N 8 8-1663 0 Comprehensive Rotorcraff Analysis Methods
The paper describes the development and application of comprehensive rotorcraft analysis methods in the field of rotorcraft technology. These large scale analyses and the resulting computer programs are intended to treat the complex a_'.romechanicM phenomena that describe the behavior of rotorcraft. They may be used to predict rotor aerodynamics, acoustics, performance, stability and control, handling qualities, loads and vibrations, structures, dynamics, and aeroelutic stability characteristics for a variety of applications including research, preliminary and detail design, and evaluation and treatment of field problems. The principal comprehensive methods developed or under development in recent year1 and generally available to the rotorcraft community because of US Army Aviation Research and Technology Activity (ARTA) sponsorship of all or part of the software systems are the Rotorcraft Flight Simulation (C81), Dynamic System Coupler (DYSCO), Coupled Rotor/Airframe Vibration Analysis Program (SIMVIB), Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics (CAMRAD), General Rotorcraft Aeromechanical Stability Program {GRASP}, and Second Generation Comprehensive Helicopter Analysis System (2GCHAS). 312 https://ntrs.nasa.gov/search.jsp?R=19880007247 2018-04-23T06:50:56+00:00Z
Use of rotorcraft computer analysis for U.S. government design assessment
Abstract Rotorcraft Computer Analysis is used by the U.S. Government to evaluate independently new concepts and responses to request for proposals (RFPs). This paper will describe how it is used during concept formulation and on source selection evaluation boards (SSEBs), why it is essential, and how it must be integrated with other considerations. The Army Helicopter Improvement Program (AHIP) SSEB and the LHX Concept Formulation effort will be used as examples.
A doublet lattice method for the determination of rotor induced empennage vibration airloads. Analysis description and program documentation
An efficient state-of-the-art method was developed to determine the unteady vibratory airloads produced by the interaction of the main rotor wake with a helicopter empennage. This method was incorporated into a computer program, Rotor Induced Empennage Vibration Analysis (RIEVA). The program requires the main rotor wake position and the strength of the vortices locates near the empennage surfaces. A nonlinear lifting surface analysis is utilized to predict the aerodynamic loads on the empennage surfaces in the presence of these concentrated vortices. The analysis was formulated to include all pertinent effects such as suction of the interacting vortices and the shed vorticity behind the empennage surfaces. The analysis employs a time domain solution. The output of the program consists of chordwise and spanwise airload distributions on the empennage surfaces. The airload distributions are harmonically analyzed and formulated for input into the Coupled Rotor/Airframe Vibration Analysis.