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Aviation History
1949
1949 - 1875.PDF
FLIGHT, 17 November 1949 641 So, we see that normal developments in air warfare have resulted in: — A great increase in aircraft all-up weight—up to a four- fold increase; a greater increased complexity in design and equipment, and, in consequence, a great increase in the design effort required—somewhat proportional to the all-np weight, and, therefore, a lengthening of the time-scale for design, development and production. Inflationary tendencies are likely still further to raise the present high design costs. If we are to continue in business, action is necessary to halt these spiralling tendencies. Effect of Complexities on Production Effort.—The increased technical effort in aircraft design—shown, as the years have gone by, by the increase in the number of drawings required— has its counterpart in the increased productive effort called for in the shops. This increased productive effort results not only from an increase in complexity and size of aircraft, and from the wider range of equipment to be carried, '>ut also from the almost revolutionary changes which have taken place in air- craft design. The fabric-covered aircraft of the 1914-1918 war, wire-braced, composite, wood-and-metal structures, were easily made with simple metal- and wood-working machine- shop facilities. As the whole structure was open until the last operation of fabric covering, it was an easy matter to instal equipment, piping, and electric cables. With increasing air speeds came the internally braced mono- plane with its lower drag. Stressed-skin, metal structures be- TABLE II: DESIGN EFFORT TO FIRST FLIGHT ACCORDING TO TYPE (AVERAGE, 1935-45) TABLE III: ACTUAL MAN-HOURS FOR COMPLETE ASSEMBLY OF BOMBER CENTRE-SECTION Type Bomber Fighter Primary Trainer Naval Aircraft Advanced Trainer Draughtsman- weeks Ib a.u.w. 0.143 0.287 0 287 0.395 0687 Ib a.u.w./Draughts- man weeks 6.75 3.5 3.5 2.5 1.45 Period At start After 12 months After 15 months After 17 months Man-hours 1.014 592 346 230 Percentage 100 58.3 34.1 22.6 came standard practice. A new technique was called into being, with elaborate tooling, forging, presswork, heat treat- ment, etc. In final erection, equipment installation could no longer be treated as something to be wholly left until the structure had been assembled. Equally, it was more diffi- cult to modify equipment layout. With increasing size and weight came the need for power-operated services (pneumatic, hydraulic, and electric) and for a host of applications pre- viously not even visualized. [At this point the lecturer showed, in graphical form, the cumulative costs of the drawing-office work on the Harrow,(of composite metal and fabric construction) in 1935-1936, and the corresponding figures for the stressed-skin Halifax. The graph illustrated, also, cumulative labour costs for jigs, prototype, and production aircraft of both types; these costs were plotted against the development time from the start of design.] It is noteworthy that the simpler Harrow prototype, with less technical effort required in the drawing office, was flying in under half the time of that required for the Halifax. Had pre-war production man-hours remained during the 1939- 1945 war we should never have obtained the war output re- quired. It was only by the economies effected in quantity pro- duction that the effort was reduced. As an illustration of these reductions, figures for the manufacture of a centre-section during different phases of production are given in Table III. With the general trend at the present towards greater com- plexity in design, and with the small scale ok peace-time manu- facture, the part played by production assumes more and more importance, and it is necessary to review possible future developments, and consider their effect on productive effort To be concluded.) BAROMETRIC PARACHUTE-RELEASE •HPHOUGH not entirely new in conception—the principle has •A attracted inventors for many years past—adoption of barometric automatic release for parachutes has been brought considerably nearer realization by the Irving A i r c h u t e of Great Britain, Ltd., whose ex- periments in this direc- tion culminated last week in a successful demon- stration. Of obvious value to pilots of fast, high-flying military aircraft, such a device combines the prin- cipal advantage of the static line parachute (i.e., independent opening even in the event of the wearer being unconscious) with- out the attendant grave disadvantage which limits the static-line type to balloon and paratroop operation, namely, the inevitable risk of entan- glement with an aircraft that is out of control. As will be seen from the illustration, the Irving device adds little complication to a stan- dard harness. The small metal box contains the two elements responsible for automatic actuation, a barometric capsule and Maj. Willans wearing the Irving barometric-release parachute. a clockwork mechanism. A static line—the loop-ended wire visible in the photograph—is secured in the aircraft; its purpose, however, is not to release the canopy, but simply to render the mechanism automatically "live," rather after the manner of a bomb fuse, as the wearer goes overboard. The capsule can be set by a simple control to provide auto- matic opening at any required pressure-height, while the clockwork mechanism is similarly adjustable to give a delay of 1 to 10 seconds from the moment the capsule operates until ejection of the canopy takes place. This delay provides a safety-margin should the wearer be unable to leave the aircraft before the predetermined pressure-height has been reached The clockwork trips a powerful compression spring, which then pulls the rip <ft>rd. As a final precaution, a manual over-ride (visible in the photograph as a pear-shaped knob) is provided. The successful demonstration was given on November 10th at Stanstead Airfield, Essex, when Maj. T. W. Willans—who made a number of operational jumps into occupied territory during the war—stepped out of a Kearsley Airways Dakota at 15,000ft. The barometric release was set to give opening at 6,000ft, and Maj. Willans-timed his free fall by stop-watch As closely as it was possible to check—"certainly within 200ft," said Maj. Willans—the canopy opened at the pre- determined figure, and a comfortable landing was made. K.A.C. CELEBRATION TO mark the close of another successful year, Mr McEwanKing, as managing director of the King Aircraft Corpora tion, welcomed a number of guests from all sides of the industry to Glasgow last week-end. The visitors toured the works and were shown, among many other products, the fabricated version of the King cowling fastener (described in Flight of December 23rd, 1948). In its new form the fastener is capable of taking 9,000 lb in shear for a weight of only six ounces. Other development work displayed included spring-loaded drain valves for fuel tanks and anti-icing vent valves for high-speed, high-flying aircraft After having seen the quality of Scottish man-made objects the guests were treated to a coach tour of the Trossachs and Highlands in order to sample natural beauties. The weather was on its very best behaviour and the trip was thoroughly appreciated by the party.
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