Aerospace EMC: qualification, certification and operational safety
In aviation, controlling the electromagnetic environment is essential to the qualification of airborne equipment, its integration and the operational safety of aircraft.
EMC testing applies to electronic equipment and subassemblies as well as to integrated systems and complete aircraft. It verifies electromagnetic emissions, susceptibility to conducted and radiated disturbances, and the ability to withstand electrical transients, high-intensity RF fields and the indirect effects of lightning.
These tests may require very wide frequency coverage, high field levels and dedicated equipment to reproduce the electromagnetic environments encountered in service.
The RTCA DO-160 / EUROCAE ED-14 standards, supplemented by certification requirements and programme-specific specifications, are key references for the environmental qualification of airborne equipment.
HEMERA RF supports manufacturers, equipment suppliers and laboratories in defining and integrating EMC, RF, microwave, high-field and lightning test facilities, from needs analysis through to automation, commissioning and metrology follow-up.
RTCA DO-160 / EUROCAE ED-14: the qualification standards for airborne equipment
The RTCA DO-160 and EUROCAE ED-14 standards define environmental conditions and test methods for characterising the behaviour of equipment intended for installation on board aircraft.
They cover a wide range of environmental stresses, including thermal, mechanical, electrical and electromagnetic.
RTCA DO-160 / EUROCAE ED-14: two harmonised references
The RTCA DO-160 and EUROCAE ED-14 standards define the environmental conditions and test methods used to qualify equipment intended for installation on board aircraft.
They are developed by RTCA (Radio Technical Commission for Aeronautics) in the United States and EUROCAE (European Organisation for Civil Aviation Equipment) in Europe respectively. Corresponding editions are developed in a coordinated manner to maintain technical equivalence of requirements and test methods. DO-160G and ED-14G are therefore technically equivalent, even though they are published by two separate bodies.
In practice, DO-160 is by far the most widely used reference in the international aviation industry, while ED-14 is its European counterpart. Which standard should be cited in a programme or qualification depends on the applicable contractual and certification framework.
Several sections are directly relevant to EMC and RF activities:
- Section 16 Power Input: power supply characteristics and disturbances.
- Section 17 Voltage Spike: voltage spikes.
- Section 18 Audio Frequency Conducted Susceptibility: conducted susceptibility at audio frequencies on power supplies.
- Section 19 Induced Signal Susceptibility: susceptibility to signals induced in cabling.
- Section 20 Radio Frequency Susceptibility: conducted and radiated RF susceptibility.
- Section 21 Emission of Radio Frequency Energy: RF electromagnetic emissions.
- Section 22 Lightning Induced Transient Susceptibility: susceptibility to lightning-induced transients.
- Section 23 Lightning Direct Effects: direct effects of lightning.
- Section 25 Electrostatic Discharge: electrostatic discharge.
The applicable tests and their levels depend in particular on the qualification category, the location of the equipment in the aircraft and the programme requirements.
This diversity calls for test facilities able to reproduce very different phenomena, from low-frequency electrical disturbances to high-amplitude RF fields and transients.
Electromagnetic emissions: Section 21
Section 21 of DO-160 / ED-14 addresses radio-frequency energy emissions generated by airborne equipment.
The aim is to control disturbances likely to affect the aircraft's other electronic systems, including communication, navigation and surveillance equipment, computers and control systems.
Tests cover conducted and radiated emissions, in accordance with the methods and frequency bands
Measurement equipment must be selected taking into account the frequency ranges, emission limits, cabling configurations and measurement methods specified by the standard.
Conducted and radiated RF susceptibility: Section 20
Section 20 of DO-160 / ED-14 verifies the ability of equipment to operate when subjected to radio-frequency disturbances.
The tests include, in particular, two complementary approaches.
Conducted RF susceptibility
RF disturbances are injected onto the equipment's cables and interfaces to assess their effect on its operation.
Test setups may combine RF generators, amplifiers, injection clamps, current probes, coupling devices and measuring instruments.
Radiated RF susceptibility
The equipment is exposed to a controlled electromagnetic field to verify its behaviour under the conditions defined by its qualification category.
Depending on the application, these tests may require fields from several tens to several hundred V/m, over frequency bands extending into the GHz range.
Performing these tests requires appropriate sizing of generators, RF amplifiers, antennas, field probes and levelling equipment.
Covering a wide frequency band often requires several complementary amplifier and antenna technologies.
HIRF: high-intensity radiated fields
Aircraft may be exposed to HIRF (High-Intensity Radiated Fields).
These environments may be associated in particular with the proximity of radars, communication transmitters or other high-power RF installations.
HIRF requirements aim to ensure that the electrical and electronic systems concerned maintain the performance needed for the aircraft's safe operation.
The issue goes beyond the qualification of a single piece of equipment. It may require an assessment of equipment integration, cabling, protection and the behaviour of complete systems.
HIRF certification relies in particular on specific standards and guidance documents, such as EUROCAE ED-107B, in addition to equipment qualification testing.
Wide frequency coverage and high field levels
Aerospace EMC testing can cover phenomena ranging from low frequencies up to RF and microwave.
Depending on the standards and applications, generation or measurement equipment may have to operate over bands reaching several GHz, or even several tens of GHz for certain specific applications.
Target levels can also vary considerably, from low-amplitude disturbances to fields of several tens or hundreds of V/m.
These values are indicative orders of magnitude: the frequencies and levels actually applicable depend on the test, the qualification category and the programme specifications.
Sizing the RF chain must take into account, in particular, the available power, transmission losses, antenna gain, test distances, the geometry of the installation and the size of the equipment under test.
CW, modulation and pulsed signals
Aviation electromagnetic environments can include different types of signals: CW (Continuous Wave), modulated signals and pulsed signals.
The applicable test methods determine the waveforms and modulations to be used. HIRF tests and certain specific applications may also require complex RF environments to be reproduced.
The choice of test equipment must then take into account:
- the frequency and the band to be covered
- the target field level
- the type of modulation
- continuous or pulsed operation
- average power and, where relevant, peak power
- amplifier and antenna performance.
This diversity may mean combining several complementary RF chains to cover all the requirements of an aerospace laboratory.
Indirect lightning: Section 22
Section 22 of DO-160 / ED-14 addresses the susceptibility of equipment to lightning-induced electrical transients.
When an aircraft is struck by lightning, the associated currents and electromagnetic fields can induce transient voltages and currents on the cabling and interfaces of electronic equipment.
The tests verify how equipment behaves under these stresses, according to the applicable waveforms, levels and qualification categories.
They require dedicated transient generators, injection and coupling devices, and instruments capable of measuring fast, high-amplitude phenomena.
Pin Injection
Pin Injection tests involve applying the specified transients to the appropriate interfaces of the equipment.
They assess its ability to withstand the electrical stresses defined by the standard.
Cable Bundle Tests
Cable Bundle Tests reproduce the transients induced on cable bundles.
They require suitable coupling devices, combined with dedicated generators and measurement equipment.
Multiple Stroke and Multiple Burst
Depending on the applicable category, tests may also include Multiple Stroke and Multiple Burst stress sequences.
These tests verify how equipment behaves when subjected to successive transients, not just a single isolated pulse.
Indirect lightning is thus a technical specialism distinct from continuous-wave RF testing, requiring dedicated generation, injection and measurement equipment.
Direct lightning effects: Section 23
Section 23 covers the direct effects of lightning on equipment and components subject to direct exposure.
It should be distinguished from Section 22, which addresses transients induced on equipment and its interfaces.
At aircraft level, lightning protection also requires consideration of structures, possible attachment zones, current paths and protection devices.
The applicable tests and demonstrations then depend on the level considered and on certification requirements.
From equipment to the complete aircraft
Qualifying equipment to DO-160 / ED-14 is not, on its own, sufficient to demonstrate the electromagnetic compliance of a complete aircraft.
Integration into the aircraft introduces additional parameters:
- equipment location
- electrical architecture
- cable routing
- shielding and bonding
- interfaces between systems
- proximity of RF transmitters and receivers
- lightning protection
- exposure to HIRF environments
- criticality of the functions performed.
Compliance testing and demonstrations may therefore take place at several levels: equipment, subsystem, integrated system and complete aircraft.
Certification requirements are defined according to the type of aircraft, the functions concerned and the applicable regulations.
In Europe, this process falls in particular under the framework of EASA (European Union Aviation Safety Agency).
In the United States, it falls in particular under the FAA (Federal Aviation Administration).
These authorities publish requirements and guidance material that may draw on the DO-160 / ED-14 technical standards and on other means of compliance.
Complex EUTs to control and monitor during testing
An aerospace susceptibility test is not just about applying an electromagnetic field or an electrical transient.
The functional behaviour of the equipment must also be checked during and after exposure, in accordance with the applicable performance criteria.
EUTs (Equipment Under Test) may be computers, avionics equipment, communication systems, control devices, electronic racks or complete subsystems.
Their qualification may require:
- controlling different operating modes
- monitoring power supplies and interfaces
- monitoring critical functional parameters
- checking communications
- detecting faults and loss of functions
- logging events
- synchronising data acquisition with test sequences
- correlating anomalies with the applied frequency, field level or transient.
For large EUTs or integrated systems, the design of the test facility must also take into account the size, cabling, interfaces and operating conditions of the equipment.
Automation coordinates the generation chain, the measuring instruments and functional monitoring to improve the repeatability, traceability and analysis of results.
From the standard to the aerospace test facility
Designing a test facility starts with identifying the standard sections, qualification categories, frequency ranges, levels and waveforms to be covered.
Depending on the project, HEMERA RF can size and integrate:
- RF and microwave generators
- RF power amplifiers
- antennas and field probes
- EMI receivers
- LISNs
- injection clamps and current probes
- transient generators
- indirect lightning generators
- Pin Injection and Cable Bundle devices
- shielded and anechoic chambers
- positioning equipment
- measuring instruments
- EUT control and monitoring systems
- automation software.
The diversity of tests often requires combining several technologies and several specialist manufacturers.
The aim is to build a test chain consistent with the laboratory's requirements, rather than selecting each instrument in isolation.
The HEMERA RF approach to aerospace projects
HEMERA RF acts as general contractor and multi-brand integrator for the design and delivery of EMC and RF test facilities for aerospace applications.
Its involvement can cover the entire project: needs analysis, identification of normative requirements, sizing of RF and transient chains, turnkey project management, sourcing of specialist manufacturers and innovative solutions, hardware and software integration, automation, commissioning and metrology follow-up.
This independence from any single manufacturer makes it possible to select the most relevant technologies for each function: RF generation, amplification, antennas, injection, indirect lightning, measurement, shielding, automation and functional monitoring.
HEMERA RF's responsiveness and technical support also make it possible to adapt solutions to the particular constraints of each programme and to laboratories' changing needs.
Experience with leading French aerospace players
HEMERA RF has references with some of the most renowned French aircraft manufacturers and equipment suppliers in the aerospace sector, as well as with specialist test laboratories.
This experience enables HEMERA RF to understand the technical and normative constraints specific to aerospace applications and to support its customers from the analysis of RTCA DO-160 / EUROCAE ED-14 requirements through to the delivery of high-performance, automated and scalable turnkey test facilities.
HEMERA RF's multi-brand approach thus combines technical expertise, sourcing capability, project management, responsiveness and a commitment to customer satisfaction.
Frequently asked questions
Frequently asked questions
Aerospace
Which EMC standards apply to aerospace and defence?
In aerospace and defence, the standards include:
• RTCA DO-160 for airborne equipment
• its European counterpart, EUROCAE ED-14
• various MIL-STD standards for military applications
• specific requirements for individual programmes and platforms
The exact requirements must be identified before sizing the test setup.
What is an indirect lightning test?
It reproduces:
• transient voltages
• transient currents
• the disturbances that may be induced in wiring and electronic equipment during a lightning event
It concerns induced electrical and electromagnetic effects, not the physical impact of a direct lightning strike on the structure.
What is the difference between the direct and indirect effects of lightning?
• Direct effects: the physical consequences of the lightning current on the structure.
• Indirect effects: transient voltages and currents induced in wiring, interfaces and electrical or electronic equipment.
Which standards govern indirect lightning testing in aerospace?
They include:
• RTCA DO-160 Section 22
• EUROCAE ED-14 Section 22
• other standards or specifications depending on the programme concerned
What is Section 22 of RTCA DO-160 / EUROCAE ED-14?
It covers in particular:
• the susceptibility of equipment to lightning-induced transients
• the applicable waveforms
• test levels
• injection methods
• the corresponding qualification categories
What is the difference between pin injection and cable bundle tests?
Pin injection:
• direct injection of the transient
• applied to pins or interfaces
Cable bundle:
• disturbance applied to the harness
• reproduces coupling onto the installation’s cables
The generators and injection devices may therefore differ.
Which waveforms are used for indirect lightning testing?
The standard specifies different waveforms depending on:
• the coupling mechanism
• the method
• the qualification category
• the test level
• the interface concerned
You therefore need to identify the waveforms to be covered before choosing the generator.
What equipment is needed for testing to RTCA DO-160 / EUROCAE ED-14 Section 22?
Depending on the method:
• transient generators
• injection networks
• transformers or couplers
• calibration fixtures
• current probes
• voltage probes
• acquisition instrumentation
• suitable accessories and loads
How are test levels and waveforms chosen under RTCA DO-160 / EUROCAE ED-14 Section 22?
They depend in particular on:
• the qualification category
• the equipment
• its installation
• the interfaces
• programme requirements
The choice should therefore not be dictated solely by the capabilities of the available generator.
How can the injected current or voltage be measured and monitored during the test?
The measurement chain may include:
• current probe
• voltage probe
• suitable attenuation
• appropriate cabling
• oscilloscope or high-speed acquisition system
The bandwidth and dynamic range of the whole chain must be checked to ensure the measured transient is reproduced accurately.
How do you size a lightning test bench for aerospace equipment?
You need to determine:
• the standard
• the category
• the waveforms
• the levels
• pin injection / cable bundle methods
• harness characteristics
• the equipment to be tested
• measurement and calibration needs
What are the CS114, CS115 and CS116 tests?
These methods correspond to different types of conducted susceptibility in the military domain.
They differ in particular in:
• the type of signal
• the frequency range
• the coupling mode
• the levels
• the equipment required