Weather Conditions and Night Flying.
The safety of the machine and the reliability of an air service largely depend on accurate weather forecasts. In order to co-ordinate the meteorological work of the country as a whole, and for the special assistance of aviation, the Meteorological Services of Great Britain have been amalgamated under the Department of Civil Aviation, and, working in close co-operation with the Communications Branch of the Department, have made improvements in the rapid collection and distribution of meteorological information for all purposes. In addition to the forecasts issued four times daily, collective reports are issued hourly by wireless from the London terminal aerodrome at Croydon and copies are distributed to transport companies and others concerned.
A feature of meteorology which is often overlooked is its economic value. By making use of a knowledge of the wind at different heights, aircraft can complete journeys more quickly than would otherwise be possible, and thereby save their own fuel and their passengers' time. This will be specially useful in the tropics where the regularity of the surface winds has its counterpart in the upper air, but even in Europe time-tables can be drawn up with due attention to the favourable and unfavourable effect of prevailing winds. The planning of airship routes in particular, must be considered in close connection with this aspect of weather conditions.
To-day, however, the aeroplane may be considered as an "all-weather" craft, save for mist and fog—the enemies of all transport and particularly to that of the air—to which unfortunately England is particularly liable during the winter. Experiments have been carried out on the dispersal of fog, the illumination of aerodromes by fog-piercing lights, and instruments to record the exact position of the aeroplane and its height above the ground, but success has not yet been achieved.
Similar to the problems of flying and landing in mist and fog is that of night flying. Until night flying is practicable, only half the value of the aeroplane's speed is obtainable, since other transport services run continuously day and night. Further, as machines become rapidly obsolete owing to technical progress, it is essential that they should be in use for the greatest number of hours during their life. Much has been done in the lighting and marking of aerodromes and in the equipment of aeroplanes with wireless telephone and direction-finding apparatus.
It may here be mentioned that there are two methods of obtaining the position of aircraft by means of wireless telegraphy, known as direction-finding and position-finding. Direction-finding is effected by means of two coils set at right angles in the aircraft, by means of which the bearing of a transmitting ground station with reference to the aircraft's compass can be taken. When two or more bearings on different ground stations, whose position is known, have been obtained, a "cut" or "fix" of the aircraft is obtained. The position-finding system consists of two or more ground stations fitted with apparatus capable of taking bearings with respect to true north and connected by direct telephone line. The aircraft calls up by wireless one of these stations, requests her position and then makes a series of signals for about half a minute. The stations take the aircraft's bearings, plot its position, and transmit the information to the aircraft. Wireless direction and position-finding, as well as wireless telephony, have on several occasions proved their value to navigation, but in spite of instances of successful night flying, developments have not been such as to render night services practicable.
Marine experience has been a valuable guide, but aerial illumination has entailed many new problems of its own—the distribution of light through very wide angles, the installation of light and powerful lamps in aircraft, the elimination of shadows and the prevention of dazzle, the provision of apparatus to indicate the strength and direction of the wind, and the like.
Very shortly the first organized and equipped night-flying route will be available; that between London and Lympne on the Continental air highway. The Boulogne-Paris section will probably be ready a little later. There will be four lighthouses on the English section, of which two will be automatic, requiring no attention for twelve months at a time. These, and many other, facilities will much assist the progressive establishment of services during the hours of darkness, and will provide valuable data for the establishment of other night-flying routes. There is no real difficulty given a reasonably clear atmosphere.