Experimental characterization of a novel nose landing gear shimmy damper using a small-scale test rig

Abstract

This paper presents the design and fabrication details of a small-scale testing system for characterizing a novel nose landing gear shimmy damper. This test rig is designed to simulate take-off and landing conditions of an aircraft nose landing gear in the laboratory environment. A roller drum is employed to simulate the forward speed of the aircraft on the ground, while an impact hammer mechanism is used to induce shimmy through a small initial tire slip. Weights can be used to induce vertical force exerted by the fuselage. The vibration signals are recorded using accelerometers, and processed numerically to obtain shimmy characteristics. A prototype of the novel shimmy damper designated as the Symmetric Torque Link Damper (STLD) is fabricated. The specifications of STLD are discussed in previous publications and summarized in the current paper. The experimental results including rotational vibration time histories, peak frequencies, and attenuation characteristics for the STLD are presented and compared with those of the baseline system without a shimmy damper, as well as with the built-in shimmy damper trends. Overall, this experimental work confirms the stability gain offered by the STLD, while it does not outperform the built-in damper in all scenarios. Instead, STLD has the attractive features of being retrofittable to existing landing gears and is symmetric in design, leading to an even distribution of dynamics loads on the gear. Furthermore, the testing apparatus presented in this work contributes to shimmy mitigation practice by offering a novel, yet simple, validation approach suitable for early prototype developments.