Overview of DO-254: Design Assurance Guidance For Airborne Electronic Hardware

DESIGN ASSURANCE GUIDANCE
FOR AIRBORNE ELECTRONIC HARDWARE
by
OAK SYSTEMS PRIVATE LIMITED
www.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 the
development of airborne electronic hardware such that
it safely performs its intended function, in its specified
environments
 Is based on industry‑experience
 Includes LRUs, circuit board assemblies, application
specific integrated circuits, programmable logic
devices, etc.
 This guidance is applicable to current, new, and
emerging technologies.

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 those
objectives

Descriptions of the evidence that indicate
that the objectives have been satisfied

System Aspects

System Levels
Five levels of system are def ined in
DO-254. Each system level has a
specif ic set of objectives that must
be satisf ied

System Levels

Complexity considerations
A 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.

Organisation of DO-254

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]

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

Developing a hardware item with different subitems at
different stages of development require a means to provide
a reasonable amount of control of the design process in
order to manage the risk of starting the next process before
all elements of the previous process are complete.
 Transition criteria, defined as the minimum data used to
assess movement from one process to another.
 Transition criteria should be documented in the
hardware plans.
 Use of transition criteria does not imply any particular
life cycle model or prevent such development strategies
as rapid prototyping and concurrent engineering.
Transition Criteria

Hardware Design Life cycle processes
 Hardware Planning Process ‑ to define the means by
which the functional & airworthiness requirements are
converted into a hardware item with acceptable amount of
evidence of assurance that the item will safely perform its
intended functions.
 Hardware Development Processes ‑ produce the
hardware product. (Requirements capture, conceptual &
detailed design, implementation and production transition)
 Supporting processes – to ensure the correctness,
control, and confidence of the Hardware design life cycle
processes and their outputs. (Verification & Validation
process, CM process, PA process and Certification
Liaison process)
Let us look into these ...

H/W Planning process - Objectives
 The hardware design life cycle processes are
defined
 Standards are selected and defined.
 The hardware development and verification
environments are selected or defined.
 The means of compliance of the hardware
design assurance objectives, including strategies
identified using guidance, are proposed to the
certification authority.

Hardware Plans
In order to achieve the DO‑254 objectives, following plans
are 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)

Hardware Development Processes (5.0)

Hardware Development Processes (5.0)
 HDL design representations use coded text based
techniques that are similar in appearance to those
used for software representations. This similarity in
appearance can mislead one to attempt to use
software verification methods directly on the design
representation of HDL or other equivalent hardware
specification languages.
 The guidance is applicable for design assurance for
designs using an HDL representation.

Requirements Capture Process
The requirements capture process identifies and records
the hardware item requirements. This includes those
derived requirements imposed by the proposed hardware
item architecture, choice of technology, the basic and
optional functionality, environmental, and performance
requirements as well as the requirements imposed by the
system safety assessment.
This process may be iterative since additional reqs may
become known during design.

Conceptual Design Process
The conceptual design process produces a high-level
design concept that may be assessed to determine the
potential for the resulting design implementation to meet
the requirements. This may be accomplished using such
items as functional block diagrams, design and
architecture descriptions, circuit card assembly outlines,
and chassis sketches.

Detailed Design Process
The detailed design process produces detailed design data
using the hardware item requirements and conceptual
design data as the basis for the detailed design.

Implementation Process
The implementation process uses the detailed design data
to produce the hardware item that is an input to the testing
activity

Production Transition Process
In this process, manufacturing data, test facilities and
general resources should be examined to ensure
availability and suitability for production. The production
transition process uses the outputs from the
implementation and verification processes to move the
product into production.

Validation Process
The validation process is intended to ensure that the
derived requirements are correct and complete with
respect to the system requirements allocated to the
hardware item through the use of a combination of
objective and subjective processes.
Validation may be conducted before or after the hardware
item is available, however, validation is typically conducted
throughout the design life cycle.

Verification Process
The verification process provides assurance that the
hardware item implementation meets the requirements.
Verification consists of reviews, analyses and tests applied
as defined in the verification plan.
The verification process should include an assessment of
the results.

Verification & Validation Methods
Test
Test is a method that confirms that the hardware item
correctly responds to a stimulus or series of stimuli.
Examples of tests include functional test on the hardware
item, system bench test, system validation facility test and
aircraft test.
Tests may be conducted using manual, automated or
specialized test equipment.

Analysis
Analysis is a detailed, repeatable, analytical method for
evaluation of specific hardware item characteristics to
demonstrate that a specific requirement is met. Examples
of analyses are stress analysis, design margin analysis,
common mode failure analysis, worst case analysis and
test coverage analysis.

Reviews
A review is a qualitative method for evaluation of the plans,
requirements, design data, design concept or design
implementation.
Reviews should be held throughout the hardware design
life cycle as identified in the relevant plan.
All reviews to be used for certification credit should be
identified in the validation and verification plan.

Configuration Management Process
The process is intended to provide the ability to
consistently replicate the configuration item (CI),
regenerate the information if necessary and
modify the CI in a controlled fashion if
modification 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.

Process assurance ensures that the life cycle
process objectives are met and activities
have been completed as outlined in plans or
that deviations have been addressed.
Process assurance activities should be
achieved with independence in order to
objectively assess the life cycle process,
identify deviations and ensure corrective
action.

To establish communication and understanding
between the applicant and the certification
authority throughout the hardware design life
cycle 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 item
should be described in the Hardware
Accomplishment Summary (HAS)

Tool Assessment & Qualification Process
●
Hardware design/development tools
●
Hardware Verification tools
The tool assessment & qualification process may be
applied to either a single tool or a set of tools.
Tools often contain capabilities beyond those needed
for a specific design or verification activity on any
specific project. It is only necessary to assess
those functions of the tool used for a specific
hardware life cycle activity, not the entire tool.

Tool Assessment &
Qualification Process

Summary
●
DO‑254 Provides Guidance for determining, in a
consistent manner and with an acceptable level of
confidence, that the airborne electronic hardware
complies with airworthiness requirements
●
Hardware is realised through the Planning,
Development and Supporting Processes by following
the objectives, activities prescribed and standards
adopted
●
Rigor of Verification Processes depends upon the
Hardware Design Assurance Level

Questions ?
Please write to pradeep@oaksys.net

Thank You
www.oaksys.net
Note: All patents & copyrights are acknowledged to their respective owners

Overview of DO-254: Design Assurance Guidance For Airborne Electronic Hardware

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