Quality Assurance within DO-178 And DO-254

25 Jul

<extracted from private research by Vance Hilderman>

Quality   Assurance (“QA”) is arguably the most critical aspect of avionics software   and hardware certification within DO-178C and DO-254.  However, QA is almost never given the   attention, or credit, befitting its crucial role.  Consider the following statements and assess   whether they are true or false; answers and explanations are provided within   this paper: 

  1. 1.       QA’s most important   role is assessing final product quality (?)
  2. 2.       QA personnel perform   technical reviews (?)
  3. 3.       QA personnel assess   avionics development engineer’s adherence to criteria specified in DO-178C   and DO-254 (?)
  4. 4.       The four Stage Of   Involvement (“SOI”) events represent the four QA audits of the avionics   development process (?)
  5. 5.       Every Level A and   Level B avionics development project requires at least three persons, and the   most crucial of those is the QA person (?)


Easy questions?  Not at first glance; in fact, answering the   above without understanding the overall DO-178C and DO-254 framework is like   understanding Fourier transforms without first understanding The   Calculus:  impossible for mere mortals.  



In DO-178 and DO-254, QA has two   primary responsibilities:

  1. 1.       Ensuring the   project specific development plans and standards comply with DO-178/254, and
  2. 2.       Assessing then   ensuring that the separate development organization has followed those plans,   from project inception through completed delivery.


In   other, non-avionics development activities, “quality assurance” implies a   more adjunct, and more passive, measurement role.  Wikipedia, for example, aptly states QA “is the systematic measurement, comparison   with a standard, monitoring of processes and an associated feedback loop that   confers error prevention.”   The weakness of such a traditional, yet   common,  QA interpretation within   safety-critical systems is obvious: 

  •   Who ensures those “standards”   are correct and compliant to ARP 4754A, DO-178C, and DO-254?
  •   Who ensures those “processes” are deterministic,   repeatable, clearly defined, and compliant to ARP 4754A, DO-178C, and DO-254?
  •   Who is responsible for ensuring proof exists that   errors were appropriately dispositioned and closed?


In avionics, the answers to the   above are simple:  “Quality Assurance”.

DO-178   and DO-254 are somewhat “flexible” regarding the  manner in which QA processes are defined,   scheduled, and performed. The Quality Assurance Plan, typically authored but   always signed by QA, is one of five project-specific plans which define how   that project intends to meet the applicable DO-178 and DO-254 objectives. While   flexible in process, DO-178 and DO-254 are not pushovers:  QA must ensure the following objectives are   met:

  •   All requisite development plans and standards are developed   per DO-178/254 and are then followed (including suppliers)
  •   Tansition criteria are satisfied
  •   Conformity Reviews are performed
  •   Audits are performed to ensure data exists which   affirms the above


Upon   first glance, the above list of avionics QA objectives seems easy; almost   obvious.  In fact, in other,   non-avionics development environments, “quality assurance” appears to embody   similar objectives:  assess product   implementation to measure and improve quality.  Virtually every consumer electronics   product manufactured today has some form of basic quality assurance performed   upon it.


However,   closer examination then understanding of DO-178/254’s QA framework reveals   more proactive and robust QA guidance. In avionics, there are five required   plans for every safety-related airborne system.  While all are important (and the FAA/EASA   wisely decline to state “which” plan or objectives are most important),   avionics certification experts generally agree that the order of importance   of the five required plans is:

  1. 1.       Certification Plan
  2. 2.       Quality Assurance Plan
  3. 3.       Configuration Management Plan
  4. 4.       Development Plan
  5. 5.       Verification Plan


The   2nd most important plan is the QA Plan which must describe QA   processes which ensure each system:

  •   has a complete set of plans/standards which embody 100%   of all applicable DO-178/254 objectives
  •   has mechanisms to assess whether the actual processes   used throughout the development process complies with those plans
  •    <Extracted from Vance Hilderman’s primary paper; see main paper for remaining content>

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