Aircraft Structure Validation via Integrated Roll Test Modal Analysis
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Solution Overview
Problem
The process of validating finite element (FE) models for wide-bodied aircraft is time-consuming and expensive due to the need for extensive ground vibration tests, which are typically performed just before the maiden flight, and there is a need to reduce the effort involved in this validation process.
Innovation Solution
Conducting part or all of the vibration tests to validate the FE model as part of roll tests, where the aircraft structure is excited by rolling over uneven ground, allowing for the use of existing sensors and potentially reducing the need for additional equipment, and employing an output-only modal analysis to determine the structural dynamic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ground vibration tests are conducted to validate the FE model, then the validation accuracy is improved, but the time and cost required increase significantly
Solution Approach 1:
The patent combines the previously separate ground vibration test and roll test into a single integrated roll test procedure. By doing so, the modal data for FE model validation is obtained during the roll test itself, eliminating the need for a separate ground vibration test. This merging of test procedures directly reduces the total testing time while maintaining validation accuracy through the use of output-only modal analysis techniques.
Solution Approach 2:
The roll test is enhanced to serve multiple functions: it qualifies the landing gear and engines (original purpose) and simultaneously validates the FE model through modal analysis (new function). This multi-functionality allows the same test to achieve multiple certification objectives, reducing overall testing time and resource requirements while maintaining measurement precision through advanced signal processing techniques.
2Measurement precision
If ground vibration tests are conducted to validate the FE model, then the validation accuracy is improved, but the cost and resource requirements increase
Solution Approach 1:
The patent merges the equipment requirements for ground vibration tests and roll tests into a single set of equipment needed for the integrated roll test. By conducting modal analysis during the roll test using existing sensors and signal processing methods, the patent eliminates the need for separate ground vibration test equipment, acceleration sensors, and wiring infrastructure, thereby reducing device complexity and resource requirements while maintaining validation accuracy.
Solution Approach 2:
The roll test procedure is enhanced to self-validate the FE model using its own measurement data. The existing sensors on the aircraft structure during the roll test capture the necessary vibration data, which is then processed through output-only modal analysis to validate the FE model. This self-service approach eliminates the need for separate validation equipment and external testing infrastructure.
3Reliability
If separate ground vibration tests are conducted before maiden flight, then the FE model validation is ensured, but the scheduling flexibility is reduced
Solution Approach 1:
The patent combines FE model validation with the roll test that is already scheduled as part of the certification process. By integrating the modal analysis into the roll test, the patent eliminates the need for a separate ground vibration test milestone, thereby ensuring FE model validation while improving scheduling flexibility and overall certification productivity. This merging allows manufacturers to complete validation activities during routinely scheduled tests rather than adding separate dedicated test events.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces the time and resources required for validation, allowing for more efficient use of existing testing procedures and potentially eliminating the need for stationary vibration tests, thereby saving time and material while ensuring accurate FE model validation.
Implementation Method 1
the aircraft structure is excited to vibrate by rolling the landing gear over uneven ground
Implementation Method 2
The vibrations of the aircraft structure are recorded with individual acceleration sensors
Data Source
Figure 1
AI summary
The method involves positioning a model of an aircraft structure (1) of an aircraft (2), using finite elements (FEs), and performing vibration tests for validating FE model (4). Stimulated vibrations of the aircraft structure are detected. A flatter stability analysis of the aircraft structure is performed based on the validated FE model. Roll tests for a qualification of an undercarriage (5) of the aircraft are performed. A part of the vibration tests is performed within the roll tests. The aircraft structure is measured by rollers of the undercarriage over surface unevenness (11-13).