Abstract: “This paper focuses on design alternatives of a helicopter tail rotor driveshaft utilizing shape memory alloy (SMA). The conventional tail rotor designs segment the complete shaft into multiple shafts due to its long length which would have low bending natural frequencies. Using multi-segmented shafts introduce multiple in-span bearings and flexible couplings to accommodate misalignment due to manufacturing. This leads to a heavy and maintenance-intensive design. The paper explores the application of Shape Memory Alloy (SMA) and ways it can be introduced in the driveline system to reduce its weight. The proposed design alternatives aim to reduce the number of segments of shaft which leads to lesser number of in-span bearings and flexible couplings. However, the natural frequencies of the system decrease, which may lead to supercritical operation of the driveline. The underlying design ideas have been presented with a specific example of a tail rotor driveline.”

Keywords: driveshafts, shape memory alloys, natural frequency, helicopter tail rotor