An effort to dramatically reduce the acoustic signature of helicopters has been launched by the US Defense Advanced Research Projects Agency (DARPA). It will begin by developing new computational tools to enable novel blade designs that reduce rotor noise without having an impact on performance.

Initial responses to DARPA's call for proposals for Phase I of its helicopter quietening programme were submitted at the end of April, with the first contracts expected to be awarded in June. While later phases of the programme will cover the design and flight test of quiet rotors, the 24-month first phase "is focused on developing predictive models that will create a new design capability for rotorcraft", says DARPA.

The goal of Phase I is to create a physics-based design tool that will enable virtual testing of innovative approaches ranging from unconventional blade tips to movable flaps or slats. After the first year, DARPA wants a tool able to predict blade surface pressures and pitching moments; after 24 months, the design tool should also be able to model flow-field velocities, and in-plane and far field sound pressure levels.

Source: Flight International