Study on the shimmy stability of aircraft nose landing gear with the radial and axial clearance at torque link connection

Abstract

With the use of the nose landing gear, its friction parts will generate clearance due to wear, affecting the stability of the aircraft shimmy. This clearance is a complex situation where both axial and radial clearances exist, but it has not been investigated in the current study. Herein, we analyze the location between the upper and lower torque links, which are prone to wear, and proposed axial clearance models and radial clearance models applicable to the location. Furthermore, we simulate and analyze the influence of the single radial clearance case, single axial clearance case, and radial clearance and axial clearance coupling case on the nose landing gear shimmy stability with the critical anti-shimmy damping coefficient as the evaluation index. The results show that the radial clearance at the upper and lower torque links has no significant effect on the shimmy stability of the nose landing gear, while the increase of the axial clearance will increase the critical anti-shimmy damping coefficient and reduce the shimmy stability. And when the anti-shimmy damping design is 400Nꞏmꞏs/rad, the axial clearance between the upper and lower torque links should not exceed 0.54mm, otherwise, periodic ±0.08° reciprocating rotation will occur between the inner cylinder and the outer cylinder. The larger the axial clearance, the larger the reciprocating torsional Angle will be. These works provide a reference for the design and maintenance of the nose landing gear.