Understanding the Effect of Rotor-to-Rotor Interference on CH-47D Helicopter Dynamics

2021 ◽  
Author(s):  
Feyyaz Guner ◽  
David G. Miller ◽  
J. V. R. Prasad
Keyword(s):  
Flight Control ◽  
Influence Factors ◽  
Flight Test ◽  
Flight Simulation ◽  
Flight Control System ◽  
Pressure Potential ◽  
Handling Qualities ◽  
Helicopter Flight ◽  
Lateral Inflow ◽  
Lateral Axis

During the development of the Boeing CH-47D helicopter flight simulation model, test pilots reported mismatch between the flight simulator results and flight test data of the hover and low-speed lateral axis handling qualities, especially for the case without the automatic flight control system. In addressing the observed mismatch, the gains of the longitudinal and lateral components of the inflow model were selected to be significantly higher than their theoretical values. In this study, a detailed understanding of the rotor-to-rotor inflow interference is pursued using a recently developed multi-rotor pressure potential superposition inflow model. It is shown that the coupling between the inflow gradients of individual rotors exists in a tandem rotor, which can be approximated by using higher values for the longitudinal and lateral inflow gains of individual rotors. Further, it is shown that the need for empirical tuning of aerodynamic hub moment influence factors can be eliminated by properly accounting for the rotor-to-rotor interference in the inflow model.

Design, Flight Simulation, and Handling Qualities Evaluation of an LPV Gain-Scheduled Helicopter Flight Control System

2000 ◽  
Vol 6 (6) ◽  
pp. 553-566 ◽  
Author(s):  
Ian Postlethwaite ◽  
Ioannis K. Konstantopoulos ◽  
Xiao-Dong Sun ◽  
Daniel J. Walker ◽  
Adrian G. Alford
Keyword(s):  
Control System ◽  
Flight Control ◽  
Flight Simulation ◽  
Flight Control System ◽  
Handling Qualities ◽  
Helicopter Flight ◽  
Gain Scheduled

Design and Flight Test of a Cable Angle Feedback Flight Control System for the RASCAL JUH-60 Helicopter

2014 ◽  
Vol 59 (4) ◽  
pp. 1-15 ◽  
Author(s):  
Christina M. Ivler ◽  
J. David Powell ◽  
Mark B. Tischler ◽  
Jay W. Fletcher ◽  
Carl Ott
Keyword(s):  
Control System ◽  
Flight Control ◽  
Flight Test ◽  
Feedback System ◽  
Military Operations ◽  
Flight Control System ◽  
Handling Qualities ◽  
Maneuvering Flight ◽  
Rate Feedback ◽  
Tailored Approach

The ability of a helicopter to carry externally slung loads makes it very versatile for many civil and military operations. However, the piloted handling qualities of the helicopter are degraded by the presence of the slung load. A control system is developed that uses measurements of the slung load motions as well as conventional fuselage feedback to improve the handling qualities for hover/low-speed operations. Prior research has shown a fundamental trade-off between load damping and piloted handling qualities for a feedback control system with cable angle/rate feedback. A new task-tailored approach proposed and implemented herein uses a method of switching between a load damping mode and a piloted handling qualities mode. These modes provide appropriate load feedback depending on the piloting task and flight regime. This provides improved handling qualities for maneuvering flight and for improved precision load control at hover. A new mission task element for precision load placement is developed (for possible inclusion into ADS-33E-PRF) to test the ability of the cable feedback system to improve load placement task performance. The improvements provided by this control system are demonstrated in a piloted flight test on the JUH-60A RASCAL fly-by-wire helicopter. The average load set-down time was reduced by a factor of two for the 1000-lb load on a 56-ft sling.

Distributed Turbulence Model with Rigorous Spatial Cross-Correlation for Simulation of Helicopter Flight in Atmospheric Turbulence

2019 ◽  
Vol 64 (4) ◽  
pp. 1-13
Author(s):  
Honglei Ji ◽  
Renliang Chen ◽  
Pan Li
Keyword(s):  
Atmospheric Turbulence ◽  
Turbulence Model ◽  
Cross Correlation ◽  
Turbulence Models ◽  
Flight Test ◽  
Longitudinal Direction ◽  
Flight Simulation ◽  
Quality Analysis ◽  
Frequency Range ◽  
Helicopter Flight

This paper presents a distributed turbulence model with rigorous spatial cross-correlation for helicopter flight simulation in atmospheric turbulence and for future handling-quality analysis. First, digital filters with longitudinal correlations of the von Kármán turbulence are developed to generate discrete turbulence velocity components. Meanwhile, transverse turbulence correlations are considered by relating the filters in different positions with mathematically rigorous spatial cross-correlation. Then, the distributions of the related filters on the transverse plane in front of helicopter and their velocity components in the longitudinal direction of airspeed, as well as turbulence models of helicopter aerodynamic surfaces, are established. Finally, a flight dynamics model coupled with the turbulence model is developed and validated against the flight-test data. The proposed model can achieve accurate real-time simulations of helicopter response to atmospheric turbulence in the frequency range of interest of handling qualities. The effect of transverse turbulence correlations on helicopter frequency response is also analyzed. The results show that the simulation model regardless of transverse turbulence correlations would aggravate the "rotor-to-body attenuation" effect of the main rotor and therefore underpredict the helicopter roll, pitch, and heave rate responses to atmospheric turbulence in the frequency range of interest.

scholarly journals A Novel Comprehensive Kinematic and Inverse Dynamic Model for the Flybar-Less Swashplate Mechanism: Application on a Small-Scale Unmanned Helicopter

Symmetry ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 1849
Author(s):  
Jianbo Liu ◽  
Rongqiang Guan ◽  
Yongming Yao ◽  
Hui Wang ◽  
Linqiang Hu
Keyword(s):  
Dynamic Model ◽  
Flight Control ◽  
Virtual Work ◽  
Influence Factors ◽  
Parallel Manipulators ◽  
Small Scale ◽  
Unmanned Helicopter ◽  
Inverse Dynamic ◽  
Inverse Dynamic Model ◽  
Helicopter Flight

In this paper, we propose a novel kinematic and inverse dynamic model for the flybar-less (FBL) swashplate mechanism of a small-scale unmanned helicopter. The swashplate mechanism is an essential configuration of helicopter flight control systems. It is a complex, multi-loop chain mechanism that controls the main rotor. In recent years, the demand for compact swashplate designs has increased owing to the development of small-scale helicopters. The swashplate mechanism proposed in this paper is the latest architectures used for hingeless rotors without a Bell-Hiller mixer. Firstly, the kinematic analysis is derived from the parallel manipulators concepts. Then, based on the principle of virtual work, a methodology for deriving a closed-form dynamic equation of the FBL swashplate mechanism is developed. Finally, the correctness and efficiency of the presented analytical model are demonstrated by numerical examples and the influence factors of the loads acted on actuators are discussed.

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