Aircraft e.g. helicopter, landing assisting system e.g. instrument landing system, has transponders whose positions with respect to runway and frequencies are determined from aircraft by deducing trajectory towards entry of runway

摘要

The system has a set of beacons disposed near a runway (14), where each beacon has a set of hyper frequency transponders. Each transponder reflects a hyper frequency wave emitted by an aircraft by phase modulating the hyper frequency wave according to two states and a frequency characteristic of one of the transponders. Positions of the transponders with respect to the runway and frequencies are determined from the aircraft by deducing the trajectory towards the entry of the runway.