An analytical investigation of the gust-alleviating properties of a simple pitch damper

Norman L. Crabill
naca-tn-4173
Dec 1957


The response to atmospherc gusts of a lightly damped airplane model flying at a Mach number of 0.7 at sea level has been studied analytically with elevator fixed and with varying amounts of viscous restraint of a mass-overbalanced elevator. Although in a sharp-edge gust the viscously restrained mass-overbalanced elevator has negligible effect on the motion of the airplane center of grravity until the first peak on the normal-acceleration response of the model has been reached, the effective damping ratio of the subsequent motion can be more than trebled by a suitable choice of viscous restraint with some reduction in frequency of oscillation. In continuous gusts, calculations indicate that for the model considered there results a 20-percent reduction in root-mean-square normal acceleration at the center of gravity over a broad range of elevator viscous restraint.

An Adobe Acrobat (PDF) file of the entire report:
http://naca.central.cranfield.ac.uk/reports/1958/naca-tn-4173.pdf