Dependency distance and directionality in aviation maintenance English

Abstract Dependency distance minimization (DDM) operates as a universal principle in naturally evolving languages, driven by cognitive efficiency pressures favoring shorter dependencies. However, diachronic investigation of controlled languages remains absent. This study explored syntactic complexity evolution in aviation maintenance English over four decades of implementation of Simplified Technical English (STE), the dominant controlled language standard in international aviation. Situated within dependency grammar, we tracked both large-grained indices (dependency distance and direction) and fine-grained indices (dependency types and part-of-speech distributions) in continuously revised aircraft maintenance manuals from an industry-leading manufacturer (1982–2024). Results showed dependency distances increased before stabilizing around 2002–2003, while structures shifted toward more head-initial patterns. Fine-grained analysis revealed how grammatical changes across four subsystems collectively shaped these large-grained patterns. These findings extend DDM theory to controlled language contexts, carrying implications for controlled language design and training for the global aviation maintenance workforce, where second language English readers predominate.