Certifiable Condition-Based Maintenance in Civil Aviation: A Review of Regulatory Approaches

Abstract

One of the biggest innovation fields in the aviation industry is currently its digital transformation. With the vast technological challenges associated, various aspects of a digitalized aerospace sector have been subject to numerous research fields already. Since aircraft maintenance contributes significant portions to the overall operating expenditures for an airline, it has received substantial research focus in the past decade. In particular, the introduction of Condition Based Maintenance (CBM) strategies promise substantial cost saving potentials by avoiding unscheduled maintenance events due to unforeseen failures and reducing scheduled maintenance efforts such as repetitive inspections or functional checks. Consequently, much research has focused the development of technical capabilities for an automated condition monitoring, fault diagnosis, and failure prognosis. However, still, the application of these technologies as certified scheduled maintenance alternate is often limited to non-safety-critical functions. While the need for change in the regulatory framework has been recognized by industry and regulatory bodies, the developed ideas for a potential pathway for certification leave issued that will need to be addressed. Among others, these are: (a) IP180 & IP211 have introduced a Level 3 analysis to the industry-standard MSG-3 methodology to identify an Aircraft Health Management (AHM) alternate for a scheduled maintenance task. However, while it requires to determine the effectiveness and timeliness of failure detections by AHM technologies, no further guidance is given how this determination can be made, (b) arguably, it will be necessary for future AHM alternates to provide the capability of a maintenance ground interface – be it because of remote vehicle operations or because of extensive computation requirements. The current ideas mentioned above do not address this off-board processing and maintenance decision making, (c) currently, the definition of scheduled maintenance tasks is performed as part of the Maintenance Review Board (MRB) process in accordance with CS25.1529 – mostly separated from the system design process as of CS25.1309. However, since AHM technologies will need to be an integral part of any future system design concepts (in alignment with the established OSA CBM model for the development of End-to-End processes), this strict distinction will need to be critically evaluated. Therefore, with this presentation, we will review existing standards for the certification of health monitoring technologies – such as the Health and Usage Monitoring System (HUMS) for rotorcraft applications – and map their key characteristics with the steps of an End-to-End automated maintenance process. As a consequence, we can identify, how the existing solutions can be applied to the certification of scheduled maintenance for commercial fixed-wing aircraft and what key pieces are missing and will need to be defined by future research. Additionally, we will be able to derive recommendation for the technological maturation of automated condition monitoring technologies to expedite the transfer from research to (certified) commercial applications.