Energy-Saving Periodic Flight at Transonic Speeds

Abstract

AbstractWe 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 two-phase 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.