AVIATION TECHNOLOGY GRADE 10 COURSEBOOK | STRAND 3_THEORY OF FLIGHT 1

2. STRAND 3_THEORY OF FLIGHT 1

Specific Objectives.

At the end of the strand, the learner should be able to:

State briefly the historical development of aviation.
Identify the various types of aircraft
Identify major parts of an aircraft.
Explain basic science concepts
Explain the concepts of flight
Construct simple aircraft MODEL

Sub-STRANDs

a. Introduction

b. Historical highlights.

c. Aircraft Classification

d. Nationality and registration marks.

e. Parts of an Aircraft.

f. Basic science concepts.

g. Bernoulli’s Principle and the aerofoil.

h. Construction of a simple aircraft

Introduction

.The history of aviation extends for more than two thousand years. From the earliest forms of aviation such as kites and gliders, attempts at tower jumping to supersonic and hypersonic flight by powered, heavier than air jets.

Flying has always fascinated man. We also have the Greek mythology where father and son built wings to escape from prison.

On 21^st November 1783 John Francois de Roise and Marquis de Arlandes took off in a Montgolfier balloon over Paris in France. They flew over the city for 23 minutes landing 10 kilometers away.

Historical highlights.

13^th Century

Rodger Bacon, an English philosopher wrote on the possibility of man flying a machine sitting in the middle turning a mechanism to gain motion by artificial wings.

15^thCentury

Leonardo da Vinci wrote notes and made sketches on flying machines.

19^thSeptember 1783

The Montgolfier brothers flew a hot air balloon over Paris city.

1783

Louis Sebastian designed a parachute.

1804

Sir George Cayle wrote the first clear outline of aeronautical principles. He designed a machine powered by a steam engine and operating a propeller. He did not fly it but was able to demonstrate how a curved surface generates lift. He is known as the father of aviation. He used a glider that actually flew over a valley and over villages.

1884

Charles Reynolds and Luther Weber flew the first controllable airship.

1893

Lawrence Hargraves invented a rotating engine and also a box kite.

1903

The Wright Brothers took all the credit for the first heavier than air aircraft.

1907

Paul Cornu, an aircraft mechanic was the first man to fly a helicopter.

1914

The first airline flight was made in Tampa U.S.A

1930

Amy Johnson was the first woman to fly an aircraft from U.K to Australia.

1937

The “nerdeilberg” an airship exploded in America in 6^th May.

1941

The first practical helicopter by Igor Sirkosky, solved the torque problem.

1967

Apollo rocket exploded during a test flight.

1964

Neil Armstrong was the first man to walk on the moon.

1975

The Concorde aircraft (supersonic jetliner) began passenger flight in France.

1981

Creation of the first space shuttle.

1986

The Challenger space shuttle exploded killing all the astronauts on board.

1992

The first human powered was launched.

2003

The Concorde suspended all the commercial flights after an accident over Paris that killed all the passengers and the crew.

Lighter than air aircraft.

These aircraft are also referred to as aerostats. Lighter than air aircraft get lift principally from buoyancy instead of generating lift through the use of aerofoil. Examples of such aircraft include:

i. Hot air balloons.

ii. Airship.

i) Hot air balloon.

A balloon works on the principle that lift force is greater than the weight force. The air inside the balloon is heated by a propane burner making it lighter than the air outside the balloon. To gain height, the air is heated more and to loose height, less gas is burnt. For landing, a valve at the top of the balloon is opened to release the hot gases out slowly.

ii) Airship

It is a balloon which has a power source and is mechanically driven to propel it through the air. An engine and the ability to steer distinguishes an airship from hot air balloons.

Heavier than air aircraft.

These are that generate lift by allowing air to flow over the aerofoil shaped wings. This flow creates a pressure difference between the upper and lower surfaces of the wings and this pressure difference is the lifting force.

Heavier than air aircraft can be categorized as:

a. Mechanically driven.

b. Non- mechanically driven.

a. Mechanically driven

These are aircraft that have an engine as a source of power to propel the forward. They are further classified to as:

- Rotary wing.

- Fixed wing

Rotary wing.

These are aircraft that have aerofoil shaped blades mounted at the top of the airframe that when they are rotated, they generate both lift and thrust.

These aircraft include:

1) Helicopter.

2) Gyroplane

1) Helicopter.

This is a heavier than air aircraft with a power source that drives an overhead rotor shaft to generate both lift and thrust.

2) Gyroplane.

It is a plane with two rotors; one rotor is a propeller used to generate thrust while the other automatic rotor which responds to the rotation by wind to generate lift.

Fixed wings

These are aircraft that have aerofoil shaped wings that generate lift by relative flow of air over them. They include:

1) Amphibians.

2) Sea planes.

3) Land planes.

1) Amphibians.

They are powered aircraft that can land on both water and on land. They have floats for landing on water and wheels to use on land.

2) Sea planes

These are aircraft that land on water only. They use float that are filled up with compressed nitrogen to allow them to float on water.

3) Landplanes.

This category constitutes the largest number of planes. They can only land on designated areas called runways that are tarmacked.

NATIONALITY AND REGISTRATION MARKS

• The nationality mark of an aircraft is a group of two capital letters in roman characters and the registration is a group of these capital letters in roman characters.

• The registration letter are assigned by the Director of Kenya Civil Aviation Authority (KCAA).

• Aircraft nationality marks are assigned by ICAO. The nationality marks given to Kenya by ICAO is 5Y.

• The nationality marks are painted at strategic areas of the aircraft, ensuring clear visibility from a distance.

• The colour of the marks should contrast that of the background and there should be no obstruction.

• The nationality and registration marks are separated with a hyphen.

Position of aircraft nationality and registration markings.

Aircraft nationality and registration markings are usually placed on the following areas:

Ø On the sides of the vertical stabilizer [equidistant, from leading edge and the trailing edge].

Ø On the side of the fuselage between the trailing edges of the wing and the leading edge of the horizontal stabilizer.

Ø Below the left wing or may extend the whole length of the wing [span]

Ø On helicopters, the markings can be placed on both sides of the tail boom and sometimes on the engine nacelles.

Ø On airships the markings are placed on both sides of the hull.

Ø On hot air balloons, the markings are placed on two sides diametrically opposite.

Parts of an aircraft

An aircraft consists of five major parts namely:

i. Fuselage

ii. Undercarriage [landing gear]

iii. Main planes [wings]

iv. Power plants [engines]

v. Empennage [tail section]

Fuselage

This is the central part of the aircraft and has the following functions:

v It provides attachment for other aircraft parts e.g Wings, Undercarriage etc.

v In single engine aircrafts, it holds the power plant.

v It has a cabin which provides the space for carrying cargo and passengers.

v It protects the passengers from the harsh atmospheric conditions experienced during flight.

v It has a cockpit which holds all the flight operation controls, and housing the flight crew.

v It provides a passage for the aircraft control cables and wiring.

Undercarriages

These are structures that are located beneath the fuselage structure, and can also be referred to as landing gears. Their functions include the following:

v To support the aircraft during ground operations like taxing, parking and towing.

v It has a wheel assembly which allow ground movement of the aircraft before take-off and after landing.

v It has brakes which assist in slowing the aircraft after touch down.

v It acts as a shock absorber during landing.

v It has a steering mechanism to enable the aircraft maneuver while on the ground.

v It provides enough ground clearance for the engines and propellers.

Main planes

They are also known as wings, and are usually in a pair. One is attached to the right side of the fuselage, while the other is attached to the left side of the fuselage. The functions of the main plane include the following:

v To generate the lift force required to support the aircraft in flight.

v To provide the space for storing fuel.

v To provide the attachment for the engines in multi engine aircrafts.

v To provide the stowage area [wheel well] for undercarriages.

v To hold weapons especially in military aircrafts.

v To provide hinge surface for flight control surfaces like Flaps, Ailerons, and Spoilers etc.

Power plant

It is also known as engines, and can be wing mounted or fuselage mounted. The function of the engine include:

v To generate thrust force required to move an aircraft forward during flight.

v To generate electricity for cabin lighting and powering of aircraft systems through engine driven generators.

v To provide bleed air to be used for cabin pressurization and air conditioning, de-icing and anti-icing, and also for running gyroscopic instruments.

v To provide a means of slowing the aircraft after touchdown through thrust reversers.

v It provides a means of turning an aircraft on the ground through power differential.

Empennage

This is the tail section of the aircraft and consists of fixed surfaces like the Fin, Tail plane and the Tail cone, and movable surfaces like the rudder and elevators.

The empennage has the following functions:

v It has a fin/vertical stabilizer which assist in stabilizing the aircraft vertically.

v It has a tail plane/horizontal stabilizer to assist in stabilizing the aircraft horizontally.

v It has a tail cone which encloses the rear end of the fuselage, thus streamlining it.

v It houses the auxiliary power unit (APU) in large airplanes.

v It anchors the power plant in some aircraft models

bAsic science concepts

Science Concepts refers to a methodology of using tools for recognizing, representing and manipulating various knowledge domains. The following are the basic science concepts that are applicable in Theory of Flight:

Mass

• Mass (M) is the quantity of matter in an object.

• The mass of an object is not dependent on gravity and is therefore different but relates to the weight of an object.

• The thrust produced by an aircraft propeller or jet engine is dependent on the mass flow of air through the engine.

• The SI Unit of mass is Kilogram (Kg)/ Pounds (Lb.).

• Other units for mass are:- grams(g) - milligrams(mg) - Tonnes(t)

• Mass = Density ×Volume

Weight

• The weight of an object is the force with which the object is attracted to the Centre of the earth.

• It is a product of the mass of the object and acceleration due to gravity (g).

• The SI Unit for weight is Newton (N). 1 Newton is the force required to give a body of 1 Kilogram an acceleration of 1m/s.

• Other units for weight are Kilo newton(KN)

• Weight=Mass×Gravitational Acceleration.

Force

• This is a pull or a push of an object.

• The SI unit of force is Newton (N).

Force = Pressure × Area

There are four principle forces that act on an aircraft during flight, these are:-

a. Weight - It is a force that acts downwards from the center of gravity and tends to pull the aircraft towards the center of the earth.

b. Lift - It is a force that acts upwards from the wing center of pressure and tends to oppose or overcome weight.

c. Drag - It is the force that acts backwards from the center of gravity and resists the aircraft movement through the air.

d. Thrust - It is a force that acts forward from the engine and propels the aircraft forward.

Energy

• Energy is the ability of a system to do work.

• It can also be defined as the capacity of a physical system to do work.

• The SI unit of energy is Joules (J).

• Energy can be classified into two forms:-

i) Potential Energy (P.E)

ii) Kinetic Energy (K.E)

Potential energy: It is a form of energy possessed by a body because of its configuration or its position. For example;

a) An object raised at height-(position)

b) A tightly wound spring-(condition)

c) A gas stored in a cylinder-(condition)

Kinetic energy: It is a form of energy possessed by a body due its motion. For example

a) When a hammer is raised to hit a nail.

b) When water is released to rotate the turbines to produce hydroelectric power.

c) When wind drives turbines to drive electricity.

d) When a bullet is shot by a gun.

Kinetic energy= (1/2) ×Mv²

LAWS OF CONSERVATION OF ENERGY

• It states that energy can neither be created nor destroyed, but can be transformed from one form to another.

• This means that the total amount of energy in the universe is constant.

Various forms of energy include: -Heat Energy. - Chemical Energy. - Nuclear Energy. - Solar Energy. - Mechanical Energy. etc.

Momentum

• Momentum refers to the quantity of motion that an object has.

• It can also be define as the product of mass and velocity of an object.

• The SI Unit for momentum is Kg.m/s

• Momentum = Mass × Velocity

Angular momentum is the tendency of a rotating body to continue spinning about an axis

Pressure

• This is the force acting perpendicularly per unit area.

• The SI Unit for pressure is N/m²

Pressure = Force÷Area

• Other units for pressure are:- a) Atmosphere (Atm.) b) Millibars (mb) c) Inches of Mercury (in Hg) d) Pounds per Square Inch (Psi) e) Millimeters of Mercury (mm Hg)

Density

• It refers to the mass per unit volume of an object.

• The SI Unit for density is Kg/m³or g/cm³

Density = Mass÷Volume

Speed

• This is the rate of change of distance with time.

• Speed can also be defined as how fast or slow an object moves.

• Speed is a vector quantity.

• The SI Unit for speed is Km/h

Speed = Distance÷Time

Velocity

• This is the rate of change of displacement with time.

• Velocity is a vector quantity. i.e. It has both direction and magnitude.

• The SI Unit for velocity is m/s

Velocity = Displacement÷Time

Acceleration

• This is the rate of change of velocity with time. It is a scalar quantity.

• The SI Unit for acceleration is m/s²

Acceleration = Change in Velocity÷Time

Centre of gravity

• This is a point in an object from where all its mass tends to act from.

• It is the point about which all gravitational moments adds up to zero.

• In an aircraft, it is assumed to be the point where the three principle axes meet.

Moments

• This is the turning effect of a force.

• It can also be defined as a tendency of a body to rotate.

• This is the product of force and perpendicular distance, separating the point of application of the force and the fulcrum/pivot.

• The SI unit of moments is Nm.

Moment= Force × Perpendicular distance

• Aircraft primary controls are placed at the furthest distance from the center of gravity to give them a long moment arm so that just a small force is able to control them.

Force and motion

Effects of force

ü Can make a stationary object move.

ü Can change the shape of an object.

ü Can change the direction of an object.

ü Can stop a body in motion.

• The concept of force and motion is well explained in Newton’s Laws of Motion as follows:

Newton’s -First law of Motion

· It states that body in the state or in uniform linear motion will continue in that state unless acted upon by external forces.

This law is also referred to as the law of inertia.

Inertia: - The tendency of a body to remain in a state of rest or uniform motion in a straight line for example

If a car in motion stops instantly, the passengers tend to jerk forward as their masses resist stoppage.

Newton’s -Second law of motion

• This law states that the acceleration of a body is directly proportional to the force causing it and inversely proportional to its mass that is, a large mass requires a huge force to accelerate it or to stop it.

Acceleration= Force÷Mass

Newton’s -Third law of motion

• This law states that for every action there is an equal and opposite reaction force. For example, for an aircraft to move forward, a propeller or a jet engine pushes large mass of air backwards and in turn a reactive force is generated which pushes the aircraft forward.

Bernoulli's Principle And the aerofoil

Bernoulli's Principle

Daniel Bernoulli, a Swiss scientist of 18^th Century, discovered that if a fluid is flowing through a pipe with a restriction (narrow point) when it approaches this point, its velocity increases while its pressure decreases.

Bernoulli's Principle states that; In a steady, non-viscous and incompressible fluid in motion, the total energy of a fluid particle is constant at all points on its path.

Study of fluid flow in a closed tube

• Suppose a stream of water is flowing through a venturi tube as shown below:

• The fluid flow at the tube inlet has a certain velocity and static pressure. Since the fluid flow is enclosed within the tube the mass flow along the tube remains constant.

• As the fluid flow approaches the constriction at the center of the tube, the velocity increases as the pressure decreases.

• Towards the venture tube outlet the velocity of the fluid decreases and static pressure increases. The total energy of the air stream remains constant.

The Aerofoil

Aircraft wings and helicopter rotors are examples of aerofoil. When an aerofoil is moved through the air, it generates both lift and drag.

LIFT GENERATION

• As the airflow approaches the leading edge of the wing, it separates into two flows

• The first airflow flows above the upper surface of the wing. While the second flows below the lower surface of the wing which is flat or has a very small curvature.

• Due to the upper surface camber, the air molecules travelling above the wing has a longer distance to cover as compared to the one travelling below yet both flows must meet at the trailing edge at the same time.

• This makes the airflow above, which has a longer distance to cover to move faster than the airflow below the aerofoil.

• According to Bernoulli's principle, the higher velocity above the aerofoil creates a region of low pressure while the slow airflow below the aerofoil creates a region of high pressure.

• This pressure difference creates a differential force called lift.