Lift and Drag.ppt
- 1. Theory of Flight 6.05 Lift and Drag References: Transport Canada Study and Reference Guide Glider Pilot FTGU pages 91-98
- 2. Review 1. Name the 4 forces acting on an aircraft. 2. What are Newton’s 3 laws? 3. Is an aircraft considered to be in a state of equilibrium when it is on the ground.
- 3. 6.05 Lift & Drag • MTPs: – Bernoulli’s Principle- how lift is created – Airfoil terms – Angle of attack versus lift – Angle of Incidence – Types of airfoils – Types of Drag – Wingtip Vortices – Streamlining
- 4. Bernoulli’s Principle • Bernoulli’s Principle – An increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.
- 5. Bernoulli’s Principle Speed Pressure Speed Pressure
- 6. Bernoulli’s Principle – Airfoils are shaped in a way to manipulate air pressure based on Bernoulli’s principle. – Air moves faster over the upper surface of the wing, decreasing pressure (or increasing suction) – Air moves slower over the lower surface of the wing and creates a higher pressure, or pushing force.
- 7. Airfoil Terms Terms related to airfoils • Relative Airflow • Angle of Attack • Centre of Pressure
- 8. Relative Airflow – The direction of the airflow with respect to the wing. – It is created by the movement of the airplane as well as the movement of air. – Relative airflow is usually opposite to the flight path. – Relative airflow itself is not related to lift
- 9. Angle of Attack –The angle at which the airfoil meets the relative airflow
- 10. Centre of Pressure • Is the average of the pressure on an airfoil – Sum of the distributed pressures on the airfoil acting through a single straight line • Moves forward on an airfoil as the angle of attack is increased
- 12. A of A versus Lift • Now we know how we get lift but how much can we get? • One factor affecting lift is Angle of Attack – As the angle of attack increases, what happens to lift? – BUT… As the angle of attack increases, what happens to drag? Lift Increases Drag Increases
- 13. A of A versus Lift Angle of Attack Lift/ Drag
- 14. Angle of Incidence – The angle of incidence is the angle between the mean aerodynamic chord of the wing and the longitudinal axis of the aircraft – The angle of incidence impacts forward visibility, take-off and landing characteristics, and drag in level flight
- 15. Types of Airfoils • Airfoil A two-dimensional surface designed to obtain a reaction from the air through which it moves. The shape of an airfoil will affect how air flows over the wing Airfoil – 2D vs. Wing – 3D
- 16. Types of Airfoils • What are some functions of airfoils? – Create lift – Create thrust – Attachment point for the control surfaces (including flaps, slots, slats, etc) – House fuel tanks and instrument components –Stability
- 18. Confirmation 1. Label where the high pressure and low pressure are: 2. Fill in the blanks __________________: The angle at which the airfoil meets the relative airflow __________________: airflow with respect to the wing __________________:the average of the pressure on an airfoil
- 19. Confirmation 3. Lift acts 90o to the ________________. 4. Bernoulli’s principle states that: An ____________ (increase/decrease) in the speed of a fluid occurs simultaneously with a _____________________ (increase/decrease) in pressure or a _______________ (increase/decrease) in the fluid's potential energy 5. As lift increases, drag _______________.
- 20. Drag – Is the resistance an airplane experiences in moving forward through the air
- 21. Types of Drag There are 2 main types of Drag: 1. Parasite Drag– This drag is further broken down – Form drag – Skin Friction 2. Induced Drag
- 22. Parasite Drag Drag of all those parts the airplane which DO NOT contribute to lift – This drag is hard to eliminate but it can be minimized • Form drag is caused by the shape of the aircraft – Landing gear – Antennas – Struts – Wing tip fuel tanks
- 23. Parasite Drag • Skin Friction – The tendency of air flowing over the body to cling to its surface – What causes it to resist motion? • Ice on the wings • Dirt build up
- 24. Induced Drag – Caused by those parts of an airplane which are active in producing lift – Cannot be eliminated Lift Drag
- 25. Induced Drag • Induced drag can be reduced with a high aspect ratio
- 26. Wing Tip Vortices • Over the top of the wing the airflow goes inward • Under the bottom of the wing the airflow moves outward Due to the pressure changes This creates a swirling motion off the wing tip called a vortex
- 27. Streamlining • The less drag you have… – Flying a glider: the further you can fly – Flying an airplane: the less fuel you use • Therefore streamlining is important – A design device by which a body is shaped to minimize drag
- 28. Confirmation 1. Fill in the diagram 2. Is it possible to eliminate induced drag? Why or why not?
- 29. Wingtip Vortices