Abstract: A low-noise multi-propeller system includes at least two propellers, each propeller including at least two blades. The propellers rotate in a first direction and define an angular phase relative to one another. A drive system corotates the propellers at substantially equal rotational rates in the first direction. The propellers are substantially phase-locked at a predefined relative phase offset that reduces the overall sound power of the fundamental tone at a blade passage frequency.

Abstract: A method for adaptive phase control of a distributed propulsion (DP) aircraft includes deriving an estimated source noise level of the aircraft's propulsors with respect to a designated low-noise area on the ground. Responsive to the estimated source noise level, a phase generator module estimates a ground noise level using the source noise level. The method includes determining an optimized set of relative azimuthal propulsor blade positions/phase angles, via the phase generator module, with such optimized phase angles being sufficient for reducing the estimated ground noise level. Phase control signals from a flight controller to the respective propulsors establishes the optimized set of relative phase angles, and thereby reduces community noise in the designated low-noise area. The DP aircraft includes an aircraft body, the flight controller, and the above-noted phase generator module.

Abstract: A low-noise multi-propeller system includes at least two propellers, each propeller including at least two blades. The propellers rotate in a first direction and define an angular phase relative to one another. A drive system corotates the propellers at substantially equal rotational rates in the first direction. The propellers are substantially phase-locked at a predefined relative phase offset that reduces the overall sound power of the fundamental tone at a blade passage frequency.

Abstract: A method for adaptive phase control of a distributed propulsion (DP) aircraft includes deriving an estimated source noise level of the aircraft's propulsors with respect to a designated low-noise area on the ground. Responsive to the estimated source noise level, a phase generator module estimates a ground noise level using the source noise level. The method includes determining an optimized set of relative azimuthal propulsor blade positions/phase angles, via the phase generator module, with such optimized phase angles being sufficient for reducing the estimated ground noise level. Phase control signals from a flight controller to the respective propulsors establishes the optimized set of relative phase angles, and thereby reduces community noise in the designated low-noise area. The DP aircraft includes an aircraft body, the flight controller, and the above-noted phase generator module.