Journal of Theoretical
and Applied Mechanics

33, 3, pp. 687-710, Warsaw 1995

Influence of induced velocity modelling on helicopter stability

Paweł Mazurek, Janusz Narkiewicz
An influence of modelling of main rotor induced velocity distribution on helicopter stability is investigated for various flight conditions: hover, vertical and forward flight with and without the ground effect.

Closed formulae describing rotor inflow models are reviewed and their applicability to stability analysis is evaluated. Selected inflow models are utilised for calculation of parameters of steady flight, linearized equations of helicopter motion and eigenvalues and eigenvectors of the state matrix. Investigation of stability of a helicopter in steady flight reveals that the differences between the results obtained using different formulae based on the Glauert method i.e., harmonic for azimuth and linear along the blade are negligible.

Other induced velocity models, like the Mangler-Squire and dynamic inflow, do not change the character of helicopter motion but they influence quantitatively the results of stability investigation.