Full-Scale Flight Tests of Active Flow Control to Reduce Tiltrotor Aircraft Download

Abstract

approximately 10% of rotor thrust, or about 6000 lb for the V-22. Various mechanical means have been experimentally tried to reduce this penalty, but none has been implemented, largely because of mechanical complexity. This paper describes the research conducted on the application of active flow control to the problem, since this technique may offer a solution without large weight penalties and unacceptable complexity. The research was conducted as part of the Defense Advanced Research Projects Agency Micro Adaptive Flow Control program. TheworkculminatedinJune2003,whentheNASA/U.S.Army/BellXV-15tiltrotoraircraft wasusedtosuccessfully demonstrate the effectiveness of active flow control in reducing airframe download during hover. The wing flaps were fitted with zero-mass-flow actuators that periodically injected/removed air in the flap upper surface boundary layerthroughslotsfromtheinteriorofthe flap.Theactive flowcontrolwaseffectiveindelaying flowseparationfrom the flap, which reduced the download on the wings. The flight tests were the culmination of extensive laboratory experimentsontwo-dimensionalmodelsandonapoweredfull-span16%-scalemodeloftheXV-15aircraft.TheXV15 flighttestsconfirmedthelaboratory findingsbysuccessfullyreducingthedownloadmeasuredinhoverbyasmuch as14%,demonstratingthattheaerodynamicprinciplesofactive flowcontrolcanbeappliedtofull-scaleairvehicles.