为探讨被动变弦长对变转速尾桨性能的提升潜力，建立直升机飞行性能分析模型，包括旋翼动力学综合模型、尾桨模型、机体模型与前飞配平模型，由UH-60A直升机飞行试验数据验证了模型正确性。研究结果表明，直升机悬停时，变弦长对尾桨功率影响很小；低中速飞行时，变弦长使功率小幅增加；高速飞行时，变弦长可大幅降低功率。被动变弦长适应于尾桨转速降低后的气动环境，高速飞行时，尾桨转速降低，变弦长伸长量增加，变弦长降低尾桨功率效果增强。前飞速度300 km/h、90%额定转速时，功率增加10.1%，布置变弦长后为1.59%。变弦长适合布置于尾桨半径70%~90%处。直升机高速飞行时，变弦长伸长量增加，功率节省量增加。直升机起飞重量降低，功率节省量增加。
To study the performance improvement potential of variable speed tail rotors by the passively extendable chord, we establish a helicopter flight performance analysis model, including a comprehensive rotor model, a tail rotor model, a fuselage model, and a propulsive trim method. The flight data of the UH-60A helicopter is utilized to validate this model. The results show that the extendable chord has little effect on the power while the helicopter is hovering. During low to medium speed flight, the extendable chord slightly increases the power, while during high speed flight, the power can be significantly reduced. When the tail rotor speed is reduced, the passively extendable chord is adapted to the aerodynamic environment. During high speed flight, the chord length increases with the reduced speed, and the tail rotor power reduction is increased. When the forward speed is 300 km/h and the tail rotor speed is 90% of the nominal speed, the power increases by 10.1%, which then turns to 1.59% when the extendable chord is used. The extendable chord is suitable to be placed in the range of 70%R~90%R (tail rotor radius). The power saving increases with the extendable chord length increase during high speed flight, or when the helicopter take-off weight decreases.
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