Design Methodology for Developing Concept Independent Rotorcraft Analysis and Design Software

Many comprehensive rotorcraft performance analysis tools have been developed to assist engineers during the preliminary and detailed phases of rotorcraft design. However, most of these tools are not appropriate for conceptual design because they are either too concept specific or too cumbersome for sizing and comparing the performance of vastly different concepts in a timely manner. A need exists to develop software tools which are capable of quickly sizing various concepts (i.e. single main rotor helicopter, coaxial rotor helicopter, tilt rotor, etc.) in order to assist engineers in selecting the best concept to satisfy a set of mission requirements. As an illustration, the Concept Independent Rotorcraft Analysis and Design Software (CIRADS) developed at Georgia Institute of Technology is presented to demonstrate the applicability of such software tools. CIRADS is a modular object oriented software application with a graphical user interface (GUI) developed using the Java programming language and optimization algorithms developed in MATLAB but compiled as a stand alone Windows executable. The GUI is used to define mission and sizing requirements, aircraft configurations, engines, and airfoils which are saved as separate transferable object files for use in analysis or design simulations. Performance parameters are calculated using a modified momentum theory based model developed using a generic rotorcraft concept with arbitrary rotor nacelle angle and optional wings, auxiliary propulsion, and anti-torque. Additional provisions for combined blade element momentum theory (CBEM) based performance models have been planned and partially developed for future integration. Iterative ratio of fuel (RF) sizing and optimization algorithms are used to determine the minimum gross weight for a given configuration based on the mission requirements and rotorcraft component parameters. Advanced design features accommodate the sizing and analysis of innovative concepts such as coaxial mono-tilt rotors, boxed wing tail sitters, and aircraft with dynamically morphing rotor diameters and airfoil properties. Through the development of CIRADS and its predecessors, three recommended objectives have been established for developing future software tools. The software should 1) have a broad capability of quickly modeling various rotorcraft concepts with different mission requirements, 2) have a very intuitive graphical user interface that allows users of different backgrounds and experience levels to use it without extensive formal training, and 3) allow users to specify different levels of component detail and different calculation methods with varying degrees of accuracy and processing time to support multiple phases of design. CIRADS has proven to be very effective in assisting rotorcraft design teams at Georgia Tech during the AHS student design competitions and will potentially be a model for developing future software tools which are widely used for conceptual and preliminary design in the rotorcraft industry.