Abstract
A validation study on the performance and vibration analyses of the XH-59A compound helicopter is conducted to establish techniques for the comprehensive analysis of lift-offset compound helicopters. This study considers the XH-59A lift-offset compound helicopter using a rigid coaxial rotor system as a verification model. CAMRAD II (Comprehensive Analytical Method of Rotorcraft Aerodynamics and Dynamics II), a comprehensive analysis code, is used as a tool for the performance, vibration, and loads analyses. A general free wake model, which is a more sophisticated wake model than other wake models, is used to obtain good results for the comprehensive analysis. Performance analyses of the XH-59A helicopter with and without auxiliary propulsion are conducted in various flight conditions. In addition, vibration analyses of the XH-59A compound helicopter configuration are conducted in the forward flight condition. The present comprehensive analysis results are in good agreement with the flight test and previous analyses. Therefore, techniques for the comprehensive analysis of lift-offset compound helicopters are appropriately established. Furthermore, the rotor lifts are calculated for the XH-59A lift-offset compound helicopter in the forward flight condition to investigate the airloads characteristics of the ABC™ (Advancing Blade Concept) rotor.
Highlights
Conventional helicopters have the advantages of vertical take-off/landing and hovering, but their maximum forward flight speed, which is approximately 150–170 knots, is very slow compared to fixed-wing aircraft
ABC can be expressed as lift-offset (LOS), which can be calculated by dividing the rolling moment of each rotor by its thrust
This study considers the XH-59A technical demonstrator as a validation model of the comprehensive analysis of the liftoffset compound helicopter
Summary
Conventional helicopters have the advantages of vertical take-off/landing and hovering, but their maximum forward flight speed, which is approximately 150–170 knots, is very slow compared to fixed-wing aircraft. ABC is a technology that enables high-speed forward flight of helicopters, and it uses a counterrotating rigid coaxial rotor. In case of the XH-59A helicopter, flight test results showed serious 3P cockpit vibration during highspeed forward flight due to the rigid coaxial rotor and the absence of a vibration control system [3]. Both performance and vibration analyses are important when developing compound rotorcrafts using a rigid coaxial rotor. Few studies using comprehensive analysis codes for performance and vibration analyses have been conducted, despite the development of lift-offset compound helicopters
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