Influence of Landing-Gear Design on Helicopter Ground Resonance
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Bibliographic record
Abstract
The influence of landing-gear design on a ground-resonance phenomenon is investigated with the aid of finite-element software. Ground resonance is a vibration phenomenon that occurs at certain rotor speeds when the helicopter is on the ground. Mathematically, the instability occurs when the regressing lead-lag frequency of the rotor couples with one of the natural frequencies of the fuselage, which in turn is modelled as a rigid body supported on a flexible landing gear. In this paper, two approaches are proposed to study the effect of landing-gear design parameters on ground-resonance instabilities. In the first solution, ANSYS is used to define a detailed finite-element model of a particular landing-gear configuration and then, to obtain the mass, stiffness, and damping matrices of the gear with respect to the craft's center-of-mass degrees of freedom. These matrices are subsequently used in a standard ground-resonance mathematical model to calculate the regions of instability of the helicopter. The second approach uses a modal analysis of the fuselage and the uncoupled rotor system in ANSYS. The fuselage is modelled as in the first approach while the rotor is represented with a finite-element model, consisting of flexible blades interconnected to rigid offsets with lead-lag hinges and springs. This methodology provides a good approximation of the center of the ground-resonance instability, but does not predict its severity. By contrast, the coupled ground-resonance analysis (first approach) predicts the severity and width of the instabilities, in addition to their location as a function of rotor speed. Results obtained with both methods for landing gear manufactured from aluminium and composite materials are presented. As well, variations in landing-gear height, cross-tube spread, and location of cross-tube attachment points to the fuselage are investigated for their effect on ground-resonance instability. All results are integrated to develop landing-gear-design guidelines to prevent the ground-resonance instability.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it