Modern avionics systems have intelligently evolved over the years with three clear goals in mind: increase automation within the cockpit, reduce workload for pilots and, last but not least, increase safety. This journey of evolution has been extremely beneficial to the industry as a whole due to the fact that is has helped to increase safety levels across the board.
Under specific conditions however, differences in core design features of modern avionics, like auto-pilot systems, when added to the increased complexity caused by automation, conspire to create potentially hazardous situations - even for experienced flight crews.
There have been cases when failures in non-vital aircraft systems actually contributed to major aviation disasters by triggering degraded operational modes in autopilot or auto-throttle systems.
In one example, a faulty captain-side radar-altimeter activated an auto-throttle move to idle and caused the auto-pilot to enter ‘retard-flare’ mode at an incorrect time; having gone unnoticed, this factor was latter flagged as a major contributing factor to the eventual crash of the aircraft. In another example, an incorrect setting of autopilot mode subsequently led to disconnection of the auto-throttle which allowed the plane to descend to a dangerous, low-speed course near the ground, again resulting in a crash.
It’s well known that aircraft manufacturers have fundamentally different approaches to controlling authority limits of autopilot systems. In an interesting twist, there are now experts expressing a need for less automation, or at least for a different approach when developing newer versions of the systems that control aircrafts.
Software, of course, plays a major role in the reliability and safety of end-systems development. Although the process of avionic specification and design is well defined, performed and controlled by the major OEMs, there is a clear role to be played by companies specializing in software testing, safety and reliability.
Changes need to happen if the industry is to progress from its current state. Although it sounds obvious, possessing the right knowledge of systems being developed from a technical point of view – and using the right tools for the job – is a fundamental part of increasing safety. Extensive experience provides the basis for a wide knowledge base and is what is lacking in the industry at present.
In addition, more companies need to take a thorough approach when it comes to RAMS and look to truly understand how human factors impact safety. Efficiently implementing a structured development and testing strategy, where thorough testing of the end system plays a core role, would also prove of substantial benefit. Interdependence between development and testing teams is vital to provide a solid plan, including a comprehensive overview of risks and mitigation strategies, which of course takes human factors into consideration.
The good news is that some companies are working in the right way already. As experts in software testing frameworks for safety-critical embedded systems, Vector Software’s extensive research in software testing and world-class team of support and technology partners allows them to deliver unparalleled "next generation" test tools to the marketplace, helping hundreds of customers worldwide. As one of those partners, CRITICAL Software possesses an extensive avionics knowledge base built from decades of experience. This experience is supported by a Quality Management System that complies with the most demanding standards, offering customers high levels of efficiency and flexibility and lower costs.
Working together, companies like these are solving the complexity problem through improved system capability, delivering higher levels of software safety within the aerospace domain.
About the authors
Ricardo Camacho is Services Manager at Vector Software and Luis Gargaté, Business Development Manager at CRITICAL Software
CRITICAL Software provides systems, software and data engineering services for safety, mission and business-critical applications, helping to ensure clients meet the most demanding quality standards for safety, performance and reliability. CRITICAL Software’s core competencies cover a wide range of areas, including system planning and analysis, system design, verification, development, integration and maintenance. The company has been operating in mature markets since 1998, with NASA its first client, and has offices in Portugal, the United Kingdom, Brazil, Germany, USA, Mozambique and Angola. To find out more, visit www.criticalsoftware.com.