Introduction Of Aerospace Engineering

 The history of aerospace engineering is full of firsts, such as the first balloon flight, the first aeroplane flight, the first helicopter flight, the first artificial satellite flight, the first manned spacecraft flight, and many others. In this first chapter, these many firsts are discussed in the context of the aerospace engineering involved in making these historic events happen. 

The first flight of a new vehicle design is a significant achievement and milestone. It is usually the culmination of years of hard work by many people, including engineers, technicians, managers, pilots, and other support personnel. First flights often represent firsts in the application of new aerospace engineering concepts or theories that are being validated by the actual flight. 

As an aerospace engineer, you have the opportunity to contribute to the first flight of a new aircraft, a new spacecraft, or a new technology. Aerospace engineers are involved in all facets of the design, analysis, research, development, and testing of aerospace vehicles. 

This encompasses many different aerospace engineering discipline specialities, including aerodynamics, propulsion, performance, stability, control, structures, systems, and others. Several of these fundamental disciplines of aerospace engineering are introduced in this text. 

The aerospace engineer tests the vehicle, on the ground and in flight, to verify that it can perform as predicted and to improve its operating characteristics. Flight testing is usually the final test to be performed on the complete vehicle or system. In manyareasofengineering and technology, there is sometimes a perception that there is nothing left to be done, or that there is nothing left to be invented. 

The impressive successes of our aerospace past may appear, to some, to dim the prospects for future innovations. Aerospace engineers have indeed designed, built, and flown some of the most innovative, complex, and amazing machines known to humanity. 

However, there is still ample room for creativity and innovation in the design of aerospace vehicles, and opportunities for technological breakthroughs to make the skies and stars far more accessible. By the end of this textbook, you will have greatly increased your knowledge of aerospace engineering, but you will also be humbled by how much more there is to be discovered.

Information About Aircraft

FTT: Your Familiarization Flight

                      McDonnell Douglas F/A-18B Hornet supersonic fighter.

                 Three-view drawing of the McDonnell Douglas F/A-18A Hornet 

This is the first of many flight test techniques (FTTs) that are “flown” in the text. The FTT is a precise and standardized method, used to efficiently collect data during flight tests, research, and evaluation of aerospace vehicles. This first FTT introduces you to aerospace engineering in an exciting way, by taking a flight in a supersonic jet aircraft. 

A flight test engineer (FTE) often flies a familiarization flight in an aircraft before performing test flights, especially if this is an aircraft that is new to the FTE. As the name implies, this flight serves to familiarize the FTE with the aircraft and the flight environment. 

The areas of familiarization usually include the aircraft’s performance, flying qualities, cockpit environment, avionics, or other special test equipment and instrumentation. The present FTT provides a general description of a familiarization flight, but the primary objective is to introduce you to a wide range of aerospace engineering and test concepts that are explored in later chapters. 

Your familiarization flight will raise many technical questions about aerospace engineering and flight tests, and this provides motivation to seek answers in the chapters to come.

For your familiarisation flight, you will be flying the McConnell Douglas (now Boeing)F/A-18B Hornet supersonic jet aircraft, shown in Figure 1.2. The F/A-18B is a two-seat, twin-engine, supersonic fighter jet aircraft, designed for launching from and landing on an aircraft carrier. 

          Selected specifications of the McDonnell Douglas F/A-18B Hornet.

with these types of drawings of aerospace vehicles, where typically side, top, and front views of the vehicle are these specifications, such as what defines a “low bypass turbofan jet engine with an afterburner” or why wing area, maximum weights, or load factor limits are important. 

Before you can go flying in an F-18, you need to be properly dressed. You don an olive-green flight suit, black flight boots, and an anti-G suit, an outer garment that fits snuggly over the lower half of your body. Inflatable bladders, sewn into the anti-G suit, inflate with pressurized air to prevent blood from pooling in your lower extremities, keeping the blood in your head so that you do not lose consciousness when the aircraft is manoeuvring at high load factors or g’s. 

You slip your arms into a parachute harness that buckles around your chest and both legs. You are wearing the harness for the parachute, but not the actual parachute, as you will buckle this harness into your ejection seat, which contains your emergency parachute in the headrest. 

With your flight helmet, oxygen mask, and kneeboard, a small clipboard-type writing surface, in your helmet bag, you walk out to the airport ramp, where the jet is parked. As you walk up to the aircraft, you note its general configuration.

You observe that the landing gear looks quite sturdy, designed for harsh aircraft carrier landings. The jet is powered by twin engines, with semicircular air inlets on each side of the fuselage and side-by-side exhaust nozzles at the aft end of the fuselage. 

The two aviators sit in a tandem configuration, beneath a long “bubble” canopy that is hinged behind the aft cockpit. Your test pilot will be seated in the front cockpit and you will be in the aft cockpit. 

You approach the aircraft from its left side, next to the cockpit, as shown in Figure 1.4. Before you climb into the cockpit, you perform a walk-around of the jet to learn a little more about it. Underneath the left wing, near the fuselage, you look into the left engine inlet, which is a semicircular opening.

                                        F/A-18B Hornet walk-around, left-wing

This inlet feeds air to the turbofan jet engine. Later, we will learn about why the inlet is shaped in this way and how the air mass flow, which is ingested through the inlet, is related to the production of thrust. 

Looking underneath the fuselage, you see a large cylindrical fuel tank with pointed ends, hung underneath the centerline of the fuselage. Of course, you know that the fuel quantity carried aboard the aircraft dictates how far and how long the aircraft can fly. 

We will see that the range and endurance are a function of more than just the fuel quantity; it is also a function of key parameters related to the aerodynamics and propulsion of the vehicle. We will also learn about how to obtain range and endurance through flight testing. 

You move towards the leading edge of the left wing. You observe that the wing is thin, with a somewhat sharp leading edge, and that the wing's leading edge is swept backwards. There is a large hinged flap surface at the inboard wing trailing edge. We will explore the aerodynamics of three-dimensional wings and their two-dimensional cross-sectional shapes, known as airfoils. 

We will learn why airfoils and wings are shaped differently for flight at different speeds, including why wings are swept back. We will discuss how hinged flaps increase the lift of a wing. Fundamentally, we will discuss how a wing produces aerodynamic lift and will discuss the many ways of quantifying the lift and drag of an aircraft, through analysis, ground test, or flight test. 

Nowyouareattherear of the aircraft, looking at the two engine nozzles. The nozzles have interlocking metal petals that can expand and contract to change the nozzle exit area. We will examine how the flow properties change with area in subsonic and supersonic nozzle flows. 

We will learn how to calculate the velocity, pressure, and temperature of the gas flowing through the nozzle. You look down the afterburner of the jet engine, which appears to be an almost empty duct. We will discuss the various components of the jet engine, including the afterburner, and will explain their functions. 

The jet engine is an amazing engineering achievement. We will explore its beginnings and the engineers who invented it. We also learn about how engines are tested in the ground and flight environments.

                       F/A-18B Hornet walk-around, engine nozzles

Comingaroundtheright,aftendoftheairplane,asshowninFigure1.6,youlookatthehorizontal and vertical tail surfaces. We will learn why these surfaces are critical to the stability and control of the aircraft. 

We will see that the locations and sizes of these surfaces are important parameters in defining the aircraft’s stability in flight, and will also learn about the control forces associated with deflection of these surfaces in an air stream. We will discuss several different flight test techniques used to quantify an aircraft’s stability. 

        F/A-18B Hornet walk-around, aft, right empennage, and right-wing flaps.

Near the nose of the aeroplane, you notice several L-shaped tubes mounted on the lower side of the fuselage. We will learn about these Pitot tubes, which are used to measure the F-18’s airspeed and will investigate how they work in subsonic and supersonic flight. 

We will also see that flight testing is required to calibrate these probes to obtain accurate airspeed information. You come to the aircraft nose, which has a pointed shape. 

We will explore the aerodynamics of two and three-dimensional bodies, such as this nose shape. We will also touch on the interesting phenomena that occur when these types of pointed shapes are at high angles of attack. 

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