航空通用空气动力学英文课件

1、2Airline Transition CourseATP Chapter 5Aerodynamics and Flight Characteristics3First of all - what is aero?What is aeronautics? What is the difference between aircraft & airplane?What is are the four forces?What is stability?Multiengine AerodynamicsTakeoff FactorsHigh Altitude FlightHigh Speed Fligh

2、tFlight Controls4First of all - what is aero?Aero is a Greek prefix signifying air. Air is made up of a mixture of gasses, and thus is itself a gas. Air is referred to as a fluid. For instance, air obeys the laws of fluid dynamics. The technical definition of a fluid states that a fluid is any subst

3、ance that flows. Obviously water flows, but so does air and so do powders! So, technically speaking, air and powders are fluids. Most important to our study of aeronautics is the fact that air obeys the physical laws of fluids.5What is aeronautics?Aeronautics is typically defined as the art or scien

4、ce of flight, or the science of operating aircraft. This includes a branch of aeronautics called aerodynamics. Aerodynamics deals with the motion of air and the way it interacts with objects in motion, such as an aircraft. Both of these branches are a part of the tree of physical science. Aviation,

5、however, refers to the operation of heavier-than-air craft.6How did aeronautics begin? The theoretical basis for these branches stems from the work of Sir Isaac Newton in the 1600s. Newton developed laws that defined the effects of forces acting on objects in motion or at rest. He also developed the

6、 concept of viscosity, or fluid friction, which is the resistance of air or any other fluid to flow. Daniel Bernoulli, in the 1700s, developed the principle that the speed of a fluid is directly related to pressure. That is, the faster the flow of a fluid, the lower the pressure that is exerted on t

7、he surface it is flowing over. 7What is an airplane?What is the difference between aircraft and airplane? Aircraft is the more general term, and refers to any heavier-than-air craft that is supported by its own buoyancy or by the action of air on its structures. Airplane is a heavier-than-air craft

8、that is propelled by an engine and uses fixed aerodynamic surfaces (i.e. wings) to generate lift. So, every airplane is an aircraft, but not every aircraft is an airplane! 8Gliders are aircraft that are not airplanes. The Space Shuttle is definitely an aircraft, but it is not an airplane. It does no

9、t carry engines for propulsion. Helicopters are also aircraft that are not airplanes because their aerodynamic surfaces are not fixed - they rotate.9The Forces of Aeronautics 10The Work of Wings 11Unbalanced Forces12LiftWeightThrustDragTOPICS13LiftLift counters weightIt always acts perpendicular to

10、the flight pathPrinciple of flight is based on the production of liftBalanced lift and weight allows an aircraft to remain in level flight. Any imbalance causes the aircraft to climb or descendOn an airplane lift is generated by the wings14Angle Of Attack15Planform Wing AreaPlanform Area can be chan

11、ged through the use of Slats and FlapsMost turbine aircraft are equipped with both slats and flapsWith Slats/Flaps extended greater lift can be produced at lower approach speeds.16QuestionWhat true airspeed and angle of attack should be used to generate the same amount of lift as altitude is increas

12、ed?The same true airspeed and angle of attack.A higher true airspeed for any given angle of attack.A lower true airspeed and higher angle of attack.17AnswerWhat true airspeed and angle of attack should be used to generate the same amount of lift as altitude is increased? B. A higher true airspeed fo

13、r any given angle of attack.18WeightA downward forces that always acts toward the center of the earth.In order to achieve flight the force of weight must be countered. This is achieved by the production of lift.If weight is greater than lift the aircraft will descend.19Control of WeightAll objects i

14、n the universe exert an attractive force on each other that is called gravity. The magnitude of this force is dependent on the mass of the object. In our day-to-day lives this attractive force is recognizable only for objects with enormous mass, such as the Earth. Gravity is the word we use to defin

15、e the attractive force specifically between the Earth and all the objects that are within its influence. Included in a list of these objects would be people, aircraft - even the moon!20The Earths gravitational pull weakens as objects move farther away from it. Thus we say that objects that are far f

16、rom the Earth weigh less than when they are on the Earth. For objects on and close to the Earth (we will assume that airplanes fly at altitudes close to the Earth) the weight of an object can be considered constant. Weight is the force that measures the effects of gravity.21ThrustThrust is developed

17、 by an aircrafts power plantThrust must counter the force of drag on an aircraftBalanced thrust and drag allows an aircraft to remain in unaccelerated flight. Any imbalance causes the aircraft to slow down or speed up22Pilot Control of ThrustThrust is developed by the powerplant.In a turbine aircraf

18、t thrust is achieved by moving a mass of air rearward.In a turboprop a large mass is moved rearward with a small acceleration.In a turbojet or turbofan a small mass is moved rearward with a large acceleration.F=ma23DragDrag is what opposes thrust.Drag acts parallel to the flight path of the aircraft

19、 It comes in two forms: Parasite and Induced24Parasite and Induced DragParasiteCaused by the aircraft moving through the air.Proportional to the square of the airspeedInducedCaused by the production of liftInversely proportional to the square of the airspeed.25Pilot Control of DragDrag can be contro

20、lled by airspeed.At L/Dmax lift is maximized for a minimum dragAllows for best glide and best enduranceDrag can also be controlled by adding more interference into the air stream.26IN A CONSTANT SPEED CLIMB ALL FORCES ARE EQUALTHRUST = DRAGLIFT = WEIGHT27DragWhat is the effect on total drag of an ai

21、rcraft if the airspeed decreases in level flight below that speed for maximum L/D?Drag increases because of increased induced drag.Drag increases because of increased parasite drag.Drag decreases because of lower induced drag.28DragWhat is the effect on total drag of an aircraft if the airspeed decr

22、eases in level flight below that speed for maximum L/D?B. Drag increases because of increased parasite drag.29Four ForcesBy changing the angle of attack of a wing, the pilot can control the airplanesA.Lift, gross weight, and drag.B. Lift, airspeed and drag.C.Lift and airspeed but not drag.30Four For

23、cesBy changing the angle of attack of a wing, the pilot can control the airplanes.B. Lift, airspeed and drag.31Questions?JUST DROPPED BY THE FARM 32StabilityStaticPositiveNeutralNegativeDynamicPositiveNeutralNegativeAxesLongitudinalLateralVertical33Static StabilityStatic Stability refers to what the

24、 aircraft will do initially after being disturbed.If an aircraft exhibits positive static stability the aircraft, after being disturbed, will move back toward its original state.If an aircraft exhibits negative static stability it will move even farther from its original state.If an aircraft exhibit

25、s neutral static stability it will stay in the state it has been moved to.34Dynamic StabilityPositive Dynamic Stability - the oscillations decrease in amplitude and the displaced aircraft ultimately returns to its original attitude. Neutral Dynamic Stability - the oscillations continue without incre

26、ase or decrease in amplitude. Negative Dynamic Stability - the oscillations increase in amplitude.35Three Axes of an Aircraft36Lateral Axes37Vertical Axes38Longitudinal Axes39Longitudinal AxisPitch StabilityRuns from the nose to the tail. Various aircraft parts contribute to longitudinal stability.W

27、ings stabilizingFuselage destabilizingEngine Nacelles stabilizingHorizontal Tail - stabilizing 40WingsStabilizing if the center of gravity (CG) is ahead of the aerodynamic center (AC).In a stabilizing location the AC-CG relationship will bring the aircraft back to its original state.41WingsWhat char

28、acteristic should exist if an airplane is loaded to the rear of its CG range?Sluggish in aileron control.Sluggish in rudder control.Unstable about the lateral axis.42WingsWhat characteristic should exist if an airplane is loaded to the rear of its CG range?C. Unstable about the lateral axis.43Fusela

29、geRam air on the forward fuselage creates a force in the direction of the original displacement.This is a destabilizing force.44Horizontal TailThe Horizontal Tail is stabilizing.The angle of attack change on the horizontal tail creates a stabilizing pitching moment.45Vertical AxisDirectional/Yaw Sta

30、bilityVertical Axis runs vertically through the center of gravity.Various parts of the aircraft contribute to vertical stability.WingsFuselageEngine NacellesVertical Tail46Wings47WingsSwept wings provide a small stabilizing moment.Swept wings cause the aircraft to yaw in the direction opposite of th

31、e initial yaw.This is caused by increased drag on the wing opposite of the direction of yaw.48Vertical TailThe vertical tail is the main stabilizing force.Like the horizontal tail, changes in the angle of attack on the vertical tail create a stabilizing yawing moment.49Lateral AxisRoll StabilityLate

32、ral axis runs through the center of gravity and perpendicular to the longitudinal axis.The aircraft parts that affect roll stability are:WingsVertical Tail 50Dihedral and AnhedralDihedral When you stand in front of an aircraft, looking toward the tail, the wings are usually higher at the wing tips t

33、han at the wing root (where the wing attaches to the fuselage). This upward angle from wing root to tip is called DIHEDRAL. On an aircraft with dihedral, when one wing drops, it will produce slightly greater lift than the other wing. The aircraft tends to return to a level status providing lateral s

34、tability to the aircraft.51Dihedral and AnhedralAnhedral does the opposite. It creates more angle of attack on the raised wing causing the aircraft to continue rolling.52High WingA high wing is stabilizing due to pendulum effect.The center of gravity resides below the wings. Acts like a pendulum or

35、a swing.53QuestionIdentify the type stability if the aircraft attitude remains in the new position after the controls have been neutralized.Negative longitudinal static stability.Neutral longitudinal dynamic stability.Neutral longitudinal static stability.54AnswerIdentify the type stability if the a

36、ircraft attitude remains in the new position after the controls have been neutralized.C. Neutral longitudinal static stability.55Effect of CG Position56Effect of CG PositionAt the aft CG limit, the airplane will have its:Lowest stall speedHighest cruise speedLeast stability about the lateral axis57Q

37、uestionWhat are some characteristics of an airplane loaded with the CG at the aft limit?Lowest stall speed, highest cruise speed, and least stability.Highest stall speed, highest cruise speed, and least stability.Lowest stall speed, lowest cruise speed, and highest stability.58AnswerWhat are some ch

38、aracteristics of an airplane loaded with the CG at the aft limit?Lowest stall speed, highest cruise speed, and least stability.59QUESTIONS60Multiengine Aerodynamics61Multiengine AerodynamicsTakeoff Profile SegmentsV1V2Balance Field LengthCritical Engine62Takeoff Profile SegmentsGround Roll: from rel

39、ease of brakes to liftoff. Occurs totally on the ground. Runway1 2GrndRollVr35ftAcceleration1500ftFinal400ft63Takeoff Profile SegmentsRunway1 2GrndRollVr35ftAcceleration1500ftFinal400ft1st Segment: from liftoff to 35 AGL and V2. Called the 1st segment since it is the first airborne segment. Adequate

40、 climb capability in this segment requiresa 0.5% climb gradient (5 altitude per 1000 of horizontal distance) with 3 out of 4 engines operating.a 0.3% climb gradient (3 altitude per 1000 of horizontal distance) with 2 out of 3 engines operating.a positive climb rate with 1 out of two 2 engines operat

41、ing.V264V1Takeoff Decision SpeedFAR 25 Definition:the airspeed at which a decision must have been made to abort or continue after a takeoff anomaly, especially an engine failure. Below V1, an abort is feasible; after V1, takeoff must be continued. For safety considerations, V1 VMCG, since at and aft

42、er V1, the airplane is committed to take off.65Takeoff Profile SegmentsRunway1 2GrndRollVr35ftAcceleration1500ftFinal2nd Segment: from 35 AGL to 400 AGL. V2 is maintained during this segment, called the 2nd segment, since it is the second airborne segment. Adequate climb capability in this segment r

43、equiresa 3.0% climb gradient (30 altitude per 1000 of horizontal distance) with 3 out of 4 engines operating.a 2.7% climb gradient (27 altitude per 1000 of horizontal distance) with 2 out of 3 engines operating.a 2.4% climb gradient (24 altitude per 1000 of horizontal distance) with 1 out of two 2 e

44、ngines operating.400ft66V2Takeoff Safety SpeedFAR 25 Definition:the speed after takeoff that gives an adequate climb angle (adequate climb capability) from 35 AGL to 400 AGL with an engine inoperative. For large swept wing jet transport airplanes (but not for light twins), V2 is typically less than

45、VXSE or VYSE. V2 must be at least 1.2 VS (1.15 VS for some airplanes) for takeoff flaps setting, and at least 1.10 VMCA.67Takeoff Profile SegmentsRunway1 2GrndRollVr35ftAcceleration1500ftFinal400ftAcceleration Segment; sometimes subdivided into 3rd and 4th Segments): segment where airplane accelerat

46、es from V2 to 1.25 Vs (clean) at 400 AGL. The 3rd Segment ends when flaps are retracted. The 4th segment ends when the first throttle reduction occurs. 68Takeoff Profile SegmentsRunway1 2GrndRollVr35ftAcceleration1500ftFinal400ftFinal Segment; also sometimes called the 5th Segment: clean configurati

47、on climb from 400 AGL to 1500 AGL at a speed no lower than 1.25 Vs. Adequate climb capability in this segment requires:a 1.7% climb gradient (17 altitude per 1000 of horizontal distance) with 3 out of 4 engines operating.a 1.5% climb gradient (15 altitude per 1000 of horizontal distance) with 2 out

48、of 3 engines operating.a 1.2% climb gradient (12 altitude per 1000 of horizontal distance) with 1 out of 2 engines operating.69Factors Affecting: VrVR 1.10 VMU (minimum unstuck speed), or VR 1.05 Vmu (engine out minimum unstuck speed) to avoid getting airborne at a speed where the airplane probably

49、will not fly out of ground effect. VR 1.05 VMCA, to preclude inadvertent loss of control.VR V1, for safety reasons. Abort after rotate is a risky undertaking.70VMUMinimum Unstick SpeedVMU - slowest airspeed where the airplane can be forced off the ground with all engines operating. At this speed, th

50、e airplane will fly in ground effect but stall out of ground effect and the settle back toward the ground.Vmu - slowest airspeed where the airplane can be forced off the ground with one engine inoperative 71VMCMinimum Control SpeedsVMC minimum control speed due to asymmetrical thrust with one engine

51、 inoperative. This speed is subdivided into:VMCG minimum control speed during takeoff ground roll with the nose wheel still on the ground.VMCA minimum control speed in the air or on the ground with the nose wheel off the ground after rotation for takeoff.72Accelerate-GoandAccelerate-Stopaccelerate-g

52、o distance distance an airplane uses to accelerate to V1, experience a critical engine failure, then continue accelerating, lift off, and achieve an altitude of 35 AGL.accelerate-stop distance distance an airplane uses to accelerate to V1, then decelerate to a stop using only brakes and spoilers. 73

53、Balanced Field LengthBalanced field length is the runway length where, for a given gross weight, elevation, and takeoff configuration, accelerate-stop distance and accelerate-go distance are the same .if an engine failure occurs prior to V1, the aircraft will have adequate runway remaining to stop w

54、hen an abort is initiated.If an engine failure occurs at or above V1, the aircraft will achieve 35AGL by the end of the runway if the takeoff is continued.Contd 74Balanced Field LengthBalanced field length is the runway length where, for a given gross weight, elevation, and takeoff configuration, ac

55、celerate-stop distance and accelerate-go distance are the same .if an abort is initiated after V1, the aircraft will overrun the runway.if an engine failure occurs prior to V1 and takeoff is continued, the aircraft will not achieve 35 AGL by the end of the runway. 75An airplane should never attempt

56、to depart from a runway shorter than the balanced field length for its particular gross weight, elevation, and takeoff configuration, sincea decision to abort just below V1 will result in runway overrun.a decision to continue just above V1 will result in achieving less than35 AGL by the end of the r

57、unway.If V1 is changed from the V1 corresponding to balanced field length, the runway length to depart safely increases, sincewhen V1 decreases, accelerate-go distance increases, and takeoff commitment occurs at V1.When V1 increases, accelerate-stop distance increases, and a commitment to abort exis

58、ts below V1.The balanced field length concept ordinarily should be used to determine decision speed V1. 76Factors AffectingV1 and Balanced Field Lengthslippery runway a slippery runway is one where poor braking action (rain, freezing rain, very light ice or packed snow) increases accelerate-stop dis

59、tance but not accelerate-go distance. An increase in balanced field length will occur as a result. V1 must be decreased to allow a greater abort rollout. VR and V2 remain unchanged.cluttered runway a cluttered runway is one where precipitation on the runway increases accelerate-go distance but not a

60、ccelerate-stop distance. Balanced field length will increase, as will V1, because it takes longer to achieve a ground speed compatible with reaching V2 and 35 AGL by the end of the runway. 77Critical EngineThe critical engine of a twin engine airplane is the one with the center of thrust closest to