FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1955
1955 - 1745.PDF
868 FLIGHT APHIS AND AIGLET —and Jassid and J5G: a Cotton-spraying Pilot's Day By TERENCE KELLY \ THE Geziia cotton-growing area in the Sudan begins sometwenty-six miles south-east of Khartoum, and extends onehundred and ten miles in a south-easterly direction. Its average width is twenty-five miles and the area is bordered on theeastern side by the Blue Nile. If one approaches by air from Khartoum the area is easilyidentified by the sight of green cotton crops contrasting sharply with the yellow sand of the surrounding desert. The crop isdivided into ninety-acre blocks, each bearing an Arabic name— e.g., Hag Abdullah, Fahl, Ghubshan—and each divided bynumerous canals that supply water to the irrigation ditches running through the cotton. The plants grow to a height of two feet; andthey have to be sprayed with insecticide to kill the Aphis, Jassid and other pests which, if allowed to nourish, will quickly ruin avaluable crop. The spraying operation oh which the writer has recently beenengaged has been conducted with Auster J5G and Aiglet aircraft. These machines, painted yellow and with black British or Belgianregistration letters, are fitted with a 45-gallon tank containing the insecticide. The tank is situated immediately behind the frontseats, and the liquid is fed to two spray-bars extending from wing- tip to wing-tip. The insecticide is pumped from the tank by awindmill pump fitted underneath the fuselage. When he wishes to begin spraying, the pilot operates a leverat die top of the control column. This starts the pump, and after a delay of two seconds the insecticide begins to spray from thenozzles. To stop it, the lever is simply released. The technique requires some practice for proficiency; aboutfifty hours' flying is necessary before one gets really used to it. The aircraft are supposed to be flown, at between 65 and 70 m.p.h.,at a height of ten feet. This is in accordance with official instruc- tions; but where the entomologists are inspecting the crops, theyoften signal the aircraft to fly lower, in order to ensure greater penetration of the spray into the crop. It is not unusual to seesome of the bolder spirits trailing the wheels of their aircraft through the top of the cotton as they work. Permanent State of Flap ~ When an Auster is taken off with a full load of insecticide aboard,the flaps are set in the No. 1 position (about one-third flap) and the tail of the aircraft raised quickly. The flaps are left in thesame position throughout die flight to give die extra lift required. Take-off and landing can be hazardous, for the dirt strips fromwhich the flying is done are narrow and bordered by a canal bank on one side and on the other by the ploughed fields inwhich the cotton grows. In a take-off or landing in a cross-wind, with a load of insecticide aboard, any error of judgment can resultin a badly damaged aircraft—and pilot! Unlike Sutton harness, a lap strap does not give sufficient protection in a bad crash, as thestrap, although of adequate strength, does not take the weight of die body evenly in the event of sudden deceleration. In oneinstance a pilot was unfortunate enough to spin in from 30ft during a spraying campaign and might not have sustained a brokenleg and bad cuts if the aircraft had been fined with Sutton harness. Without wishing to dwell on accidents, it may beremarked that die type of flying demanded by spraying allows very little margin of error; and, even if one's flying is perfect,there are freak winds which occasionally blow over the sea and can cause trouble. The areas are sprayed methodically. The canals in die cottonblocks run parallel to one another and are about a mile apart. Between diem, and at right angles to them, run small irrigationditches. The distance between each ditch is about the width of the Auster's wing span. The aircraft is flown from one canaland down die field until the next canal is reached. A wide dumb- bell turn is then made to port, during which one climbs to 100ft.The aircraft is then lined up with the next strip, at the same time descending to spraying height again. With a fully loaded aircraft,the turn is never more than Rate 1, owing to the danger of stalling. As the load of insecticide on board decreases die rate canbe increased, but careful flying is necessary for the beginner. During die first fifty hours' flying, in particular, a tendency tohurry and finish spraying a larger acreage of cotton has to be guarded against. As die aircraft sprays up and down the field the number ofstrips of cotton completed has to be counted, and die best way to remember die total is to set it on the compass grid ring. Whenthe tank is empty, the aircraft is flown back to the nearest land- ing site for refuelling. The insecticide tanker is usually situatedhalf-way along the landing strip and, after refuelling, one takes O-T from the tanker's position, the object being to avoid delayingother aircraft waiting to land. When taxying on the strip we found it necessary to use thebrakes as litde as possible; owing to the heat in which the work was being done, excessive braking resulted in the brake drumsoverheating, with a risk of burst tyres. Servicing was done by qualified engineers, one working on each of the landing strips,and die aircraft were kept in excellent condition throughout the campaign. The personnel were housed in tents and life wascomfortable, except for die mid-day heat. Boredom was liable to set in during one's off-duty time, as activity was generallylimited to eating (out of tins, of course!), writing letters, and resting. After several days flying, one's shoulder muscles tend to becomeextremely sore. This is due to the continuously altering load on the control column as the insecticide is pumped out of the tank.It is impossible to keep trimming die aircraft, as all one's con- centration has to be on maintaining accuate flying, close tothe ground. Pilots who are new to the job do die first part of their flyingwith the spray tank only half-full and are advised not to remain airborne for more man two hours at a time. After two hours' fly-ing there is normally a period of two hours' rest, dien one is airborne again for another two hours. Flying starts at dawn,widi breaks for breakfast and rest. As die day progresses die heat and glare become more intense until, at mid-day, work stopsand a rest period is taken until three o'clock in the afternoon. Owing to the intense heat there is some turbulence at timesand occasionally a "dust-devil" will blow across the area. This is a localized circular wind covering an area of only a few squareyards, but it moves fairly fast, giving warning of its approach by raising dust from die landing strips and carrying it upwards to aconsiderable height. It is most unpleasant to be caught in one of these while airborne, and the only action to be taken is to increaseengine power and keep the controls neutral. The aircraft rocks violently once or twice but usually flies through die wind withoutaccident. There is an instance of a pilot being caught by one of these affairs just after touching down. His aircraft swung offthe landing strip and over a canal bank, and he pulled up just in time to save himself an unexpected wetting. The aircraft had aheavy load of insecticide and, owing to the steepness of the canal bank and die position of the tank inside die cabin, the fuselagewas badly twisted. Through the Barrier Aldiough crop-spraying is somewhat hazardous at times, seriousaccidents are few. Occasionally a pilot accidentally flies through die telegraph wires which run along the banks of some of thecanals. The aircraft's speed, plus its weight and the weight of the spray gear, take one right through the wires. Too much of diissort of thing, however, does not improve relations between the crop-spraying company and the telephone and telegraphauthorities . . . A bonus is paid to the pilots—on top of a basic salary—for thearea of cotton sprayed. If a strip is missed it does not escape notice, for its cotton turns from green to brown after about a fortnight.The operating company are paid by the cotton-growers only for areas satisfactorily sprayed, and when faulty strips are foundthe pilot loses that much bonus. It is easy to miss a strip of crop between two of die ditches as a result of a miscount; hence dieprecaution of setting die number sprayed on the compass grid ring—which on the Auster is easy to reach, being die P.12 type,just above one's head. The Auster is ideal for the type of work carried out in theSudan, because of its robustness and relatively cheap operation. Helicopters would give maximum efficiency in spraying, but theirhigh cost is prohibitive to the operator. The company for which the writer was flying is a large concern and until recendy had nocompetition in die Sudan. There are, however, odier groups forming and contracting to spray crops, and at Khartoum Airportone solitary Tiger Moth was seen with spray canisters fitted to its wing-tips; its operator is on his own and makes a good living outof spraying. The campaigns are carried out twice a year, from Februaryto March and October to November, these being the dry seasons; and the period of each operation is approximately seven weeks.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
