Stability analysis of a free falling pararotor

Nadal Mora, Vicente J. and Sanz Andres, Angel Pedro (2006). Stability analysis of a free falling pararotor. "Journal of Aircraft", v. 43 (n. 4); pp. 980-986. ISSN 0021-8669.


Title: Stability analysis of a free falling pararotor
  • Nadal Mora, Vicente J.
  • Sanz Andres, Angel Pedro
Item Type: Article
Título de Revista/Publicación: Journal of Aircraft
Date: 2006
ISSN: 0021-8669
Volume: 43
Faculty: E.T.S.I. Aeronáuticos (UPM)
Department: Vehículos Aeroespaciales [hasta 2014]
Creative Commons Licenses: Recognition - No derivative works - Non commercial

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The pararotor is a decelerator device based on the autorotation of a rotating wing. When it is dropped, it generates an aerodynamic force parallel to the main motion direction, acting as a decelerating force. In this paper, the rotational motion equations are shown for the vertical flight without any lateral wind component and some simplifying assumptions are introduced to obtain analytic solutions of the motion. First, the equilibrium state is obtained as a function of the main parameters. Then the equilibrium stability is analyzed. The motion stability depends on two nondimensional parameters, which contain geometric, inertia, and aerodynamic characteristics of the device. Based on these two parameters a stability diagram can be defined. Some stability regions with different types of stability trajectories (nodes, spirals, focuses) can be identified for spinning motion around axes close to the major, minor, and intermediate principal axes. It is found that the blades contribute to stability in a case of spin around the intermediate principal inertia axis, which is otherwise unstable. Subsequently, the equations for determining the angles of nutation and spin of the body are obtained, thus defining the orientation of the body for a stationary motion and the parameters on which that position depends.

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Item ID: 39721
DC Identifier:
OAI Identifier:
DOI: 10.2514/1.16746
Official URL:
Deposited by: Biblioteca ETSI Aeronauticos
Deposited on: 18 Mar 2016 08:30
Last Modified: 18 Mar 2016 08:30
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