Aerospace Electromagnetic Compatibility Testing

EMC in aerospace

The use of electronics in safety-critical areas of civil and military aircraft, coupled with the growing severity of High Intensity Radiated Field (HIRF) environments, has lead to the international aviation and defence authorities demanding evidence that aircraft are immune to a specific external electromagnetic environment, HIRF testing in support of airworthiness compliance and HIRTA testing - clearance assessments of military aircraft.

Test and measurement techniques include:

􀁺 Low level swept current (LLSC)

􀁺 Direct current injection (DCI)

􀁺 Radiated field susceptibility (RS)

􀁺 Bulk current injection (BCI)

􀁺 Low level direct drive (LLDD)

􀁺 Low level swept field (LLSF)

􀁺 EMP Testing

EMC requirements for Aerospace testing are continually evolving.  The largest changes in recent years are a huge increase in the field strengths for radiated immunity testing and the requirement for lightning tests to be performed as multiple stroke and multiple burst waveforms.

HIRF testing

The quantum change of levels from typically 200 V/m to typically 3000V/m for radiated immunity has led to this test becoming known as High Intensity Radiated Field HIRF testing. 

Programme timescales are also constantly being reduced in all aspects of engineering, and this pressure is being felt within the aerospace industry. Efforts to reduce time and the cost of setting up the product for testing, which for a complex system can take weeks, are paramount before testing can start. 

Aircraft design and assembly is a global activity. Today, systems can be designed, manufactured or tested in any country, only being shipped for final integration in the assembly plant. This global process relies on a standardised set of test procedures being in place.

The process starts with equipment manufacturers who, logically, want their equipment to be fitted in as many different aircraft types as possible. However, aircraft manufacturers do not make identical aircraft. Each aircraft type is unique, with a specific set of test requrements that only the final system integrator can define. So where does this leave the equipment manufacturer who wants to remain neutral and thus have the highest chance of commercial success. As a result, a set of generic tests have been developed that provide an indication to system integrators of suitability for the task in hand.

Competition is driving new developments in the design of aircraft, not least the desire to seek that competitive edge. To fly further, carry more passengers, be more fuel efficient or ideally, both.

The A380 is the largest commercial jet. But to achieve performance targets, higher amounts of composite material than in any previous Airbus have been employed. Up to 26%. This will enable the A380 to deliver more passengers over a long distance. The Boeing 787 too will include a phenomenal 60% composites and will be the first fully electrical aircraft, no more hydraulics, no more bleed air.

It is easy to see that lightning events will interact differently with the airframe and the electronics will experience unique interference. Both these aircraft have their own specifications. Airbus have already announced the A350 as a competitor to the Boeing 787, and one thing is sure, the test requirements will continue to evolve.

Electronic components EMC testing

Typical Types of Electronic Components that are regularly tested are

Aerospace Electrical and RF Connectors

Terminal blocks

Aerospace Relays

Aerospace Integrated Circuits

Aerospace Inductors

Chip Inductors

Aerospace Transformers

Aerospace Chokes

Aerospace Capacitors

Aerospace Thermistors

Chip Thermistors

Carbon Resistors

Wire-Wound Resistors

PCMCIA Cards

Aerospace Coils

Aerospace Switches