Common cause analysis align expectations regarding avionic safety with real-world scenarios that could actually occur.
All aspects covered within the safety and compliance domain are studied to ensure there are no gaps within the system. There is a certain level of acceptance of scenarios that may occur, in which case common analysis is critical.
Multiple systems need to be assessed to find independent failures that may be present. Specific studies are necessary to ensure that independence can be assured or deemed acceptable. This is why ARP4761 common cause analysis provides safety requirements that can trace back to implementation and results.
Primary objectives of ARP4761 common cause
SAE ARP4761 CCA is primarily concerned with preventing events that could lead to hazardous conditions. That’s where an extensive set of guidelines is necessary to ensure that no unforeseen circumstances are left out. The protocol also covers what precautions can be taken, and what checks need to be performed prior to initiation.
Common cause analyses (CCAs) are conducted to substantiate claims made under FHA. Areas such as redundancy, separation, and independence of events can be studied under the CCA conducted. Safety requirements can then be initiated based on the findings of the analysis, along with optimizing safety protocols within the system.
Detecting common failures is also a key component of a thorough common cause analysis. They can be prevented with an extensive set of checks performed prior to take off. The aviation system can also be studied within the framework designed under ARP4761, along with key objectives present in common cause analysis.
There are three analytical methods under the CCA framework, which allow for complete compliance with safety best protocols.
I – Zonal Safety Analysis (ZSA)
CCA and ZSA are leveraged to find common causes that may be impacting multiple flights on aggregate. The independent parameters are studied within the ZSA, which may contribute to failures that may occur over time.
Maintenance protocols are also studied under ZSA, to ensure that they comply with best practices. Ensuring that the system has zero errors is the end goal of an extensive ZSA, which is accomplished through careful analysis.
Every area of the aircraft is studied, from its original design to the engineering. This is done to ensure that the system and equipment installations are at an adequate safety level that regards to the standards set.
II – Particular Risks Analysis (PRA)
Particular risks are events that are external to the system designed, which may include bird strikes, lightning, leaking fluids, fire, etc. These events need to be studied as risks, to ensure compliance with best practices and keep potential consequences from occurring.
The cascading effects of PRA parameters are also studied to understand the collective impact of individual forces. Every risk is segregated and studied individually to get a better understanding of the likelihood and impact of the event. Failure-trees can be constructed under the analysis, to gauge the impact level of specific scenarios.
III – Common Mode Analysis (CMA)
The CMA is designed to test the validity of the combinatorial effects of independent considerations. The testing mechanism helps to decipher key results within the avionics system, as it relates to errors in various domains.
Areas such as crew faults, design errors, and maintenance flaws are studied. These individual factors could ultimately defeat the idiosyncrasies of certain events. The control of these risks is what’s important, which should be studied under the CMA protocol.
A given failure condition can be set, and individual factors can be studied to understand the collective impact on the accident. This gives rise to risk protocols that can be designed to mitigate any issues that may arise.
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