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  • Friday, 15 May 2020 02:25
    Over the last few years CSL has embraced Eliminative Argumentation (EA) as a notation for describing system assurance cases, and more importantly, as a mode of thinking about overall system assurance. EA was proposed by Goodenough and Weinstock as an extension to Goal Structured Notation (GSN), the conventional method used to express assurance cases [1]. Their objective was to create a method to improve “confidence” in an argument by systematically eliminating reasons to doubt the argument’s validity.In this blog post, we will argue that EA is both a natural means of arguing about system safety and that it ultimately leads to more comprehensive and useful safety arguments...
  • Thursday, 18 September 2014 20:17
    Cybersecurity and Safety for Aircraft and Aircraft Systems: DO-326A guidance CSL has been an active member of the international committee, RTCA SC 216, charged with the responsibility of developing guidance material that will help ensure safe, secure and efficient operations amid the growing use of highly integrated electronic systems and network technologies used on-board aircraft, for CNS/ATM systems and air carrier operations and maintenance. Recent efforts of the committee have resulted in a revision of RTCA DO-326 “Airworthiness Security Process Specification” that was released on the RTCA web site in August 2014. The guidance of DO-326A is intended to augment current guidance for aircraft certification to handle the information security (i.e., cybersecurity) threat to aircraft safety. In a nutshell, this new document describes a security engineering process that includes generic activities with corresponding compliance objectives. The scope of DO-326A not only covers the...
  • Friday, 06 September 2013 15:39
    EN ISO 14971 or not EN ISO 14971?The European community recognised EN ISO 14971:2012 in July 2012. EN ISO 14971:2012 supersedes EN ISO 14971:2009 which was based on ISO 14971:2007 ‘Medical devices - Application of risk management to medical devices’.In general, the EC committee felt that the application of ISO14971:2007 did not meet the Essential Requirements described in the European Medical Device Directive 93/42/EEC. Therefore the EC group reviewed ISO14971 to identify these areas in the standard that are not compliant with the MDD and formally document these deviations.EN ISO 14971:2012 applies only to manufacturers with devices intended for the European market; for the rest of the world, ISO 14971:2007 remains the standard recommended for risk management purposes.Standard outlineThis standard published* in 2012 is somewhat unusual in its layout: it includes three annexes located at the beginning of the document and then includes a copy of the 2007 corrected version of ISO 14971....
  • Friday, 26 July 2013 22:36
    FAA recognizes RTCA DO-178C and Associated Technical Supplements (July 2013)The FAA published AC20-115C on July 19, 2013. In this Advisory Circular (AC), the FAA recognizes RTCA DO-178C, three associated technical supplements and the 'Software Tool Qualification Considerations' document.The actual documents that are the subject of this AC are the following RTCA documents:• DO-178C, Software Considerations in Airborne Systems and Equipment Certification.• DO-330, Software Tool Qualification Considerations, dated December 13, 2011.• DO-331, Model-Based Development and Verification Supplement to DO-178C and DO-278A.• DO-332, Object-Oriented Technology and Related Techniques Supplement to DO-178C and DO-278A.• DO-333, Formal Methods Supplement to DO-178C and DO-278A. It has been a long-awaited recognition since the release of RTCA DO-178C in December 2011. (In terms of comparison, RTCA DO-178B was endorsed by the FAA only one month after its publication). Similarly, to the previous AC...
  • Tuesday, 16 July 2013 20:03
    Correctness vs. SafetyOne of the examples that we regularly use in our training material is the catastrophic loss of Lufthansa Flight 2904 on September 14, 1993 when it ran off the end of the runway in Warsaw Poland.  It is an interesting and very useful teaching example because it illustrates some of the main themes of the training that we regularly provide to clients on system/software safety. This accident is particularly effective as an introduction to the training material because students quickly realize that we are not simply talking about defect prevention or quality assurance.When an Airbus 320 lands, the crew relies on the combination of brakes, ground spoilers and reverse thrusters to slow the aircraft.  However in the case of Flight 2904 the activation of all three of these critical systems was delayed such that the aircraft reached the end of the runway at a speed of 72 knots and hit an embankment resulting in 2 fatalities.The official investigation...
  • Wednesday, 22 May 2013 17:38
    Alarm Management  Our clients appreciate the fact that we are involved in projects across a wide spectrum of industries becausewe bring insights from common challenges experienced by other industries that lead to innovative solutionsto their problems.  A good example is alarm management which is a consideration in the design of almostevery kind of critical system.  Although the details of alarm management may vary considerably betweentechnical domains, our approach to helping clients with alarm management is based on the same fundamentalconcepts and principles.Thanks to Hollywood and movies such as The China Syndrome (1979), most of us have a sense of theadrenaline fueled drama of a control room during an emergency with alarm bells ringing and lights flashing.  But helping a client develop a sound approach to alarm management goes well beyond thinking about therare moments of high drama.For example, an operator could eventually become desensitized to a spurious alarm that is...