Operational Benefits of an Optimal, Widely Variable Speed Rotor

Although used for attaining higher speeds and reduced noise, slowed or variable speed rotor operation has never been used to improve efficiency of a helicopter over the entire flight envelope. An optimum speed rotor (OSR) system allows a rotorcraft platform to operate well below 100% RPM to maintain the optimal blade loading and reduce the power required for a particular flight condition. Benefits of an OSR system include improvements in fuel consumption, range, endurance, flight ceiling, and payload capacity. These operational benefits of OSR systems will ultimately improve maintainability, survivability, and operational tempo. Boeing and the Aviation Applied Technology Directorate (AATD) are currently working to quantify the benefits of OSR technologies on the A160T Hummingbird unmanned rotorcraft though envelope expansion testing.