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Über dieses Buch

Knowledge is not merely everything we have come to know, but also ideas we have pondered long enough to know in which way they are related, and 1 how these ideas can be put to practical use. Modern aviation has been made possible as a result of much scienti c - search. However, the very rst useful results of this research became ava- able a considerable length of time after the aviation pioneers had made their rst ights. Apparently, researchers were not able to nd an adequate exp- nation for the occurrence of lift until the beginning of the 21st century. Also, for the fundamentals of stability and control, there was no theory available that the pioneers could rely on. Only after the rst motorized ights had been successfully made did researchers become more interested in the science of aviation, which from then on began to take shape. In modern day life, many millions of passengers are transported every year by air. People in the western societies take to the skies, on average, several times a year. Especially in areas surrounding busy airports, travel by plane has been on the rise since the end of the Second World War. Despite becoming familiar with the sight of a jumbo jet commencing its ight once or twice a day, many nd it astonishing that such a colossus with a mass of several hundred thousands of kilograms can actually lift off from the ground.

Inhaltsverzeichnis

Frontmatter

1. History of Aviation

It is generally recognized that

Wilbur

and

Orville Wright

were the first to perform manned powered flight in 1903. Nevertheless, they were not at all the first to attempt flight. It is an exceptional trait of early aviation history — in contrast to other technical disciplines — that many, during an extended period of time, tried in vain to conquer the skies. Eventually success was achieved in developing the correct basis and methods enabling the construction of wings capable of sufficient lift and engines capable to provide enough propulsive thrust. Man has been able to navigate through the air in balloons since 1783, though only succeeded with powered flight from 1903; manned space flight has been carried out with the use of rockets since 1961. The origin of these three principles of flight have, however, been public knowledge since the middle ages.

The following overview will start with a brief history of the work performed by pioneers of aviation in the 19th century. Although most of them did not achieve flight, they have contributed to the knowledge and techniques required for manned flight. Thereafter will follow a brief overview of the development of aviation in the 20th century. The emphasis of this chapter is less on events and dates and much more on the factors that have played a roll in the development of the way many pioneers tackled the problems and how they were influenced by others. This overview will also contain certain achievements of Dutch aviation development. Main points of focus will be on the development of aircraft rather than essential components of modern aviation such as airports, navigational and landing aids and air traffic control.

2. Introduction to Atmospheric Flight

3. Low-Speed Aerodynamics

In the history of aviation, flight speeds have constantly increased due to the development of more powerful engines and the improvement of aerodynamic properties. Especially, the introduction of jet engines and sweptback wings made it possible to approach and even exceed the speed of sound. This

sonic speed

, the propagation speed of very small pressure disturbances in the atmosphere, plays an important role in determining which flow phenomena will occur. In the low-speed range, all flow velocities around the aeroplane are significantly smaller than the speed of sound. The pressure disturbances caused by the aircraft can propagate forward – in a way the air is “warned of” the oncoming aircraft – and the air particles recede for the

leading edge

of a wing or the nose of a body. This is no longer the case when the flight speed exceeds the speed of sound. Then the flow pattern is greatly changed by the occurrence of

shock waves

, nearly discontinuous pressure changes. These are caused by the

compressibility

of the atmospheric air, that is, the ability of air to change

specific volume

and

density

with increasing pressure.

4. Lift and Drag at Low Speeds

In the previous chapter the flow around basic bodies such as cylinders, spheres and wings was treated. Special attention was paid to drag. Although the discussed aerodynamic principles are valid for other parts of an aircraft as well, it is particularly important for any knowledge of aeronautics to understand how lift is generated and which consequences the lifting force has for the drag of an aeroplane. This chapter will focus on the properties of

aerofoils

and

aerofoil sections

. An aerofoil is a streamline body designed in such a way that, when set at a suitable angle to the airflow, it produces much more lift than drag. Aircraft wings and tailplane surfaces are examples of aerofoils, though tail surfaces are functionally different from wings and will be discussed separately in Chapter 7. This chapter is restricted to lift and drag at subsonic speeds at which the compressibility of air can be presumed irrelevant. Aerodynamic properties of high-speed aerofoils will be discussed in Chapter 9.

5. Aircraft Engines and Propulsion

Aircraft rely on the reaction principle much more than ground vehicles. They almost exclusively use chemical energy released by combustion of liquid fuels or propellants.

Air breathing engines

use atmospheric air for generating power by combustion and obtain their

thrust

by reaction to the backward acceleration of ambient air or exhaust gases. Rocket engines are nonairbreathers carrying their

propellant

internally; they will only be mentioned superficially in this tbook.

6. Aeroplane Performance

The discipline of aircraft

performance analysis

intends to give an answer to the following question: Does the aircraft meet the requirements to which it has been designed or those of (future) users? Using the properties of the atmosphere, the aircraft and its propulsion system, the motion of the aircraft’s centre of gravity during different phases of the flight can be calculated. The results lead to the most important performance data of an aircraft for general use.

7. Stability and Control

The term

flying qualities

denotes primarily the combination of stability and control properties which have an important influence on the ease and precision with which a pilot can maintain a state of equilibrium and execute manoeuvres, and thereby on flight safety and operational effectiveness. The term

stability

characterizes the motion of an aeroplane when returning to its equilibrium position after it has been disturbed from it without the pilot taking action. Aircraft

control

describes the response to actions taken by a pilot to induce and maintain a state of equilibrium or to execute manoeuvres. For military aircraft, the definition of flying qualities is broadened with an assessment of the precision and effectiveness with which tasks can be performed. Qualities like agility and targeting precision are closely associated with

handling qualities

, a term which denotes the short-term dynamic response of an aeroplane as a reaction to control.

Flight dynamics

deals with the relatively short-term motion of an aeroplane in response to the pilot’s actions or to external disturbances like gusts, wind gradients, or turbulent air. In contrast to aeroplane performance, which is governed by forces along and normal to the flight path, stability and control is dominated by aerodynamic moments about the

centre of gravity

, with a rotational motion as a response to these moments.

8. Helicopter Flight Mechanics

An aeroplane becomes airborne only when its (fixed) wings have sufficient forward airspeed for producing the lift required to balance the aircraft’s weight. Alternatively, lift can be produced by a

rotor

that can be seen as a large and relatively slowly rotating

propeller

in a (near-)horizontal plane.

9. High-Speed Flight

Backmatter

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