The localizer guides lateral alignment
Antennas beyond the far end of the runway transmit a signal that lets the aircraft determine whether it is left or right of the centerline. Pilots or autopilot systems follow that course toward touchdown.
The glide slope provides vertical guidance
A separate transmitter creates the descent path, typically around three degrees. The aircraft intercepts it from below and follows it while descending toward the runway.
Approach categories define how low the operation can continue
Category I, II and III procedures correspond to progressively lower decision heights and visibility requirements. Lower categories need more capable airport and aircraft systems.
Critical areas around the antennas must be protected
Vehicles or aircraft near the ILS transmitters can distort the signal. In low visibility, airports use special procedures to keep those areas clear.
Autoland is possible but not universal
Approved aircraft can couple autopilot systems to the ILS and perform automatic flare and rollout under certain conditions. Many ILS approaches are still hand-flown or disconnected before landing.
ILS has limitations despite its precision
Terrain, signal interference, runway geometry and maintenance requirements can constrain installation. Satellite-based approaches increasingly complement ILS rather than making it instantly obsolete.
The localizer provides lateral guidance
A ground transmitter helps the aircraft stay aligned with the runway centerline as it approaches.
The glide slope provides vertical guidance
A second signal defines the desired descent path, allowing crews to follow a stable angle toward the runway.
Different ILS categories support different minima
Airport equipment, aircraft capability, crew qualification and operating approval determine how low an approach may continue in poor visibility.
Signal protection matters near the runway
Vehicles or aircraft can disturb ILS signals, so airports protect critical areas more strictly during low-visibility operations.
Pilots monitor rather than simply follow the needles
Crews verify the approach against altitude checks, navigation data and expected geometry. An unstable or unreliable indication can require a missed approach.
Satellite approaches increasingly complement ILS
Modern navigation can provide precise instrument guidance without every runway needing a full ILS installation, although capabilities and minima vary.
More aviation guides
Explore more aircraft, pilot, airport and aviation guides on SY.com.
Explore aviation