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Aviation History
1952
1952 - 0047.PDF
FLIGHT, 4 January 1952 15 METEOROLOGY and NAVIGATION The Importance of Upper-air Data: a Lecture to the Institute of Navigation IN presenting his paper under the above title before the Institute of Navigation on December 21st, Lt. Cdr. P. G. Satow, D.S.C., R.N., said that, unlike the marine user, the airborne navigator was generally in no position to take far-reaching avoiding action or to await improved conditions. Aircraft without navigation facilities had to be controlled from ship or shore, and the controller had to have a complete picture of upper winds, cloud and temperatures up to maximum operating heights. Aircraft with navigational facilities required careful flight-planning before they took off, and detailed forecast data for the intended flight. Lastly, and perhaps most important, they required forecasts for their intended terminal airport and for diversion airfields. Upper-air charts were constructed, not for selected altitudes, but for suitable pressure-levels. Contours of the 1,000-millibar level were first drawn: the vertical thickness pattern was then added graphically to obtain contours for 700 mb (approximately 10,000ft). Observed upper winds were taken into account in drawing the contour lines. This procedure was continued up to 500 mb (approximately 18,000ft) and to 300 mb (approximately 30,000ft). Up to the present, most long-distance flights had been made at heights not exceeding 25,000ft. For these, charts and forecasts up to 300 mb had been adequate. The Series I Comet (D.H. Ghost turbojets), to be brought into operation shortly by British Overseas Airways Corporation, had a normal peak cruising altitude of about 40,000ft (approximately 190 mb). The Series 2 Comer (Rolls-Royce Avons) was expected to reach 45,000ft (approximately 150 mb). British upper-air bulletins had been extended to include the 200 mb (approximately 39,000ft), and 100 mb (approximately 54,000ft) levels, for which observed and predicted contour charts were now being issued twice in every 24 hours. Although these charts were built up from 300 mb, observed data were often sparse at these heights, and most countries had agreed to extend their soundings to reach the 100 mb level as soon as practicable. By so doing, each country would be assisting her own ground-forecasting FOLLOWING upon our recent review of the early days of Sabena's Congo services and a description of their operations today, we have received an account of the experiences of a Continental journalist, M. Jean-Paul Darmsteter, who has also visited the Belgian Congo recently. The following are extracts from an article he has written, entitled The Magnificent Growth of Aviation in the Belgian Congo; it covers the more popular side of Colonial services. The character of air transport in Africa, says M. Darmsteter, differs profoundly from air travel in Europe. In the Belgian Congo aircraft have become a necessity and the lines are essentially operated as a public utility. Air routes are welding together the great centres of the Congo. For the people living in the interior the days of eating out of tins and existing on meagre local products are gone, and the carriage of fresh provisions by air is undoubtedly a most important aspect of commercial aviation in the Congo. There are many mixed-cargo flights carrying both freight and pro visions, and movable seats permit of loading which always allows the maximum to be carried. The less favoured regions regularly receive vegetables, butter, fruit and meat. Costermansville, for example, distributes its strawberries over a range of 1,000 kilo metres, particularly in the Katanga area, and mail, medicine, currency, books, journals, films and even oysters from Ostend and Swiss Camembert cheese are carried by air. Aviation has also permitted the exploitation of the inexhaustible treasures of Africa—coffee, oil, copper, zinc, gold, diamonds, wood, and, not least, uranium. Thanks to the helicopter, which has now begun insectidal operations on a large scale, contaminated regions are now becoming more and more rare and will soon have disappeared completely. While the black population of the Congo exceeded 11 million a year ago, the other races amounted to only 53,176. On its African services in addition to making valuable contributions to air navigation. Air temperatures were assuming a greater importance, mainly at take-off, when a rise of 1 degree would cause a loss of power from the gas turbine five times greater than with a piston-type engine. Operation of these new British air liners would provide valuable in-flight reports from high altitudes. In approaching air terminals a high percentage of correct landing decisions—at present gener ally made by the pilot descending to see for himself—were required. If diversions could be made whilst still at cruising height, a great deal of extra fuel need not be carried in favour of additional payload. However, neither pilots nor passengers would accept diver sions which would prove subsequently to have been unnecessary. To be successful, this procedure would entail a considerable advance in detailed local forecasting, and the closest co-operation between the airline operator, the air-traffic controller and the duty forecaster. Tables of equivalent headwinds on some principal world air routes were already proving of great value to operational staffs for long distance flight-planning. Upper-air analysis was being made at 14 standard pressure levels, from the surface up to 40 mb (approximately 72,000ft). It was being carried out by a new branch of the Meteorological Office, which was believed to be the only existing organization of its kind. The strongest winds were to be found in the upper half of the troposphere, and velocities generally decreased on entering the lower stratosphere, where some flights of the Avon-Comet would be made. To meet the new requirements of gas-turbine aircraft at high altitudes, "strong-wind warnings" were being issued in the U.K. for expected upper winds exceeding 80 kt at 500 mb; 100 kt at 400 mb; and 120 kt at 300 mb. One of the greatest remaining problems in forecasting was the location and tracking of jet streams in the regions 15,000 to 40,000ft, which might give winds in a confined region, but over considerable distances, of up to 200 kt. Adequate facilities for air navigation at high altitudes were therefore most necessary. network alone, Sabena carried 29,271 passengers during 1950, and thus it can be seen that more than hall of the Congo's white popu lation used aircraft as a means of transport. The Congo is a para dise for aviation, but aviation pays it back in full. On the subject of navigation and meteorology, M. Darmsteter says that until recently magnetic anomalies have not permitted the drawtng-up of precise maps upon which correct variation lines are shown for all regions, and this situation, though temporary, represents a serious inconvenience to private aviation, whose navigators rely on dead reckoning. Airlines, however, can enjoy an extensive network of radio beacons. The administration established by the Service de l'Aeronautique undertakes the build ing and maintenance of landing grounds and a network of radio stations and radio beacons. It also looks after the dissemination of meteorological information. The radio beacons are worked only on demand from aircraft, but their network, which already carries a large portion of the territory in the Belgian Congo and the Ruanda Urundi, will continue to be expanded. In addition to established broadcasts from a scattered network of meteorological stations, pilots and navigators rely particularly on weather "actuals," which are transmitted regularly. At the Equator, the seasons are not clearly defined, and the weather is uniformly inclined to thunderstorms—which is not to say that it will not include exceptionally fine days. Cu-nim clouds are particularly dangerous, but fortunately they are isolated and can be circumnavigated. Should an aircraft encounter a con tinuous chain of violent storms, known as a line squall, its crew can be sure of a particularly difficult passage, and might be wiser to turn back. But even in these conditions Sabena has achieved magnificent regularity on its African routes, which goes to show that weather conditions do not constitute a handicap to the development of aerial navigation if they are fully appreciated. It is simply a matter of adhering strictly to the essential precautions. CONGO POSTSCRIPT
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