LS – Landing System – Navigation

Introduction

Landing System – Navigation (LS) encompasses the complete spectrum of ground-based and airborne navigation aids and avionics that enable precise approach, landing, and missed approach procedures for aircraft. It includes both legacy and state-of-the-art technologies, underpinned by stringent international standards such as ICAO Annex 10, and ensures safe arrivals under all meteorological conditions—from global hubs to regional airfields.

LS navigation architecture is layered, combining ground-based radio transmitters (ILS, VOR, DME, marker beacons), satellite augmentation (GBAS), and visual aids (PAPI, VASI). These provide continuous guidance from the initial approach fix to the runway. Modern cockpits integrate these signals via displays, flight management computers, and autopilot systems, enabling real-time situational awareness and advanced procedures like autoland.

The LS concept has evolved to include sophisticated simulation tools for development and certification, plus modern vision-based and augmented reality landing aids for next-generation aircraft. LS navigation is foundational for both precision and non-precision approaches, making safe landings possible even in zero-visibility conditions (e.g., CAT III ILS). Its integration, standardization, and rigorous testing make LS navigation a pillar of aviation safety and reliability.

Key Concepts and Components

LS (Landing System)

Definition:
The Landing System (LS) is an integrated collection of technical infrastructure and avionics delivering precise navigation guidance during aircraft approach and landing. While centered on ILS (Instrument Landing System), it includes marker beacons, DME, visual aids (PAPI, VASI), and advanced systems like GBAS and vision-based landing aids. LS is governed by ICAO Annex 10, ensuring global interoperability and performance.

Operational Use:
LS is fundamental at airports worldwide, allowing approaches and landings in both visual and instrument conditions. Pilots typically engage the system via the LS or APPR button, activating cockpit navigation displays for localizer (lateral) and glideslope (vertical) guidance. Autopilots can interface with LS for automated approaches and autoland.

Technical Details:
A full LS installation includes a localizer antenna array beyond the runway, a glideslope antenna near the touchdown zone, marker beacons or DME along the approach, plus airborne receivers. The system is designed with redundancy and strict integrity requirements, regularly maintained and flight-inspected.

Navigation Signals Simulation and Analysis

Definition:
Navigation signals simulation and analysis refers to generating, manipulating, and evaluating radio navigation signals in controlled environments to test navigation equipment. It’s vital for development, certification, and maintenance of LS systems, ensuring compliance with standards like ICAO Annex 10.

Operational Use:
Used in labs, manufacturing, certification, and airline maintenance, simulation tools generate synthetic signals (ILS, VOR, DME, GBAS), assessing performance under varied conditions (interference, multipath, fading). Regulatory authorities use simulations for compliance and pilot training.

Technical Details:
Signal simulators replicate modulation, envelope, and timing as per ICAO specs. They support multi-channel outputs, noise injection, and automated test sequences. Analysis tools record device responses, measuring sensitivity, flag accuracy, and response time.

ILS (Instrument Landing System)

Definition:
ILS is the core precision approach aid, providing intersecting radio beams for lateral (localizer) and vertical (glideslope) guidance. It may also include marker beacons and DME. ILS supports autoland in near-zero visibility (CAT III).

Operational Use:
ILS is standard at most airports. Pilots select the ILS frequency and follow cockpit indicators. CAT II/III operations require certified equipment and integrity monitoring.

Technical Details:

• Localizer: 108.10–111.95 MHz (lateral)
• Glideslope: 329.15–335.00 MHz (vertical)
• Markers: 75 MHz at fixed approach points
• DME: Paired for slant-range distance

Localizer

Definition:
The localizer provides lateral guidance via an antenna array beyond the runway, transmitting a beam aligned with the centerline. Aircraft receivers display deviation on a horizontal indicator.

Technical Details:

• Frequency: 108.10–111.95 MHz (odd tenths)
• Coverage: ±35° (10 nm), ±10° (18 nm)
• Course Width: 3–6°
• Modulation: 90 Hz/150 Hz tones

Glideslope

Definition:
Glideslope delivers vertical guidance using an antenna near the touchdown zone, transmitting beams at 329.15–335.00 MHz, usually at a 3° descent angle.

Technical Details:

• Coverage: 1.4° above/below glide path, 10 nm
• Course Width: About 1.4°
• Modulation: 90 Hz/150 Hz tones

Marker Beacons

Definition:
Marker beacons are 75 MHz transmitters along the ILS approach path, providing fixed position cues via cockpit lights and sounds.

Technical Details:

• OM (Outer): Blue light, 400 Hz, dashes
• MM (Middle): Amber, 1,300 Hz, dot-dash
• IM (Inner): White, 3,000 Hz, dots

DME (Distance Measuring Equipment)

Definition:
DME is a UHF (962–1213 MHz) system measuring aircraft distance from a ground station using time delay of pulse exchanges.

Technical Details:

• Accuracy: ±0.2 nm or 3% of slant range
• Update Rate: ~30/sec
• Capacity: 100+ aircraft

VOR/(D)VOR (VHF Omnidirectional Range)

Definition:
VOR transmits azimuth information for bearing determination; DVOR adds electronic rotation for accuracy.

Technical Details:

• Frequency: 108.00–117.95 MHz
• Accuracy: ±1–2° (DVOR: ±0.5°)
• Coverage: Up to 200 nm

GBAS (Ground-Based Augmentation System)

Definition:
GBAS provides localized corrections to GNSS signals for precision approaches, supporting multiple runways from a single installation.

Technical Details:

• Broadcast: VHF, digital data link
• Accuracy: ≤1 m lateral/vertical
• Supports: Multiple approach paths

PAPI (Precision Approach Path Indicator)

Definition:
PAPI is a row of four light units beside the runway, providing color-coded cues (red/white) to indicate glide path position.

Technical Details:

• Location: 300–900 ft from threshold, 50–200 ft from edge
• Standard Slope: ~3°

Summary

Landing System – Navigation (LS) is the backbone of modern aviation approach and landing safety, integrating ILS, VOR, DME, GBAS, marker beacons, and visual aids like PAPI. Governed by international standards, LS ensures precise, reliable, and safe aircraft operations under all weather conditions, and continues to evolve with technology for future air traffic needs.

For more detailed technical standards, refer to ICAO Annex 10 and local aviation authorities. Reach out to our specialists for consultation or demonstrations on implementing advanced LS navigation solutions.