eprintid: 25
rev_number: 4
eprint_status: archive
userid: 4
dir: disk0/00/00/00/25
datestamp: 2004-06-10
lastmod: 2015-05-29 19:45:37
status_changed: 2009-04-08 16:52:06
type: report
metadata_visibility: show
item_issues_count: 0
creators_name: Champneys, A.
contributors_name: Aigner, A.
contributors_name: Balanov, S.
contributors_name: Champneys, A.
contributors_name: Eyres, R.
contributors_name: Friswell, M.
contributors_name: Gravesen, J.
contributors_name: Halse, C.
contributors_name: Hjorth, P.
contributors_name: Janson, N.
contributors_name: Lloyd, D.
contributors_name: Ockendon, J.R.
contributors_name: Silchenko, S.
contributors_name: Wagg, D.
contributors_name: Wang, C.
contributors_name: Wood, D.
contributors_name: Wright, J.
contributors_name: Xu, X.
title: Helicopter tail rotor instability
ispublished: pub
subjects: aerodef
studygroups: esgi46
companyname: Westland Helicopters
full_text_status: public
problem_statement: Data obtained by Westland Helicopters from a simulation of a teetered tail rotor shows instability at su ciently high forward velocity of the aircraft, and also indicates a rotor natural frequency at nearly three times the rotor rotation frequency. The Study Group was asked to provide an explanation of these observations. Using a linear model for the teetering motion and the umbrella   ap  mode of the tail rotor blades, the Study Group showed that parametric terms, containing the forward velocity, provide excitation at frequencies which are once and twice the blade rotation frequency. Taking the classical damped Mathieu equation as a  toy  model of the system, and observing the near 3:2 ratio between the natural rotor frequency and the second excitation frequency, suggested that the observed instability arises as the forward velocity passes into the 3:2 resonance tongue of the stability map of the Mathieu equation. The current  snapshot  eigenvalue method, in use at Westland Helicopters, does not capture this instability. The Study Group recommended instead that Floquet theory be applied to a time-dependent linearised model.
date: 2003-04
date_type: published
pages: 19
citation:   Champneys, A.  (2003) Helicopter tail rotor instability.  [Study Group Report]     
document_url: http://miis.maths.ox.ac.uk/miis/25/1/RotorInstability.pdf