eprintid: 108
rev_number: 4
eprint_status: archive
userid: 5
dir: disk0/00/00/01/08
datestamp: 2007-06-19
lastmod: 2015-05-29 19:47:29
status_changed: 2009-04-08 16:54:16
type: report
metadata_visibility: show
item_issues_count: 0
creators_name: Barton, David
creators_name: Wood, David
contributors_name: Coetzee, Etienne
contributors_name: Aguareles, Maria
contributors_name: Asgari, Mahboubeh
contributors_name: Chiu-Webster, Sunny
contributors_name: Hunt, Giles
contributors_name: Mason, Joanna
contributors_name: Parker, David
contributors_name: Rodrigues, David
contributors_name: Sola-Morales, Juan
contributors_name: Vella, Dominic
title: Shimmy in aircraft landing gear
ispublished: pub
subjects: aerodef
studygroups: esgi56
companyname: Airbus
full_text_status: public
abstract: Shimmy is an oscillation in aircraft landing gear that can occur both on landing and take-off, typically in a band of velocities. It causes excessive wear on components and can cause accidents. The nose wheel is roughly like a caster on a shopping trolley: the horizontal axle of the wheel is mounted in an assembly that is free to rotate about a vertical axis. Shimmy is (or at least includes) oscillation of the wheel assembly about this vertical axis. The current engineering approach has little understanding of the physical mechanisms causing shimmy, but relies on the use of shimmy dampers, and on systematic maintenance and replacement of landing gear components. Simulations are carried out with finite element models and multi-body systems, and there are theoretical models due to Stépán and Somieski. In fact shimmy can also involve lateral oscillation of the landing gear (as well as torsional) and can be coupled to and caused by flutter of the airframe. The phenomenon is multi-scale in nature, as it can be linked to normal mechanical wear of key components at one scale, and gross flexibility effects at the vehicle scale. Airbus wish to identify it earlier in order to address passenger comfort, pilot comfort, manage mechanical wear and avoid overfatiguing the system elements. Specifically, Airbus wish to identify key system elements that may cause shimmy, when given a particular configuration of an aircraft. At early stages of development the configuration may involve the shape and size of the fuselage and design of the landing gear, whilst at the other end of the development process, the configuration may also consist of detailed system elements such as actuators, etc. Airbus relies on systematic maintenance and replacement of landing gear components, thereby avoiding the occurrences of the abovementioned phenomena.
problem_statement: Shimmy is an oscillation in the landing gear of an aircraft that can occur during taxiing, take-off or landing. Traditional shimmy analysis considers the effect to be linear. The Study Group considered a simplified nonlinear model for shimmy and studied its linear stability, and its nonlinear behaviour numerically, and showed that it has supercritical Hopf bifurcations. These results are broadly in agreement with observations of shimmy in some circumstances, but a more complex model would need to cover effects that are neglected here.
date: 2007-04-17
date_type: published
pages: 11
citation:   Barton, David and Wood, David  (2007) Shimmy in aircraft landing gear.  [Study Group Report]     
document_url: http://miis.maths.ox.ac.uk/miis/108/1/Airbus-ShimmyReport.pdf