Measured and predicted dynamic response characteristics of a flexible airplane to elevator control over a frequency range including three structural modes

Henry A. Cole, Jr., Euclid C. Holleman
naca-tn-4147
Feb 1958


The longitudinal frequency response of a large flexible swept-wing airplane, as determined from its measured response to elevator pulses, is presented over the operating Mach number range at altitudes from 15,000 to 35,000 feet. Response quantities for the nose, center of gravity, wing tip, and tail are shown for frequencies from the airplane short-period mode to the fuselage first-bending mode. Comparisons are made between the measured responses and responses predicted by dynamical analyses with up to three structural degrees of freedom. The forms of transfer functions needed to simulate the response over several frequency bands are shown. The dynamic response measured in flight is interpreted in terms of lines of low response, and comparisons are made with predicted lines of low response and node lines predicted by free-free analysis and measured in ground vibration tests.

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