The Effect of blade torsional elasticity on helicopter flight dynamics

Download

index.pdf

Date

2017

Author

Akel, Ezgi

Metadata

Show full item record

Item Usage Stats

315
views

322
downloads

Helicopter design and test stages require more complex and high fidelity flight dynamic models to aid the design process of the helicopters. In the common approach, rigid rotor blades models are used in the flight dynamics models and since this is a fast modeling method. However, increased flexibility of the rotor blades necessitates the use of elastic blade models to have more accurate prediction of the rotor loads and the control angles. Elasticity brings extra fidelity to the flight dynamics model which is extensively used in design stage of a helicopter. In this study, an in house helicopter flight dynamics code (TOROS) which is in Matlab/Simulink Environment and developed by TUSAS Helicopter department is used as the analysis tool. This tool includes a trim model and a six degree of freedom helicopter model with blades modeled rigidly modeled in flap, lag and torsional direction. The mathematical model of a helicopter generated in in house tool is first validated with the commercial FLIGHTLAB model. In the next stage, elastic blade model is integrated to TOROS. In this study, in the elastic blade model flexibility is added only to the torsional degree of freedom. The added torsional flexibility of the blade accounts for change in the aerodynamic and inertial forces with respect to rigid blade model, resulting in more accurate prediction of the control angles. Tip deflections of the torsionally elastic blade is compared with the results of the finite element based multibody dynamics code Dymore. A finite element modelling capability is added to the in house flight dynamics model to perform trim in level flight, autorotation and transient analyses utilizing both rigid and torsionally elastic blade models. Static longitudinal stability analyses of the helicopter are conducted with rigid and elastic blade models to investigate the effect of elastic blade in the torsional direction on the flight mechanics trim analyses and stability. The result of the study is elastic blades in torsional direction has a direct effect on pitch angle of the blades and hence on collective control. The static stability of the system is also affected in a negative way when the blades are elastic in torsion. Elastic effects should be considered during design process.

Subject Keywords

Blades., Torsion., Elasticity., Helicopters.

URI

http://etd.lib.metu.edu.tr/upload/12621654/index.pdf
https://hdl.handle.net/11511/26890

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Development of a comprehensive and modular modelling, analysis and simulation tool for helicopters Yücekayalı, Arda; Kutay, Ali Türker; Department of Aerospace Engineering (2011) Helicopter flight dynamic, rotor aerodynamic and dynamic analyses activities have been a great dispute since the first helicopters, at both design and test stages. Predicting rotor aerodynamic and dynamic characteristics, helicopter dynamic behavior and trimmed flight conditions is a huge challenge to engineers as it involves the tradeoff between accuracy, fidelity, complexity and computational cost. Flight dynamic activities such as; predicting trim conditions, helicopter dynamic behavior and simulation of...
Multidisciplinary and multiobjective design optimization of an unmanned combat aerial vehicle (UCAV) Çavuş, Nesrin; Tekinalp, Ozan; Department of Aerospace Engineering (2009) The Multiple Cooling Multi-Objective Simulated Annealing Algorithm is used for the conceptual design optimization of a supersonic Unmanned Combat Aerial Vehicle (UCAV). Single and multiobjective optimization problems are addressed while limiting performance requirements between desired bounds to obtain viable aircraft configurations. A conceptual aircraft design code was prepared for planned but flexible combat missions. The results demonstrate that the optimization technique employed is an effective tool f...
Modeling and controller design of a VTOL air vehicle Önen, Anıl Sami; Tekinalp, Ozan; Kurtuluş, Dilek Funda; Department of Aerospace Engineering (2015) This thesis focuses on modeling, controller design, production and flight test of a VTOL unmanned air vehicle. The air vehicle that is designed and manufactured for this study has three propellers. A nonlinear mathematical model of the aircraft is developed. For this both numerical codes as well as wind tunnel tests have been carried out. A simulation code is then written in MATLAB/Simulink environment that describes the physical properties of the system in detail. After trimming the air vehicle at appropri...
Development of an advanced composite external fuel tank for air platforms Karahan, Uğurcan; Parnas, Kemal Levend; Department of Mechanical Engineering (2014) This thesis provides a design approach for an external fuel tank, which permits external mounting to the air platforms including rotorcrafts and aircrafts. The development stages include both a computational and an experimental study. In this thesis, unique combination of advanced composite material solutions is investigated in the structural design process. Filament-wound tank structure is modeled as multi-layered orthotropic structure. Various worst-case loading scenarios defined by internationally recogn...
An ontology for trajectory simulation Durak, Umut; Oğuztüzün, Mehmet Halit S.; Ider, S. Kemal (2006-12-06) From the concept exploration for a weapon system to training simulators, from hardware-in-the-loop simulators to mission planning tools, trajectory simulations are used throughout the life cycle of a weapon system. A trajectory simulation can be defined as a computational tool to calculate the flight path and flight parameters of munitions. There is a wide span of trajectory simulations differing widely with respect to their performance and fidelity characteristics, from simple point-mass simulations to six...

Citation Formats

E. Akel, “The Effect of blade torsional elasticity on helicopter flight dynamics,” M.S. - Master of Science, Middle East Technical University, 2017.