Review of Control Technologies for Quiet Operations of Advanced Air-Mobility

The current technologies for developing quiet rotor noise in urban canyons are reviewed. Several passive noise control approaches are discussed with their limitations in reducing both tonal and broadband noise. Blade tip modifications are seen to be one of the more successful in reducing tonal noise, with serrations at the trailing edge useful in reducing trailing edge broadband noise. Due to the adverse performance limitations of passive control, several optimization approaches are reviewed to discuss the possible improvements in performance of rotors. Additionally, a few legacy control technologies for helicopters are discussed. Active control technologies are investigated. The overall outlook and challenges to these methods are discussed with an eye on Advanced Air Mobility Vehicles (AAM).