Presentation on theme: "THEORY OF FLIGHT 1 PO 402 CI Norwood References: FTGU Pages 9-50, Pilot’s Handbook of Aeronautical Knowledge Chapters 1-3."— Presentation transcript:
THEORY OF FLIGHT 1 PO 402 CI Norwood References: FTGU Pages 9-50, Pilot’s Handbook of Aeronautical Knowledge Chapters 1-3
Review from last class 1. What is the VFR weather minima for fixed wing aircraft <1000’ AGL in uncontrolled airspace? 2. You are on final approach and you receive a flashing red light from the tower. What does it mean and what do you do?
Topics to be covered today The fuselage and empennage Parts of the airplane Four forces acting on an aircraft How lift is created Boundary layer
What is an airplane? The Canadian Air Regulations defines an airplane as: “A power driven, heavier-than-air aircraft, deriving its lift in flight from aerodynamic reactions on surfaces that remain fixed under given conditions of flight”
Definitions Aircraft: any machine capable of deriving support in the atmosphere from the reactions of the air Glider: heavier-than-air aircraft not equipped with a motor, which derives its lift from aerodynamic reactions on surfaces which remain fixed under given conditions of flight Airframe: Total structure of the aircraft including fuel systems and fuel tanks but excluding instrumentation and engines
Classification Aircraft can be classified according to: Position and number of wings The number of engines configuration of the undercarriage
Parts of the Airplane
Fuselage The fuselage is the main body of the aircraft Holds all passengers and cargo Almost all parts of the aircraft are attached to the fuselage Three types of fuselage construction: Truss type Monocoque Semi-monocoque
Truss Type (SGS 2-33A) Steel or aluminum tubing (wood in antique aircraft) Strength is achieved by welding tubes into triangles called “trusses” Longerons make up the frame which are supported by diagonal and vertical members
Monocoque (Katana) Uses a stressed skin to handle all loads Main construction consists of formers to give shape and bulkheads to seal off and connect sections Very strong but heavy due to the strength requirement of the skin
Semi-Monocoque (Airbus 320) Structure of formers, bulkheads and stringers to create a frame Frame is covered by a stressed skin to take some of the bending stresses Most common type of fuselage construction
Review 1. What is an aeroplane according to the CARs? 2. What are the main parts of an airplane? 3. What are the three types of fuselage construction?
Empennage Horizontal stabilizer – Non movable horizontal surface Elevator – Movable surface attached to the horizontal surface Fin or Vertical stabilizer – Non movable vertical surface Rudder – Movable surface attached to vertical stabilizer
Canard In some aircraft, the horizontal tail is moved forward Seen in early aircraft such as the Wright Flyer and modern aircraft such as the Beech Starship and fighter aircraft Canard
Stabilator One piece movable surface that replaces the elevator and horizontal stabilizer Stabilators have a movable surface called an anti-servo tab which act as trim tab to relieve control surfaces
The Wings and Lifting Surfaces Two main types of wing configuration Monoplane – One wing Biplane – Two wing
Wing Positioning Three positions for the wing relative to the fuselage: High-wing – Attached on top Mid-wing – Attached in the middle Low-wing – Attached on the bottom
Review 1. What surfaces make up the empennage? 2. What is a stabilator? 3. What are the three types of wing positioning?
Construction of the Wing Spar – Run from wing root to tip, stiffens the wing Ribs – Run from leading edge to trailing edge and give wing its shape Compression struts – Tubes placed between spars to handle compression loads
Construction of the Wing Drag and anti-drag wires – Resists bending forces from the wing going through the air Ailerons – Movable surface on the outboard sections that control roll. Move in opposite directions on each wing
Construction of the Wing Flap – Movable section next to the wing root Wingspan – Distance from wingtip to wingtip
Construction of the Wing Chord – Imaginary straight line from the leading edge to the trailing edge Struts – External bracing that support the wings, mainly seen in high wing aircraft Struts
Review 1. What are the main components of the wing? 2. What do ailerons do? 3. What is the chord?
Landing Gear Absorbs shock of landing Allows the movement of the aircraft on the ground Can be either fixed or retractable
Type of Landing Gear Conventional (Tail dragger)Tricycle (Nose wheel) Mono-wheel
Conventional Gear Less parasite drag Cheaper Better ground handling Better handling on rough strips More difficult to land Has tendency to nose- over Poor ground visibility Poor crosswind handling AdvantagesDisadvantages
Tricycle Gear Easy to land Good ground visibility Good crosswind handling Very small chance of ground looping More parasite drag Poor ground clearance for propeller Poor performance on rough surfaces AdvantagesDisadvantages
Propulsion System For smaller GA aircraft the main parts of the propulsion system are: Engine: Provides rotation for the propeller Propeller: Creates thrust through rotation Cowling: Covers the engine and provides cooling through air ducts
Review 1. What are the two types of landing gear? 2. What are some advantages/disadvantages of those landing gear? 3. What are the main components of the propulsion system?
The Four Forces
Lift Lift opposes weight through aerodynamic reactions Creation of lift can be explained through two separate principles: Newton’s Three Laws of Motion Bernoulli’s Principle
Newton’s Three Laws of Motion 1 st law: An object in motion will stay in motion and an object at rest will stay at rest unless acted on by another force 2 nd law: Acceleration of an object is inversely proportional to the mass of the object and proportional to the force applied (ex. You trying to push a school bus as opposed to a soccer ball) 3 rd law: Every action has an equal and opposite reaction
Bernoulli’s Principle Energy in a system must remain constant If we look at a venturi tube, the amount of air entering in the tube must equal the air exiting the tube (flow rate)
Bernoulli’s Principle As the tube decreases in size the velocity of the air must increase to maintain the same flow rate, therefore kinetic energy increases This causes the pressure to drop and the energy remains constant
How lift is actually created As the air flows over the wing, it accelerates as it moves over the cambered surface (just like in a venturi tube) This causes the pressure above the wing to decrease, creating a force that sucks the wing into the air
How lift is actually created On the underside of the wing, the air is deflected downwards which pushes up on the wing Also, air flowing off the top of the wing is deflected downwards, this contributes to lift This phenomenon is called downwash and is a result of Newton’s 3 rd law Force acting on air Force acting on wing DOWNWASH
Review 1. What is Bernoulli’s Principle? 2. What are Newton’s three laws of motion? 3. How does a wing create lift?
Weight Weight is the downward force created on the aircraft due to gravity All of the weight acts through a single point called the centre of gravity
Thrust Thrust is force that moves the aircraft forward through the air While there are many ways of producing thrust, all rely on the principle of moving air backwards to create a reaction to push the aircraft forward
Drag Resistance to the motion of the aircraft through the air There are two main types of drag: Parasite drag – Created by parts of the aircraft that do not contribute to lift Induced drag – Created by parts of the aircraft that contribute to lift
Parasite drag Form Drag: Drag created by the shape of the aircraft. Can be reduced through streamlining Skin friction: Drag created by the roughness of the skin, can be made worse through dirt and ice accumulation Interference drag: Drag created by two parts of the aircraft that create eddies where they intersect (such as the struts and wings) Parasite drag increases as speed increases
Induced drag Created by parts of the plane that create lift Cannot be completely eliminated Greater the lift, greater the induced drag Reduces as speed increases
Review 1. What do we call the point at which all weight acts through? 2. How is thrust generally produced? 3. What are the two types of drag?
Airfoils An airfoil is any surface designed to create lift Most suitable surface for creating lift is a curved or cambered surface
Camber Camber is the curvature of the upper and lower surfaces of the wing Usually the upper surface is more curved that the lower surface
Equilibrium When two forces are equal and opposite, they are said to be in equilibrium When the forces are equal, the aircraft will continue to move at a constant rate of speed
Couples When two forces are opposite and parallel, but not acting through the same point, a couple is created This couple will cause rotation about a given axis An example of this would be drag acting opposite and parallel above thrust, this would cause the nose of the aircraft to rise
Relative Airflow (Relative Wind) Direction of the airflow with respect to the wing Created by the motion of the aircraft through the air Can also be created by air moving around a stationary object When an aircraft is on the take-off roll, the aircraft will be subjected to the relative wind by it’s own motion through the air and by the wind
Review 1. What is camber? 2. What is equilibrium and when would an aircraft be in equilibrium? 3. What is a couple and what can it do to an aircraft? 4. What is relative airflow?
Aileron Drag When an aircraft banks to turn, one ailerons moves up, the other one goes down The down going aileron compresses the air underneath the wing and creates more lift, rolling the aircraft By creating more lift, more drag is created and the aircraft yaws opposite turn This is called adverse yaw
Secondary Effects of Controls Yawing moment in the direction of the turn created by the relative airflow hitting the side of the fuselage ahead of the c of g Rolling moment in the direction of the turn due to the outside wing moving faster through the air creating more lift AileronsRudder
Lift and Drag Curves Lift and drag are dependant on several factors: Angle of attack and the shape of the airfoil – C L and C D Wing area – S The square of the velocity – v 2 Density of the air – ρ Lift equation: L = ½ C L v 2 ρ Drag equation: D = ½ C D v 2 ρ
Lift and Drag Curves
Center of Pressure If we consider the pressure distribution across the wing as a single force, it will act through a straight line This is called the centre of pressure
Center of Pressure As lift increases, the center of pressure moves forward until the wing stalls The C of P then moves backwards, this can cause the aircraft to become unstable
Review 1. What is aileron drag and what does it create? 2. What factors affect lift and drag? 3. What is the center of pressure and how does it move when the angle of attack is increased?
Boundary Layer The boundary layer is a thin sheet of air that sticks to the wing This occurs because air is viscous (or has a resistance to flow) The airflow slows down as it gets closer to the surface as a result of friction between the air and the surface If we use a wing as an example, the airflow would be smooth at the front of the wing, this is called the laminar flow region
Boundary Layer As the air continues to flow back, it slows down due to friction and eventually becomes turbulent, this is called the turbulent flow region The point at which it changes from laminar to turbulent flow is called the transition point
Airfoil Design - Conventional Thick airfoil that allows for better structure and lower weight Camber is maintain further rearward which increases lift and reduces drag Good stall characteristics Thickest part of the wing is at 25% of the chord
Airfoil Design - Laminar Designed for faster aircraft because of the reduced drag Thinner than the conventional airfoil and the cambering is almost symmetrical Thickest part of the airfoil is 50% of the chord
Review 1. What is the boundary layer? 2. What happens to the boundary layer as air flows back over a wing? 3. What is the main difference between a conventional and laminar airfoil
Angle of Incidence Angle at which the wing is permanently inclined to the horizontal axis Most airplanes have a small angle of incidence to ensure a small angle of attack and therefore a greater visibility during cruise
Wash-in/Wash-out Reduces the tendency for the entire wing to stall at the same time The wing is slightly twisted so that the wing root is has a higher angle of incidence (hence a higher angle of attack) than the wing tip, forcing it to stall first This allows for the pilot to have more control during a stall
Flaps High lift devices attached to the trailing edge of the wing at the root They will provide the pilot with: - Better take off performance - Steeper approach angles - Slower approach and landing speeds
Spoilers and Divebrakes Spoilers and divebrakes are devices attached to the upper and lower surfaces of the wing When extended into the airflow, they will decrease lift and increase drag This allows for a steeper approach angle without having to increase speed
Spoilers and Divebrakes
Review 1. What is wash-in/wash-out and why would we have it on an airplane? 2. What do flaps do? 3. What do spoilers and divebrakes allow the pilot to do?
Wing Fences Fins attached to the upper surface of the wing Control the movement of air over the wing to allow for better handling at low speed and improve stall characteristics
Winglets Mounted vertically on the wingtips Small airfoil surfaces Break up the wingtip vortices which flow towards the upper surface of the wing
Slats and Slots Extra airfoil on the leading edge of the wing When a high angle of attack is encountered, the slat moves forward to allow for more airflow and increase lift Passageway built into the leading edge of the wing Increases airflow over the wing at high angles of attack Remains stationary SlatSlot
Slats and Slots
Vortex Generators Small airfoils placed along the wing When the air flows over them, small vortices will be created, re-energizing the flow which prevents the air from separating and becoming turbulent This helps increase lift and decrease drag
Review 1. What are wing fences? 2. What’s the difference between a slat and a slot? 3. What do vortex generators do?
More review 1. What are the three types of fuselage construction? 2. What are the four forces acting on an aircraft? 3. How is lift created? 4. What is equilibrium? 5. What are flaps? 6. What do slats do?
Summary Today we have covered: Parts of the aircraft Forces on the aircraft How lift is created Boundary layer Next class we will continue theory of flight!