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EASA PART-66 MODULE 8.2 : AERODYNAMICS

May 06, 2015

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Slide for student who want to take EASA part66 exam
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  • 1.8.2 AERODYNAMICSwww.part66.blogspot.com

2. Effect of Shapes on Streamlined Flow (a) Flat Plate 100% Resistance (b) Sphere 50% Resistance (c) Ovoid 15% Resistance (d) Streamlined 5% ResistanceSTREAMLINED 3. Boundary LayerUnaffected airflowEach layer experience retardation untilsome distance away from surface Next layer slowed down but not stopAirflow nearest the surface come to rest STREAMLINED 4. Boundary Layer STREAMLINED 5. Separation and turbulence at variousAOASTALLING 6. AERODYNAMIC TERMStagnation pointVelocity = 0m/s Wing tip vortices 7. Airfoil Shape Symmetrical no lift at zero angle of attack Asymmetrical lift created even at small angleof attack AIRFOIL 8. Airfoil Shape Medium and high speed aircraft much lesscurvature lift comes from their additional speedthrough the air. Low speed aircraft cambered not for high speed(excess lift as well as drag)AIRFOIL 9. CAMBER (CURVE) Camber curvature of an aerofoil (wing)above and below the chord lineCamber (curvature) of an aerofoil PRODUCTION OF LIFT 10. AIRFOIL @ AEROFOIL Any surface which produces a reaction (lift) as airpasses over it The airfoil should provide this reaction (lift), whilsthaving a shape which presents the least possibleresistance, or drag, to its passage through air AIRFOIL 11. T/C AND FINENESS RATIO Thicness/Chord ratio = CDAB 12. MEAN AERODYNAMIC CHORD Average distance between leading and trailingedge of wing Mean chord = Wing AreaWing Span 13. ANGLE OF ATTACK The acute angle formed between the relative windstriking an airfoil and the chord line. Increasing the angle from zero degree to a maximum(between 15 degrees and 18 degrees) will increaselift, but will also increases drag. CENTER OF PRESSURE 14. ANGLE OF INCIDENCEo Angle formed by theintersection of the wingchord line and thehorizontal plane orlongitudinal axis of aircrafto Positive Angle of Incidence(AOI) leading edge higherthan trailing edgeo Correct AOI low drag +longitudinal stabilityo Wash out higher AOI atwing root than at wing tipo Wash in higher AOI atwing tip than at wing rootANGLE OF INCIDENCE 15. WASH IN AND OUT Wash in : Angle of incident increase from root to tip Tip will stall 1st Wash out : Angle of incident decrease from root tip Root will stall 1st 16. CENTER OF PRESSURE (c.p) The position whereby the resultant force (lift) cutsthrough chord line and considered to actTotal Lift Shape of airfoil and angle of attack influence the c.p Position of lines denoteslocation and direction direction of liftLength of line denotemagnitude of lift Direction of airflowCenter of Pressure CENTER OF PRESSURE 17. CENTER OF PRESSURE (c.p)o Position of c.p varies during flight as the angle of attack (AOA)altereda. Increase AOA c.p moves forwardb. Decrease AOA c.p moves backwardo In normal flight the AOA usually between 2 and 4 (seldombelow 0 or above 16)Small AOAMedium AOA Large AOA Nose Heavy Balance OF PRESSURE CENTER FlightTail Heavy 18. WING SHAPE 19. ASPECT RATIO Ratio of aircraft wingspan to its mean chordlength 20. PRODUCTION OF LIFT To keep flying aircraft must produce a force equal to its own weight Greater force to lift the aircraft from the ground Force (lift) is provided by the wing The production of lift is based on Bernoullis theoryPRODUCTION OF LIFT 21. LiftWeight 22. Bernoullis theorem Air velocity increase the pressure decreases (and viceversa) The total energy of a moving fluid is made up of threeforms of energy: Potential Energy due to height or position Kinetic Energy due to motion Pressure Energy due to pressure In a streamline flow of an ideal fluid, the sum of all thoseenergy is constant Potential + Kinetic + Pressure = ConstantPRODUCTION OF LIFT 23. Venturi Effect A short circular tube withlarge opening at both thefront and rear end +restrictor between theopening Venturi is aconvergent/divergentduct Bernoullis Theory isbeing proven by passinga streamline flow of airthrough a venturi duct PRODUCTION OF LIFT 24. Venturi Effect PRODUCTION OF LIFT 25. Venturi EffectINLET CENTRE (THROAT) OUTLETAirspeed normal Airspeed maximum Airspeed decreasePressure normal Pressure minimum Pressure increase (equal to inlet area)PRODUCTION OF LIFT 26. Camber (Curved) Airflow around the cambered wing behave exactly as airflow in a venturi tubePRODUCTION OF LIFT 27. Airflow on wing (Lift distribution)Increased SpeedProvide 70% of the wings Total LiftDecreased SpeedDecreased pressure70% of Total LiftIncreased pressure Providing 30% of the wings Total LiftDecreased SpeedIncreased Speed30% of Total Lift PRODUCTION OF LIFT 28. STREAMLINED Streamline shape or contour that presents aminimum resistance to the air A perfect streamlined form is similar to the top viewof a fish Air flows around non-streamlined object air swirlsinto eddies + streamline distorted disappear Airstream becomes turbulent Streamline air appears as smooth parallel lines Smoke jets introduce smoke into air to observeand illustrate movement of air around objectSTREAMLINED 29. Effect of Shapes on Streamlined Flow STREAMLINED 30. DRAGAs an aircraft passes through the air, the air offers a resistance to the passage.This resistance, is known as Drag.(Resistance to forward motion)The total amount of drag on an aircraft is made up of many types of drag forces. Common type of drag:-i. Form dragii. Parasite dragiii. Induced dragDRAG 31. DRAGRESISTANCE TO FORWARD MOTION DRAG 32. FORM DRAGCaused by the shape or form of the aircraft Reducing form drag Streamlining aircraft shaped to produce leastresistance to the airflow For least resistance object length between 3-4times greater than maximum thickness Fineness ratio ratio between length and maximumthicknessDRAG 33. PARASITE DRAG A combination of many different drag forces Any exposed object on an aircraft offers someresistance to the airflow, and the more objects inthe airstream, the more parasite dragReducing parasite drag reducing the number of exposed parts to as few aspractical and streamlining their shape. DRAG 34. Streamlining Fixed landing gear 35. SKIN FRICTION DRAGA type of parasite drag most difficult to reduceAir particles in contact with surface of the aircraftReducing skin frictionglossy flat finisheseliminating protruding rivet heads, roughness, and otherirregularities.DRAG 36. INDUCED AND TOTAL DRAG Lift created by the airfoil also created drag induced drag Just as lift increases with an increase in angle ofattack, induced drag also increases as the angle ofattack becomes greater. TOTAL DRAG DRAG 37. THRUST AND WEIGHT Thrust is forward force produce by engine Determine by size and type use in propulsionsystem Weight is a mass of aircraft act verticallydownward Determined by size and material used inaircraft 38. FORCES ACTING ON AIRCRAFT IN THRUSTFLIGHT The aircrafts propelling forceLIFT Arranged symmetrically to theActs at right angle to the line ofcentre lineflight & through the Centre of Act parallel to the line of flight Pressure of the wings DRAG Opposes the forward motion [email protected] GRAVITY Regarded as a rearward acting Acts vertically downwards throughforce the Centre of Gravity FORCES ACTING ON AIRCRAFT IN FLIGHT 39. LIFT AND DRAG COEFFICIENT Theoritical value base onairfoil shapeLift = CL x 1/2v2 x SDrag = CD x 1/2v2 x SIDEAL ANGLE 40. POLAR CURVE Drag Polar is the relationship between the liftand its drag interm on coefficeient 41. STALL Sudden lost of lifti. Increase AOA separation moves forward (turbulent) Insufficient pressure drop on upper surface no pressure differential to create liftii. Increase to higher AOA excessive turbulence Drag increase higher than lift created Critical Angle of Attack airflow separate + turbulence Critical AOA = 15 and above STALLING 42. AIRFOIL CONTAMINATION Any contamination on wing will affect itsperformance Need to provide method to remove thecontamination during flying Type of contamination : Ice Snow Frost