Aviation is an incredibly complex field. The mechanical details of avionics—the science specific to the electronics used in designing and creating aircraft—requires years of study and experience to truly understand and master. Fortunately, there are plenty of documents available to ensure that the mechanics working on our private, commercial, and military aircraft are able to effectively do their jobs.
DO-178c, officially titled “Software Considerations in Airborne Systems and Equipment Certification,” is one of the more essential manuals in circulation. It focuses exclusively on commercial systems, a global industry valued at $2.7 trillion in 2018 according to the International Air Transport Association (IATA). Many certification authorities worldwide—such as the Federal Aviation Administration (FAA), European Union Aviation Safety Agency (EASA), and Transport Canada—rely on DO-178c to approve all commercial software-based aerospace systems.
Flying Safe and Sound
Safety is the primary focus of DO-178c. The document allows software systems in aircraft to be evaluated by a safety assessment process and in-depth hazard analysis surrounding the effects of a failure condition within said system; they are then given a Software Level (also known as the Design Assurance Level, DAL, or Item Development Assurance Level, IDAL) based on how seriously the failure condition affects the aircraft, crew, and passengers. The categories are as follows:
- Level A: Catastrophic. System failure may cause deaths, usually along with the loss of the airplane.
- Level B: Hazardous. System failure has a large negative impact on safety or performance, reduces the ability of the crew to operate the aircraft due to physical distress or a higher workload, or causes serious or fatal injuries among the passengers.
- Level C: Major. System failure significantly reduces the safety margin or significantly increases crew workload. Additionally, it may result in passenger discomfort or cause minor injuries.
- Level D: Minor. System failure slightly reduces the safety margin or slightly increases crew workload. Anything causing passenger inconvenience or a routine flight plan change is categorized as Level D.
- Level E: No Effect. System failure has no impact on safety, aircraft operation, or crew workload.
As a result of these specifications, avionic engineers are better able to prepare for any failure conditions that may arise; once a DAL has been determined for the software, DO-178c can be examined to figure out what objectives must be satisfied. In total, this is a three-step process: planning, development, and correction/integration. With DO-178c in their hands—which is considered to be the aviation industry’s bible when it comes to avionic system development—engineers are able to ensure that their software is safe to use in commercial flights.
The Bigger Picture
In the aviation industry, certification is essential. The FAA, EASA, Transport Canada, and other aviation agencies and administrations around the world need to guarantee that their aircraft are safe and reliable; after all, if you weren’t reassured that your flight would make it to its destination intact and with all of its passengers, would you take the risk and climb aboard? Aircraft rely on incredibly technical and sensitive systems and software to fly, navigate, and land; without a universal way to approve these systems, reliability would fly right out the window.
As an industry-standard, DO-178c performs a major role in providing such reliability. When everyone has the same manual and plays by the same rules, chance and risk are significantly reduced. The next time you board a flight—whether you’re headed to the sandy beaches of California or the snow-capped peaks of Switzerland—you can rest easy; your plane’s delicate systems are tested, supported, and assured by DO-178c.
