ILS Systems
Report over outer marker inbound. Familiar phrase if you are on a instrument approach using the ILS System.
The Jepp Charts indicate the distance from the end of the runway and the height of the airplane should be when the indicator for that particular beacon lights up on the instrument on your plane's panel.
There are three lights. The outer beacon marker is the first you come in contact with, on a ILS approach, it emits a blue colored flashing light and a tone. (to catch your attention) This provides a check on the correct function of the glide-slope. In modern systems the DME is installed in your aircraft and provides the aircrafts distance to the runway. The DME (distance measuring equipment) is co-located with the ILS.
The tower asks you to "Report Outer Marker Inbound" on a instrument approach. When the Outer Marker Beacon in your plane signals you, that is your clue to report back on the tower frequency, "Outer Marker Inbound." The tower should reply, "Cleared for landing."
The middle marker beacon is the second light that flashes a amber color and emits a tone of "dots and dashes" (Morse Code style) at the rate of two per second. The missed approach point and the point where you should have a visual sighting of the runway is very near.
Middle Markers are no longer required in the United States. You may have equipment, in older aircraft that have a instrument that has all three beacon lights.
The inner marker beacon is located near the runway threshold to indicate, in very low visibility conditions, the runway is just a short distance away. It emits a white flashing light and a tone that is a continuous series of "dots" Morse Code style.
Since I am an ancient relic of the "Good Old Days" the Marker Beacons are being phased out and replaced by DMEs that provide slant range measurement of distance to the runway in nautical miles. The DME provides more accurate and continuous monitoring of correct information on the ILS glide-slope to the pilot.
The safety word here is "continuous." The importance of "continuous knowledge of exactly where you and your plane are in the airspace." Updating equipment is a necessary evil for your own safety.
