CLOUD-STREET FLYING

Abstract

If a cross-country fllght is carried out in conditions which permit it to be made without circling, the criterion in which must be applied in order to achieve maximun average speed ls similar to the MacCready criterion for determlning optimun speed between thernals in a normal cross-country flight. However, the datum vertical velocity (denoted by w* in the analysis, and corresponding to the datum setting of a MacCready variometer ring) is determined by the overall distribution of vertical air veloclty along the flight path together with some overall condltion such as zero change of energy helght between the beglnnlng and the end of the flight. In practice, a pilot would have to proceed by a process of successive approximation. Some calculatlons have been made for fixed-geometry sailplanes flying through air which has a constant vertical velocity over part of the fllght path and is at rest elsewhere.