Introduction to the Role of Failure Mode and Effect Analysis (FMEA) within an EASA Design Environment

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Sofema Online (SOL) www.sofemaonline.com considers the use of FMEA as part of the certification process.

Introduction

Failure Mode and Effect Analysis (FMEA) is a systematic, proactive method for evaluating a process or a system to identify where and how it might fail and to assess the relative impact of different failures in order to identify parts of the process that are most in need of change.

FMEA typically involves cross-functional teams, fostering collaboration and knowledge-sharing among different stakeholders, leading to a more comprehensive analysis.

FMEA allows us to proactively identify potential failure modes and their effects on the system. By addressing potential failure modes and their effects, FMEA helps in designing robust systems with enhanced safety and reliability, reducing the likelihood of accidents and incidents, Implementing FMEA helps organizations meet industry standards and regulations.

Key Benefit: Identifying and mitigating failure modes during the design or early development stage is more cost-effective than addressing them later when the system is already in operation.

FMEA provides valuable insights into critical failure modes, enabling better decision-making regarding risk mitigation strategies and resource allocation.

Note that FMEA is not a one-time exercise. It can be revisited periodically to account for changes in the system, evolving risks, and lessons learned from real-world failures. This promotes a culture of continuous improvement.

>> Essentially, FMEA is a bottom-up risk analysis technique that is used to uncover potential failures at the most basic component level of a system, and then to assess the possible cascading effects of these failures at higher system levels.
>> FMEA involves reviewing as many components, assemblies, and subsystems as possible to identify failure modes, their causes, and their effects.

o A failure mode is the manner in which a failure is observed; it generally describes the way the failure occurs. The effect analysis looks for the potential consequences of each failure. For each component, the failure modes and their resulting effects on the rest of the system are recorded in a specific FMEA worksheet.

Criticality

The term "criticality" in the context of FMEA refers to the significance of the potential failure mode in terms of its impact on the system.

>> Two main characteristics are assessed here: the severity and occurrence of each failure.

o Severity describes the seriousness of the failure's effect on the system. The more serious the effect, the higher the severity rating.
o Occurrence, on the other hand, represents the likelihood of the failure occurring. The more frequently the failure is predicted to occur, the higher the occurrence rating.
o The severity and occurrence together determine the risk associated with each failure mode.

FMEA Use within Certification Programs

FMEA is particularly crucial within aircraft certification programs. Aircraft are highly complex systems where failures can have catastrophic consequences.

>> Therefore, during the certification process, each potential failure mode in an aircraft or its subsystems is scrutinized in detail using FMEA. This analysis not only identifies potential failure modes but also enables engineers to design redundancies and safeguards into the system to minimize the risks associated with each potential failure.
>> The certification authority assesses these risks, and a threshold is set for an acceptable level of risk.
>> This threshold is an inverse relationship between severity and probability - a high-severity failure mode must have a very low probability of occurrence to be acceptable. If the risk associated with a failure mode is deemed unacceptable, then changes must be made to the design or manufacturing process to either lessen the chance of the failure occurring or to mitigate its effects.

Challenges of FMEA

>> Conducting FMEA requires gathering vast amounts of data and information about the system being analyzed. This process can be time-consuming and challenging, especially for complex systems with numerous components.
>> The success of FMEA heavily relies on the expertise and experience of the individuals conducting the analysis. Different analysts may perceive risks differently, leading to variations in the results.
>> It can be difficult to anticipate and recognize all potential failure modes, especially those that are rare or unforeseen. This may lead to overlooked risks that could have significant consequences.
>> Some systems have intricate interdependencies between components, and failures in one part may cascade into other areas, making it challenging to accurately assess the overall impact of failure.
>> In some cases, historical failure data may not be readily available, making it harder to quantify failure rates and probabilities accurately.

Next Steps

Sofema Aviation Services (www.sassofia.com) offers training to cover CS 25 System Safety Assessments – please see the following Type Certification System Safety Assessment – 5 Days.

For additional questions or comments – please email [email protected]

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