“BASKETWORK” AEROPLANES

Otago Daily Times, Issue 23703, 10 January 1939, Page 12

“BASKETWORK” AEROPLANES

GEODETIC CONSTRUCTION ' NEW DISCLOSURES USEFUL LOADS AUGMENTED (Fhom Oub’Own Corresponpenx; (By Air Mail) LONDON. Dec. 15. Secrets of “geodetic” construction, the extraordinary British invention embodied in ; the structure' of the 'longrange monoplanes'that flew non-stop from Egypt to ■ Australia, • have been disclosed. Nearly three years have elapsed since general reference to this novel form of aircraft building was officially permitted. In the meantime, these planes, have proved their strength arid efficiency in the arduous round of routine service. • ;• ,

Increased performance of aeroplanes during the past few years brought to light , many new and formerly unsuspected structural problems. High speeds may be most easily attained by adoption of monoplane design, with the wings and fuselage carefully shaped to minimise head resistance, Investigation originated by Mr B. N. Wallis, inventor of geodetic construction, showed' that the chief features of a successful monoplane should include an “ aspect ratio ” (wing span divided by average wing depth from front to rear) of not less than 9 or 10; great rigidity of the wing structure against twisting, forces; great stiffness and rigidity in the fuselage; and light structural weight.. Wing structural weight may be considered to vary at a rather greater rate than the square of the aspect ratio. For example, wings of the desirable aspect ratio " 9 ” will weigh approximately three times as much as wings of aspect ratio “6.” Hence, argued Mr Wallis, progress in aircraft performance was blocked by structural limitations. His answer was to evolve an entirely new system of aircraft manufacture, which he has developed during several years in conjunction with the Vickers company. Metal Basketwork

Geodetic construction employs the material in concentrated form. Metal members, curved to follow goedetic (the shortest possible) lines along the shape of wings and fuselage, form a kind of basketwork. They are located along the lines in which the principal forces acting in flight are known to act. The basketwork is made _up_ of two goedetic “ systems,” one spiralling diagonally from end to end of the structure in one sense and the other exactly balancing it in the other. Where the interlacing members cross they are firmly secured to one another; at these "nodal” points the forces required to maintain the members in equilibrium without distortion are exactly balanced. Hence, a very light gauge of metal is sufficient to obtain great stiffness and high strength factors, .. . j The resultant structure of wings and fuselage is extremely light. In building the wings of the Wellesley-—the first all-goedetic aeroplane—advantage was taken of this exceptionally light structure to adopt wings of exceptionally high aspect ratio. Vickers-Arm-strong. Ltd., which now has in production the twin-engined Wellington bomber—second all-geodetic monoplanes can carry heavier loads faster, farther and higher than machines embodying a different kind of construction. The geodetic structural members are produced from coils of light alloy strip in special rolling mills at the rate of 20 feet a minute. An ingenious arrangement of the rollers, three pairs of which are adjustable, at will the required curvature- in the member. One of the advantages l of this kind of construction, which dispenses with major internal bracing members, is that the fuel tanks may be easily and neatly installed inside the wings. In very large geodetic airliners, such as may be built in future, passenger cabins may be located Inside the wings, and the aeroplane become the true “flying wing” which Is the dream-of designers. Long-range Bomber

The structure of the Wellesley is covered externally with fabric applied in a manner devised to ensure great strength and rigidity. Designed for long-range bombing, torpedo-carrying and general purpose duties, the Wellesley is powered with a single Bristol Pegasus 800/835 h.p. air-cooled engine, which drives a constant-speed airscrew. It has enclosed cockpits for pilot and gunner with inter-communi-cation between them. The under-car-

riage is retractable into recesses in the central portion of the wings. ’ Carrying full normal, load, including 425 gallons of fuel-, the Wellesley attains under ideal conditions a maximum speed 0f'228 m.p.h. at a height,of nearly 20,000 feet. V s Its “ ceiling ” |s , 35,250 feet, and it climbs from sea-level at the rate of 1200 feet a minute.' - The ■ distance record flight has proved bei ‘ yond dispute that- the Wellesley .may fly non-stop approximately 8000 miles; ( the journey from Egypt to Australia, accomplished for the greater part against adverse winds and'at no time '* with help from the wind, measures 7162 miles by the “great circle" or shortest possible distance, and not less than 7350 miles by the route actually followed. In calm air the aeroplanes would obviously easily exceed 8000 miles. “ Non-stop ” Performance

Extraordinary flights become possible to an aeroplane disposing of this order of range. Calcutta to San Francisco; Bulawayo to Auckland; Panama to Basra; London to , Puerto Montt, Chile; Honolulu to Montevideo: New York to Bombay; Perth to Nome, Alaska—these are some of the possibilities. And the attainable range of the Wellington, twin-engined succes L sor- to the Wellesley, is still longer. Wing Commander O. R. Gayford, commander of the Lond Range Development Flight, has indicated that a Wellington might be prepared to fly nonstop the 10,000 miles from England to Australia.