Overview
ISO 20894:2018 - Aircraft - LED based taxiing lightsystem - General requirements defines functional, photometric and interface requirements for LED-based taxi and runway turnoff (RTO) lighting systems on aircraft. The standard addresses the transition from sealed-beam lamps to LEDs, capturing expectations for luminous intensity, chromaticity, illuminance distribution, electromagnetic compatibility and environmental durability over the unit’s operating life.
Key Topics and Requirements
- Scope and purpose: Specifies characteristics and interface requirements for the LED taxiing light system (taxi and RTO lights), and can apply to other future light sources that replace LEDs.
- Operating life: Defines effective operating life as the time until photometric minimums (luminous intensity and chromaticity locus) are no longer met. Degradation of LEDs, lenses and control electronics must be considered.
- Photometric performance
- Initial luminous intensity and chromaticity locus must be established and monitored for degradation.
- Illuminance distribution: horizontal distribution must meet a cosine-based requirement across −74° to +74° and a minimum reference illuminance (example value E_C = 54 lux). An enhanced level example is E = 70 lux.
- Combined taxi + RTO illuminance may be evaluated together; minimum three measurement points required.
- Colour: Light shall be white and permit sufficient perception of airport markings; chromaticity limits must be maintained throughout life.
- Thermal and mechanical: LED junction temperature must never exceed each LED’s maximum junction temperature; plastic lenses must resist UV and environmental conditions for the required life.
- Electromagnetic interference (EMI): Conducted emissions testing per ISO 7137 (Table 1, Section 16, Category B limits) unless specified otherwise.
- Quality assurance and testing
- Component testing on specimens mounted in simulated real conditions.
- Photometric measurements after warm-up: minimum 30 minutes for LED sources or until thermal stabilization (light output change ≤3% over 15 minutes).
Applications and Users
ISO 20894:2018 is intended for:
- Aircraft manufacturers and systems engineers designing taxi and RTO lighting
- Avionics and lighting suppliers developing LED luminaires and control units
- Certification and compliance teams preparing test evidence
- Maintenance planners and MRO organizations evaluating lifecycle and replacement schedules
Keywords: ISO 20894:2018, LED taxiing light system, aircraft taxi lights, RTO lights, illuminance distribution, luminous intensity, chromaticity, LED junction temperature, electromagnetic interference.
Related Standards
- ISO 7137:1995 - Aircraft environmental conditions and test procedures for airborne equipment (referenced for EMI, environmental and power-source tests)
- SAE/ARP 693 - referenced locations for illuminance comparison
- FAR 25.1397 - referenced for aviation white chromaticity domain (CIE1931)