • He thought, however, that we still had a long way to go before we could popularise JC-ray inspection. The work was often laborious, and the workers must be allowed to do the work in their own way and immediate results not expected. He expressed the hope that the Geddes Committee would be sympathetic to this kind of research work. Mr. Bowden said he could see one way in which radiology could be the means of saving an enormous amount of money. If it were possible to increase the penetration to about 6 ins., so that ingots of this size could be examined, he thought there was an enormous future for X-ray work. He under stood that, in the case of a ship, the power curve increased as the cube of the speed. He hoped that the curve repre senting the penetration of X-rays, on a basis of voltage, would not be found to increase in a similar manner, so that to increase the penetration from 3 to 6 ins. would mean impracticable voltages. Col. O'Gorman said he was not so critical as some of the speakers, but thought that radiology might be found to be a great help in aircraft construction. For one thing, if, as he was not quite convinced, radiography did show defective welding, it would be of the very greatest value. Welding might then come back into aircraft construction, since good welding was extremely satisfactory in aircraft. It was the bad weld which was dangerous, and at present we had no means of detecting the bad weld, with the consequence that welding had to be abandoned for stressed parts. When, he said, two pieces of 25-ton steel were welded together it was often found that, as a result of the heat, the metal near the weld had its strength decreased to about 10 tons. If radiology could detect this change in the structure of the steel it would be of enormous value, and we, as aircraft engineers, should welcome any weapons which would enable us to make our structures more safe without making them, heavier. He then called upon the audience to pass a hearty vote of thanks to the lecturer. Dr. Pullin had another appointment, and asked to be allowed to reply to the various questions in writing. Model of the R.A.F. War Memorial to be erected at the head of the Whitehall Stairs, on the Embankment, about midway between Charing Cross and Westminster Bridges. The Memorial has been designed by Sir Reginald Blomfield, R.A., and the eagle is being carried out from his design by Mr. Reid Dick, A.R.A. ' The Memorial, as will be seen, consists of a lofty pylon of Portland stone, supporting a large bronze eagle encircled by the Zodiac. The dedication inscription will be cut on the panel facing the Embankment, with the badge of the Air Force above it, and on the band of stone below the cornice the motto of the Air Force, '' Per ardua ad astra." A shorter inscription in larger letters, and the Pilots' Badge, will be carved on the side facing the river. 180 , ,
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