Why is the ILS needle is so sensitive?
Localizer course narrows as you get closer to the runway, at the OM approx 300' is the lateral displacement from centerline/per dot deflection to the MM which is 100' per dot to intersection at touchdown
Glide path full deflection (too high to too low) at 10nm is approx 1500' narrowing to feet at touchdown.
More info at FAA-H-8083-15A Chapter 7-38 , AIM 1-1-9 and beyond!
