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Stability Derivatives of Helicopter Rotors


Dykes, John Christopher (1938) Stability Derivatives of Helicopter Rotors. Master's thesis, California Institute of Technology. doi:10.7907/N0GE-EA65.


At present there are only three published papers dealing with the stability of helicopters, all based on helicopters with rigid rotors. Since all rotors are, in practice, constructed with the blades free to "flap", these analyses are not sufficiently general.

Below, the blade motion equation has been written in terms of small incremental accelerations and velocities; for which an approximate solution is obtained. This is then used to calculate the actual forces and moments that are produced on the rotor; by taking suitable mean values, it has been found possible to express these forces and moments without reference to the actual position of the blades at that instant, but only as functions of the position of the whole helicopter. The aerodynamic mechanism of the rotor has therefore been expressed in a a series of equations, and the stability of the helicopter now becomes solely a dynamical problem.

It appears that a helicopter is most likely to become unstable when hovering; this analysis is confined to this case.

Calculated values for a helicopter of the same size as the "C.30" autogyro, are given to show the dimensions of the various forces and moments.

Item Type:Thesis (Master's thesis)
Subject Keywords:Aeronautical Engineering
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • von Kármán, Theodore
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 January 1938
Record Number:CaltechETD:etd-10282005-161504
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:4287
Deposited By: Imported from ETD-db
Deposited On:01 Nov 2005
Last Modified:03 Oct 2019 23:33

Thesis Files

PDF (Dykes_jc_1938.pdf) - Final Version
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