BRITISH DISCOVERY.

Manawatu Standard, Volume LVI, Issue 64, 13 February 1936, Page 8

BRITISH DISCOVERY.

CONSTRUCTION OF AIRCRAFT. Details have been disclosed of one of the most notable advances yet- made in aircraft constructional methods, an advance which is likely to exercise great influence upon the development of long-distance aircraft, both civil and military. This is the system of “geodetic” construction invented by the British engineer, Mr B. N. Wallis, who designed the successful rigid airship RIOO, and put into production for the first time in the Vickers Wellesley medium bomber monoplane which has been ordered in quantity for tlio Royal Air Force. The system permits drastic weight reductions to be made in wings and fuselage without any loss of strength, and it also permits the use of wings of very largo span for their chord—or depth from front to back—with consequent gain in efficiency. At the Vickers works at Weybridgc, “geodetic” wings and fuselages, stripped down to show the internal structure, present to the eye one of the most fascinating spectacles offered by any branch of aeronautical engineering. The fuselage is composed of metal strips which wind their way from end to end, crossing each other, and forming ail interlacing .pattern. Beyond this network of metal strips there is nothing—no internal bracing wires, no struts, no tie rods, or bays. The fuselage framework is built up entirely of the winding strips, and they derive their strength from the pattern. Exactly the same thing occurs in tlio wings. The strips wind their waj round the contours of each wing, crisscrossing at short intervals, and tliero are no spars, compression struts, or I other internal members. Both wings and fuselage are completely hollow, and thoir strength resides in the members which form their shapes, and in the way in which those members are disposed. Tlio covering can be of thin metal or fabric, or any other suitable material, and it can be fixed direct to the geodetic members, The reason they arc called geodetic members is that they follow “geodetic” lilies in their windings along wings and fuselage. Mr Wallis gives the broad definition of a geodetic line as the line that will be taken up by a flexible string when tightly stretched over a curved surface between two points lying in that surface. It is the shortest distance between any two points in a curved surface when the path lies wholly in the surface. Professor A. J. Sutton Pippard, a loading English engineer, with two assistants, is now engaged upon a mathematical analysis of geodetic construction, and expects to be engaged for two years on it. Meanwhile, the general principles are fundamentally simple. The forces.with which the wing has to deal, instead of being shunted to spars and struts in the wing’s interior, as in the orthodox pattern, are made to “crawl” round the surface where all of the material is concentrated in the form of bars or tubes. The olfeot is to obtain a remarkable increase in strength, with no loss in stillness, or, if desired, a great saving in weight when compared with other structures of equal strength. Alternatively, the geodetic methods may bo used to build structures such as wings in an attenuated form of high aspect ratio, which is difficult, to attain by other means without exceeding a reasonable figure for weight. In view of the increasing favour in which the long, narrow wing is now held by aeronautical engineers, this quality is of great importance. Speed, range, and permissible load of the Wellesley monoplane bear out Mr Wallis’s contentions, and tbe “geodetic” aeroplane shows very substantial gains under all three heads o performance. It can be over-loaded beyond its normal gross weight by several thousands of pounds, yet retains the full safety factors imposed by commercial airworthiness regulations. In I military form, it can carry a large load lof bombs at a cruising speed of more i than three miles a minute over a distance non-stop of thousands of miles. If it could be loaded only, with fuel instead of passengers or other load, the Wellesley could fly 8000 miles non-stop in still air. . . Geodetic construction has interesting possibilities, no only lor military but also for commercial types ol planes. Mr Wallis visualises a very large treodctic machine, in which the interior of the wings is used to from the pasof the wings is used to form the pasIn forming the spars of the airship IUOO Mr Wallis employed a form of construction which may be said to hate been the forerunner of the existing geodetic system. He used strips of metal wound. upon one another m spirals in opposite senses. The lesult was a tubular spar of great strength and lightness.