Interview Questions
1)
What is DO-178B?
Ans:
Software
Considerations in Airborne Systems and Equipment Certification is a guidance
document that focuses on software processes and objectives to comply with in
these processes.
a)Developed by RTCA (Radio Technical Commission for
Aeronautics) a group composed of industry and Federal Aviation Administration
(FAA) representatives.
b) A software process used
primarily in FAA certified applications that attempts to ensure that any
software used in airborne applications is safe.
c)FAA mandates that any
software system installed on commercial aircraft must meet DO-178B objectives.
2) What is Software Life Cycle Process?
Ans:
Software Life Cycle process is
a) Planning Process
b) Development Process
i)
Requirements
ii)
Design
iii)
Coding
iv)
Integration
c) Integral Process
i)
Verification
ii)
Configuration Management
iii)
Software Quality and Certification
d) Life Cycle definition.
3) What is Software Planning Process?
Ans:
Objectives:
a) Process activities, plans, standards are defined.
b) Software Life Cycles, Development Environment, Methods,
Tools are defined,
c) Transition criteria between processes are established.
d) All Objectives on DO-178B Guidelines, Table A-1
Deliverables:
a) Plan for Software Aspects of Certification.
b) Software Development Plan.
c) Software Verification Plan.
d) Software Quality Assurance Plan.
e) Software Configuration Management Plan.
f)
Software Requirements Standards.
g) Software Design Standards.
h) Software Coding Standards.
4) What is software Development Process?
Ans:
Objectives
a) Software high-level requirements, architecture, low-level
requirements, source code, and executable object code are developed
b) All Objectives on DO-178B Guidelines, Table A-2
Life Cycle Processes:
a) Software Requirements Process
b) Software Design Process
c) Source Coding Process
d) Source Integration process
Deliverables are:
a) Software Requirements Data
b) Software Design Description (HLD & LLD)
c) Source Code (and other configuration files)
d) Executable Object Code
5) What is software Verification process?
Ans:
Software
Verification includes
a) Reviews
b) Analysis
c) development of test cases and procedures
d) execution
of test procedures
The
purpose of software verification process is to detect and report errors that
may have been introduced during the software development processes. Removal of
the errors is an activity of the software development processes.
The
Verification process provides traceability between the implementation of the
software requirements and verification of those requirements
The
traceability between software requirements and the test cases is accomplished
by requirements-based coverage analysis
The
traceability between the code structure and the test cases is accomplished by
structural coverage analysis
Inputs:
a) The relevant Process outputs to be reviewed.
b) The inputs used for generating the process output
c) Software Verification Plan
d) The
relevant review checklist
Output:
a) Review record/ Defect Record
b) Analysis Reports.
6) What is software Configuration Management Process?
Ans:
Objectives:
a) Configuration items identified.
b) Problems reported.
c) Changes controlled and reviewed.
d) Archival, retrieval, release managed.
e) Load control managed.
f)
All Objectives on DO-178B
Guidelines, Table A-8
Deliverables:
a) SCM Records.
b) Software Configuration Index
c) Problem Reports
d) Software Life Cycle Environment Configuration Index
7) What is software Quality assurance process?
Ans:
Objectives:
a) Processes comply with approved plans and standards.
b) Transition criteria for software life cycle processes are
satisfied.
c) All Objectives on DO-178B Guidelines, Table A-9
d) Software conformity review is conducted.
e) Software life cycle processes are complete.
f)
Software life cycle data is complete.
g) Executable Object Code is controlled and can be regenerated.
Deliverables:
a) Software Quality Assurance Records.
8) What is Certification liaison process?
Ans:
Objectives:
a) Establish communication and understanding between applicant
and certification authority (at start).
b) Agreement on means of compliance is obtained (at start).
c) Compliance substantiation is provided (at end).
d) All Objectives on DO-178B Guidelines, Table A-10
Deliverables:
a) Plan for Software Aspects of Certification (? certification
authority at start).
b) Software Configuration Index (? certification authority at
end).
c) Software Accomplishment Summary (? certification authority
at end).
d) Availability of all Software Life Cycle Data and producing
up on request.
9) What is all the coverage of requirement based testing of all
the levels?
Ans:
Level A: Modified Condition Decision Coverage (MCDC) + Level
B.
Level B: Decision Coverage+ Level C.
Level C: Statement Coverage.
Levels D & E: Not needed.
Levels A-C: Data and Control Coupling.
10) Why Structural coverage analysis is performed?
Ans:
Structural Coverage Analysis is
performed to determine if any un-covered code is due to:
a) Inadequate requirements-based tests: fix them!
b) Inadequate requirements: fix them!
c) Dead code: remove it!
d) Deactivated code: show that it can’t be inadvertently
executed.
11) What is RTCA?
Ans:
Radio
Technical Commission for Aeronautics.
RTCA, Inc. is a private, not-for-profit corporation that develops consensus-based recommendations regarding communications, navigation, surveillance, and air traffic management system issues. RTCA functions as a Federal Advisory Committee.
RTCA, Inc. is a private, not-for-profit corporation that develops consensus-based recommendations regarding communications, navigation, surveillance, and air traffic management system issues. RTCA functions as a Federal Advisory Committee.
12) What is FAA?
Ans:
Federal
Aviation Administration, the organization responsible for controlling air
traffic safety in the United States.
FAA lists DO-178B as a means of compliance that is acceptable to the regulators of software in the avionics community.
FAA lists DO-178B as a means of compliance that is acceptable to the regulators of software in the avionics community.
13) What is EUROCAE?
Ans:
European Organization for Civil
Aviation Equipment.
It is the European equivalent of RTCA. EUROCAE documents are considered by Joint Aviation Authorities as means of compliance to Joint Technical Standard Orders and other regulatory documents.
It is the European equivalent of RTCA. EUROCAE documents are considered by Joint Aviation Authorities as means of compliance to Joint Technical Standard Orders and other regulatory documents.
14) What is JAA?
Ans:
Joint
Aviation Authorities in Europe.
The
JAA and the FAA work together to create air traffic safety standards.
15) Who is DER?
Ans:
A DER, Designated Engineering
Representatives, is an experienced engineer designated by the FAA to approve
engineering data used for certification.
A
DER evaluates processes for compliance with certification objectives. He
ensures process complies by assessing plans and procedures for compliance.There
are no DER in the JAA context.
16) What are failure conditions and Software levels?
Ans:
DO-178B
defines five software levels based on severity of failure
Each
level is defined by the failure condition that can result from anomalous
behavior of software. The software level is determined after system safety
assessment and the safety impact of software is known
Failure Condition
|
Software Level
|
Catastrophic
|
Level A(66 Objectives)
|
Hazardous/Severe-Major
|
Level B(65 Objectives)
|
Major
|
Level C(57 Objectives)
|
Minor
|
Level D(28 Objectives)
|
No Effect
|
Level E
|
17) Failure Conditions and Categories?
Ans:
Catastrophic: Failure conditions which would prevent continued safe
flight and landing.
Ex. Flight Control System
Hazardous/Severe-Major: Failure conditions which would reduce the capability of the
aircraft or the ability of the crew.
Ex. - Cabin Air Conditioning and
Temperature Control System
Major: A significant reduction in safety margins or functional
capabilities, a significant increase in crew workload.
Example: Integrated Cooling System
(ICS) & Forward Cargo Air Conditioning (FCAC).
Minor: Failure conditions involve crew actions that are well
within their capabilities and significantly reduce aircraft safety.
Ex: In-Flight Entertainment System of any
commercial aircraft in service
No Effect: Failure conditions which do not affect the operational
capability of the aircraft or increase crew workload. Ex. Vending machine on aircraft.
18) Does DO-178B can be applied for both Civil and Military
aircraft application?
Ans:
The guideline applies only for commercial
aircrafts and there are separate
military standards but and at times defense
may use it.
19) Who decides on the level of software to be qualified?
Ans:
System Safety assessment department within
an equipment manufacturing organization
would provide the first level inputs on the
same. This in itself is a detailed process.
20) What is Requirement process?
Ans:
The software requirements process uses the outputs of the
system life cycle process
to
develop the software high-level requirements. These high level requirements
include
Functional,
performance, interface and safety-related requirements.
Inputs:
a) System requirements allocated to software
b) Safety requirements allocated to software including software
level
c) Hardware definitions/interfaces and system architecture
d) Clarifications
received from time to time on requirements during the requirement phase.
e) Software development plan
f) Software requirement standards
Outputs:
a) Software Requirements Specifications which defines the
Software High Level Requirements and identifies the Derived High Level
Requirements.
b) Establishment of traceability to System Requirements
21) What is Design Process?
Ans:
The design description is definition
of the software architecture and the low-level
Requirements
that will satisfy the software high-level requirements. This data should
Include
§ Description of software architecture
defining the software structure
§ Data flow and control flow of the
design
§ Resource limitations, scheduling
procedures and inter-processor/task communication
§ Partitioning methods and means of
preventing partition breaches
Inputs:
a) SRS (Requirement data and other document)
b) Software Development Plan
c) Software Design Standard
d) High
Level Design (software architecture)
e) Review feedback
Outputs:
a) Detailed Design Document defines software Low Level
Requirements that will satisfy Software High Level Requirements. Derived Low
Level requirements are identified separately.
b) Updated Traceability.
22) What is Coding Process?
Ans:
In the software coding process, the
Source Code is implemented from the software
Architecture
and the low-level requirements.
Inputs:
a) Software Development Plan
b) High-level design (SW Architecture)
c) Detailed design (Low-level requirement)
d) Coding
standards and guidelines
Outputs:
a) Software Identification, including name and date of revision
b) Compiler instruction
c) Linking and loading
data.
23) What are the Different Stages of Involvements(SOI) ?
Ans:
a) Software Planning review
Stage of Involvement (SOI) #1
b) Software Development review - Stage of Involvement (SOI) #2
c) Software Verification review
Stage of Involvement (SOI) #3
d) Final
Certification review - Stage of Involvement (SOI) #4
24) What is CC1 and CC2 ?
Ans:
If
an item, artifact is CC1 then it must have all those attributes in the table in
section 7. Meaning it needs to have baselines, change management, etc.
If
an item/artifact is CC2 then it doesn't need all of those items. It really only
needs to be retained. Simply put a CC1 item needs to be tracked where as a CC2
item needs to be stored.
Typically
a CC2 items tends to be "one-shots" like meeting minutes, reports,
problem reports themselves, etc.
Whereas
CC1 items tend to be documents that need to be maintained, tracked and base
lined. Is it a big deal in DO178B, well yes. If you don't maintain the CC1 data
as per the table, one isn't following the process and hence can't build the
substantiation data required.
25) What is ATA number?
Ans:
a) The ATA(Air Transport Association) 100
Chapter numbers was a common referencing standard for all commercial aircraft documentation.
b) This commonality permits greater ease of learning and
understanding for pilots, aircraft maintenance technicians, and engineers alike
26) What is the Difference between Level A & Level B
Ans:
26) What is the Difference between Level A & Level B
Ans:
1. MCDC
2. Source to Object code verification,(Refer 6.4.4.2 b in DO178B.PDF)
27) Why Derived Requirements ?
Ans:
We build systems to meet the requirements of our users. As we build systems, we take our user's requirements and derive more requirements from them. Derived requirements are lesser than user requirements. It is easy, however, to forget this relationship, and this can cause many problems for our projects.
A derived requirement is something that we infer or derive from a user requirement. (For this article, let's use the term user for the customer, user, and client. Let's also use the term "user requirement" for something that the user wants.) For example, suppose a user requirement is "the system must work outdoors, 12 months a year in Minnesota." Several derived requirements are (1) the system must work in temperatures below 10 degrees F and (2) the system must work in the snow. We derive these requirements by delving into the details of the user requirement.
2. Source to Object code verification,(Refer 6.4.4.2 b in DO178B.PDF)
27) Why Derived Requirements ?
Ans:
We build systems to meet the requirements of our users. As we build systems, we take our user's requirements and derive more requirements from them. Derived requirements are lesser than user requirements. It is easy, however, to forget this relationship, and this can cause many problems for our projects.
A derived requirement is something that we infer or derive from a user requirement. (For this article, let's use the term user for the customer, user, and client. Let's also use the term "user requirement" for something that the user wants.) For example, suppose a user requirement is "the system must work outdoors, 12 months a year in Minnesota." Several derived requirements are (1) the system must work in temperatures below 10 degrees F and (2) the system must work in the snow. We derive these requirements by delving into the details of the user requirement.
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