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Aviation History
1963
1963 - 0012.PDF
FLIGHT International, 3 January 1963 12 SAFETY HEIGHT •<lt it a sobering thought that, despite the very considerable publicity given to the Mt Canigou accident, one still hears unpressurized aircraft requesting IFR clearance between Toulouse and Perpignan at (light level 75." BY CAPTAIN ROY L. H. McDOUGALL, DFC* HERE is a further contribution to the discussion of why so many British public transport aircraft—seven in five years, killing 167 people—have flown into high ground. In the issue of November 15, pages 792-794, Captain T. F*eer, following publication of the report into the Derby Airways DC-3 crash on Mt Canigou near Perpignan, put forward a set of suggested new rules. This further contribution from another experienced transport pilot will, we believe, stimulate fresh thought on the essential question: Are the maps and charts good enough ? THE arguments put forward by Capt Freer on the subject of map construction and the use that should be made of con tour lines will be of considerable interest to all pilots and, we hope, cartographers. The application of his rule that high ground should be deduced from the values of the contours until reaching the topmost contour, when the spot-height is the final authority, is one which, I think, should be followed on several maps—as the answers are not what one would expect. GSGS 4649 Sheet 42/2: Marseilles This map was drawn up 14 years ago and published ten years ago for the Ministry of Civil Aviation. Contour values must be determined by the dubious * Capt McDougall, who has I3,500hr in his lag-book, is deputy chief pilot and navigation officer of Euravia (London) Ltd. Previously he was with LTV, the German independent, as chief pilot; with BO AC from 1945-1955, flying Argonauts, Hermes, Yorks and Lancastrians on the Empire routes; and during the war with RAF Bomber Command, flying Hampdens and Liberators. In recent years he has made a special study of flight guides, having experience of five types of airline presentation, and is representative in the UK for the American flight-guide publishers Jeppesen. method of counting the colours or contour lines. No indication is given of any rules which govern the use that may be made of the spot heights. Highest contour line is drawn at 6,560ft and maxi mum height anywhere on the chart is 9,555ft. It would be a poor map to use when flying from Toulouse to Perpignan, as Toulouse lies outside the chart. Safety height, allowing 2,000ft clearance because the area is mountainous, would be 11,600ft as the 25-mile safety lane crosses the 6,560ft contour line which is cut off by the spot height at Sap- tuario. This is also the highest point on the chart. GSGS 4715 Sheet 319B: Toulouse This map was drawn in 1951 and revised up to 1953 and published in 1958. Contour lines are written in over most of the chart; spot heights are given but no defining rules cover their use. Obstructions are not shown. Tou louse and Perpignan are both drawn in. Highest contour is 9,000ft and highest point is 11,165ft. The 25-mile safety lane shows a 9,000ft contour carrying a spot height of 9,135ft (Mt Canigou). Next to this is another 9,000ft contour which does not have a limiting spot height. Does one assume that its highest point is less than the Mt Canigou spot height of 9,135ft (this would seem logical) thereby giving a safety height of 11,200ft? Or should one be governed by the rule that as no spot height is shown it must be taken tnat it could be anything up to the highest point on the chart of 11,165ft, giving a safety height of 13,200ft? WAC Series 319: Pyrenees Mountains Drawn in 1949, revised in 1959 and printed in 1960. Contour lines show values and the rules governing spot heights state that the position is accurate while the maximum vertical error possible is 100ft and is the highest point in the general area. Warning is also given that the chart carries a fortnightly revision service. Highest contour is 9,000ft with a maximum elevation on the chart of 11,168ft. Inspection shows that the 9,000ft contour surrounding Mt Canigou is missing, so that the contour rule would give the highest point as a possible 9,000ft and a safety height of 11,000ft. This is
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