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Aviation History
1953
1953 - 1047.PDF
FLIGHT, 14 August 1953 ENTOMOLOGICAL WAR IN SWITZERLAND .... between mountains over 10,000ft high and has a climate all its own. Vertical air currents can be considerable, due to the strone sunshine on the rocks, and wind direction varies considerably with height. Sometimes the aerodrome was in still air while in the spraying area strong turbulence tossed the aircraft around The wind changed with little warning, and alertness was essential if the maximum of four hours' spraying was to be achieved by each pilot. Another hazard arose from cables, the Swiss being very cable-minded since electricity and transport by cable are cheap; high-tension lines extend up to 6,000-7,000ft and are some times 200-300ft above the slope itself. The spraying area is in fact normally prohibited for low-flying. To overcome this difficulty the pilots were supplied with aerial photographs on which all cables were carefully marked, so that any hazards were known beforehand. In addition, red flags were hung on the cables, although these did not show up very well from the air. The cables themsdves were very hard to see, even when their position was known, and especially early in the morning when the sun was low and the slopes of the Alps in shadow. Contour flying was used successfully at about 50ft above the trees, at a speed of about 60 m.p.h. for the fixed-wing and 35-40 m.p.h. for the rotary-wing aircraft. Apart from the main base at Sim two more fields were used, one at Aix-les-Bains, and the other at Chavais, the latter about 350 yards long. Flying from Sim was sometimes difficult, due to the heavy traffic of Swiss Air Force aircraft which were doing an amazing amount of peace-time flying in Vampires, Dewoitines, Harvards and Moranes. At one time local manoeuvres with artillery had to be stopped as spraying aircraft were flying in the artillery area. The Auster J.5G, fitted with the very efficient spray gear developed by Pest Control, Ltd., had a sufficiently good take-off and ceiling fully loaded to carry out all the duties required of it. The aircraft made a good impression on the Swiss who concentrate almost entirely on American light aircraft. No difficulties were encountered with the spraying pilots' greatest enemy, the bird, and hardly any were seen; it was their absence, in fact, which had caused the maybug to multiply so tremendously during the last three years. A central office in Sim dealt with all reports of maybugs from the different communes, and infested areas were marked on pilots' maps, so that next morning the killing D.D.T. emulsion was sprayed as the insects emerged from the ground, and the leaves were coated with crystals which could kill by contact up to 14 days after treatment. Results were really impressive, and a few hours after treatment the dead bugs began dropping from the trees, until the Alpine roads were blackened with the bodies of millions of dying insects. Flying crop-spraying aircraft in the Alps has some psychological problems, but, once these are overcome, it can become a fine art offering the reward of an ever-changing backcloth of mountain scenery. An ample reserve of power (often a critical factor) and sufficient air speed formed the basis of safe flying. A reconnaissance from a safe height before entering a valley to spray, and a plan of the runs in and out had to be made beforehand, from the air, as the maps gave no definite guidance; this, combined with a pre-flight survey on the ground, avoided risks. Difficulty was experienced with constantly changing air currents as it was impossible to detect them without vertical speed indicators; a drop in air speed without a change in attitude, however, gave some warning of a 201 Where fields and cables end, the steep wooded slopes begin: agility is a prerequisite for operations in this type of terrain. down current. Spraying runs along slopes of 70-80 deg needed some practice because of the proximity of the rotor- or wing-tips to the slope, and good cockpit visibility was of primary importance. Turning towards the mountainside also needed practice, as dis tances were sometimes deceptive. The helicopter, when it has sufficient power to climb vertically at full load at altitude, is the ideal machine for contour flying in such regions as this; and it is not restricted by a minimum turning radius or the need for con stant forward speed. Flying was carried out very early in the morning, when the air was ideal for spraying, and late in the afternoon when midday turbulence died down. Some spraying down the slopes was tried, but available flap-area was insufficient to prevent the air speed building up when following the slope down with closed throttle. Markers were nor generally used, only the heavily infested areas being marked by people holding white flags, and in such a spot one helicopter pilot reported the rare instance of a spraying pilot being able to see his quarry blackening the trees below. .Each day an average of 1,800 to 2,000 acres was covered, and apart from the fact that the areas were large and mostly not sprayable from the ground, the difficult slopes tackled were most impressive. Close collaboration between entomologists and pilots successfully defeated the menace of the maybug. Apart from the entomological success, however, the expedition was also remark able as being the first in which fixed-wing aircraft were success fully employed for spraying in the Alps. Farmers in this rich and lovely Rhine valley can now look forward to a safe harvest for another two years, as the soil is free of the larvae which fed on the roots of their crops. J.M.H.H. (Below, left) An Auster and the two Hillers are prepared for operations. The Austers were flown out to Switzerland but the Hillers have only just been unwrapped from the shrouds in which they were carried out by the ground convoy (right).
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