25 Mar
FRACAS (Failure Reporting, Analysis, and Corrective Action System) is a reliability system that is widely spread and used by most manufacturers in the aerospace industry. The FRACAS process is deeply tied to the continuing airworthiness of aircraft and can be divided in three steps: Failure Reporting, Failure Analysis, and Corrective Actions.
The first two steps; Failure Reporting and Analysis, provide the necessary data to the system. All the failures that required a maintenance action are analysed and stored in the system. Using said analysis, the real MTBF (Mean Time Between Failures) of each aircraft component can be obtained and compared to the values provided by the part manufacturer.
What are the Corrective Actions?
Corrective
Actions, the focus of this article, consist of the measures taken by the
aircraft manufacturer based on the collected data. Corrective Actions, which
are normally abbreviated to “CAs”, are essential in order to meet the
reliability goals of a product, be it an entire aircraft or an airborne system.
When and why should CAs be considered?
Usually, all products have a design MTBF, which is higher than the target MTBF. By analysing the failures that occur during the lifespan of the product, the real MTBF value is calculated. This number should be equal or higher than the target MTBF. However, failure analysis can show that the reliability of the product is underperforming compared to the design. FRACAS enables the manufacturer to track the component failures of the system, meaning that the real MTBF of a part can be compared to the GTBF (Guaranteed Time Between Failures) provided by the supplier. If the MTBF of a part is considerably lower than the GTBF, a corrective action should be considered.
Another reason to consider initiating a corrective action would be that a part is replaced too many times without finding any kind of failure. Also, if a part is consistently misused by the crew to the point of breaking down, a corrective action could be considered to address this issue. In these two cases, the component itself might not have failed, but it is still causing a disruption in the use of the system.
Who is responsible for the CAs?
Corrective actions are solely a responsibility of the manufacturer of the product. Component suppliers or product users have no say in the matter. However, their interests should always be considered, since they will be affected by the corrective actions undertaken by the company. In most organizations, corrective actions are carried out by a reliability review board. Although the FRACAS process is performed on a weekly or even daily basis, the review board meets up periodically, from a monthly to a yearly basis, unless there is a huge issue that requires immediate action.
How are CAs implemented and tracked?
Normally, the work of the review board starts with an initial meeting, during which the data obtained from FRACAS is analysed. Components with recurring failures or an MTBF lower than intended are considered for a corrective action. The review board looks into the problem and tries to figure out a solution. For example, the component might be misused by the crew of the aircraft, it may be subjected to too much tension, the maintenance process might be erroneous or the supplier may have provided faulty data. According to the findings of the board, a corrective action is agreed to, such as updating the maintenance process, issuing a service bulletin with a new required modification or changing the supplier of the component.
An example of how to add a new corrective action to the database using the FRACAS module of the Robin RAMS assistant can be seen below. It is required to specify the AC type and the reason of the CA, and it is recommended to also fill the affected part, its ATA chapter, priority of the CA and any comment the user might deem interesting. The CA can be closed right away, although this is not usually the case. The list of CAs and their status can be tracked on a table containing all the relevant data.
After the initial meeting, the review board performs a tracking of the performance of the affected component in order to establish if the corrective action has resulted in the intended outcome. Usually, this translates into an improvement of the MTBF of the part. To do this, a reliability assessment at the relevant level (fleet, AC, system, part) is to be performed. The results can be plotted over time and compared to the target. After the reliability target for the component is achieved, the review board closes the corrective action.
Seen above are the resulting graphs obtained using Robin FRACAS. This module provides the user with a very convenient tool that allows for the computation of reliability assessments in an intuitive way with the possibility of analysing different levels, establishing conditions and specifying a given timeframe. After this, plotting the resulting statistics and graphs is very easy and helpful at the same time with Robin. Returning to the graph above, it shows how the MTBF of the part was considerably smaller than the GTBF. However, after the corrective action was implemented at the initial CA meeting, the part reliability rose above the target level. Once this was deemed satisfactory, the CA was closed during the final CA meeting.
Common practices in the industry
This process of
opening, tracking and closing the corrective actions is usually done with a
program assistance. Although acceptable results could be obtained using simply
Excel, most organizations use a specialized tool to track the effects of the corrective
actions on the component performance.
On a final note,
it is a common practice in the industry to subcontract part of the FRACAS
process to companies specialized on reliability. However, the manufacturer
should never give up the entire control over FRACAS to another company due to
the importance and possible ramifications of FRACAS to the performance of the
product.
Robin RAMS as a tool for FRACAS
Developed by DMD Solutions, Robin is a RAMS assistant tool that has been designed by aerospace engineers to support RAMS analyses. Relevant to this article is the FRACAS module of Robin, on of five offered by this tool. Robin FRACAS facilitates the collection, process, and analysis of failure reports and corrective actions in an effective and intuitive way.
Robin provides the user with full FRACAS capabilities, allowing them to manage the failure reports of a system or aircraft through a user-friendly platform. All data is integrated in a safe repository with secure management. Smart charts as the one seen above and integrated analysis for reliability parameters such as the MTBF can be obtained with Robin FRACAS. Moreover, Robin provides the user with an outstanding flexibility, allowing them to comfortably manage their data by facilitating data import and export.
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