Rotorcraft Model Research Articles

Response of a rotorcraft model with damping non-linearities

The linearized equations of motion of a helicopter in contact with the ground have solutions which can be linearly stable or unstable, depending on the system parameters. The present study includes physical non-linearities in the helicopter model. This allows one to determine if a steady-state response exists and, if so, what the frequency and amplitude of the oscillations will be. In this way, one can determine how serious the linearly unstable operating regime is and whether destructive oscillations are possible when the system is in the linearly stable regime. The present analysis applies to helicopters having fully articulated rotors.

Limit Cycle Oscillations of a Nonlinear Rotorcraft Model

Les etudes anterieures de la stabilite d'un helicoptere se sont basees sur une formulation lineaire du systeme. On examine ici le probleme de la stabilite d'un point de vue non lineaire, et on etudie le comportement de cycle limite d'un appareil ayant une caracteristique d'amortissement non lineaire. L'influence des variations des parametres sur la reponse du systeme a ete examinee, et les differences entre un modele lineaire et un modele non lineaire presentees

A General Rotor Model System for Wind-Tunnel Investigations

A complex rotorcraft model system has been developed for the NASA Langley Research Center and the U.S. Army Air Mobility R&D Laboratory, Langley Directorate, for aerodynamic and acoustic experimental investigations in the NASA Langley V/STOL tunnel. This generalized rotor model system has a powered main rotor, tail rotor, and auxiliary engine capability. It may be configured to represent a variety of rotorcraft configurations. The first investigation was conducted to determine the performance, acoustic, stability, and control characteristics of the NASA/Army Rotor Systems Research Aircraft with an articulated rotor. In a second investigation, a V*-scale AH-1G configuration with a teetering rotor is being represented to determine if a V-tail will improve the directional characteristics. Future programs are planned to investigate advanced rotor blade airfoils for improved performance and acoustic characteristics.

1303. Electron density behaviour near the axis of a turbulent hypersonic sphere wake: D Heckman et al, Can J Phys, 52 (4), 1974, 355–360

The availability of accurate models for helicopter aeromechanics is becoming more and more important, as rotorcraft flight control systems have to meet progressively more stringent performance requirements: as the required control bandwidth increases, model accuracy becomes a vital part of the design problem. In this paper, the results of a joint industry-academia research project aimed at developing a novel time/frequency domain approach to rotorcraft model identification will be presented and discussed. The proposed approach will be illustrated by means of a case study based on data collected during piloted simulations of a state-of-the-art flight dynamics code.