overview of do-254: design assurance guidance for airborne electronic hardware
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DESIGN ASSURANCE GUIDANCEFOR AIRBORNE ELECTRONIC HARDWARE
by
OAK SYSTEMS PRIVATE LIMITEDwww.oaksys.net
Overview of
DO-254
August 2016 Oak Systems: DO-254 Overview 2
Introduction to DO-254 DO‑ 254: is a Guideline document
"To provide design assurance guidance for thedevelopment of airborne electronic hardware such thatit safely performs its intended function, in its specifiedenvironments
Is based on industry‑experience
Includes LRUs, circuit board assemblies, applicationspecific integrated circuits, programmable logicdevices, etc.
This guidance is applicable to current, new, andemerging technologies.
August 2016 Oak Systems: DO-254 Overview 3
Introduction to DO-254
DO‑254 guidelines are organised as ‑ Objectives for hardware design life cycle
processes Descriptions of activities and design
considerations for achieving thoseobjectives
Descriptions of the evidence that indicatethat the objectives have been satisfied
August 2016 Oak Systems: DO-254 Overview 6
System LevelsFive levels of system are def ined in
DO-254. Each system level has a specif ic set of objectives that must be satisf ied
August 2016 Oak Systems: DO-254 Overview 8
Complexity considerationsA hardware item is identif ied as simple only if a comprehensive combination of deterministic tests and analyses appropriate to the design assurance level can ensure correct functional performance under all foreseeable operating conditions with no anomalous behavior.
When an item cannot be classif ied as simple, it should be classif ied as complex.
For a simple hardware item, extensive documentation of the design process is unnecessary. The supporting processes of verif ication & conf ig mgmt need to be performed and documented for a simple hardware Item, but extensive documentation is not needed.
August 2016 Oak Systems: DO-254 Overview 10
DO-254 Objectives
DAL Level D – 31 objectives
DAL Level C – 37 objectives
DAL Level B – 39 objectives
DAL Level A – 40 objectives
Objectives >>> Activities >>> LifecycleData >>> Certif ication
[Around 100 activities ; Around 20 artifacts]
August 2016 Oak Systems: DO-254 Overview 11
Hardware Design Lifecycle Process Hardware Planning process
Hardware Design process
Supporting processes● Verif ication & Validation process● Conf iguration Management process● Process Assurance Process● Certif ication Liaison process
August 2016 Oak Systems: DO-254 Overview 12
Developing a hardware item with different subitems atdifferent stages of development require a means to providea reasonable amount of control of the design process inorder to manage the risk of starting the next process beforeall elements of the previous process are complete.
Transition criteria, defined as the minimum data used toassess movement from one process to another.
Transition criteria should be documented in thehardware plans.
Use of transition criteria does not imply any particularlife cycle model or prevent such development strategiesas rapid prototyping and concurrent engineering.
Transition Criteria
August 2016 Oak Systems: DO-254 Overview 13
Hardware Design Life cycle processes
Hardware Planning Process ‑ to define the means bywhich the functional & airworthiness requirements areconverted into a hardware item with acceptable amount ofevidence of assurance that the item will safely perform itsintended functions.
Hardware Development Processes ‑ produce thehardware product. (Requirements capture, conceptual &detailed design, implementation and production transition)
Supporting processes – to ensure the correctness,control, and confidence of the Hardware design life cycleprocesses and their outputs. (Verification & Validationprocess, CM process, PA process and CertificationLiaison process)
Let us look into these ...
August 2016 Oak Systems: DO-254 Overview 14
H/W Planning process - Objectives
The hardware design life cycle processes aredefined
Standards are selected and defined.
The hardware development and verificationenvironments are selected or defined.
The means of compliance of the hardwaredesign assurance objectives, including strategiesidentified using guidance, are proposed to thecertification authority.
August 2016 Oak Systems: DO-254 Overview 15
Hardware Plans
In order to achieve the DO‑254 objectives, following plansare to be defined –
Plan for Hardware Aspects of Certification (PHAC)
Hardware Design Plan
Hardware Verification Plan
Hardware Validation Plan
Hardware Configuration Management Plan (HCMP)
Hardware Process Assurance Plan (HPAP)
August 2016 Oak Systems: DO-254 Overview 17
Hardware Development Processes (5.0)
HDL design representations use coded text basedtechniques that are similar in appearance to thoseused for software representations. This similarity inappearance can mislead one to attempt to usesoftware verification methods directly on the designrepresentation of HDL or other equivalent hardwarespecification languages.
The guidance is applicable for design assurance fordesigns using an HDL representation.
August 2016 Oak Systems: DO-254 Overview 18
Requirements Capture Process
The requirements capture process identifies and recordsthe hardware item requirements. This includes thosederived requirements imposed by the proposed hardwareitem architecture, choice of technology, the basic andoptional functionality, environmental, and performancerequirements as well as the requirements imposed by thesystem safety assessment.
This process may be iterative since additional reqs maybecome known during design.
August 2016 Oak Systems: DO-254 Overview 19
Conceptual Design Process
The conceptual design process produces a high-leveldesign concept that may be assessed to determine thepotential for the resulting design implementation to meetthe requirements. This may be accomplished using suchitems as functional block diagrams, design andarchitecture descriptions, circuit card assembly outlines,and chassis sketches.
August 2016 Oak Systems: DO-254 Overview 20
Detailed Design Process
The detailed design process produces detailed design datausing the hardware item requirements and conceptualdesign data as the basis for the detailed design.
August 2016 Oak Systems: DO-254 Overview 21
Implementation Process
The implementation process uses the detailed design datato produce the hardware item that is an input to the testingactivity
August 2016 Oak Systems: DO-254 Overview 22
Production Transition Process
In this process, manufacturing data, test facilities andgeneral resources should be examined to ensureavailability and suitability for production. The productiontransition process uses the outputs from theimplementation and verification processes to move theproduct into production.
August 2016 Oak Systems: DO-254 Overview 23
Validation Process
The validation process is intended to ensure that thederived requirements are correct and complete withrespect to the system requirements allocated to thehardware item through the use of a combination ofobjective and subjective processes.
Validation may be conducted before or after the hardwareitem is available, however, validation is typically conductedthroughout the design life cycle.
August 2016 Oak Systems: DO-254 Overview 24
Verification Process
The verification process provides assurance that thehardware item implementation meets the requirements.
Verification consists of reviews, analyses and tests appliedas defined in the verification plan.
The verification process should include an assessment ofthe results.
August 2016 Oak Systems: DO-254 Overview 25
Verification & Validation Methods
Test
Test is a method that confirms that the hardware itemcorrectly responds to a stimulus or series of stimuli.
Examples of tests include functional test on the hardwareitem, system bench test, system validation facility test andaircraft test.
Tests may be conducted using manual, automated orspecialized test equipment.
August 2016 Oak Systems: DO-254 Overview 26
Verification & Validation Methods
Analysis
Analysis is a detailed, repeatable, analytical method forevaluation of specific hardware item characteristics todemonstrate that a specific requirement is met. Examplesof analyses are stress analysis, design margin analysis,common mode failure analysis, worst case analysis andtest coverage analysis.
August 2016 Oak Systems: DO-254 Overview 27
Verification & Validation Methods
Reviews
A review is a qualitative method for evaluation of the plans,requirements, design data, design concept or designimplementation.
Reviews should be held throughout the hardware designlife cycle as identified in the relevant plan.
All reviews to be used for certification credit should beidentified in the validation and verification plan.
August 2016 Oak Systems: DO-254 Overview 28
Configuration Management Process
The process is intended to provide the ability toconsistently replicate the configuration item (CI),regenerate the information if necessary andmodify the CI in a controlled fashion ifmodification is necessary.
Objectives:1. CIs are uniquely identified and documented.2. Consistent and accurate replication of CIs is
ensured.3. A controlled method of identifying and tracking
modification to CIs is provided.
August 2016 Oak Systems: DO-254 Overview 29
Process Assurance Process Process assurance ensures that the life cycle
process objectives are met and activitieshave been completed as outlined in plans orthat deviations have been addressed.
Process assurance activities should beachieved with independence in order toobjectively assess the life cycle process,identify deviations and ensure correctiveaction.
August 2016 Oak Systems: DO-254 Overview 30
Process Assurance Process
To establish communication and understandingbetween the applicant and the certificationauthority throughout the hardware design lifecycle to assist in the certification process.
Driven by PHAC and Plans
A summary of the design processes followed,outputs produced and status of the hardware itemshould be described in the HardwareAccomplishment Summary (HAS)
August 2016 Oak Systems: DO-254 Overview 31
Tool Assessment & Qualification Process● Hardware design/development tools
● Hardware Verification tools
The tool assessment & qualification process may beapplied to either a single tool or a set of tools.
Tools often contain capabilities beyond those neededfor a specific design or verification activity on anyspecific project. It is only necessary to assessthose functions of the tool used for a specifichardware life cycle activity, not the entire tool.
August 2016 Oak Systems: DO-254 Overview 33
Summary● DO‑254 Provides Guidance for determining, in a
consistent manner and with an acceptable level ofconfidence, that the airborne electronic hardwarecomplies with airworthiness requirements
● Hardware is real ised through the Planning,Development and Supporting Processes by followingthe objectives, activities prescribed and standardsadopted
● Rigor of Verification Processes depends upon theHardware Design Assurance Level
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