> _Since the natural frequencies do not match the frequencies of rotor (40.75 Hz for LUH Rotor Bending and 62.86 Hz for LUH Rotor Torsion), the helicopter is stable and safe for flight._ ## Overview This research investigates the dynamic behavior of the horizontal stabilizer and vertical fin of the **Light Utility Helicopter (LUH)**. The study is grounded in technical comparisons with the **Cheetal helicopter**, a re-engined variant of the Cheetah (Alouette II), known for its high-altitude performance. The study employs finite element analysis (FEA) to determine the natural frequencies of these components and assess their stability in flight. Ensuring that these frequencies do not match rotor vibration frequencies is crucial for the safety and structural integrity of the helicopter. Simulation setup in Altair Hypermesh

## Key Features - **Finite Element Analysis (FEA):** Conducted using HYPERMESH and NASTRAN to determine modal characteristics. - **Material and Design Considerations:** Composite fiber materials used for weight reduction and improved performance. - **Natural Frequency Calculation:** Comparison with rotor vibration frequencies to ensure stability. - **Structural Stability Evaluation:** Identifying potential resonance risks and ensuring the components' safety in dynamic conditions. ## Technical Specifications The study utilized reference data from the Cheetal helicopter to establish baseline performance metrics: - **Engine:** Turbomeca TM 333 2M2 (801 kW / 1073 shp) with FADEC control. - **Max Speed:** 280 km/h. - **Transmission:** Main Rotor Head operates at **353 RPM**. - **Service Ceiling:** Capable of high-altitude landings (record set at 23,220 ft / 7,070 m). ## Technologies Used - **HYPERMESH:** Altair Hypermesh for finite element meshing and model creation. - **NASTRAN:** For conducting modal analysis and obtaining natural frequencies. - **MATLAB:** Used for computing natural frequency and time response curves. - **Cheetah and Chetak Helicopter Systems:** Reference models used for transmission and structural behavior comparisons. ## Challenges and Learnings - **Complexity of Helicopter Dynamics:** Understanding the interaction of structural components with rotor-induced vibrations. - **Finite Element Modeling Accuracy:** Ensuring precise mesh generation and material property assignment for reliable results. - **Computational Limitations:** Balancing computational efficiency with high-fidelity analysis. - **Real-world Validation:** Comparing theoretical findings with real-world helicopter performance data. ### Model Information and Results

## Outcome The study confirms that the natural frequencies of the horizontal stabilizer and vertical fin do not coincide with the rotor’s vibration frequencies (40.75 Hz for bending and 62.86 Hz for torsion). This ensures that the LUH maintains stability and safety in flight. Future research can further refine computational models and explore the impact of additional structural modifications for enhanced performance. ## Presentation [Presentation in PDF](https://dhruvhaldar.vercel.app/documents/DynamicAnalysisofHorizontalStabilizerandVerticalFinppt.pdf)