Author: Charles J. Donlan

Publisher:

Published: 1942

Total Pages: 19

ISBN-13:

Some problems relating to longitudinal stability in power-on flight are considered. A derivation is included which shows that, under certain conditions, the rate of change of the pitching moment coefficient with lift coefficient as obtained in wind tunnel tests simulating constant power operation is directly proportional to one of the indices of stability commonly associated with flight analysis, (the slope of the curve relating the elevator angle for trim and lift coefficient). The necessity of analyzing power-on wind tunnel data for trim conditions is emphasized, and a method is provided for converting data obtained from constant thrust tests to simulated constant throttle flight conditions. It is demonstrated how a downward tail load required to trim an airplane results in decreased stability in power-on flight and why a longitudinal center-of-gravity movement is likely to affect the stability characteristics less in power-on flight than in power-off flight.