Software Level

Section 08: Software Certification (DO-178C)

Definition

The designation of the software development assurance effort required for a software item, based on the failure condition classification of the system function to which the software contributes. Software levels correspond to Development Assurance Levels (DALs): Level A software contributes to functions whose failure could cause or contribute to a catastrophic failure condition; Level B to hazardous; Level C to major; Level D to minor; and Level E to no safety effect. The software level determines which DO-178C objectives are applicable, the number of objectives that must be satisfied with independence, and the overall rigor of the development and verification processes.

Where This Shows Up

Software level assignment is one of the most consequential decisions in an avionics certification program because it directly determines the development cost and schedule. Level A requires satisfaction of all 71 DO-178C objectives with many requiring independence between the developer and verifier; Level D requires only a subset. The software level is derived from the system-level safety assessment (FHA and PSSA) through the DAL assignment process described in ARP4754B.

Primary Sources

RTCA DO-178C, Section 2.4

Defines software level and its relationship to failure condition severity.

SAE ARP4754B — Development of Civil Aircraft and Systems

Describes the process for assigning DALs that determine software levels.

Related Terms

Development Assurance Level (DAL)RTCA DO-178C / EUROCAE ED-12C — Software Considerations in Airborne Systems and Equipment Certification (DO-178C)Failure Condition ClassificationSAE ARP4754B — Guidelines for Development of Civil Aircraft and Systems (ARP4754B)

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