Aerodynamics Principles

Transcription

1 Aerodynamics Principles Stage 1 Ground Lesson 3 Chapter 3 / Pages :00 Hrs Harold E. Calderon AGI, CFI, CFII, and MEI

2 Lesson Objectives Become familiar with the four forces of flight, aerodynamic principles of stability, maneuvering flight, and load factors. Gain basic understanding of stall/spin characteristics as they relate to training airplanes. Learn the importance of prompt recognition of stall indications.

3 Completion Standards Demonstrate understanding during oral quizzing by instructor at completion of lesson. Student completes Chapter 3 questions for section A, B, and C with a minimum passing grade of 80%.

4 Academic Content A - Aerodynamics Principles Airfoil Characteristics Airfoil Components Bernoulli s Principle Newton s 3 rd Law of Motion Aspect Ratio B - Forces of Flight Angle of Attack Stall CLmax Flight Controls

5 Academic Content C - Aerodynamics of Maneuvering Flight Three Axes of Rotation Left Turning Tendencies D - Stability Angle of Incidence Center of Gravity Lateral Stability Longitudinal Stability Horizontal Stability

6 Aerodynamics Section A

7 AERODYNAMICS

8 What s Aerodynamics? Could be defined as the forces developed upon a moving object. (AIRFOIL)

9 Airfoil Characteristics Any surface designed to provides aerodynamic force, when it interact with a moving stream of air.

10 Airfoil Components Concepts: Relative Wind Upper Camber Lower Camber Leading Edge Trailing Edge Chord Line Angle of Attack

11 Bernoulli s Principle States, if the pressure of a fluid increases, its velocity decreases. States, if the velocity of a fluid increases, its pressure decreases. Fluids = Liquid or gas Formula: +P-V +V-P

12 Newton s 3 rd Law of Motion LIFT States that for each action there is an equal or opposite reaction.

13 Forces of Flight Section B

14 Four Forces of Flight Lift Weight Thrust Drag Inertia

15 Four Forces of Flight Lift & Weight - Thrust & Drag (Level Flight) = Equal

16 Wing Planform A - Elliptical Wings B - Rectangular Wings C - Square Wings D - Sweepback Wings E - Delta Wings

17 Aspect Ratio Could be defined as the ratio of the wing span and the average chord. Data: 50 feet wing span 2 feet chord = 50/2 =25 Aspect Ratio of 25

18 CLmax Maximum coefficient of lift is proportionally related to the angle of attack. Exceeding the maximum angle of attack results in stall condition.

19 Angle of Attack vs. Stall 1) Airstream separation begins to occurs over the upper camber. 2) Airstream separation moves forward. 3) Airfoil finally stall due to high pressure on the upper camber and low pressure on the lower camber.

20 Angle of Attack Positive Angle of Attack High pressure vs. Low Pressure (H.P. FWD toward leading edge) Neutral Angle of Attack High Pressure vs. Low Pressure (H.P. FWD toward leading edge) Negative Angle of Attack High Pressure vs. Low Pressure (H.P. FWD toward leading edge)

21 Flight Controls Primary Secondary Aileron Elevator (Stabilator) Rudder Flaps Spoilers Trim tabs

22 Airfoil vs. Flaps Flaps makes airfoils to become high lift devices.

23 Flaps Types Plain Flat Slotted Fowler

24 Airflow Patterns - Airfoil Upwash Deflection of oncoming airstream upward & over the wing. Downwash The downward deflection of the airstream as it passes over the wing and past the trailing edge.

25 Stall Occurs when the maximum angle of attack of an airfoil (wing) is exceeded.

26 Wing Root vs. Wing Tip Angle of Attacks Wingtip (Lower angle of attack) Wing Root (Higher angle of attack)

27 Stall Recognition Signs Mushy feeling in the flight controls Reduction in flight control effectiveness A reduction in the sound of air flowing along the fuselage. Aural (Bell on board) Kinesthetic Sense recognize changes in directions and speed.

28 Types of Stalls Power-on stall Power-off stall Accelerated stall Imminent stall Secondary stall Crossed-Controlled Stall

29 Stall Recovery (Standard Procedures) 1) Decrease the angle of attack. 2) Smoothly apply maximum allowable power. 3) Adjust the power as required and keep coordinated flight and adjusting power to a normal level. Always review Pilot Operating Handbook

30 Spin A spin could be defined as an aggravated stall which results in the airplane descending in helical or corkscrew path.

31 Spin Recovery 1) Move throttle to idle 2) Neutralize the ailerons 3) Determine direction of rotation 4) Apply opposite rudder 5) Apply forward elevator pressure 6) Neutralize the rudders 7) Return to level flight

32 Aerodynamics of Maneuvering Flight Section C

33 Three Axes of Rotation Longitudinal Axis Nose to tail Lateral Axis Wingtip to wingtip Vertical Axis Intercept C.G.

34 Longitudinal Axis Ailerons makes the airplane to revolve about the longitudinal axis of the airplane.

35 Lateral Axis Elevators or Stabilators makes the airplane to revolve about the lateral axis.

36 Vertical Axis Rudder makes the airplane to revolve about the vertical axis.

37 Rearward Component of Weight Excess of thrust is necessary to counteract rearward component of weight.

38 Forward Component of Weight Power on descent Excess of thrust Power off descent FWD Comp W. and Weight

39 Descent vs. FWD Comp. of Weight Descent could be achieved by the use of power or no power at all.

40 Turning Flight Before an airplane turn inertia should be overcome. We can accomplished that by using ailerons to bank the airplane and change the straight line direction.

41 Vertical vs. Horizontal Comp. Lift Lift resultant vs. Load factor Vertical component of lift vs. weight Horizontal component of lift vs. centrifugal force

42 Adverse Yaw Adverse yaw occurs when the outside wing opposite to the turn direction, produces more lift and drag, in comparison to the inside wing. Always use coordinated flight controls.

43 Over Banking Tendency This is caused due to the outside wing traveling faster than the inside wing. Its produces more lift and airplane tends to roll beyond the desired bank angle.

44 Load Factor Is the ratio of the load supported by the airplane s wings to the actual weight of the airplane and its contents. (Weight and Centrifugal Force Resultant) Example: 1G, 2G s, 3G s

45 Limit Load Factor The amount of stress that an airplane can Withstand before structural damage or failure. As a primary function of aircraft design the limit load factor is published in the POH. VA = Design maneuvering speed

46 Load Factor vs. Category Airplanes are classified by category: Positive Negative Normal 3.8 G s 1.52 G s Utility 4.4 G s 1.76 G s Acrobatic 6.0 G s 3.0 G s

47 Left Turning Tendencies P-Factor Torque Spiraling Slipstream Gyroscopic Precession

48 Asymmetrical Thrust (P-Factor) Descending propeller vs. Ascending propeller Higher angle of attack vs. Lower angle of attack

49 Torque Newton s 3rd Law of Motion For each action there is an equal or opposite reaction.

50 Spiraling Slipstream Propeller airstreams moving backward and striking left hand side of empennage.

51 Gyroscopic Precession Any force applied to a spinning object is deflected approximately 90 degrees on the same plane of rotation.

52 Stability Section D

53 Stability Positive Static Stability Return to initial path Positive Dynamic Stability Short series of decreasing oscillations POSITIVE STATIC & DYNAMIC STABILITY

54 Angle of Incidence The angular difference between the longitudinal axis of the airplane and wing dihedral angle.

55 Longitudinal Stability The pitching motion of an airplane to move about its lateral axis. Features: Center of gravity vs. Center of pressure (lift)

56 Center of Gravity Position (Lon) C.G. Limit Envelope (Forward and AFT Range)

57 C.G. Too Far Forward (Lon) C.G. becomes to far forward of the forward C.G. Limit, the airplane will be too nose heavy.

58 C.G. Too Far AFT (Lon) C.G. becomes to far forward of the forward C.G. Limit, the airplane will be too nose heavy.

59 Horizontal Stabilizer (Lon) The nose-heavy tendency is offset by the position of the horizontal stabilizer, which is designed with a negative angle of attack.

60 Thrustline (Lon) The thrustline in most general aviation airplane is parallel to the longitudinal axis and above C.G. This creates a slight pitching moment around the C.G. minimizing the destabilizing effects of power changes.

61 Lateral Stability The stability about an airplane s longitudinal axis. Features: Dihedral, Weight distribution, Sweepback and Keel effect

62 Dihedral Angle The upward angle of the airplane s wing with respect to the horizontal. The increased angle of attack on the low wing produces more lift for that wing.

63 Sweepback The angled backward from the wing root to the wingtip. This feature keep center of lift behind the C.G. and help reduce wave drag on aircraft flying at supersonic speeds.

64 Keel Effect Vertical fin and side area of the fuselage provides react to the airflow very much like the keel of a ship.

65 Directional Stability Stability about the vertical axis. The primary contributor to directional stability is the vertical tail which causes an airplane in flight to act much like a weather vane.