Reconsidering the Theory and Application of Helicopter Maneuverability

Energy-maneuverability diagrams are an important tool that operational pilots use to understand helicopter maneuver performance across a wide range of conditions, however these representations are based upon a number of assumptions that have not been rigorously investigated. The present work reports the results of an investigation into the theory and application of helicopter maneuverability through simulation and flight test. The computational portion of the work focused on a systematic investigation into some of the key simplifying assumptions that are commonly applied in the creation of energy-maneuverability representations. This investigation included aerodynamic simulations of steady maneuvers using a dynamic inflow model as well as a free vortex method. The flight test portion of the work provided important operational context for understanding the practical application of the simulation results. The study illustrated that the fundamental assumption employed in estimating maneuver power requirements for energy-maneuverability representations appears to be reasonable in conditions of the greatest practical relevance, however another key assumption that is invoked to convert excess power into climb performance would likely lead to overestimating the vehicle capability in important operational conditions. Additionally, the flight test data demonstrated that energy-maneuverability results for high angles of bank should be considered for trending information rather than for detailed climb performance values.