Development of an Aeromechanics Solver for Loads and Stability of Hingeless Tiltrotors

Abstract

This paper presents a comprehensive prediction and validation of hingeless hub tiltrotor loads and stability. Compared to their present-day gimbaled hub counterparts, there is less understanding of hingeless hub tiltrotors. A new aeromechanics solver was developed at the University of Maryland for predictions of performance, loads, and aeroelastic stability of these proprotors. The solver was verified with U.S. Army results for a hypothetical rotor and validated with the only full-scale test data available: the Boeing Model 222 tests at the NASA Ames wind tunnel in 1972. The predictions showed satisfactory agreement with the U.S. Army results. Some discrepancies were observed with the limited Boeing test data. An exploration was then carried out over a wider envelope to discover the unique flutter characteristics of these hubs. The principal conclusion is that their behavior is very different from gimbaled hubs, and higher speeds might be achieved in cruise if higher loads can be absorbed in transition. There appears to be a wealth of physics waiting to be discovered through systematic wind tunnel tests and analysis in the future.