Energy-Saving Periodic Flight at Transonic Speeds Abstract:

Abstract

We examine possible energy saving by periodic
changes in speed and altitude relative to steady state cruise, in
the transonic regime. We develop a theoretical model of twophase periodic flight with altitude variation in the transonic
regime and compare it with a steady horizontal flight at the
same average speed. The model predictions are verified by wind
tunnel experiments. For example, by periodically accelerating
from M=0.7 to M=1.1 while losing altitude, and then climbing
back to the original height while decelerating, one can achieve
savings of about 20% relative to steady flight at the same
average speed and constant altitude.