1.
AVIONICS SYSTEM STANDARDS
INTRODUCTION
Avionics is the electronic system used in Aviation.
As the advancement in Avionics had grossing
demand inducing the incompatibility and conflict in
Avionics application which soon realized the usual
approach to seek the safety and reliability will not
work for safety critical system, there was great
need for the solution of design error, thus which
prompted the Avionics System Standards.
Submitted By : Jeran Rai (VTU-8429)

2.
GENERAL CATEGORY OF AVIONICS
STANDARDS
In General, Avionics system standards are
mainly classified in following categories;
●
Avionics Hardware Standards.
●
Avionics Software Standards.

3.
AVIONICS HARDWARE STANDARDS
The importance of Avionics hardware is often overlooked
because of the small size of most items. However, the safe
and efficient operation of any Aircraft depends on correct
selection and use of Avionics Hardware which is also to be
determined by the certain standard.
As result, The DO-254 specification was created by Radio
Technical Communication For Aeronautics (RTCA)
committee back in the 1990s, and was written to apply to all
levels of hardware, including circuit boards, resistors, and
capacitors—as well as chips.

4.
DO-254
Simply stated, Design Assurance Guidance For Airborne
Electronic Hardware ( DO-254 ) is a requirements-driven
process-oriented safety standard used on commercial
electronics that go into aircraft. (Conceptually speaking,
this standard applies to all electronics in anything that flies
or could crash and pose a hazard to the public.)
DO-254 was specified in 1990s, however when the
Federal Aviation Administration ( FAA ) enacted the DO-
254 specification as policy in 2005, it chose to limit the
scope to “complex custom micro-coded components” like
PLDs, FPGAs, and ASICs.

5.
DO-254
The DO-254 standard is the counterpart to the well-
established software standard RTCA
DO-178B/EUROCAE.
There are levels of compliance defined by the five
Criticality Levels, A through E, which depend on the
effect a failure of the hardware will have on the
operation of the aircraft, where DO-254 Level A being
most critical and DO-254 Level E being least critical
and is must be determined by FAA system safety
assessment process and must be verified by FAA.

6.
DO-254 CRITICALITY LEVELS
➢
DO-254 Level A : DO-254 Level A hardware is hardware whose
anomalous behavior, as shown by the system safety assessment
process, would cause or contribute to a failure of system function
resulting in a catastrophic failure condition for the aircraft. Failure of
DO-254 Level A hardware could be typified by total loss of life.
Approximately 20-30% of avionics systems and 40% of avionics
hardware implementation must meet DO-254 Level A criteria.
➢
DO-254 Level B : DO-254 Level B hardware is hardware whose
anomalous behavior, as shown by the system safety assessment
process, would cause or contribute to a failure of system function
resulting in a hazardous/severe-major failure condition for the aircraft.
Failure of DO-254 Level B hardware could be typified by some loss of
life. Approximately 20% of avionics systems and 30% of avionics
hardware implementation must meet DO-254 Level B criteria.

7.
DO-254 CRITICALITY LEVEL
➢
DO-254 Level C : DO-254 Level C hardware is hardware whose
anomalous behavior, as shown by the system safety assessment
process, would cause or contribute to a failure of system function
resulting in a major failure condition for the aircraft. Failure of DO-254
Level C hardware could be typified by serious injuries. Approximately
25% of avionics systems and 20% of avionics hardware
implementation must meet DO-254 Level C criteria.
➢
DO-254 Level D : DO-254 Level D hardware is hardware whose
anomalous behavior, as shown by the system safety assessment
process, would cause or contribute to a failure of system function
resulting in a minor failure condition for the aircraft. Failure of DO-254
Level D hardware could be typified by minor injuries. Approximately
20% of avionics systems and 10% of avionics hardware
implementation must meet DO-254 Level D criteria.

8.
DO-254 CRITICALITY LEVEL
➢
DO-254 Level E : DO-254 Level E hardware is hardware whose
anomalous behavior, as shown by the system safety assessment
process, would cause or contribute to a failure of system function
with no effect on aircraft operational capability or pilot workload.
Failure of DO-254 Level E hardware would have no impact on
passenger or aircraft safety. Approximately 10% of avionics
systems and 5% of avionics hardware implementation must meet
DO-254 Level E criteria (note however that the amount of DO-
254 Level E implementation is increasing due to passenger
entertainment and internet communications subsystems that are
currently designated Level E; it is deemed likely by us that the
criticality levels of these systems will increase due to integration
with other, more critical, avionics systems).

9.
DO-254 COSTS AND BENEFITS
➢
DO-254 is often thought to add 50-200% to avionics
hardware development. In reality, actual additional
DO-254 cost should be on the order of 30%-50%,
presuming basic high-reliability hardware
engineering principles are used from the onset.
➢
In addition to being necessary for flight products,
DO-254 benefits include: verifiable hardware quality,
higher reliability, consistency, greater re-usability,
lower lifecycle costs, decreased maintenance cost,
faster hardware integration, and greater portability.

10.
AVIONICS SOFTWARE STANDARDS
Avionics software is embedded software with legally
mandated safety and reliability con-cerns used in avionics.
In early 80s, the cost of Computers went down due to the
introduction of personal computer and the Aviation industry
started replacing or enhancing the conventional Airbrone
System with Software functionality. Thus, increased use of
Software and Computer Systems for Safety Critical
application MOTIVATED to develop First Version DO-178
( Software Considerations in Airborne Systems and
Equipment Certification ) jointly by RTCA and EUROCAE.

11.
DO-178
➢
Since it was the first of its kind, so it was initially written
at a conceptual level.
➢
The rules to be standardized were developed by trial
and error over time.
➢
Since the Airbrone system were being
replaced/enhanced with software functionality which
lead to introduce the first concept of Software
Verification.
➢
The software application were divided into three level of
categories: Critical, Essential And Non-essential.

12.
DO-178A
➢
Published in 1985.
➢
The feature introduced:
➔
Systematic and Structured detail, Software
Development verification processes.
➔
Concept of Software application level 1, 2 and 3
corresponding to criticality safety level.
➢
There was total lack of understanding of the purpose.
➢
Misinterpretation led to disqualification Software
development cycle.

13.
DO-178B
➢
Evolved from DO-178A, cira 1985.
➢
DO-178B is guidance document only and focuses on
software processes and objectives to comply with these
processes.
➢
Recommended certification to obtain approval of Airborne
softwares.
➢
DO-178B is not prescriptive.
➔
Vendors are allowed how objectives are satisfied.
➢
DO-178B objectives varies, how to software failure can
effect system safety.

14.
DO-178B CRITICALITY LEVELS
DO-178B defines five safety levels :
➔
Level A : Catastrophic;
✔
Failure results in preventing the flight from continuing Safely and/or
Landing. An example of such system is an engine controller
software.
➔
Level B : Hazardous;
✔
Failure results to serious or fatal injuries to the aircraft occupants.
Examples are Primary Flight Displays (PFDs) and failures of
pressurization system software.

15.
DO-178B CRITICALITY LEVELS
➔
Level C : Major;
✔
Failure results in causing discomfort or injuries to the occupants.
Examples are Flight Management System (FMS), autopilot and
auto landing systems.
➔
Level D : Minor;
✔
Failure results in causing some inconvenience to the occupants.
Examples are such systems include transponders and
communication equipment.
➔
Level E : No Effect;
✔
Failure of in-flight entertainment functions and satellite phone and
internet access.

16.
DO-178C
➔
It was completed in November 2011, approved by
RTCA in December 2011, available for sale and use
in january 2012 and FAA approved in 19, july 2013.
➔
Includes formal Methods - Mathematical based
techniques used for specification, development and
verification of a avionics software.
➔
Formal methods can be used to "prove that software
is an accurate representation of the mathematical
expressions”.

17.
DO-178C
➔
Object Oriented Programming Languages like
C++ and Ada are highly standardized because
they are at a higher level of abstraction than
other languages which lead to promote re-use
and promise more efficient development.
➔
Model-Based development which model
systems at veryhigh-level, domain-specific
languages, are often used to automatically
generate source code directly from the model.

18.
DO-178C CRITICALITY LEVELS
➔
Level A : Catastrophic;
✔
Failure may cause deaths, usually with loss of the
airplane.
➔
Level B : Hazardous;
✔
Failure has a large negative impact on safety or
performance, or reduces the ability of the crew to
operate the aircraft due to physical distress or a
higher workload, or causes serious or fatal injuries
among the passengers.

19.
DO-178C CRITICALITY LEVELS
➔
Level C : Major;
✔
Failure significantly reduces the safety margin or significantly
increases crew workload. May result in passenger discomfort (or
even minor injuries).
➔
Level D : Minor;
✔
Failure slightly reduces the safety margin or slightly increases crew
workload. Examples might include causing passenger
inconvenience or a routine flight plan change.
➔
Level E : No Effect;
✔
Failure has no impact on safety, aircraft operation, or crew workload.

20.
CONCLUSION ON DO-178( )
Note : The DO-178( ) solely focuses on design assurance
where the required assurance is defined on the basis of the
respective criticality levels. The major concern with DO-178( ) is
that it is often misunderstood as software development standard
rather than a assurance standard.
●
DO-178C is the best assurance standard because its source
codes are traceable, provide clearer language and terminology,
provide more consistency, clearify the hidden objectives and so
on.
●
So, DO-178C is the currently applied means for the software
aspects of airborne avionics systems and equipment
certification.

21.
THANK YOU !
“FLIGHT SAFETY IS SIMPLE, THE
NUMBER OF SUCCESSFUL LANDING
SHOULD EQUAL THE NUMBER OF
TAKE-OFFS”