Introduction to flight 1

Prof. Galal Bahgat Salem Aerospace Dept., Cairo University

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AER 101 Introduction to AeronauticsInstructor : Prof. Dr. Galal Bahgat Salem

Textbook : John D. Anderson, Jr, Introduction to Flight , 4th Edition ,

2000.

Term Work : 25 +25 = 50 Marks

Final Exam: 50 +50 = 100 Marks


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AER 101 A Introduction to Aeronautics ( 2 + 1 )

• History of Flight• Nature of Aerodynamic Forces• Airplane components and Configurations• Scope of Aeronautical Engineering• Fluid Properties and Characteristics• Atmosphere• Basic Aerodynamics : Kinematics, Continuity and

Bernoulli’s Equations, Boundary Layer Concept, Skin Friction, Pressure Drag, Flow Separation, Streamlining


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AER 101B Introduction to Aeronautics ( 2 + 1 )

• Geometric and Aerodynamic Characteristics of Airfoils• Dimensional Analysis and Aerodynamic Force

Coefficients• Elements of Airplane Performance: Drag-Speed Curve,

Cruising Flight Performance, Climbing Performance, Gliding Performance

• Elements of Propulsion: Propellers, Piston Engines, Reaction Principle, Jet Engines, Rocket Motors

• Elements of Airplane Stability and Control


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Chapter 1History Of Flight

What is Flight ?

■ Flight is a motion in air free from ground topography

■ It is a high-speed motion through a low-resistance ( low density ) medium which is air

N.B. Compare flight in air, having a density of 1.225 Kg/m3, with shipping in water of density 1000 Kg/m3


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Short History of Flight1. Imitating Birds

• People attempting to fly by using artificial wings strapped to their arms and-or legs

• The flapping of wings generate lift• The Greek myth of Daedalus and his son Icarus

imprisoned on the island of Crete in the Mediterranean Sea illustrates man’s flight

• The idea of strapping a pair of wings to arms fell out of favor

• It was replaced by concept of wings flapped up and down by various mechanical devices,


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Powered by human arm, leg, or body movement• These are called Ornithopters • Ornithopters first designed by Leonardo da

Vinci ( 1452-1519 )


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Leonardo da Vinci


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Why Don’t Ornithopters Work?

• G. A. Borelli (1680 ) realized the fact that ( power/weight) ratio of a man is much less than that of bird

• Hence man will never be able to fly like a bird, by his own power only

2. Lighter-than-Air Balloons[Unpowered Flight]

● Firstly hot air balloons discovered by the Montgolfier Brothers in France (1783)


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• Later on gas balloons of Hydrogen/Helium were used by Charles

• Charles found that ballooning is based on Archimedes principle of buoyancy

• Unmanned Balloon Manned Balloon


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3. Lighter-than-Air Dirigibles (Airships)[Powered]●Firstly invented by Count von Zeppelin in

Germany (1900) ●They are more rigid (the first airframe) than

balloons, controlled and directed (using stabilizing surfaces) and propeller droved

●Large bags of gas inside the rigid airframe●Count von Zeppelin (1929), flew around the world

in 21 days●Hydrogen fired in “Hindenburg” dirigible in 1937


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4.Sir George Cayley (1799) ●First pioneered the concept for the modern airplane

configuration in 1799 - Fixed wings, tail, fuselage - Separate mechanism for propulsion “separation of lift and propulsion”● Recognized that the function of thrust was to overcome

aerodynamic drag ●Drew the first lift-drag vector diagram in the historyN.B. Before this time flapping wings were supposed to

provide both lift and propulsion


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Lift Resultant Aerodynamic

Force

Drag

Thrust


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5.Heavier-than-Air Unpowered Gliders (Sailplanes)

• Gliders first designed and flew by Otto Lilienthal, a German mechanical engineer, in 1891

• Lilienthal is known as the glider’s man• Gliders characterized by un-sustained flight


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He died in 1896, after stalling a glider he was flying


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6.Heavier-than-Air Powered Airplanes

• Samuel P. Langley was contracted to build a flying machine for the U.S. government

• Began a series of aerodynamic experiments in 1887• Successful in flying several small scale, unmanned,

powered aircraft, which he called aerodromes• These were the first steam-powered, heavier-than-air

machines to successfully fly• Langley’s attempt to build a manned aerodrome failed• Lunched and crashed on Oct. 7 and December 8, 1903


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Langley’s aerodrome shortly after launch


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• The Wright Brothers • Wright brothers (Orville&Wilbur) were the

inventors of the first practical manned flight on 17 Dec.,1903 (Flyer I )

• It was a strut-and-wire biplane configuration• Propulsion was achieved by a four-cylinder in-

line engine designed and built by Orville Wright• It produced close to 12 hp and weighed 140 Ibs• It drove two propellers via a bicycle-like chain

loop


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• The control feature of Wright flyer is one of the basic reasons for its success

• Flyer I had a wing span of 12 m , flew a distance of 256 m, and lasting 59 sec

Wright Flyer Engine


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Wright Flyer engine


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■ Hydrostatics of Lighter-than-Air Flight

• The lifting force is the buoyancy force• The basic laws of hydrostatics (fluid at rest) are:

a- fluid pressure p is uniform in horizontal

planes, as well as the density

b- p varies only with height z according to the

Hydrostatic equation z

datum


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dp/dz = -ρg

Integrating, in case of constant density:

p + ρ g z = constant

This is the hydrostatic equation

non-uniform

p distribution

on a body immersed

in a fluid at rest

p

p + ρ g z

z

B


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• The resultant fluid-pressure force is called the buoyancy force B, acting vertically upward, and equals to the weight of the displaced fluid

• B = ρ g V

where ρ density of fluid

g acceleration of gravity

V volume of immersed body

N.B. The basis of Heavier-than-air Flight will discussed later


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Anatomy OF THE AIRPLANE

■The Main Components of the Airplane


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• The basic airplane components include: fuselage, wing, tail assembly, control surfaces, landing gear, and power plant(s)

1.The Fuselage

♦ It carries the payload.

♦ It is the central structural member of the

airframe to which other members are attached.

♦ It is generally streamlined to reduce drag.

♦ Designs vary with the mission to be performed,

as illustrated in figure


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2.The Wing

● It generates the lift force. • It includes the flaps for lift augmentation during

landing and takeoff, and ailerons for banking the airplane during turning.

• The wing cross-section is called Airfoil• The airfoil shape, wing planform shape, and

placement of the wing on the fuselage depend upon the airplane mission.

• The figure illustrates wing shapes and placements


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3.Tail Assembly and Control Surfaces

• The tail assembly (empennage) represents the collection of structures at the rear of the airplane

• The tail assembly consists of:

1- The vertical stabilizer (fin) and rudder which

provide directional stability in yaw

2-The horizontal stabilizer and elevator which

provide longitudinal stability in pitch

● The figure illustrates different forms of tail assembly


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4.Landing Gear

• The landing gear (undercarriage) supports the airplane while it is at rest on the ground and during the takeoff and landing

• The gear may be fixed or retractable• The wheels are attached to shock-absorbing

struts that use oil or air to cushion the blow of landing

• Special types of landing gear include skids for snow and floats for water

• For carrier landings, arrester hooks are used


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4.Power Plants

• Power plants used to produce the thrust force necessary to propel the airplane to overcome the drag

• The power plant consists of the engine (and propeller, if present) and accessories

• The main engine types are:

-Reciprocating (or piston type)

-Reaction engines such as turbojet, turbofan, turboprop, ram jet, pulse jet, and rocket engine

The figure shows several some of engine placements


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■The Aircraft Structure

• The figure shows a cutaway drawing of an aircraft structure


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Basic Elements of Aircraft Structure

■The wing


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• Wing structure basically same in all aircraft types

• Modern aircrafts have all metal and composite material wings but many older had wood and fabric wings

• The wing is a framework composed of spars, ribs and (possibly) stringers (see figure)

• Spars are the main members of the wing. They extended lengthwise of the wing (crosswise of fuselage)

• Most wing structures have two spars, the front spar and the rear spar


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• Front spar near the leading edge, while the rear spar at about two-thirds the distance to the trailing edge

• The ribs are the parts of the wing which support the covering and provide the airfoil shape

• A skin covers the wing framework


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■The Fuselage


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• The fuselage structural elements are:

1-Bulkheads, which form the cross-sectional shape of the fuselage

2-Longerons, which are heavy strips that run the length of the fuselage and are attached to the outer edge of the bulkheads

3-Fuselage skin, which is attached to the longerons

N.B. Keelson is a strong beam placed at the bottom of the fuselage. The keelson is frequently used in military fighter aircrafts


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■ Aerodynamic Basis of Heavier-than-Air Flight

• This is the real flight• It needs a lifting force to balance the weight;

since the buoyancy force is not sufficient• The source of the lifting force is the fact that

when a fluid is in motion, its pressure varies not only with height, as in the case of rest, but also with its velocity

• The relation between p, V, and z is expressed by Bernoulli’ equation (1738) :


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p + (1/2) ρ V2 + ρ gz = constant

• Where p static pressure

• (1/2) ρ V2 dynamic pressure

• ρ g z head pressure

• The shape of an airplane-wing cross section (known as aerofoil or airfoil) was evolved from the Venturi tube, as shown :


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• When a fluid flows over a body (or a surface), or when a body is forced to move through a fluid, the fluid velocity relative to the body surface may be increased or decreased (depending on surface shape and altitude)

• And consequently the fluid pressure p may decrease or increase according to Bernoulli’s equation

• The resultant will be a net fluid force F acting on the body which is completely different than the Buoyancy force (and may be many times greater than it)


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How does an Airplane fly?

• The key to the generation of lift is the specially-designed streamlined body, called the wing, and characterized by a special cross-section, called airfoil

• When the wing is propelled through air at a suitable angle of attack, and with a relatively-high speed, the air flowing around its surface is accelerated and/or decelerated according to Bernoulli’s equation

• The integration of the air-pressure distribution over the surface of the wing results in a resultant aerodynamic force F


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• The component of R perpendicular to flight direction (direction of relative motion) is called the Lift L

• The component of R opposite to flight direction is called drag D


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Forces on an AirplaneBasically, the four forces acting on an airplane are

weight, thrust, lift, and drag


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• Weight: The weight includes the airplane itself, the payload, and the fuel. Since the fuel is consumed as the airplane flies, the weight decreases. Weight acts in a direction towards the center of the Earth.

• Thrust: The driving force of whatever propulsive system is used, engine driven propeller, jet engine, rocket engine, and so forth, is the thrust. It may be taken to act along the longitudinal axis of the airplane.

• Lift: This force is generated by the flow of air around the airplane, the major portion resulting from the wing. It represents the component of the resultant aerodynamic force normal to the flight direction.


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• Drag: This force arises from the flow of air around the airplane and is the component of the resultant aerodynamic force opposite to the flight direction

• For un-accelerated (Steady) level flight:

L = W T = D


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Scope of Aerospace Engineering

• Aerospace engineering means airplane, missiles (Rockets), and satellite design, manufacturing, testing, maintaining, repairing, overhauling, and performance analysis

▄ The Main Topics A.E. are: (1) Aerodynamics (2) Airframe Design (3) Propulsion (4) Flight Mechanics & Control


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■ The Associated Topics are: ►Flight navigation ►Electronics ( + Flight navigation = Avionics ) ►Meteorology ►Metallurgy ►Production Engineering ►Fluid-power engineering (pneumatic, hydraulic, pressurization, and air-conditioning systems) ►Instrumentation ►Chemical & fuel engineering ►Flight regulations & Airworthiness


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■ The Associated Topics are: ►Flight navigation ►Electronics ( + Flight navigation = Avionics ) ►Meteorology ►Metallurgy ►Production Engineering ►Fluid-power engineering (pneumatic, hydraulic, pressurization, and air-conditioning systems) ►Instrumentation ►Chemical & fuel engineering ►Flight regulations & Airworthiness


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Aerodynamics

●Aerodynamic design of the flight vehicle/space vehicle for:

►Maximum lift production ►Minimum drag ►Max. available space for structure and payload●Determination of the aerodynamic forces on the

designed configuration at the different flight conditions (speed, attitude, and a altitude)

● Wind-tunnel testing●Flight testing


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Propulsion

●Power-plant design & construction for:

►Max. thrust/weight of engine

►Max. thrust/drag of engine

►Min. specific fuel consumption (sfc)

►Good performance at different altitudes and speeds of flight

●Power-plant manufacturing

●Power-plant testing


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Airframe Design

●Structural analysis

●Airframe design & construction for: sufficient strength and with less weight

●Airframe manufacturing techniques

●Airframe testing techniques


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Flight Mechanics & Control

●Stabilizing and control surfaces design

●Control surfaces operation and performance

●Aircraft stability analysis

●Maneuverability considerations

●Airplane systems and instrumentation

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Introduction to flight 1

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