Theory and Practice of Aircraft Performance

CHAPTER 10Fundamentals of Mission Profile, Drag Polar and Aeroplane Grid

10.1 Overview

This chapter gives an overall picture of what is required to evaluate aircraft performance. It starts with classifying the types of aircraft and with a brief introduction to progress made in aircraft capabilities. Typical mission profiles for civil and military aircraft are shown. Next, the most important term in aircraft performance, the drag polar is explained in detail. It captures the relationship between aircraft lift and drag, a topic that needs to be well understood. The crux of aircraft performance analyses is to make use of drag polar. Finally, the important aircraft performance‐related theories associated with lift and drag are presented; these embrace the scope of the chapters to follow. Good coverage of aircraft performance is given in [1–23].

There is some difference between using close‐form parabolic drag polar expressed in equation form and actual drag polar in graphical form obtained through using semi‐empirical relations, especially for high subsonic jet aircraft. The difference arises from how the Oswald’s efficiency factor “e” is treated (Section 10.9). Easy manipulation of the close‐form parabolic drag equation quickly gives aircraft characteristics, and gives valuable information of whether to proceed with more accurate actual drag polar calculations. For low‐speed aircraft operating below 0.5 Mach, the parabolic drag polar is, in general, close to actual drag polar ...