Accession Number : ADA119412

Title :   Toward a Better Understanding of Helicopter Stability Derivatives.

Descriptive Note : Technical memo.,

Corporate Author : NATIONAL AERONUATICS AND SPACE ADMINISTRATION MOFFETT FIELD CA AMES RESEARCH CENTER

Personal Author(s) : Hansen,Raymond S

PDF Url : ADA119412

Report Date : Aug 1982

Pagination or Media Count : 27

Abstract : An amended six-degree-of-freedom helicopter stability and control derivative model was developed in which body acceleration and control-rate derivatives were included in the Taylor series expansion. These additional derivatives were derived from consideration of the effects of the higher-order rotor-flapping dynamics, which are known to be inadequately represented in the conventional six-degree-of-freedom, quasi-static stability-derivative model. The amended model was found to be a substantial improvement over the conventional model, effectively doubling the usable bandwidth and providing a more accurate representation of the short-period and cross-axis characteristics. Further investigations assessed the applicability of the two stability-derivative model structures for flight-test parameter identification. Parameters were identified using simulation data generated from a higher-order base-line model having sixth-order rotor tip-path-plane dynamics. Three lower-order models were identified: one using the conventional stability-derivative model structure, a second using the amended six-degree-of-freedom model structure, and a third model having eight degrees of freedom that included a simplified rotor tip-path-plane tilt representation. (Author)

Descriptors :   *Helicopters, *Flight maneuvers, *Stability, *Mathematical models, *Derivatives(Mathematics), Degrees of freedom, Acceleration, Control systems, Rates, Taylors series, Helicopter rotors, Flight simulation

Subject Categories : Helicopters
      Numerical Mathematics

Distribution Statement : APPROVED FOR PUBLIC RELEASE