CASE STUDY
(Safety and Reliability Engineer)
Presented By:
Mohammad Wasim Akhtar
Internal
Question 1: Consider the function “to control flight” of a multirotor aircraft e.g., Volocopter’sVolocity2X model
or similar. Perform a functional hazard assessment of the function. (Max 15 subfunctions and Max 10 failure
conditions)
Answer
Function: To Control Flight of a multirotor aircraft
Funct.
Failure
Ref.
Sub
function
Flight Phase
Failure
Condition
Failure Effect
Severity
Classification
FC-001
Altitude
Control
Cruise/Hovering
/ Maneuvering
Loss of altitude
control
Aircraft could become unstable
and potentially crash.
Catastrophic
FC-002
Uncommanded
altitude change
Could lead to disorientation which
results in the loss of control by the
pilot or autonomous system.
Hazardous
FC-003
Incorrect
altitude
estimation
Flight control system may apply
incorrect corrections, leading to
aircraft instability
Major
FC-004
Delayed
response to
altitude change
Reduced ability to correct for
disturbances, leading to aircraft
instability
Major
Internal
Funct. Sub function
Failure
Ref.
Flight Phase
Failure Condition
Failure Effect
Severity
Classification
FC-005 Thrust control
Cruise/Hovering
/ Maneuvering
Loss of Thrust in
one or more motors
Loss of aircraft control which
could become unstable and
potentially crash.
Catastrophic
FC-006 Navigation
control
Maneuvering/
Descent
Loss of GPS signal
Loss of navigation will lead to
flyaway (loss of flight path)
Major
FC-007 Battery Supply
All Phase
Loss of Battery
supply or depletion
Power loss to the flight control
Catastrophic
system, leads to potentially crash.
FC-008 Communication Link
All Phase
Communication link
failure
Loss of remote control or
telemetry, potential for
uncontrolled flight or flyaway
FC-009 Sensor fusion
Cruise/
Maneuvering/
Descent
Sensor fusion failure Incorrect estimation of aircraft
Catastrophic
state (position, altitude, velocity),
leading to aircraft unstable or
potentially crash.
FC-010 Environmental
Adaptation
All Phase
Loss of
Environmental
Adaptation
Incorrect flight behavior, leading
to aircraft unstable.
Internal
Major
Hazardous
Question 2: Describe the limits of safety assessment performed on system functions and alternatives to cope
with them.
Topics
Limits of safety assessment
Alternatives
Incorrect Hazard Not all potential hazards may be identified - Brainstorming or historical data
Identification
due to either lack of experience or
- Involves teams with different expertise
insufficient information.
Assumption
Safety often rely on assumptions that may
not capture real-world complexities.
Conduct detail simulations and real-world testing to
validate assumptions.
Data Limitations Lack of reliable data
- Field data analysis
- Incorporate expert judgements
- Using Bayesian model technique
Over-Reliance
on historical
data
It may not always be indicative of future
risks, especially in rapidly evolving
technologies.
- Conduct scenarios-based analysis and Stress
testing (HALT) to explore other failures.
Human Factors
Safety assessments may not adequately
consider human errors and how they
impact safety risks.
- Evaluate human factors engineering (like Human
Reliability)
- Conduct human-in-the-loop simulations to
evaluate and mitigate risks related to human error.
Internal
Question 3: Consider a new component designed with new technology i.e., no previous experience in the company and rare
industry application in last 5 years. Assume a specific failure mode of the component in expected to occur but its
probability of occurrence is not known. What do you do to characterize the statistic of occurrence of this failure?
Topics
Action
Outcome
Literature review
and Benchmarking
- Review research papers/ patents
- Refer industry specific standards (FIDES,
NPRD, MIL 217 FN2)
Provides initial insights and broader understanding
of the potential failure mechanisms
Expert elicitation
Consult field experts for gathering
information.
Use expert judgement to understand the potential
failure mechanisms.
Theoretical Analysis
and Modeling
Develop theoretical models based on the
physics of failure(e.g, fatigue analysis) to
predict the failure mechanisms.
Evaluate the failure probability of occurrence based
on the theoretical models understanding.
Laboratory Testing
Conduct ALT in a controlled environment to Gather testing data for estimating failure
induce failure and observe their
probabilities of occurrence.
occurrences
Bayesian Technique
Apply Bayesian technique to combine prior
information (from expert judgement and
literature review) with the new data (from
lab testing or PoF)
Internal
Evaluate the failure probability of occurrence(failure
rate) from accurately estimating the posterior
distribution using Bayesian model technique.
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