ISO 20949:2018

Overview

ISO 20949:2018 - "Aircraft - Smart contactor - General requirements" defines the scope, definitions, design requirements and test methods for smart contactors used in aircraft electrical power systems. A smart contactor combines a power switching device and an intelligent driving/control circuit to perform switching, over-current protection, status reporting and interface functions. This standard provides the baseline for design, performance verification and qualification of smart contactors intended for More Electric Aircraft (MEA) and All Electric Aircraft (AEA) applications.

Key topics and technical requirements

The standard covers general and technical aspects needed to ensure safe, reliable and interoperable smart contactors:

• Definitions and scope - formal definition of a smart contactor and applicable system roles.
• General requirements - detail specification sheets, materials, construction and mounting.
• Terminals and enclosures - main and auxiliary terminal requirements, enclosure types (open, ventilated, sealed, hermetic) and grounding.
• Design characteristics - control and status signal definitions, fail‑safe behavior and compatibility with aircraft power architectures.
• Operating characteristics - timing sequences, operating/pickup/dropout voltages, quiescent power dissipation and contact voltage drop.
• Electrical and safety characteristics - contact bounce, dielectric strength, insulation resistance, overload and ground-fault interrupt (GFI) behavior, trip-free characteristics and life expectancy.
• Environmental and qualification tests - procedures for visual/mechanical checks, timing, electrical tests, dielectric and insulation verification, overload and life tests, terminal strength and sealing.

Practical applications

ISO 20949:2018 is intended to guide the development, selection and qualification of smart contactors in aircraft power distribution and protection schemes. Typical uses include:

• High-current switching and protection in primary and secondary electrical buses.
• Intelligent load management and selective protection in MEA/AEA architectures.
• Providing status and diagnostic signals for health monitoring and avionics integration.
• Reducing maintenance and improving reliability compared with conventional contactors.

Who should use this standard

• Aircraft OEMs and systems integrators specifying power distribution hardware.
• Electrical and propulsion engineers designing MEA/AEA power systems.
• Component manufacturers and suppliers developing smart contactor products.
• Certification authorities and test labs performing qualification and procurement testing.
• Maintenance planners and reliability engineers assessing component lifecycle and diagnostics.

Related standards

• Other parts of the ISO 20949 series (see ISO catalog).
• ISO/IEC Directives referenced for document preparation and conformity assessment.
• Relevant aerospace electrical and certification standards used together with ISO 20949 for qualification and procurement.

Keywords: ISO 20949:2018, smart contactor, aircraft electrical power systems, More Electric Aircraft, power distribution, qualification tests, design requirements.