SLOW RISING NEARLY CAUSED DISASTER AT THE START OF THE GREAT FLIGHT
The receiving equipment on aëroplanes and airships is arranged so as to indicate, with a comparatively high degree of accuracy, the direction from which wireless signals are received. The position of the sending, or beacon, station being known, the bearing of the aircraft from that station may be plotted on a suitable chart, in which small segments of great circles are represented by straight lines. Simultaneous bearings on two known beacon stations are sufficient to fix the observer's position with tolerable accuracy at the intersection of the lines of bearing, provided that they intersect at a reasonable angle—45 degrees or more, where possible.
With the very close tuning rendered possible by the use of continuous waves, beacon stations of the future will probably be provided with automatic means whereby directional signals can be sent out at intervals of one hour or less. Such signals will be coded, so that the crews of aircraft can identify the wireless station. The wave lengths must be chosen so as not to interfere with messages sent from commercial stations.
If there be a beacon station at the air navigator's destination, it is possible for him to direct his course so that the craft is always headed for the beacon; and in due time he will reach his objective.
This simple but lazy method, however, is not to be recommended; for, owing to the action of the wind, the route covered is longer than the straight course. To counteract drift and proceed in a direct line towards his destination, the air navigator frequently has to direct his course so that the craft is not headed straight for the objective. Hence, with a single beacon station, frequent observations of drift are necessary, if the shortest route is to be followed. Thus:
Approximate path taken by aircraft headed always towards beacon station.
Path taken by aircraft headed so as to counteract drift.