A new fixed-beam approach system

Consists of a dual-beam localizer operating in the range 108 to 112 Mc/s and a glide slope equipment operating between 329 and 335 Mc/s. It works interchangeably with existing instrument-approach-system equipment. The normal localizer has two very narrow beams, one modulated at 90 c/s and the other at 150 c/s so that it can be determined on which side the plane is "off-course." The narrowness of the beams prevent any serious reflection effects from nearby buildings. The peaks of radiation are 3deg off-course and strength is reduced to zero at 12deg off-course. There are naturally many minor lobes and to prevent any harmful effects a broad radiation pattern localizer is superimposed. The "on-course" signal from this is only 1/3 the signal strength of the main localizer and they are equal 8deg off-course. Elsewhere throughout the azimuth the broad localizer predominates by at least 3 to 1. The glide-slope equipment which provides for vertical guidance operates on the "null-reference" system. Polar diagrams and photos of the equipment are given, also a pen-record showing the type of trace produced as the plane flies across the localizer course.