ASSC215/3/44-Issue 1 : EMC Test Technique Investigations on a Ruggedised VME Modular Avionics System (Aug 01) (34 Pages)
An investigation of current modular avionic EMC issues, relevant standards and test philosophies has led to a recognition that further work needs to be carried out to develop test procedures further, particularly near field inter-module radiated interference and inter-module interference conducted on the backplane.

Some tests have been performed on some VME modules inside a rack to look at the level of these problems. SMVE/DMV-160/171 modules were used which had 25 MHz processors, the rack was a 1990’s Mektron design with 10 MHz backplane.

The far-field emission tests suggested that there would be no problems. The standard EMC tests and levels used are applicable to the whole sub-system as opposed to single modules. The effect of having multiple modules is partly considered here but needs more investigation. The tests were made without sub-system or module shielding and it is anticipated that adequate shielding would be able to be provided to overcome increased emissions from multiple modules.

In the near-field, the conclusions were that in general the emissions from the modules would not upset adjacent modules. Higher processor speeds would make emissions worse, but filtering and screening should provide adequate protection. Further tests may be needed to confirm this with new technologies such as CompactPCI which is being used widely. They have processor speeds in excess of 400 MHz, a backplane speed of 66 MHz and gigabit transfer rates.

ASSC/215/4/1-Issue 10 : A guide to the impact of modular avionics on EMC design and test philosophy (Jan 2001) (35 pages) under development
This brief document has been prepared by the ASSC Modular Avionics Electromagnetic Hazards and Compatibility Working Group to provide initial guidance on both design and testing specifically aimed at modular avionics. It is based on original information, and does not assume any particular implementation. As yet, it does not incorporate any experience gained by practical tests on modules.

The document is intended to supplement rather than supersede existing guidance and test specifications that apply to avionics based on specific-function-LRU architectures. Modular avionics could pose particular EMC problems where modules are obtained from a variety of vendors and may be inserted in a variety of positions within an enclosing rack or cabinet.

Although the guide has been prepared primarily for military applications, much of the information is equally applicable to civil avionics, and consideration of civil developments has been included.

ASSC/215/2/27-Issue 5 : More-electric aircraft EMC issues (Jan 01) (3 pages). under development
It is widely accepted that more-electric aircraft (MEA) systems will offer significant benefits for an aircraft, particularly for large civil aircraft, in terms of weight, reliability and operating costs. MEA systems involve reducing or eliminating hydraulics and replacing them with electrical equivalents. This implies changes to both electrical power generation and distribution.

Of direct relevance to this Subcommittee is the likelihood of distribution at higher currents, probably higher voltages, and variable frequency supplies.

This document raises several issues in relation to MEA systems. It should be noted that these should be considered during trade-off studies in order to make complete and rational decisions which fully include the weight, cost and volume penalties of MEA systems compared to traditional systems.