Advancing the Development of Condition-Based Maintenance for Commercial Transport Aircraft Structure

Condition-Based Maintenance (CBM) is gaining momentum in civil aviation, yet its widespread adoption remains constrained by economic and regulatory aspects (Verhagen et al. 2023, Meissner et al. 2025). In contrast, sectors like civil infrastructure, marine, and military aviation have successfully applied CBM for decades, leveraging active Structural Health Monitoring (SHM) systems to optimize maintenance and operations. This paper examines the progress and potential of CBM in civil aviation, focusing on active monitoring of structural performance. CBM relies on availability of data, which active SHM systems can provide. While modern commercial aircraft generate extensive data for flight controls, navigation and systems, data specifically useful for structural health assessment is comparatively limited. Boeing is developing passive monitoring applications, prioritizing in-service crack detection, addressing common maintenance requests. CBM offers a comprehensive framework integrating these passive methods with active monitoring technologies, enhancing maintenance strategies. As Boeing and the civil aviation industry move toward CBM frameworks, it is crucial to recognize that CBM is more than an economic tool. Beyond assisting fleet management, CBM is a predictive approach that enhances safety, anticipating structural issues before they become critical. Regulatory agencies are increasingly issuing guidelines defining requirements and scope for monitoring systems and data use. To gain certification, SHM and CBM systems must comply with these standards, and current development efforts focus on meeting them. Passive monitoring provides discrete data points, such as during scheduled inspections, whereas active SHM offers real-time data. This continuous stream of data serves two main purposes: updating predictions and validating assumptions about structural performance. For example, active SHM can monitor aircraft utilization metrics like flight cycles and operating fuselage pressures, critical to assess fatigue life and damage progression of metal details. Historically, commercial transport aircraft structure is designed based on various mission profiles such as short, medium or long flights. Durability requirements are used to design airframe structure to be crack-free up to a defined Design Service Objective (DSO), with defined reliability target and confidence level. Damage Tolerance (DT) analysis provides inspection intervals and methods based on the most critical mission profile. However, actual aircraft or fleet usage often deviates from these standard profiles. Active SHM enables user-specific mission profiles by monitoring real operational parameters, including fuselage pressure cycles, among others. This tailored data could refine predictions of fatigue and damage tolerance to provide operators relief from the baseline inspection programs. Furthermore, SHM enables automation of feedback loops through Digital Twin models, which are essential for fully realizing CBM capabilities (Fig. 1). This paper discusses examples of potential active SHM/CBM applications, focusing on monitoring inputs like fuselage pressure and temperature, illustrating how these technologies can affect maintenance practices in civil aviation. References: Verhagen WJC, Santos BF, Freeman F, van Kessel P, Zarouchas D, Loutas T, Yeun RCK and Heiets I. 2023. Condition-Based Maintenance in Aviation: Challenges and Opportunities. Aerospace, 10(9). Meissner R, Ali Pohya A, Weiss O, Piotrowski D & Wende G. 2025. Regulatory pathways to certifiable condition based maintenance solutions in aviation: A comprehensive review. Progress in Aerospace Sciences, 158.