Impact of helicopter main rotor, airframe and landing gear interactions on airframe loads during landings

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2023-1-04

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Uygun, Ahmed Levent

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The complex and challenging landing problem in helicopters has long been studied using a combination of analytical models and experimental tests. This study takes a comprehensive approach by utilizing multi-body dynamics analysis of a 6-ton class helicopter to simulate various landing maneuvers in accordance with the certification standards set by organizations such as EASA and FAA. The conventional methods tend to focus solely on the interaction between the airframe and landing gear, neglecting the crucial role of rotor dynamics. This study aims to examine the complex and nonlinear interplay between the airframe, landing gear, and rotor during landing, and its impact on airframe loads. The results of the study showed that conventional methods calculate the ground reactions relatively accurately, but not airframe accelerations. One cause of this discrepancy was found to be the gyroscopic effect of the rotor, which introduces pitch-roll coupling, leading to unbalanced forces. The study also revealed that the generally accepted assumption of constant lift during landing was invalid, as lift decreases upon touch down due to the rotor blades' flapping degree of freedom, resulting in increased critical loads. Additionally, the aerodynamic forces acting on the blades were found to fluctuate during touch down. The findings of this study highlight the limitations of conventional methods and the need for a more comprehensive approach that considers the effects of rotor dynamics and blade behavior during helicopter landing.

Subject Keywords

Helicopter, Landing, Airframe loads, Landing gear loads, Multi-body dynamics

URI

https://hdl.handle.net/11511/101984

Collections

Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

A. L. Uygun, “Impact of helicopter main rotor, airframe and landing gear interactions on airframe loads during landings,” M.S. - Master of Science, Middle East Technical University, 2023.