1. Flight Investigations TEXT BOOK CHAPTER 16 PAGE 362 - 377

2. Flight – the beginning The Wright Brothers https://www.youtube.com/watch?v=VcqxI-OJ1mk Failures / Early Attempts https://www.youtube.com/watch?v=fw_C_sbfyx8

3. Newton’s laws of motion

4. Forces acting on an aircraft The main forces acting on an aircraft in level flight can be identified as vertical and horizontal pairs. Vertical Pair – Lift and Weight Horizontal Pair – Thrust and Drag

5. Forces acting on an aircraft Lift is the upward- acting force created by a wing moving through the air Weight is the force applied to an object due to gravity Thrust is the forward force that drives an aircraft through the air Drag is the rearward- acting force that resists the motion of an aircraft through the air

6. Lift Force Acts upwards, at right angles to the airflow direction. Lift force is generated over the entire wing, although it is usually thought of as acting at one position along the wing. This position is known as the centre of lift or the centre of pressure (CP). Weight Force The weight force is considered to act through the centre of gravity (COG) - This is the point where the mass of the aircraft is considered to be concentrated and is the point of balance. If an aircraft were hung from a cable attached to its centre of gravity, it would hang level and perfectly balanced. The location of an aircrafts COG depends on the load it carries (fuel, cargo, passengers etc) In level flight the Lift Force and Weight Force are equal in size and opposite in direction.

7. Drag Force As an aircraft moves through the air in flight, it experiences air friction or drag. The faster the aircraft moves, the greater the resultant drag force. There are several different types of drag forces that act on different parts of the aircraft when in flight. The arrow used to represent the drag, refers to the resultant of all the drag forces that act on every part of the aircraft.

9. Forces acting on an aircraft In level flight, Thrust = Drag ∴ Drag = 10,000 N

10. Forces acting on an aircraft If the net force acting on an aircraft in flight is zero, it maintains constant velocity. If the net force acting on an aircraft is not zero, the magnitude and direction of the net force determines the magnitude and direction of the acceleration of the aircraft. Describe the direction of the resulting motion (acceleration) if an aircraft has the following forces acting upon it in flight: a) Lift = 5000 N, Drag = 800 N, Weight = 5000 N, Thrust = 1200 N Net Force 400 Forward – Plane accelerates Forward b) Lift = 6000 N, Drag = 900 N, Weight = 5000 N, Thrust = 900 N Net Force 1000 Upward – Plane accelerates Upward

11. Forces acting on an aircraft The Aerodynamics of Flight https://www.youtube.com/watch?v=5ltjFEei3AI&feature=related

12. Now Do Text Book - Chapter 16 Questions 1 – 3 Pg 376 ( Applying Newton’s laws to Aircraft)

13. Moving through fluids Aeronautics is concerned with the motion of aircraft through gases – in particular, air. To understand how lift in an aircraft occurs, we need to understand a little about movement through fluids. All liquids and gases are fluids. Fluids, like solids, are composed of small particles. Particles are packed less tightly in fluids than in solids, allowing movement of particles more freely.

14. Moving through fluids

15. eg1. In the diagram pictured, A1 is larger than A2. Using the equation of continuity, explain the difference in V1 and V2 in this scenario. V1 < V2 Wider pipe, slower speed Narrower pipe, faster speed

16. Moving through fluids

18. Now Do Text Book - Chapter 16 Questions 4, 5, 6, 7a Pg 376 ( Moving through fluids and Bernoulli’s Equation)

19. Fluid Speed and Pressure – Bernoulli’s Principle (total pressure)

20. Dynamic Pressure (pressure associated with movement) Fluid Speed and Pressure – Bernoulli’s Principle

21. We can apply these principles to the wing of the aircraft. An aircraft’s wing has a curved top and a flat bottom – this shape is known as aerofoil. The wing is shaped this way so that air travelling over the it’s top surface speeds up. This in turn reduces the air pressure above the wing to below normal pressure, resulting in an upward force known as the lift force. Fluid Speed and Pressure – Bernoulli’s Principle

22. Newtonian Lift …..is the name given to the effect of the action reaction pair on the wing of an aircraft. Newtonian Lift is the lift created in addition to the effects described by the Bernoulli principle. As Aerofoil passes through the air : It pushes air below it downward (an action) Consequently, the air beneath the wing pushes upward (a reaction) The greater the amount of air that is deflected downwards by the wing, the greater the upward force, or the greater the Newtonian Lift. Newtonian Lift only accounts for about 15% of the lift required for a cruising aircraft.

23. Newtonian Lift The downward flow of air caused by Newtonian Lift is called downwash The amount of downwash depends on the shape of the wing, the and the speed that the aircraft is travelling at. An effective wing design may involve trying to produce as much downwash as possible, without causing turbulence. The amount of downwash can change, due to the angle of the wing, called the angle of attack.

24. Angle of Attack The position that the wing is angled at is called the angle of attack. Increasing the angle of attack increases the lift BUT, as the airflow experiences a greater disturbance, drag is increased, so more thrust must be produced by the engines to counteract the drag If the angle of attack is increased significantly, the air is disturbed too much, increasing drag to the point of turbulence.

25. As the angle of attack increases, the planes lift increases, until the angle reaches the critical angle. At this point, lift drops, drag increases and the plane stalls.

26. Now Do Text Book - Chapter 16 Questions 12, 13, 14 Pg 376 ( Moving through fluids and Bernoulli’s Equation) Then Continue on with your report

27. More on Thrust & Drag & Drag Ratio HOMEWORK Read text book pages 368 – 370 ( up until the turning effect of a force section ) Answer questions 15 – 20 You should include of some the questions and your responses in your report, to support the concept / calculations

28. Glide Ratio The glide ratio of an aircraft is the ratio of the horizontal distance travelled (glide distance) to the loss of altitude while gliding (no power to the plane). Its value is equal to the ratio of lift to drag. Applying the equation: eg1. The engines of an aircraft fail while flying at an altitude of 500m, leaving the aircraft gliding to a safe landing 2 kms from the point of failure. a)The glide ratio b)The Lift to Drag Ratio

29. Glide Ratio eg2. The engines of an aircraft fail while flying at an altitude of 800m. If the glide ratio is 6:1, calculate the horizontal distance travelled by the aircraft after the failure. Using your paper planes from last lesson, estimate the glide ratio of your plane and compare with others in the class. Amend your plane to try and achieve a greater glide ratio.

30. Turning Effect of a force So we know that for an aircraft to maintain steady, level flight, the vertical pair and horizontal pair of forces must each be balanced. Lift Force = Weight Force = Constant Altitude Thrust Force = Drag Force = Constant Velocity

31. Turning Effect of a force

32. In an aircraft, this may be considered in the example below. A plane has 4 engines each outputting a thrust force of 20,000N. The inner engines are 10 m from the centre, the outer engines are 5 m from the centre. The outer right engine cuts out. To keep the plane in a straight line, what force must the right engine output to compensate for this loss?

34. Now Do Text Book - Chapter 16 Questions 21, 23, 24 Pg 377 ( Torque & Equilibrium)