What is do-178b?

DO-178B is a software produced by Radio Technical Commission of Aeronautics Inc. (RTCA), used for guidance related to Equipment certification and software consideration in airborne systems. It is a corporate standard, acknowledged worldwide for regulating safety in the integration of aircraft systems software. The Federal Aviation Regulations, Part 21, Subpart O explicitly establishes the requirement of airworthiness certification process. DO-178B provides one of the mandatory certification requirements, but alone does not guarantee all software safety aspects.

In airborne systems, the software level also known as design assurance level is determined from the safety assessment process as well as the hazard analysis process by determining the effects of a failure condition in the system. The failure conditions are categorized by their effects as follows:

  •  Level A - Catastrophic: Failure may cause a crash
  • Level B - Hazardous: Failure reduces the ability of the operators of the aircraft to operate it properly and hence may impact the safety or at least performance
  • Level C – Major: Failure has less impact than a hazardous failure but is significant in nature or at least significantly increases the workload of the operators
  • Level D - Minor: Failure has lesser impact than a major failure but is at least noticeable
  • Level E - No Effect: Failure has no impact on safety of aircraft or the operation or workload of operators

DO-178B is mainly divided into 5 major processes. They are:

Each of these processes has a set of expected documented outputs that need to be maintained for complying with the Federal Aviation Regulations requirements.


For a US-based tier-one supplier providing services to the commercial airline industry, HCL developed Traffic Alert and Collision Avoidance System (TCAS) or Airborne Collision Avoidance System (ACAS) for one of its major aircrafts using an entirely new architecture which would make the system easily maintainable and more efficient.

HCL developed a Back-up navigation system software embedded in Multipurpose Control Display Unit (MCDU) for the client. The MCDU was meant to serve as the main communication interface between the pilot and any connected system like Flight Management. It mainly consisted of a keyboard and display permitting the pilot to enter and read data to and from these connected systems.