DO-178C the future of Avionics Certification Martin Beeby, European Manager, Atego HighRely

What is DO-178 RTCA DO-178: “Software Considerations in Airborne Systems and Equipment Certification” Developed by Industry and Government committees Many compromises to satisfy different goals: “Consensus”: Collective opinion or concord; general agreement or accord [Latin, from consentire, to agree] Not a recipe book or “How To” guide Guidance not prescription Lawyers versus Software Engineers; who wins?

DO-178: Evolution History Doc Year Basis Themes DO-178 1980-82 498 & 2167A Artefacts, documents, traceability, testing DO-178A 1985 Processes, testing, components, four criticality levels, reviews, waterfall methodology DO-178B 1992 Integration, transition criteria, diverse development methods, data (not documents), tools DO-178C +Supplements. 2012 Reducing subjectivity; Address MBD,OO, tools, Formal methods, etc.

Avionics Safety History: 1946 - 2008

Safety: the precursor to DO-178

Safety, System, Software & Hardware Safety Assessment ARP 4761 System Development ARP 4754 Architecture Criticality Level SW Rqmts HW Rqmts Tests Tests Software DO-178 Hardware DO-254

Functional Safety The Functional Safety framework surrounding DO-178 similar to: IEC 61508 – Industrial systems development ISO 26262 – Automotive systems development EN 51208 – Railway systems IEE 7-4.3.2 – Nuclear Power Systems Objective based guidance gives development freedom with compromising the use of new technology.

Why change DO-178B Almost 20 years since DO-178B released Software Development landscape has changed ... Advancements in: Tools & automation Modelling & Simulation Object Oriented Technology Formal Methodologies Commercial world has embraced the above; Avionics has slowly followed Alternate Means of Compliance does not provide a consistent mechanism for certification

DO-178C Since 2005, committees have met to discuss, and update, DO-178B Like 178B, included Industry & Agencies Unlike 178B, more Tool Vendors Obvious focus on “acceptability” of certain types of tools, particularly “theirs” Predominantly America & Europe, nearly equal; quarterly meetings

DO-178C : Seven “Sub-Groups” (SG’s) SG1: Document Integration SG2: Issues & Rationale SG3: Tool Qualification SG4: Model Based Design (MBD) & Verification SG5: Object Oriented (OO) Technology SG6: Formal Methods (FM) SG7: Safety Related Considerations (and ground-based systems)

DO-178C Unlike the DO-178A to DO-178B update, the “core” update to 178C is modest Instead, changes are handled via four “Supplements”, which “clarify”: Tools Supplement MBD Supplement OO Supplement FM Supplement

Deliverables DO-178C/ED-12C Software Considerations in Airborne Systems and Equipment Certification DO-248C/ED-94C Supporting Information for DO-178C and DO-278A DO-278A/ED-109A Software Integrity Assurance Considerations for Communication, Navigation, Surveillance and Air Traffic Management (CNS/ATM) Systems DO-330/ED-215 Software Tool Qualification Considerations DO-331/ED-216 Model-Based Development & Verification DO-332/ED-217 Object-Oriented Technology Supplement DO-333/ED-218 Formal Methods Supplement

Software Tool Qualification Considerations (D-330) Tool Qualification Considerations is a stand alone document that is consistent with and follows the structure of DO-178C It recognizes that tools occupy their own domain They are not airborne software Tool qualification can apply to hardware and ground-based systems also DO-330 is a stand-alone approach to tool qualification that could be called out by any standard Domain Specific Guidance in the calling document Tool qualification guidance from DO-330 based on crteria defined in the domain specific guidance

Same Basic Tool Qualification Principles The tool qualification is unchanged from DO-178B: The purpose of the tool qualification process is to ensure that the tool provides confidence equivalent to that of the process(es) eliminated, reduced, or automated The higher the risk of a tool error adversely affecting system safety, the higher the rigor required for tool qualification Determining if tool qualification is needed, or unchanged from DO-178B: “…when processes of this document are eliminated, reduced, or automated by the use of a software tool without its output being verified as specified…”

DO-178C Tool Qualification Levels DO-178B Development and Verification Tools terminology is no longer used. DO-178B Definitions: Development Tools: whose output is part of airborne software and thus can introduce errors Verification Tools: that cannot introduce errors but may fail to detect them DO-178C identifies 5 Tool Qualification Levels (TQL1-5) based on 3 criteria (see next slide): For criteria 1 and 3, the basic concept and required objectives are similar to that applied under DO-178B New criterion 2 introduced to provide increased objectives for certain tool usage scenarios

Advantages of Model-Based Development (DO-331) Early animation of requirements Shared language between systems and software engineers Increased responsiveness to requirements changes Ability to use autocode and simulation as a means of verification

Model Based Development Supplement (DO-332) Provides additional guidance for Model Based Development Technology and Related Techniques The MBD Supplement provides a set of approaches that can encompass most organisations uses of MBD A Framework for using MBD is established Guidance on where certification credit for model simulation is provided Core techniques of DO-178C are maintained in MBD Requirement Levels Requirement Based Testing Traceability Structural Coverage

Object-Oriented Supplement (DO-332) Provides additional guidance for Object-Oriented Technology and Related Techniques Much of the DO-178C OOT Supplement is devoted to establishing core terminology, background and interpretation Few additional objectives or activities are identified Additional OOT objectives: Verify local type consistency Verify the use of dynamic memory management is robust

Criteria for choosing whether to use OOT Project technical criteria: Potential benefit from increased expressive power in design/code – encapsulations, class hierarchies and polymorphism Nothing new here… these were original drivers behind OOT Environmental criteria: Guidance, Human Resources, Tools In industry these are all currently available… Summary: OOT is a viable technique if the software design would benefit from its expressiveness

Formal Methods Supplement (DO-333) DO-178B allowed for consideration of formal methods as an alternate method “to improve the specification and verification of software” Included a set criteria to determine the requirements to which formal methods could be applied Safety related Definable by discrete mathematics Involved complex behavior Concurrency Distributed processing Redundancy management Synchronization

Formal Methods Supplement The formal methods supplement applies where formal methods analysis is replacing testing evidence in the submission There is no intent to suggest that formal methods adoption is an “all in” decision Can be a selective adoption/migration for subsets of the system The supplement mimics the core DO-178 document structure Does not preclude traditional software testing even when comprehensive formal methods are applied

DO-178C Supplements Summary: Changing the Level of Abstraction There is an underlying synergy between the new DO-178C documents and supplements: Object Oriented Technology (OOT), Model Based Design and Verification (MBDV), Tools, Formal Methods All are moving in a common direction: Still enforce the objectives of DO-178C Enable systematic verification and/or increased level of abstraction Enabling more powerful development techniques to tackle the issues of increased complexity and limited resources Fundamental approach of DO-178 remains intact

DO-178C: The Future DO-178C will be mandated by EASA, FAA, and others at some time in the future. When? But it will be mandated! The model of providing Technology Supplements will be applied to future standards Maintain a core approach Enable approaches for new technologies to be added Be able to react more quickly by just adding supplements

Good Engineering Practice DO-178C: The Future How will DO-178C affect systems development? How did DO-178B affect systems development? No specific life-cycle model required Say what you are going to do Do it Show the evidence you did it Analogous to ISO 9001, or CMMI Good Engineering Practice

SEI CMMI Maturity Levels SEI CMMI’s 5 Levels: Initial Repeatable (disciplined) Defined (consistent)) Managed (predictable) Optimizing (continuous improvement) Each level is a perfect superset of the preceding level

DO-178 Quality/Cost 100 % Perfection Perfection CO$T Plans & Processes Detailed Rqmts Unit Testing Functional Testing Robust. Testing Code Reviews

DO-178C: The Future By Enabling new technologies it is possible to reduce the cost of development Reduced Time of Development Ability to increase system capabilities Reduce Obsolescence Fundamental Safety approach is not compromised Functional Safety Framework remains Core approaches of DO-178 remain New technologies have to fit within this framework