Aircraft Performance

An Engineering Approach

Mohammad H. Sadraey

• Publisher: CRC Press
• Year: 2017
• Print ISBN: 9781498776554
• eBook ISBN: 9781498776585
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Mechanics

Aircraft Performance: An Engineering Approach introduces flight performance analysis techniques that enable readers to determine performance and flight capabilities of aircraft. Flight performance analysis for prop-driven and jet aircraft is explored, supported by examples and illustrations, many in full color. MATLAB programming for performance analysis is included, and coverage of modern aircraft types is emphasized. The text builds a strong foundation for advanced coursework in aircraft design and performance analysis.

CHAPTER ONE

Atmosphere

1.1 Introduction

An aircraft, as the name implies, is a vehicle that moves (flies) in air (i.e., atmosphere). The environment is the medium in which an aircraft flies. Hence, air is a significant parameter of an aircraft’s motion (flight). Aerospace vehicles are divided into two major groups: aerial vehicle, aircraft, or airplane; space vehicle, spacecraft, or space plane. An aircraft is capable of flight inside a gas medium (i.e., air) but not in vacuum (i.e., space); otherwise, it would be called a spacecraft. A spacecraft is designed to fly in space, but in order for that it must be launched into space. Spacecraft sometimes returns to Earth, such as the Space Shuttle. In such cases, a spacecraft is an aircraft as well.

Air is the primary constituent of the atmosphere. In order to study the performance of an aircraft, we must comprehend the properties of air. Since there are several parameters of air that influence an aircraft’s performance, we have to examine the atmosphere. The major parameters of air are density, pressure, and temperature. These parameters are functions of altitude, time of year, and location. In this chapter, we will examine the relationship between these parameters as functions of altitude and time of year. These calculations are a prerequisite for aircraft performance analysis. Since there must be a benchmark for analysis, we will introduce a standard atmosphere called the International Standard Atmosphere (ISA). If you are able to analyze an aircraft’s performance in an ISA condition, it should be easy to determine the performance in a non-standard condition.

The atmosphere is a dynamic system that is continuously changing. There are several phenomena that influence an aircraft’s performance: wind, gust, disturbance, lightning, rain, snow, hail, hurricane, tornado, and humidity. Although these are parameters of meteorology, both the pilot and the aircraft performance engineer must be familiar with atmospheric conditions for a safe flight. This information helps pilots to decide whether or not to take off in a specific flight condition. For these reasons, atmospheric phenomena are also briefly presented.

One of the duties of an aircraft performance engineer is to prepare an instruction manual for pilots that includes tables, charts, graphs, and data. To perform this job, one must determine and specify the limits of an aircraft and guide pilots to a safe flight. The major limits of a safe flight are imposed by the atmosphere; hence, several hints are emphasized to assist the reader to recognize safe from unsafe atmospheric flight conditions.

The certification program of a transport aircraft usually requires the aircraft to be tested in a variety of atmospheric conditions. For instance, in 2014, an Airbus A350 test aircraft headed to Canada for “cold-weather testing” as part of the A350-900 certification program. Atmospheric research is an ongoing program for NASA. For example, since 2010, NASA and NOAA scientists have been using a Global Hawk unmanned aerial vehicle (UAV) to conduct atmospheric research over Guam as part of the Airborne Tropical Tropopause Experiment.

Two important performance parameters are speed of sound and altitude. Speed of sound is mostly stated in terms of Mach number. Altitude has several applications and implications. These two variables are dealt with in more depth and explained in more detail in this chapter. They are used in a variety of performance problems throughout this book.

1.2 General description of atmosphere

The earth is surrounded by a thin gaseous envelope called the atmosphere. The atmosphere is a dynamic system, with a number of active subsystems. Life on Earth is supported by the atmosphere, solar energy, and the planet’s magnetic fields. The atmosphere absorbs energy from the Sun, recycles water and other chemicals, and works with electrical and magnetic forces to provide a moderate climate. The atmosphere also protects us from high-energy radiation and the frigid vacuum of space. The energy exchange that continually occurs between the atmosphere and the earth’s surface and between the atmosphere and space produces a phenomenon called weather.

The atmosphere is a gaseous layer surrounding the earth and is held by the earth’s gravity. The atmosphere has a mass of about 5 × 10¹⁸ kg, three-quarters of which are within about 11 km (36,000 ft) of the earth’s surface. When one views the atmosphere from the ground, it seems to be extremely deep. But when the thickness of its visible section is compared to the radius of the earth (6371 km), the atmosphere is seen to be a shallow layer. More than 99% of the atmosphere [1] is within 30 km of the sea level. This thin gaseous blanket is an integral part of the planet. The major component of the atmosphere is air. It not only provides the air that we breathe, but also acts as a shield to protect us from the dangerous radiation emitted by the Sun. If, like the Moon, Earth had no atmosphere, our planet would not only be lifeless but many of the processes and interactions that make the surface such a dynamic place could not operate.

There is no definitive answer to the question, “how much is the thickness of the atmosphere?” since the atmosphere gets thinner at a higher altitude. The atmosphere does not abruptly end at any given altitude but becomes progressively thinner with altitude. At altitudes of about 300 km, there is about one molecule of air per cubic kilometer. There is no universally accepted definition of how much air in a given volume constitutes t...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• Preface
• Author
• List of symbols
• 1 Atmosphere
• 2 Equations of motion
• 3 Drag force and drag coefficient
• 4 Engine performance
• 5 Straight-level flight: jet aircraft
• 6 Straight-level flight: propeller-driven aircraft
• 7 Climb and descent
• 8 Takeoff and landing
• 9 Turn performance and flight maneuvers
• 10 Aircraft performance analysis using numerical methods and MATLAB®
• Appendix A: Standard atmosphere, SI units
• Appendix B: Standard atmosphere, English units
• Appendix C: Performance characteristics of several aircraft
• Appendix D: Flight records
• Appendix E: A typical project for students
• Index