Design and Integration Study of a Single-Panel Krueger Flap with “Butterfly” Kinematics for HLFC Applications

This study focuses on the mechanical design, kinematics and integration assessment of Krueger flap configurations developed for application on a Hybrid Laminar Flow Control (HLFC) Ground Based Demonstrator (GBD). Two high-lift flap geometries were initially explored: articulated “bull-nose” Krueger and a simplified single-panel configuration. Following a series of CAD analyses, the single-panel Krueger with a sharp leading edge was optimized, demonstrating favorable behavior while providing superior integration within the GBD framework. This configuration, coupled with a novel “butterfly” kinematic system, fulfills stringent geometric constraints without requiring modifications to the wing’s leading edge. Moreover, the design enables reliable sealing between the Krueger panel and the wing lower surface, ensuring operational robustness. The work encompasses design studies conducted using CATIA v5 environment. Additional attention was given to geometrical and operational constraints, including insect-shielding requirements, minimum chord dimensions, and stowage limitations, all while maintaining compatibility with suction-based laminar flow technologies. Both configurations—the bull-nose and the sharp leading edge Krueger—are presented, together with the kinematic design philosophy and results based on the space allocation into the wing leading edge . These results establish a practical framework for implementing advanced Krueger flap and kinematic concepts for hybrid laminar flow control technology.