Approach Lighting System (Simple / Precision CAT I / II-III)

What It Provides

Approach lighting systems provide the principal visual transition between the instrument approach environment and the runway visual environment. Visual references extending outward from the threshold help pilots identify:

• Runway alignment and approach direction
• Horizontal reference and roll attitude
• Threshold location and runway orientation
• Visual transition during landing

What We Support

Precision AGL Solutions supports selection, engineering, supply and integration of simple and configured systems, including ICAO-style simple approach arrangements and FAA families:

• MALS, MALSF, MALSR
• ALSF-1, ALSF-2
• SSALS / SSALF where applicable
• Other authority-approved configurations

Select by approach category, runway configuration, applicable authority, approved layout, visibility requirements and project specification.

Located Along the Extended Centreline

An ALS is a coordinated field of visual aids before the runway threshold, along and around the extended runway centreline. It may contain:

• Approach centreline lights
• Crossbar and side-row lights
• Threshold lights
• Sequenced flashing lights and RAIL
• Supporting structures
• Electrical circuits, CCRs / power supplies
• Control and monitoring equipment

A Complete Engineered System

The exact combination depends on the system type. An ALS should be treated as a complete engineered system, not a collection of unrelated light fixtures.

This avoids a common procurement error: specifying a generic “approach light” without identifying the actual system configuration.

Context

In FAA usage SALS and SALSF mean Short Approach Lighting System (with sequenced flashers), whereas ICAO uses “simple approach lighting system”; confirm which meaning your specification uses. Where SALS describes a Simple Approach Lighting System, it refers to the simpler arrangement in ICAO-style standards, associated with:

• Non-instrument runways
• Non-precision approach runways
• Simple visual approach guidance

ICAO material describes a row of lights on the extended runway centreline with a crossbar 300 m from the threshold. Current ICAO-derived provisions specify a minimum practicable length of 420 m, with an 18 m or 30 m crossbar at 300 m. Confirm against national implementation and project specification.

Centreline & Crossbar

Centreline: individual point-source lights, barrettes, fixed light bars or system-specific modular fixtures. ICAO-derived guidance permits a single source or a barrette of at least 3 m, with point-source lights in a barrette spaced at not more than 1.5 m.

Crossbar: the primary transverse reference. It should be straight, horizontal as far as practicable, at right angles to the centreline and bisected by it.

MALS

FAA identifies MALS as an economy approach-lighting aid for non-precision approaches, giving enhanced visual recognition of the runway end. AC 150/5340-30J lists it among the economy systems.

• Green threshold lights
• White steady-burning centreline light bars
• Seven five-light centreline bars at 200 ft intervals, from 200 ft to 1,400 ft
• Two additional five-light bars at the 1,000 ft station, forming a crossbar effect
• Supporting approach-light structure

The MALS steady-burning field is the same as that of MALSR; MALSR adds the RAIL flashers beyond it. Verify dimensions against the applicable FAA drawing.

MALSF — MALS With Sequenced Flashers

A MALS configuration supplemented by three sequenced flashers. The flashers give a dynamic effect that improves identification of the approach-light field where surrounding lights make a steady-burning system harder to distinguish.

• Green threshold lights
• White steady-burning light bars
• Three sequenced flashers in the outer portion
• Seven centreline bars at 200 ft (approximately 61 m) intervals

Installation dimensions and tolerances follow the current approved FAA drawing.

FAA Category I Standard

FAA identifies MALSR as an economy system used as the FAA standard for Category I precision runways.

• 18–33 green steady-burning threshold lights, depending on runway width
• Nine steady-burning light bars
• Typically five sequenced flashing lights (RAIL), up to eight, starting 1,600 ft from the threshold
• 200 ft spacing for principal bars and flashers

MALSR and RAIL

The Runway Alignment Indicator Light (RAIL) gives a dynamic indication along the approach axis. FAA defines RAIL as sequenced flashing lights installed in combination with other light systems.

Treat RAIL as part of the complete MALSR system, not a generic flashing-light product.

ALSF-1 — Category I

Approach Light System with Sequenced Flashers in a Category I configuration, identified by FAA separately from ALSF-2, MALS, MALSF and MALSR. It gives a much more extensive field than an economy MALS.

• Green threshold lights
• White steady-burning centreline lights and light bars
• Crossbar and red terminating-bar elements (the red side-row lights belong to ALSF-2)
• Sequenced flashers
• Supporting structures, control and power infrastructure

Layout comes from the applicable FAA system drawing.

ALSF-2 — Category II / III

Designed for Category II/III instrument approaches, giving information on runway alignment, height perception, roll guidance and horizontal reference.

Typical FAA scope:

• 49 green threshold lights
• Red side-row lighting
• 144 high-intensity white steady-burning lights
• 15 sequenced flashers on a typical 2,400 ft system (up to 21 on a 3,000 ft system)
• 100 ft spacing between principal light stations

Flashers run sequentially from the outermost station toward the threshold, creating an apparent moving light. These numbers describe the FAA typical configuration and should not be applied automatically to non-FAA projects.

ICAO precision approach (Category I): a row of centreline lights extending, wherever possible, 900 m from the threshold, with a 30 m crossbar at 300 m. Category II/III systems add side-row barrettes and further crossbars in the inner portion. Confirm the arrangement in the applicable Annex 14 edition.

Site Coordination

• Terrain, roads, drainage
• Buildings, trees, fences
• ILS/MLS equipment
• Utility infrastructure
• Approach surfaces
• Access roads and maintenance routes
• Land availability

FAA MALSF guidance identifies minimum land of about 1,600 ft × 400 ft for its typical installation. Other systems differ.

Approach-Light Plane

FAA MALSF guidance identifies the optimum position as a horizontal plane at runway-end elevation, with permitted longitudinal slope adjustments for obstacles and supports, and beam aiming toward an assumed 3° glide path.

This affects light elevation, support height, vertical alignment, beam aiming, terrain and obstructions. The project survey controls final installation.

Typical Supports

• Low-level light supports
• Towers and poles
• Light bars
• Frangible supports
• Low-impact-resistant structures

Design Considerations

• Height and wind loading
• Frangibility
• Ground conditions and foundation
• Light alignment
• Cable routing
• Maintenance access

FAA maintains a dedicated specification for Low-Impact Resistant Structures for airport visual aids.

Technical Parameters

• Colour and intensity
• Beam direction, horizontal and vertical coverage
• Light-bar, side-row and crossbar distribution
• Flasher intensity
• RAIL / sequence characteristics

The objective is a coherent visual field from the intended approach path.

Light Source Technology

LED, halogen, incandescent, discharge-type flasher or other authority-approved technologies. LED may give long life, reduced maintenance, consistent colour, rapid switching, lower energy use, better monitoring and stable photometry.

Technology alone does not establish compliance; the fixture must meet system-specific photometric, electrical and environmental requirements.

CCR & Intensity Control

Systems may operate at low, medium and high intensity, with multiple controlled steps and system-specific flasher control. FAA MALS/MALSF/MALSR and ALSF systems each have their own intensity and control characteristics, so fixtures must suit the actual CCR/control configuration.

Control System Functions

• ON/OFF and intensity selection
• Flasher activation and sequencing
• Monitoring and fault indication
• Remote control and maintenance isolation

Interfaces: AGL control panel, ALCMS, airport operations system, ATC interface, local maintenance panel.

Monitoring May Include

• Individual circuit and CCR status
• Flasher and control status
• Lamp/LED failure
• Communication status
• Alarm indication

Serviceability

ICAO-based maintenance guidance sets specific serviceability objectives for precision approach lighting, including higher objectives for the inner portion of Category II/III systems. The airport's approved maintenance programme establishes the actual criteria.