Chapter: Communication, Light Signals, and Runway Lighting Systems

Overview

This chapter covers the aircraft lighting systems essential for safe operation, including position (navigation) lights, anti-collision lights (beacons and strobes), landing and taxi lights, and instrument panel lighting. It also addresses the regulatory requirements governing these systems, systematic troubleshooting methodologies, and the maintenance standards prescribed by FAA regulations and advisory circulars. The material emphasizes the critical relationship between electrical system integrity, regulatory compliance, and airworthiness.

Key Concepts

1. Aircraft Lighting System Classifications

Aircraft lighting systems serve distinct operational purposes and are categorized accordingly:

Position (Navigation) Lights

Red light on the left wingtip

Green light on the right wingtip

White light on the tail

Required for night operations under 14 CFR 91.205

Must meet specific color and intensity standards per 14 CFR 91.209

Anti-Collision Lights

Rotating beacon (typically red, located on the top and/or bottom of the fuselage)

Strobe lights (high-intensity flashing white lights, typically on wingtips and tail)

Required for both day and night operations under 14 CFR 91.209

Must be operational before flight; no MEL relief for Part 91 operations

Landing and Taxi Lights

Landing lights: Required for night operations per 14 CFR 91.205(b)(11)

Taxi lights: Used for ground maneuvering

High-intensity illumination for approach, landing, and taxi operations

Instrument Panel Lights

Illuminate cockpit instruments for night operations

Typically controlled by a dimming rheostat

Must not produce glare or reflections that impair pilot vision

2. Electrical Circuit Fundamentals for Lighting Systems

Understanding the electrical path from power source to light is essential for effective troubleshooting:

Power Distribution Path

32.Power source (battery/alternator/generator)

33.Bus bar

34.Circuit breaker (protection device)

35.Switch (control device)

36.Wiring (conductors)

37.Connectors/terminals

38.Load (light fixture/bulb)

Voltage Drop Principles

Every connection, switch contact, and length of wire introduces resistance

Excessive resistance reduces voltage available at the load

A dim light typically indicates high resistance in the circuit, not a complete failure

Voltage drop testing is the primary diagnostic method per AC 43.13-1B Chapter 11

Circuit Protection

Circuit breakers protect wiring from overcurrent conditions

A tripped breaker indicates an overcurrent event (short circuit or excessive current draw)

Never reset a tripped breaker without identifying and correcting the root cause

Repeated tripping indicates a persistent fault requiring systematic troubleshooting

3. Troubleshooting Methodology

Systematic troubleshooting follows a logical progression from simple to complex:

Initial Steps

52.Verify power is reaching the component (check circuit breaker, switch position)

53.Check voltage at the component terminals

54.Test the component itself (continuity, resistance)

55.Inspect wiring and connections for damage, corrosion, or chafing

Voltage Present, Light Not Working

If correct voltage is measured at the connector, the bulb or component is likely faulty

Test the bulb for continuity or replace with a known-good unit

No Voltage at Component

Trace the circuit backward toward the power source

Check circuit breaker (tripped?)

Check switch operation and contacts

Inspect wiring for opens, shorts, or chafing

Dim Light Symptoms

Indicates voltage drop due to high resistance

Check for corrosion at terminals and connectors

Verify ground circuit integrity

Measure voltage at the load and compare to source voltage

Inspect switch contacts for pitting or burning

Intermittent Operation

Often caused by loose connections or chafed wiring

Physical manipulation (wiggling) of wiring can help isolate the fault

Inspect connectors for proper seating and terminal tension

4. Regulatory Requirements

14 CFR 91.205 – Instrument and Equipment Requirements

Position lights required for night operations

Anti-collision light system required for both day and night operations (per 91.209)

Landing light required for night operations (for hire or commercial operations)

14 CFR 91.209 – Aircraft Lighting

No person may operate an aircraft during night unless position lights are lighted

Anti-collision lights must be lighted during all operations (day and night)

An inoperative anti-collision light must be repaired before flight; no deferral permitted under Part 91

14 CFR 43.9 – Maintenance Record Entries

Any maintenance performed must be recorded

Entry must include: description of work, date, mechanic's signature, and certificate number

Applies to minor repairs such as lens replacement

AC 43.13-1B – Acceptable Methods, Techniques, and Practices

Chapter 11 covers aircraft electrical systems

Provides guidance for wire repair, splicing, and protection

Emphasizes systematic troubleshooting and voltage drop testing

Requires following manufacturer's instructions for component installation and cooling

5. Wiring Maintenance Standards

Wire Repair Requirements

Chafed wiring is a fire and safety hazard requiring proper repair

Taping is a temporary fix, not an approved repair method

Approved repairs include proper splicing with soldered connections or approved connectors

Protect wires passing through bulkheads with grommets or clamps

Follow AC 43.13-1B Chapter 11 for acceptable methods

Connector and Terminal Maintenance

Secure loose connections and protect from corrosion

Inspect for signs of overheating (discoloration, melting)

Verify proper terminal tension and seating

Use approved anti-corrosion compounds where specified

6. Component-Specific Considerations

Strobe Light Power Supplies

Convert aircraft DC power to high-voltage pulses for strobe tubes

Require adequate ventilation to prevent overheating

Mount per manufacturer's instructions

Output voltage must be verified during functional testing

Faulty lamps or wiring can affect power supply output

Rotating Beacons

Electromechanical or solid-state flashing devices

Motor brushes may require replacement (component-level check after verifying power)

Verify power path: circuit breaker → switch → beacon

Rheostats (Instrument Panel Dimming)

Variable resistors controlling panel light intensity

Test with ohmmeter while rotating knob

Look for resistance jumps or open circuits indicating worn internal contacts

Test with power removed (non-energized)

Light Lenses

Must maintain proper color and intensity characteristics

Faded or discolored lenses can render lights non-compliant

Replace with approved parts (PMA or OEM)

Document replacement per 14 CFR 43.9

7. Airport Lighting Systems

Runway Edge Lights

Series circuits with constant current regulators

Tripped breakers indicate overcurrent conditions (short circuits, failed lamps)

Isolate and repair faults before resetting

Runway Centerline Lighting

Flickering often caused by loose or corroded connections

Inspect constant current regulator connections first

Tighten connections and verify proper contact

Taxiway Edge Lights

Same series circuit principles as runway lighting

Tripped breakers require fault isolation before reset

8. Post-Lightning Strike Inspection

After a lightning strike, the lighting system requires special attention:

Inspect all wiring for arcing, burning, and insulation breakdown

Check components for electrical damage

Look for latent failures that may not be immediately apparent

Verify all lighting systems function correctly before return to service

Important Procedures and Practices

Systematic Troubleshooting Sequence

147.Verify the symptom – Confirm the reported malfunction

148.Check the obvious – Circuit breaker, switch position, bulb condition

149.Verify power at the component – Measure voltage at the load terminals

150.Test the component – Continuity check or replacement with known-good unit

151.Inspect the circuit – Wiring, connectors, grounds, and switch contacts

152.Repair the fault – Use approved methods and materials

153.Functional test – Verify proper operation after repair

154.Document the work – Make required logbook entries

Voltage Drop Testing Procedure

157.Measure source voltage (battery/bus)

158.Measure voltage at the load with the circuit energized

159.Calculate voltage drop (source voltage minus load voltage)

160.Acceptable drop: typically less than 3% for lighting circuits (refer to manufacturer data)

161.Excessive drop indicates high resistance – inspect connections, switches, and wiring

Circuit Breaker Handling

A tripped breaker indicates an overcurrent condition

Do NOT reset without identifying the cause

Inspect for short circuits, chafed wiring, and failed components

If the breaker trips again after reset, the fault persists – continue troubleshooting

Document all breaker trips and corrective actions

Functional Testing Requirements

Always perform a functional test after any repair or component replacement

Verify proper operation under actual operating conditions

Check all modes (e.g., steady, flashing, high/low intensity)

Confirm proper color and intensity for position lights

Common Relationships and Principles

Dim Light = High Resistance

Dim illumination indicates voltage drop, not a complete circuit failure

Corrosion, loose connections, and worn switch contacts are typical causes

Voltage drop testing identifies the location of excessive resistance

Tripped Breaker = Overcurrent

Indicates a short circuit or excessive current draw

Failed components can cause overcurrent conditions

Always find and correct the root cause before resetting

Intermittent Operation = Loose Connection

Movement-sensitive failures indicate poor electrical contact

Wiggling wiring harnesses can help isolate the fault location

Inspect connectors, terminals, and chafing points

No Voltage at Component = Open Circuit

Trace the power path backward from the load

Check breaker, switch, and wiring continuity

A tripped breaker is a common cause of complete voltage loss

Correct Voltage Present = Component Failure

If proper voltage is measured at the load terminals, the component itself is faulty

Test the bulb or unit for continuity

Replace with an approved part

Required Equipment = Must Be Operational

Position lights, anti-collision lights, and landing lights (when required) must function

No deferral is permitted under Part 91 for these items

Inoperative required equipment grounds the aircraft until repaired

Summary of Key Regulations and References

Reference	Application
14 CFR 91.205	Equipment requirements for night operations
14 CFR 91.209	Aircraft lighting requirements
14 CFR 43.9	Maintenance record entries
AC 43.13-1B Chapter 11	Acceptable electrical system maintenance practices
FAA AMT Handbook, General, Chapter 7	Electrical system fundamentals and troubleshooting

Conclusion

Aircraft lighting systems are safety-critical components that require systematic troubleshooting and proper maintenance. Understanding the electrical principles governing these systems, the regulatory requirements for their operation, and the approved maintenance practices is essential for the AME. The key to effective troubleshooting lies in following a logical progression from verifying power at the component to testing the component itself, while always considering the most likely causes first. Proper documentation and adherence to approved methods ensure both airworthiness and regulatory compliance.

Communication, Light Signals, and Runway Lighting Systems