Embedded Systems for Commercial and Military Aviation

Balancing Innovation and Safety in the Aerospace Industry

 

And this is substantiated by the statistics. According to the IATA (International Air Transport Association), over 32 million flights took place in 2022. In total, there were 39 accidents, five of which incurred fatalities. This is a reduction compared to the five-year average (43 accidents/7 fatal), highlighting the consistent effort applied to keep commercial aviation safe. IATA states that, at the current level of risk, an individual would need to travel daily for over 25,000 years to experience a fatal incident¹.

So, how does the electronics and semiconductor industry support these metal birds? What measures are put in place to ensure safety? And are there any disadvantages to working in the aerospace industry?

 

¹ https://www.iata.org/en/pressroom/2023-releases/2023-03-07-01/

So, despite the electronic industry’s march of progress with wireless over-the-air (OTA) updates, Boeing 747-400s were still receiving monthly navigation database updates on a stack of 3.5” floppy disks in 2020².

The avionics bay of the 747 is fitted with line replaceable units (LRUs), the aviation industry’s term for modular electronic systems. Each system fulfills a specific task, such as the Flight Control Computer (FCC), Air Data Inertial Reference Unit (ADIRU), and Engine Electronic Control (EEC). Should a functionality issue arise, technicians can swap out a defective LRU “in the field” when the plane is next on the ground. This helps keep the aircraft flying and simplifies supply chain management.

LRUs are designed to ARINC 700-series standards³ that define digital systems and equipment used in production aircraft. The modules are then linked to each other and the remainder of the aircraft’s systems using avionic-specific networking protocols, no different from the approach used in industrial and automotive systems. One of these is ARINC 429, a unidirectional broadcast bus connecting a transmitter with up to ten receivers. Messages are transmitted up to 50 times per second with synchronous reception at the receiving end. 

 

² https://www.theverge.com/2020/8/11/21363122/boeing-747s-floppy-disc-updates-critical-software
³ https://aviation-ia.sae-itc.com/product-categories/arinc-standards/700-series

Ensuring avionics software is safe

 

Like the automotive industry, aerospace has continuously improved its hardware to minimize the risk of failure and contribute to keeping airlines’ millions of daily passengers safe. However, much of this hardware is dependent on software. Standard DO-178, titled Software Considerations in Airborne Systems and Equipment Certification, is used by both the commercial and military aerospace industry, although the military focus is more on mission success rather than safety. It provides guidance throughout the entire software development process, from initial planning to integral and development processes.

Similar to the safety integrity levels of automotive and industrial systems (ASIL/SIL), DO-178 assesses the risks associated with a software anomaly and the potential failure that may result. It defines five design assurance levels starting at E, where a failure condition does not affect aircraft operability. An in-flight entertainment system is an example of a Level E system. 

Level D is considered a minor failure condition that would result in inconvenience, such as a flight recorder failure. The highest level, A, is reserved for potentially catastrophic failures. Such an incident would prevent continued safe flight, such as an issue with the fly-by-wire system.

A core focus of DO-178 is software verification and, in addition to testing, it covers reviews and analyses. This process starts with high-level software requirements from which a suitable software architecture and low-level requirements are derived. Each requirement demands tests that prove the requirement has been met. Bidirectional traceability is also needed, meaning the link between high-level requirements and source code can be demonstrated in either direction. Additionally, there cannot be any dead code that doesn’t relate to a requirement.

Embedded suppliers around aerospace

 

In the past, the aerospace industry wanted MIL-SPEC equipment, a catch-all term that means something fulfills a military standard or specification. However, with many semiconductor vendors having pulled out of this market and project budgets being squeezed, commercial-off-the-shelf (COTS) solutions are increasingly used. For example, while AFDX/ARINC 664 was designed for aerospace, it is based upon the well-known Ethernet protocol and can use COTS components.

Software is another area, with some suppliers specializing in taking COTS software stacks and removing unneeded and dead code. This reengineering process and subsequent testing allow it to be certified for use in aerospace projects.

Many of the real-time operating systems (RTOS) that meet the aerospace industry’s stringent safety certification requirements have a non-avionics equivalent from the same vendor. Then there are the tool vendors providing compilers, debuggers, and software testing environments. These, too, undertake additional certification of their products and tools to meet the demands of aerospace development teams.

 

Slow innovation

 

While aircraft are a thing of wonder, the pace of innovation is slow. A decade or more can pass from conception to launch, while the aircraft itself can be in production for twenty years or more. As a result, the opportunity to work at the cutting edge of aerospace may only arise twice in your career. But, if you can live with that, the capabilities demonstrated in both commercial and military aerospace show incredible feats of engineering skill. 

And it is embedded systems and software combined with a culture of safety that keep these flying machines safe, tens of thousands of take-offs a day. This industry proves that software can keep us safe and that our lives can be entrusted to embedded systems.