instrument landing system

instrument landing system (ILS), electronic guidance system designed to help airline pilots align their planes with the centre of a landing strip during final approach under conditions of poor visibility. The ground equipment of the ILS consists of two directional transmitters that send out radio beams, sometimes of microwave frequencies (i.e., frequencies of more than 1,000 MHz), from either side of the runway’s centreline. The radio pulses are picked up by instruments on the plane...