INTRODUCTION TO AIRFIELD GROUND LIGHTING (AGL)

Terminology: “AGL” is widely used in industry for Airfield Ground Lighting. ICAO documents use the term aeronautical ground light for any light provided specifically as an aid to air navigation, and the FAA groups these systems under airport lighting or visual aids. Expect to meet all three terms in standards, specifications and exams.

Understanding AGL requires more than learning the name of each light. It requires understanding how the visual, electrical and operational elements work together as one system.

WHY IS AGL REQUIRED?

Aircraft operating on an aerodrome need reliable visual references for runway and taxiway identification, alignment, movement and safe navigation. Without appropriate visual guidance, identifying runway and taxiway geometry becomes more difficult, particularly during night operations and reduced-visibility conditions.

Depending on the airport and applicable system, AGL can help pilots identify:

• Runway edges
• Runway threshold
• Runway end
• Runway centreline
• Touchdown zone
• Taxiway routes
• Holding positions
• Runway entrances
• Approach alignment
• Vertical approach guidance

The exact arrangement depends on the runway, taxiway, approach procedure, operational requirements and applicable airport standards or specifications.

MAIN AREAS OF AIRFIELD GROUND LIGHTING

AGL can be studied by dividing the airfield into major functional areas.

Basic colour guide

Colours, spacing and the length of colour-coded zones differ between ICAO, FAA and national requirements. See Study Note 21 for the full colour treatment, and check the standard that applies to your aerodrome.

SIMPLE AGL CONCEPT

                 APPROACH AREA
                       ↓
         APPROACH LIGHTING SYSTEM (ALS)
                       ↓
      ┌───────────────────────────────┐
      │ Threshold lights + REIL       │
      │                               │
      │ Edge lights    Centreline     │◄── PAPI / APAPI
      │ (both sides)   lights         │    (beside runway,
      │                               │     near threshold)
      │ TDZ lighting (where provided) │
      │                               │
      │ Runway end lights             │
      └───────────────────────────────┘
        RUNWAY (schematic, not to scale)
                       ↓
                    TAXIWAY
                       ↓
          Edge / Centreline / Stop Bar
                       ↓
                     APRON
                       ↓
                 AIRCRAFT STAND

AGL is distributed across the approach area, runway, taxiway, apron and aircraft stand environment.

AGL AS A COMPLETE SYSTEM

A common mistake among beginners is to study every light or component as an isolated item. AGL should be understood as a complete interconnected system. A simplified electrical chain:

Each link in this chain has its own note: 07 CCR, 08 Isolating Transformers, 09 Primary & Secondary Circuits and 10 L-823 Connectors.

The primary cable forms a closed loop: current leaves the CCR, passes through the primary winding of each isolating transformer in turn, and returns to the CCR. The CCR is normally set to the required brightness step by a local or remote control system (for example an ALCMS). The complete system includes both electrical infrastructure and lighting equipment. If one part fails, the visible symptom may appear somewhere else in the circuit.

That is why AGL technicians and engineers need both Component Knowledge + System Knowledge. Understanding the complete circuit is also fundamental to systematic troubleshooting.

Basic AGL electrical concept

POWER SUPPLY
     │
     ▼
    CCR
     │
     ▼
PRIMARY CABLE
     │
     ▼
ISOLATING TRANSFORMER
     │
     ▼
SECONDARY CONNECTION
     │
     ▼
AGL LIGHT

In a typical series-circuit arrangement, the Constant Current Regulator (CCR) controls the current supplied to the series circuit. The CCR holds the current constant (commonly up to 6.6 A at maximum brightness) and changes the brightness by changing that current. Each lighting unit is connected through an isolating transformer, which couples the primary series circuit to the individual fixture while electrically isolating the lamp circuit from the primary. It is also designed to tolerate an open-circuit secondary, so a failed lamp does not break the series loop and the remaining lights stay lit. This is one of the most important concepts for students beginning AGL.

THINK LIKE AN AGL ENGINEER

When learning any AGL component, do not memorise only its name. Study four questions:

1. What is it? Definition and basic construction or arrangement.
2. Where is it used? Location and application on the airfield.
3. What colour, intensity or configuration does it use? Visual indication and applicable configuration.
4. Why is it required? Its operational purpose.

This connects definition + location + characteristics + function instead of relying on memorisation alone.

QUICK REVISION

EXAM QUESTIONS

STUDY TAKEAWAY

The first step in learning AGL is to understand the complete picture. Do not start by memorising hundreds of light types. Start with the relationship:

Once this foundation is clear, individual AGL systems become much easier to understand.

ENGINEERING & EXPERT NOTES

REFERENCES & FURTHER READING

These notes are a study aid. Verify details against the primary sources below.

EXPLORE ALL AGL STUDY NOTES