Experimental Modal Analysis of Half-Scale Business Jet Aft Fuselage Section
Bibliographic record
Abstract
Abstract Structure borne noise caused by the engine is a significant source of discomfort for business aircraft passengers. Aircraft with fuselage mounted engines have increased structure borne noise levels in the cabin due to the shortened vibration transmission path. The research objective is to reduce structure vibrations in the aircraft cabin, yielding reduced noise output and increased passenger comfort. Experimental modal testing can identify the dynamic properties of a system (i.e. natural frequencies, mode shapes) which can be used to validate finite element models. This information can be used to guide structural dynamic modifications, reducing vibration levels in the structure. This research involved using modal testing with an electromechanical shaker to excite a half-scale model aft fuselage section at the engine support yolks and measuring the response at the bulkhead. A half scale model was used to reduce the complexity and time cost of experimentation. The results from excitation at each driving point were compared. This paper details the fuselage construction, methodology of excitation, validation techniques, and results. Experimental modes within the engine operating range (50 Hz to 400 Hz) were identified. The RESF-RESF and FESF-FESF measurements yielded an average of 63% more correlated mode pairs than the RESF-FESF measurements. This was expected due to structural symmetry about the longitudinal mid-plane. The results provide a basis for verifying and updating a finite element model in future work.
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How this classification was reachedexpand
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 | 0.001 |
| 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".