Skip to main content

Introduction to GRASP—General Rotorcraft Aeromechanical Stability Program—A Modern Approach to Rotorcraft Modeling

Buy Article:

$30.00 plus tax (Refund Policy)

The General Rotorcraft Aeromechanical Stability Program (GRASP) is described in terms of its capabilities and development philosophy. The program is capable of treating the nonlinear static and linearized dynamic behavior of structures represented by arbitrary collections of rigid‐body and beam elements that may be connected in an arbitrary fashion and are permitted to have large relative motions. The main limitation is that periodic coefficient effects are not treated, restricting the solutions to rotorcraft in axial flight and ground contact conditions. Rather than following in the footsteps of other rotorcraft programs, GRASP is more of a hybrid between finite element programs and spacecraft‐oriented multibody programs. GRASP differs from standard finite‐element programs by allowing multiple levels of substructures in which the substructures can move and/or rotate relative to others with no small‐angle approximations. This capability facilitates the modeling of rotorcraft structures, including the rotating/nonrotating interface and details of the blade/root kinematics for various rotor types. GRASP differs from standard multibody programs by considering aeroelastic effects, including inflow dynamics (simple unsteady aerodynamics) and nonlinear aerodynamic coefficients. The main structural element is the aeroelastic beam element which may possess arbitrarily more than the 12 degrees of freedom common in beam elements. Although it is assumed in the analysis that the strain components in the aeroelastic beam element remain small compared to unity, no kinematical limitations are imposed on the magnitudes of the displacements and rotations. Numerical results from GRASP are presented and compared with results from an existing, special‐purpose coupled rator/body aeromechanical stability program and with experimental data far large deflections of an end‐loaded cantilevered beam. The agreement is excellent in both cases.
No Reference information available - sign in for access.
No Citation information available - sign in for access.
No Supplementary Data.
No Data/Media
No Metrics

Document Type: Research Article

Publication date: 1987-04-01

More about this publication?
  • The Journal of the American Helicopter Society is the world's only scientific journal dedicated to vertical flight technology. It is a peer-reviewed technical journal published quarterly by AHS International and presents innovative papers covering the state-of-the-art in all disciplines of rotorcraft design, research and development. (Please note that AHS members receive significant discounts on articles and subscriptions.)

    Journal subscribers who are AHS members log in here if you are not already logged in.

    Authors can find submission guidelines and related information on the AHS website.

  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
Cookie Policy
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more