Glide Slope
ChristiaanJ.....a little strong verbiage on the comeback, but you are absolutely correct about the angular and not lateral displacement.
The actual..precise...displacement (vertical)value of "one dot" depends on several factors relating to the specific implementation of each ILS. Suffice it to say that a one dot deviation at Threshold Crossing is typically equal to approximately 3 feet off the GS axis. This leads to the old saw that if the GS deviation indicator ("needle") is "on scale" at TC( within the max dots and not pegged) you will land in the paint. I doubt very much that a TCH error of 3 feet (one dot) will translate into a +/-500ft variation in TD point but there are several variables involved here.
Last edited by A310driver; 3rd Aug 2007 at 19:08.
Reason: correct poster's name