HANDLING QUALITIES OF THE H-76 FANTAILTM DEMONSTRATOR

This paper reviews handling qualities aspects of the H-76 FANTAILTM Demonstrator helicopter. The design, model test, simulation and analyses, as well as, flight test results and correlation relevant to handling qualities are addressed. Those aspects of the design critical to achieving the handling qualities requirements established for this helicopter are reviewed. Pertinent results of the wind tunnel tests, simulation and analyses leading to the present design configuration of the empennage and directional control system are discussed. Both the design criteria used to establish the FANTAIL directional characteristics and the criteria and methods employed to establish the size and configuration of the integrated empennage (fan/shroud/horizontal tail/vertical tail) are examined. Wind tunnel test data which led to these selections are presented. The simulation model developed to support the configuration design trades and analyses is also discussed. Modifications and improvements to the components of the total vehicle simulation representation, based on wind tunnel tests, are highlighted along with the approach used to model the aerodynamic surfaces of the empennage. In particular, the evolution of the fan math model, which was developed for the total vehicle simulation, is described. Correlation between test and simulation for the fan in various flight regimes is presented. The simulation model supported assessment of a number of design considerations. These encompass sizing the fan, horizontal and vertical stabilizer, as well as, vertical tail incidence selection for proper fan unloading in forward flight, optimization of horizontal location to minimize main rotor wake impingement effects, selection of mechanical couplings and modifications to the automatic flight control system (AFCS). These considerations are reviewed and rationale for the selected design and supporting data are presented. Finally, flight test results relevant to handling qualities are reviewed. This includes steady trim and maneuver characteristics along with comparisons of flight data with simulation analysis, which was developed as part of a pre-flight test ‘Smart Book’.