glide path when it is making an ILS approach along the localizer path. The glide-slope transmitter transmits a directional pattern on one of forty channels in the VHF (very high frequency) band of 329.15 to 335.4 MHz, modulated by two signals (transmitted on 90 and 150 Hz, respectively). When received with equal intensity, they are displayed by compatible airborne equipment as an “on path” indication. In this case, the horizontal needle of the cross-pointer indicator shows the pilot whether he or she is above, below, or on the glide-slope. The glide-slope is also referred to as the glide path. False glide-slope signals may exist in the area of the localizer back course approach, which can cause the glide-slope flag alarm to disappear and present unreliable glide-slope information. The pilot should disregard all such glide-slope signal indications when making a localizer back course approach unless a glide-slope is specified on the approach and the landing chart. See also false glide-slope.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved