Aircraft landing

A system to detect aircraft ground proximity comprises a transmitter 110 for transmitting a radio frequency signal along a first extended landing gear 20 of an aircraft 10; a sensor 120 for detecting a parameter of the RF signal; and a controller 130 for detecting a change in the detected parameter on the basis of an output of the sensor 120, and for issuing a landing signal when the change in the detected parameter meets a predetermined criterion which indicates a certain aircraft ground proximity. A second landing gear may act as a receiving antenna and be associated with the sensor 120, such that the transmitter 110 and 120 sensor are connected only when the first 20 and second extended landing gears are both in contact with the ground. Alternatively, there may be a coil positioned at a distal end of the extended landing gear 20, wherein the transmitter 110 generates an oscillating magnetic current in the coil when the RF signal is transmitted. The detected parameter may be capacitance, electrical current, inductance or a rate of oscillation of magnetic current.