| 摘要 |
<p>The landing approach system for an aircraft is in particular for a helicopter, in which assessments are made in the craft of signals emitted from the landing location. The angle between two beamed lobes relevant and also the heaviness of directional ariels on the underside of the craft. Restriction on the frequency band used is disadvantageous. Use is made of two spaced apart points on the landing location which emit synchronised signals. The craft altitude is limited so that the received signals have a constant difference in period of duration. The signal emitting points can be constituted by two sets of pairs of points. A helicopter (6) required to land on a location (7) is guided there by pair of signal points (2, 3) complemented by pair of points (1, 4) on the desired line of approach.</p> |
