This paper aims to analyze the characteristics of a two-bladed gimballed rotor featuring a homokinetic joint between driving shaft and rotor yoke and a fly-bar with paddles. Blades are connected to the yoke by coning hinges. A pitch--coning link is introduced for gust load alleviation. The design and testing of this rotor configuration is part of the development program of a lightweight helicopter in the VLR rotorcraft certification framework. The rotor is designed with the main objective of solving some of the negative issues that affect the use of teetering rotors on light helicopters, such as strong 2/rev oscillatory loads, poor response at low $g$'s and a pronounced sensitivity to gusts and/or large pilot inputs. The work is focused on stability issues related to the presence of coning hinges and their effects on rotor response and loads transmitted to the hub, affected by the variation of mass properties associated to (possibly non--symmetric) coning rotations. To this end a dynamic model is developed, that captures the most relevant aspects of the mechanical interactions between blades and yoke. Numerical simulation and stability analysis are performed to assess possible advantages of the configuration with respect to a conventional teetering rotor.
Stability and Response of Two-Bladed Gimballed Rotors with Coning Hinges
AVANZINI, Giulio;
2011-01-01
Abstract
This paper aims to analyze the characteristics of a two-bladed gimballed rotor featuring a homokinetic joint between driving shaft and rotor yoke and a fly-bar with paddles. Blades are connected to the yoke by coning hinges. A pitch--coning link is introduced for gust load alleviation. The design and testing of this rotor configuration is part of the development program of a lightweight helicopter in the VLR rotorcraft certification framework. The rotor is designed with the main objective of solving some of the negative issues that affect the use of teetering rotors on light helicopters, such as strong 2/rev oscillatory loads, poor response at low $g$'s and a pronounced sensitivity to gusts and/or large pilot inputs. The work is focused on stability issues related to the presence of coning hinges and their effects on rotor response and loads transmitted to the hub, affected by the variation of mass properties associated to (possibly non--symmetric) coning rotations. To this end a dynamic model is developed, that captures the most relevant aspects of the mechanical interactions between blades and yoke. Numerical simulation and stability analysis are performed to assess possible advantages of the configuration with respect to a conventional teetering rotor.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
