Published online by Cambridge University Press: 05 January 2013
Overview
In this chapter we introduce the concepts of distance flown by an aircraft with and without stop for refuelling (§ 12.1). We discuss a number of cruise programs at subsonic and supersonic speeds and some optimal problems in long-range cruise, with or without constraints. First we present the analysis of the instantaneous cruise parameters (§ 12.2), including the specific range. We then provide numerical solutions of the specific range for real aircraft (§ 12.3). For the sake of generality, we also present the range equation, which is solved in closed form (§ 12.4), and deal with the separate problems of jet aircraft at subsonic speed (§ 12.5) and propeller aircraft (§ 12.6).We show a number of more advanced studies in cruise altitude selection (§ 12.7), cruise performance deterioration (§ 12.8), cost index and economic Mach number (§ 12.9) and various other effects, such as the effects of high-altitude winds and centre of gravity position (§ 12.10). We deal briefly with supersonic aircraft (§ 12.11).
KEY CONCEPTS: Point Performance, Specific Air Range, Cruise Altitude Selection, Range Equation, Long-Range Mach, Maximum-Range Mach, Cost Index, Economic Mach Number, Effects of Winds, Centre of Gravity Effects, Supersonic Cruise.
Introduction
For most commercial aircraft the fuel consumed during the cruising phase of the flight makes up the bulk of the fuel carried and is a key factor in the productivity and direct operating costs of an aircraft. Since the early 1970s, with the price of fuel soaring, both the airlines and the military have been concerned with energy-efficient operations. For this reason, several cruise conditions have been studied.
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