From UAV-Based Sensing to Digital Twin Updating: A Traceable Framework for Aircraft Defect Inspection

Reliable and traceable assessment of aircraft wing skins remains a persistent bottleneck in Maintenance, Repair, and Overhaul (MRO), where adequate coverage, repeatability, and metrological credibility must be achieved with minimal aircraft downtime. This study proposes an integrated inspection-to-maintenance digital thread for a single dent on the left wing skin (Station 540), combining a coordinated dual-Unmanned Aerial Vehicle (UAV) workflow with a high-fidelity, interactive digital twin and standards-aligned maintenance decision support. A reconnaissance UAV performs wide-area coverage along a point-cloud-driven 3D path and flags candidate surface anomalies, logging time-synchronised imagery, vehicle state, and detection metadata to a Ground Control Station (GCS). A second UAV then executes targeted close-range acquisitions over the dent under photogrammetric constraints (overlap, baseline, and incidence control) to enable Structure-from-Motion/Multi-View Stereo (SfM/MVS) reconstruction and recovery of metric dent geometry, including depth and footprint, in the wing reference frame. Post-mission, the digital twin - initialised from high-accuracy laser scanning - is updated by projecting the defect appearance through a virtual camera configured to match the in-flight intrinsics/Field of View (FOV) and by locally deforming the mesh according to the reconstructed depth field, with reprojection residuals retained as traceability evidence. The resulting 'as-inspected' twin supports a structured Technical Advisory Group (TAG) assessment (Stages 1-2) for Principal Structural Element (PSE) relevance and repair classification, followed by Structural Repair Manual (SRM)-bounded repair definition, controlled physical execution, and post-repair verification via UAV re-scan and twin-based deviation analysis. In parallel, topological and morphological 3D analysis operators are screened to identify measurement primitives that provide repeatable, metrology-consistent outputs under reconstruction noise. The overall methodology is further consolidated within an Model-Based Systems Engineering (MBSE) model to preserve end-to-end provenance, interface contracts, and requirement-verification links, facilitating integration with MRO quality gates and future scalability to broader damage cases and operating conditions.