aERODYNAMICS

1. Kyle Black Carol Cushman aERODYNAMICS

2. What is Aerodynamics? Study of the motion of air, particularly when it interacts with a moving object.

3. Forces of Flight There are four forces of flight, what are they? • Lift • Weight • Thrust • Drag

4. Lift How is lift created? Airfoil design and usage of two principles: • Bernoulli’s Principle • Newton’s Laws of Motion

5. Lift Bernoulli’s Principle • As velocity of a fluid (air) increases, its internal pressure decreases. • How does an airfoil use this principle?

6. Lift Newton’s Law • What are Newton’s 3 laws and which applies most to an aircraft’s ability to fly? • 1st law of motion – body at rest tends to stay at rest, and a body in motion tends to stay in motion • 2nd law of motion – F = ma (Force = Mass x Acceleration) • 3rd law of motion – for every action there is an equal and opposite reaction

7. Lift Newton’s Law • What are Newton’s 3 laws and which applies most to an aircraft’s ability to fly? • 1st law of motion – body at rest tends to stay at rest, and a body in motion tends to stay in motion • 2nd law of motion – F = ma (Force = Mass x Acceleration) • 3rd law of motion – for every action there is an equal and opposite reaction

8. Lift Newton’s 3rd Law • When a certain angle of attack is reached, the relative wind hits the bottom of the wing and is deflected down. Opposite reaction is for the air to push up.

9. Lift – Airfoil Design What is an airfoil? • Any surface, such as a wing, which provides aerodynamic force when it interacts with a column of air. Two reactions desired: • High pressure lifting action from air mass below wing • Low pressure lifting action from lowered pressure above wing

10. Lift – Airfoil Design Terms

11. Lift – Airfoil Design Camber – The curve of an airfoil section from the leading edge to the trailing edge Chord Line – Imaginary straight line from the leading edge to the trailing edges of an airfoil Relative Wind – the airflow which is opposite and parallel to the airfoil’s flight path

12. Lift – Airfoil Design Angle of Attack – Angle between the airfoil’s chord line and the relative wind Angle of Incidence– Angle between the chord line of the wing and the longitudinal axis of the airplane

13. Lift – Airfoil Design Critical Angle of Attack – the angle of attack at which, if exceeded, the plane will stall Airfoil in stalled condition (Critical Angle of Attack exceeded) Airfoil in Normal Flight

14. Stalls

15. Spins What is a spin? • Aggravated stall that results in autorotation Prerequisites for a spin: • Stall • Uncoordinated Flight

16. Spins

17. Spins

18. Lift – Forces Affecting Angle of Attack • At normal operating speeds, increasing angle of attack increases lift Airspeed • Lift is proportional to the square of the airplane’s speed • If speed is doubled, lift produced is quadrupled (other factors constant) • If speed is halved, lift produced is one-quarter what was previously produced (other factors constant) • Total lift depends on the combined effects of airspeed and angle of attack

19. Lift – Devices Affecting • Flaps (Leading and Trailing Edge) • Why do flaps affect lift? • Slots & Slats • Energizes laminar flow • Delays boundary layer separation at high angles of attack

20. Weight The center of gravity on an airplane is where the weight of an aircraft is concentrated • Aircraft weight in flight is the combined weight of the airplane itself, crew, fuel, and cargo or baggage • Weight pulls the airplane downward due to the force of gravity

21. Weight • Lift must overcome weight to depart from the ground as well as to remain in the air • In level flight, the force of lift is equal to the force of weight and the aircraft neither gains nor loses altitude • Lift > weight, aircraft climbs • Lift < weight, aircraft descends

22. Thrust • Thrust must be created to move an aircraft forward through the air • Thrust produced must be greater than drag to begin moving • Speed will continue to be gained until thrust and drag are equal • When thrust is taken away, and becomes less than drag, an aircraft will slow down until thrust and drag are once again equal or its airspeed is no longer sufficient to support the aircraft in level flight

23. Thrust • What happens if thrust is reduced and level flight is maintained? • What might eventually happen? • What happens if thrust is increased and level flight is maintained?

24. Thrust At slower speeds, wing loading will be less due to the fact that with a nose up pitch attitude, thrust from the propeller is actually helping in keeping the a/c up with a vertical component of lift

25. Drag – Parasite Drag All the forces on the aircraft’s surface that slow an aircraft and includes all drag not associated with lift.

26. Drag – Parasite Drag Form Drag • Produced by an aircraft’s shape and the air that flows around it as well as the portions of a structure that protrude into the relative wind (engine cowlings, antennas, pitot tubes, outside air temperature probes, aerodynamic shape of components, etc).

27. Drag – Parasite Drag Skin Friction Drag (Viscous Drag) • The aerodynamic resistance caused by the contact of the surface of the aircraft with the air • Surface of an aircraft may appear smooth, but under a microscope, it is rough

28. Drag – Parasite Drag Interference Drag • Intersection of airstreams that produce drag of their own • Intersection of these airstreams can be caused by placing different portions of an aircraft close together (Wings-Fuselage, Fairings-Wings, etc) • Intersection causes turbulence to be 50 to 200 percent greater than when the two objects creating the airflow were tested separately

29. Drag – Induced Drag A by-product of lift: If lift is produced, induced drag is present

30. Drag – Induced Drag • Generated by the airflow circulation around the wing as it produces lift • High pressure air below joins with low pressure air from above at the trailing edge and wingtips causing a spiral or vortex which trails behind the wing

31. Drag – Induced Drag • These wingtip vortices deflect the airstream downward in the vicinity of the wing, increasing downwash. • As a result, average relative wind in comparison to the wing is downward and rearward • Lift is perpendicular to relative wind and therefore has a rearward vector • Rearward vector is induced drag

32. Drag Curve • As airspeed increases, induced drag decreases while parasite drag increases • Total drag is the sum of parasite and induced drag

33. Drag – Factors Affecting • Weight • Configuration • Altitude • Aerodynamic Designs • L/D (Lift to Drag ratio) • Amount of lift generated by a wing compared to its airfoil • Higher L/D ratios – more efficient airfoil • Lower L/D ratios – less efficient airfoil

34. Drag – Factors Affecting Coefficient of lift (CL) and Coefficient of Drag (CD) can be calculated for specific AOAs

35. Maneuvering Flight • The flight controls allow pilots to maneuver the aircraft by changing the pressure distribution (and the amount of lift created) on various parts of the aircraft. • The primary flight controls do this by changing the AOA to change the lift created - allowing the aircraft to pitch, bank, and yaw

36. Primary Flight Controls • What are the primary flight controls and which axes do they move the aircraft about? • Aileron (Longitudinal) • Elevator (Lateral) • Rudder (Vertical)

37. Pitch Control • The elevator has negative AOA and provides “tail down force” during normal flight

38. Pitch Control • Pulling back on the yoke allows increased tail down force resulting in an increase in pitch. • Result: Climb • Pushing forward on the yoke reduces AOA as well as tail down force allowing the nose to drop

39. Ailerons • Ailerons allow the aircraft to roll • Ailerons – change AOA on the wing tips

40. Ailerons • A section of the left wing has a higher AOA while a section of the right wing has a lower AOA. The left wing is producing more lift and the right is producing less lift.

41. Rudder • The rudder allows the aircraft to yaw about the vertical axis.

42. Stability • Stability is the ability to return to a trimmed condition, after a disturbance or control input • Control is the ability to take an aircraft out of a stable condition

43. Stability • Static • The INITIAL tendency of an object to return to its previously undisturbed state

44. Stability • Dynamic • An object’s tendency to return to its previously undisturbed state OVER TIME.

45. Propeller

46. Propeller

47. Propeller