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Theory of Flight

Theory of Flight. 6.05 Lift and Drag References: Transport Canada Study and Reference Guide Glider Pilot FTGU pages 91-98. Review. 1. Name the 4 forces acting on an aircraft. 2. What are Newton’s 3 laws?

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Theory of Flight

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  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 theflight 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

  11. Centre of Pressure

  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 Lift/ Drag Angle of Attack

  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

  17. Confirmation Check

  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: • 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 • Fill in the diagram • Is it possible to eliminate induced drag? Why or why not?

  29. Wingtip Vortices

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