Combined variable rotor speed and active blade twist helicopter technologies have the potential to reduce the environmental and acoustic impact of modern rotorcraft. This paper explores the aeroacoustics, environmental and ground noise impact of combined variable rotor speed and active blade twist helicopter rotors, optimized for simultaneous mitigation of source noise and NO${}_{\mathrm{x}}$ emissions. An integrated approach is employed including free-wake aeroelastic rotor modeling and time-domain aeroacoustic formulations fundamentally based on Acoustic Analogy. The overall method is incorporated into a multi-disciplinary design space exploration and surrogate-model-assisted optimization algorithm. The developed framework is deployed towards devising optimal variable rotor speed and active blade twist control for a representative twin-engine light helicopter operating in a realistic descent trajectory. The obtained rotor control schedules achieve overall ground noise reductions of up to 7 dB with concurrent NO${}_{\mathrm{x}}$ reductions of 11%, relative to the conventional rotor. The proposed approach provides new insight into rotor wake behavior and blade–vortex interactions, as well as environmental impact and ground noise footprint of combined variable rotor speed and active blade twist helicopter concepts.

结合了可变旋翼速度和主动桨叶扭曲直升机技术，有可能减少现代旋翼飞机的环境和声学影响。本文探讨了组合可变转子速度和主动叶片扭转直升机转子对航空声学，环境和地面噪声的影响，并优化了其同时减轻了源噪声和NO的影响。${}_{\mathrm{X}}$排放。采用了一种集成方法，包括基于基本声比模拟的自由尾气动力学弹性转子建模和时域气动声学公式。整体方法被纳入多学科设计空间探索和替代模型辅助的优化算法中。开发的框架用于为在现实的下降轨迹中运行的代表性双引擎轻型直升机设计最佳可变转子速度和主动叶片扭转控制。所获得的转子控制进度表可在不同时发生NO的情况下将地面噪音降低多达7 dB${}_{\mathrm{X}}$相对于传统转子减少了11％。所提出的方法提供了对转子尾流行为和叶片-涡旋相互作用以及环境影响和地面噪声足迹的新见解，可变转子速度和主动叶片扭转直升机概念相结合。