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Aviation History
1936
1936 - 0248.PDF
112 FLIGHT. JANUARY 30, 1936. A night-time view of the latest type of Chance boundary- light, the design of which is such that the pilot has a good idea of perspective. that it will collapse easily if hit by an aeroplane whilst taxi-ing. A single-core ring main is sufficient for a boundary light system, each unit containing a small trans former fitted to its base, to reduce the current from the main to approximately 6.6 volts for the actual lamp itself. Obstruction lights are electric lamps mounted in dupli cate and covered by a red shade. One lamp is in use at a time, provision being made through a solenoid-operated relay automatically to light the spare lamp should the first one fail. This provision is of great importance. The ex tinction of an obstruction light may cause a very serious disaster, and it is therefore obvious that a stand-by light with the mechanism for its automatic operation is an insur ance against accident to be purchased at a very low figure. Since flying began, night landings have been made with the aid of paraffin flares. To-day they can be regarded as emergency equipment to be kept in store in case the electric current fails or a ground mist makes an additional aid for safe landing desirable. Such flares need be no more than tins containing cotton waste soaked in paraffin, which, when lit, show a smoky red flame. They are laid out on the aerodrome in the shape of a " T " or an " L " to indi cate the direction of the wind and the positions where the pilot should touch ground and finish his landing run. Aerodrome Beacons Aerodrome beacons may be either an arrangement of neon tubes flashing a Morse character to indicate the aero drome, or a revolving optical system similar either to a marine lighthouse or an elaboration of a searchlight. An aerodrome beacon should be red in colour, except in localities where there are no other lights with which the beacon might be confused. Neon lighting offers a solution to the colour problem, but it is quite easy to impart a red colour to the other forms of beacon mentioned. An illuminated wind indicator in its most convenient form is a metal structure in the shape of a letter " T," the length of each member being 20 ft. Visibility is secured by mounting electric lamps on its upper surface. The wind keeps the indicator in the right direction by its pressure on a fin mounted below the " T " structure itself. The most satisfactory colour has been found to be white. Landing area floodlights are possibly the most important items of equipment for ensuring safe and speedy handling of night air services. The object of a floodlighting system is to illuminate the landing area so that a pilot can come in with as much confidence as in daylight. It is of vital importance that such lighting should be designed and in stalled so that the illumination is even over the whole of the landing surface, casting no hard shadows. Floodlight ing systems vary according to the nature of the aerodrome and the availability of electric current on the site, but in this country there is usually no difficulty about current supply, and therefore mobile floodlights with their own generating plant need not, as a rule, be considered. The most modern designs, some of which are illustrated in this Number, employ a reflector system, using any number from three to nine lamps to give a candle-power exceeding 1,000.000. The area illuminated by one floodlight is in the region of 5,000.000 sq. ft., with an extreme range down the centre of the beam of half a mile. The most econo mical layout is a series of three or four floodlights spactd equidistantly round the perimeter of the aerodrome, any one or two being switched on from the control tower, according to the direction of the wind. The foregoing is a brief description of aerodrome light ing apparatus and its function. There are two publica tions which should be studied by those responsible for aerodrome equipment and management. Air Ministry Pamphlet No. 55, dealing with the licensing and classifica tion of civil aerodromes, lays down certain rules about One of the three lamp and reflector units of a Chance floodlight of the type shown on page 111. lighting equipment. In addition, there is a British Standard Specification for land aerodrome and airway lighting. This Specification goes into considerable detail concerning the various items of equipment which have been mentioned, and it represents the considered opinion of a Committee whose members included representatives from the Air Ministry, leading manufacturers of lighting apparatus, and the aircraft operating companies. There are two British companies which have specialised in aero drome lighting equipment. These two concerns approached the problems involved in aerodrome lighting from different angles, and the result of their many years of experimental work is a complete range of equipment for every require ment, differing in points of detail but directly comparable in performance. A few other firms have entered the busi ness more recently, but their products are none the Im practical. A review of the work of the aerodrome lighting section of the industry will be found elsewhere in this issue-
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