Definition
A precision instrument approach procedure that uses ground-based radio signals to guide an aircraft along a precise lateral path (the localizer) and a precise descent path (the glide slope) to a specific runway. The pilot follows cockpit instrument indications generated from these signals down to a published decision altitude, at which point the runway environment must be visually identified to continue the landing.
Plain English
A landing approach where two radio beams from the airport guide the aircraft straight in toward the runway and down at the correct angle, so the pilot can find the runway in low visibility by following cockpit needles.
Context Anchor
Seen on instrument approach charts, in instrument flight training, and when a controller clears a pilot to fly an ILS approach to a specific runway.
Derivation
From 'instrument' (cockpit gauges and displays the pilot relies on instead of looking outside) and 'landing system' (a coordinated set of equipment that guides the aircraft to the runway). The full phrase signals that the entire approach is flown by reference to instruments driven by this system.
Why Pilots Care
Allows safe landings when clouds or fog hide the runway, expanding where and when flights can operate.
Grounding Statement
Picture flying toward a runway in cloud: the ILS approach gives you one guide to stay lined up with the runway and another guide to descend smoothly toward it.
Intuition Check
Do not read “approach” here as simply “getting closer to the airport.” In this context, an ILS approach is a published instrument procedure with specific guidance, settings, and limits.
Example Sentence 1
With the ceiling reported at 300 feet, the crew briefed the ILS approach to Runway 27 and configured the aircraft early to stay stable on the glide slope.
Example Sentence 2
ATC cleared the flight for the ILS approach and the pilot captured the glideslope at 1,800 feet.