What Is DO-178C? Here’s What You Need to Know


In 2019, there were a staggering 925.5 million air passengers in the US. There’s no doubt that people use flying as a fast and effective means of getting around the country.

Today, there are various safety regulations and precautions in place to guarantee passenger safety. This includes ensuring the aircraft complies with DO 178C laws.

Without it, your plane simply won’t leave the runway. 

The aviation world has changed beyond recognition since Wilbur, and Orville Wright took the first-ever powered flight on 17 December 1903. Today, compliance with DO-178C needs to happen before anyone even thinks about taking off.   

Ready to learn more? Let’s explore this topic in detail.

What’s DO 178C?

It’s a regulation that is also sometimes referred to as “Software Considerations in Airborne Systems and Equipment Certification.”

The Radio Technical Commission for Aeronautics (RTCA) published the DO-178C in 2012 to replace an earlier regulation called the DO-178B. It’s used to approve commercial software on passenger, industrial and military flights. 

Which Organizations Use It? 

The following federal organizations use the DO 178C as their go-to regulation to approve commercial software on aircraft before permitting it to fly:

  • Federal Aviation Administration (FAA)
  • Transport Canada
  • European Aviation Safety Agency (EASA)

Now let’s look at the classification of safety levels.

How Does DOC-178C Classify Safety Levels?

Five levels of safety must be met. Each level corresponds to the consequences of aircraft software failing. 

Level A: Catastrophic

This is if software failure is so severe that it causes the plane to crash, resulting in passenger deaths.

Level B: Hazardous

This is when software failure may result in passenger injury.

Level C: Major

A Level C software malfunction can result in passengers receiving minor injuries or experiencing discomfort. 

Level D: Minor

This level of failure is when the software fails and causes inconvenience to passengers, for example, a flight delay or cancellation. 

Level E: No Safety Effect

Where there’s no impact upon safety whatsoever. 

Clearly, levels A, B, and C are the most serious and have the most significant impact on passenger safety. 

DO-178B and DO-178C: What’s the Difference?

The DO-178C was created to eliminate any possible confusion in the DO-178B. It’s there to ensure that aviation software developers and engineers know whether the software on an aircraft is safe or not.

Although some of the changes between C and B are minor, there are several significant new aspects to DO-178C that are worth noting here. 

Given how fast software development moves, it was felt that the DO-178C was out of date. The DO-178C keeps to the same structure as the DO-178C, but it gives developers more exact language and terminology to ensure consistency across the board.

Not only that, but the DO-178C also has more objectives that need satisfying across the most at-risk levels A, B, and C. 

DO-178C calls for a lot more software testing at each risk level than DO-178B. It’s fair to say that DO-178C costs money and has its fair share of critics, as did its predecessor.

However, it’s a standard that needs adhering to. While it’s not cheap, it’s not necessarily expensive either. 

DO-178C Benefits

Here are a few cited benefits of DO-178C.

Fewer coding iterations: These, also known as churn, are much hated by software engineers who have to repeat coding instructions until a particular condition is met.

By using robust engineering processes as required by DO-178C, code largely only needs inputting once, without as many updates to get it right.  

Fewer bugs: With DO-178C, it’s mandatory to thoroughly test software and review codes for Levels A, B, and C during the module testing process.

Engineers also have to carry out independent code reviews for Level A and B. By reviewing codes, engineers have to complete and configure the following items before writing code:

  • Standards and checklists
  • High and low-level requirements
  • Design
  • Traceability

Fewer assumptions made: As DO-178C goes into greater detail about software requirements, assumptions are more difficult to make during this process.

Requirements needed to meet DO-178C standards are more consistent and easier to test. This results in fewer iterations and repeated tasks/rework caused by faults.   

Planning For DO-178C Compliance

To plan successfully for compliance, you need to create five plans: 

  • Plan for Software Aspects of Certification (PSAC)
  • Software Configuration Management Plan (SCMP)
  • Software Development Plan (SDP)
  • Software Quality Assurance Plan (SQAP)
  • Software Verification Plan (SVP).

For the uninitiated, this can seem daunting. However, non-profit RTCA has collaborated with the MITRE Aviation Institute to create a DOC-178C training course.

This enables software managers and engineers to fully comprehend DO-178C requirements and parameters to achieve the full FAA certification. Also, software engineers and developers need to familiarize themselves with DO-178C supplements.

Examples of Supplements:

Here are a few examples of DO-178C supplements:

  • DO-330 Software Tool Qualification Supplement: guidance on necessary tools needed
  • DO-331 Model-based Design and Verification Supplement: guidance on mapping out design and verification objectives
  • DO-332 Object-Oriented Technology Supplement: guidance on developing objects that use software such as a Black Box, which sends and receives data that needs tracing.
  • DO-333: Formal method supplement: 

These supplements are necessary because they support the DO-178C to ensure that all aviation software is fully compliant before take off. 

Before We Go

If you’ve already read our article on ‘5 Things You Need to Know When Buying an Airplane’ and want to ensure your plane is DO-178C compliant, we hope this article covers at least the basics of what DO 178C is and why it’s crucial. 

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What Is DO-178C? Here’s What You Need to Know