An Assessment of a Reaction Driven Stopped Rotor/Wing Using Circulation Control in Forward Flight

The desire of achieving faster cruise speed for rotorcraft vehicles has been around since the inception of the helicopter. Many unconventional concepts have been considered and researched such as the advanced tilt rotor with canards, the tilt-wing, the folding tiltrotor, the coaxial propfan/folding tiltrotor, the variable diameter tiltrotor, and the stopped rotor/wing concept, in order to fulfill this goal. The most notable program which addressed the technology challenges of accomplishing a high speed civil transport mission is the High Speed Rotorcraft Concept (HSRC) program. Among the long list of potential configurations to fulfill the HSRC intended mission, the stopped rotor/wing is the least investigated due to the fact that the existing rotorcraft synthesis codes cannot handle this type of vehicle. In order to develop such a tool, a designer must understand the physics behind this unique concept. The uniqueness of stopped rotor/wing vehicles that use reaction drive can be found in the tight coupling that is present between the rotor and the engine which in turn requires these subsystems to be sized concurrently rather than in isolation. A methodology and simulation tool capable of handling this coupling is under development at the Aerospace Systems Design Laboratory (ASDL) at Georgia Institute of Technology. The development of a new design tool (TJCC) and the use of a statistical technique called Response Surface Methodology linked into the V/STOL Aircraft Sizing and Performance Computer Program (VASCOMP II) has provided the capability of sizing stopped rotor/wings. The potential success of a stopped rotor/wing configuration can only be determined through direct performance comparisons with other high speed rotorcraft concepts using analytical methods of comparable sophistication. The authors have previously presented limited results from this study detailing the rotor/wing performance during hover. In this paper the forward flight regime for both the helicopter and fixed wing modes are discussed. Representative results presented include performance characteristics such as the horsepower required curves versus forward flight for both the rotorcraft and fixed wing modes of operation. Furthermore, the mass flow requirements, and transition performance associated with this aircraft are also examined in this paper.