Effects of Freeplay on Dynamic Stability of an Aircraft Main Landing Gear

Abstract

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Considering the desirable case where no shimmy occurs we define the set of allowable freeplay profiles that satisfy a conservative stability criteria.

Landing Gear Design/Maintenance Analysis for Nonlinear Shimmy

“…Clearly, the original nonlinear system equations scale with freeplay, and this carries over to the HB formulation since F 1 is a function of θ∕θ fp . This scaling is observed even in a landing gear study with multiple nonlinearities of which freeplay is the dominant one [10], and it has been experimentally verified for the aeroelastic system of [8]. Note that the equations also scale in the presence of multiple freeplay if the ratios of the freeplay values are fixed.…”

Shimmy of an Aircraft Main Landing Gear With Geometric Coupling and Mechanical Freeplay

“…The freeplay that we consider here takes the form of a lateral play in the landing gear torque links (a typical source of landing gear freeplay) which, via the system geometry, results in a torsional play. In [7] we found that freeplay of this form has a significant effect on landing gear stability, and we observed a multitude of resulting oscillatory phenomena. Furthermore, we also found the characteristics of freeplay to be influential on the observed behaviour with 'sharper' freeplay profiles allowing shimmy oscillations over more typical operating conditions.…”

“…In this work we focus on the dynamic stability of an aircraft dual-wheel main landing gear (MLG) and use the technique of numerical continuation to perform a bifurcation analysis, exploring its nonlinear dynamics. We bring together several key concepts from the earlier studies [7,8] and, in particular, focus on the the combined effects of mechanical freeplay and geometric coupling. Taken individually, these subjects formed the basis for the two earlier papers.…”

“…Furthermore, we note that axial compression and extension of the system, also neglected in many studies, forms an important component of the longitudinal dynamics, allowing the appearance of so called gear-walk; this is discussed in references [9,10] and seen later in this paper. Consideration of axial deflection is also required to express the form of freeplay we consider, which varies with landing gear extension [7]. Therefore, although a number of studies only incorporate torsional and lateral DoFs (examples of which may be seen in references [16,18,22,24]), for this study, we employ the model described in [7] which considers the MLG dynamics in terms of four structural, and two tyre DoFs.…”

Effect of noise reducing components on nose landing gear stability for a mid-size aircraft coupled with vortex shedding and freeplay

“…The work by Howcroft et al [12] indicates that the translational freeplay of the order of 10 0 mm introduced at the torque link apex produces an angular freeplay of the order of 10 À 1 degrees. Fig.…”