Definition
The angle, measured in degrees above the horizontal, of the descent path projected by the glide slope transmitter of an Instrument Landing System (ILS). It defines the vertical path an aircraft follows from the final approach fix down to the runway touchdown zone. The standard glide slope angle is 3 degrees, though some runways use steeper angles where terrain or obstacles require it.
Plain English
The downward slope of the path an aircraft flies during an ILS approach, measured as an angle above flat ground. Most runways use a 3-degree slope, which means the aircraft descends about 300 feet for every nautical mile flown toward the runway.
Context Anchor
Seen on instrument approach charts, ILS system diagrams, and approach briefings when describing the vertical path to the runway.
Derivation
From 'glide' (a steady, powered or unpowered descent along a sloping path) and 'slope' (the steepness of an incline). 'Angle' specifies that this slope is expressed in degrees rather than as a ratio. The combined term names the precise angular descent path published for a runway.
Why Pilots Care
It ensures the aircraft descends at the correct rate to clear obstacles and land at the proper touchdown point.
Intuition Check
Do not confuse glide slope angle with the airplane’s nose angle. It is the angle of the intended descent path to the runway, not the pitch attitude shown by the aircraft.
Example Sentence 1
The published glide slope angle for runway 27 is 3 degrees, giving a standard descent rate of about 650 feet per minute at our approach speed.
Example Sentence 2
Terrain may require a slightly steeper glide slope angle on some approaches.