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发表于 2009-3-20 23:41:32
Landing Gear ....................................................15-3Wings ................................................................15-3Chapter 16—Aerodynamics of the GyroplaneAutorotation...........................................................16-1Vertical Autorotation.........................................16-1Rotor Disc Regions...........................................16-2Autorotation in Forward Flight ........................16-2Reverse Flow................................................16-3Retreating Blade Stall ..................................16-3Rotor Force............................................................16-3Rotor Lift ..........................................................16-4Rotor Drag ........................................................16-4Thrust.....................................................................16-4Stability .................................................................16-5Horizontal Stabilizer.........................................16-5Fuselage Drag (Center of Pressure)..................16-5Pitch Inertia.......................................................16-5Propeller Thrust Line........................................16-5Rotor Force .......................................................16-6Trimmed Condition...........................................16-6Chapter 17—Gyroplane Flight ControlsCyclic Control .......................................................17-1Throttle ..................................................................17-1Rudder ...................................................................17-2Horizontal Tail Surfaces........................................17-2Collective Control .................................................17-2Chapter 18—Gyroplane SystemsPropulsion Systems ...............................................18-1Rotor Systems .......................................................18-1Semirigid Rotor System....................................18-1Fully Articulated Rotor System ........................18-1Prerotator ...............................................................18-2Mechanical Prerotator.......................................18-2Hydraulic Prerotator .........................................18-2Electric Prerotator.............................................18-3Tip Jets..............................................................18-3Instrumentation......................................................18-3Engine Instruments ...........................................18-3Rotor Tachometer .............................................18-3Slip/Skid Indicator ............................................18-4Airspeed Indicator ............................................18-4Altimeter ...........................................................18-4IFR Flight Instrumentation ...............................18-4Ground Handling...................................................18-4Chapter 19—Rotorcraft Flight Manual(Gyroplane)Using the Flight Manual........................................19-1Weight and Balance Section .............................19-1Sample Problem ...........................................19-1Performance Section.........................................19-2Sample Problem ...........................................19-2Height/Velocity Diagram .............................19-3Emergency Section ...........................................19-3
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发表于 2009-3-20 23:41:45
Hang Test...............................................................19-4Chapter 20—Flight OperationsPreflight .................................................................20-1Cockpit Management........................................20-1Engine Starting......................................................20-1Taxiing...................................................................20-1Blade Flap.........................................................20-1Before Takeoff.......................................................20-2Prerotation.........................................................20-2Takeoff...................................................................20-3Normal Takeoff.................................................20-3Crosswind Takeoff ............................................20-4Common Errors for Normal andCrosswind Takeoffs ..........................................20-4Short-Field Takeoff...........................................20-4xCommon Errors............................................20-4High-Altitude Takeoff ..................................20-4Soft-Field Takeoff.............................................20-5Common Errors............................................20-5Jump Takeoff................................................20-5Basic Flight Maneuvers.........................................20-6Straight-and-Level Flight..................................20-6Climbs...............................................................20-6Descents ............................................................20-7Turns .................................................................20-7Slips..............................................................20-7Skids .............................................................20-7Common Errors During BasicFlight Maneuvers ..............................................20-8Steep Turns .......................................................20-8Common Errors............................................20-8Ground Reference Maneuvers...............................20-8Rectangular Course...........................................20-8S-Turns............................................................20-10Turns Around a Point......................................20-11Common Errors DuringGround Reference Maneuvers ........................20-11Flight at Slow Airspeeds .....................................20-12Common Errors ..............................................20-12High Rate of Descent ..........................................20-12Common Errors ..............................................20-13Landings ..............................................................20-13Normal Landing..............................................20-13Short-Field Landing........................................20-13Soft-Field Landing..........................................20-14Crosswind Landing.........................................20-14High-Altitude Landing....................................20-14Common Errors During Landing....................20-15Go-Around...........................................................20-15Common Errors ..............................................20-15After Landing and Securing................................20-15Chapter 21—Gyroplane Emergencies
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发表于 2009-3-20 23:41:56
Aborted Takeoff.....................................................21-1Accelerate/Stop Distance..................................21-1Lift-off at Low Airspeed andHigh Angle of Attack ............................................21-1Common Errors ................................................21-2Pilot-Induced Oscillation (PIO) ............................21-2Buntover (Power Pushover) ..................................21-3Ground Resonance ................................................21-3Emergency Approach and Landing.......................21-3Emergency Equipment and Survival Gear............21-4Chapter 22—Gyroplane Aeronautical DecisionMakingImpulsivity.............................................................22-1Invulnerability .......................................................22-1Macho....................................................................22-2Resignation............................................................22-2Anti-Authority .......................................................22-3Glossary.................................................................G-1Index........................................................................I-11-1Helicopters come in many sizes and shapes, but mostshare the same major components. These componentsinclude a cabin where the payload and crew are carried; an airframe, which houses the various components, or where components are attached; a powerplantor engine; and a transmission, which, among otherthings, takes the power from the engine and transmits itto the main rotor, which provides the aerodynamicforces that make the helicopter fly. Then, to keep thehelicopter from turning due to torque, there must besome type of antitorque system. Finally there is thelanding gear, which could be skids, wheels, skis, orfloats. This chapter is an introduction to these components. THE MAIN ROTOR SYSTEMThe rotor system found on helicopters can consist of asingle main rotor or dual rotors. With most dual rotors,the rotors turn in opposite directions so the torque fromone rotor is opposed by the torque of the other. Thiscancels the turning tendencies. In general, a rotor system can be classified as eitherfully articulated, semirigid, or rigid. There are variations and combinations of these systems, which will bediscussed in greater detail in Chapter 5—HelicopterSystems.FULLY ARTICULATED ROTOR SYSTEMA fully articulated rotor system usually consists ofthree or more rotor blades. The blades are allowed toflap, feather, and lead or lag independently of eachother. Each rotor blade is attached to the rotor hub by ahorizontal hinge, called the flapping hinge, which permits the blades to flap up and down. Each blade canmove up and down independently of the others. Theflapping hinge may be located at varying distancesfrom the rotor hub, and there may be more than one.
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发表于 2009-3-20 23:42:07
The position is chosen by each manufacturer, primarilywith regard to stability and control.Payload—The term used for passengers, baggage, and cargo.Torque—In helicopters with a single, main rotor system, the tendency of the helicopter to turn inthe opposite direction of the mainrotor rotation.Blade Flap—The upward ordownward movement of the rotorblades during rotation.Blade Feather or Feathering—Therotation of the blade around thespanwise (pitch change) axis.Blade Lead or Lag—The fore andaft movement of the blade in theplane of rotation. It is sometimescalled hunting or dragging.Landing GearTail RotorSystemMain RotorSystemCabinAirframeTransmissionPowerplantFigure 1-2. Helicopters can have a single main rotor or a dual rotor system.Figure 1-1. The major components of a helicopter are thecabin, airframe, landing gear, powerplant, transmission, mainrotor system, and tail rotor system.1-2Each rotor blade is also attached to the hub by a vertical hinge, called a drag or lag hinge, that permits eachblade, independently of the others, to move back andforth in the plane of the rotor disc. Dampers are normally incorporated in the design of this type of rotorsystem to prevent excessive motion about the draghinge. The purpose of the drag hinge and dampers is toabsorb the acceleration and deceleration of the rotorblades.The blades of a fully articulated rotor can also be feathered, or rotated about their spanwise axis. To put itmore simply, feathering means the changing of thepitch angle of the rotor blades.SEMIRIGID ROTOR SYSTEMA semirigid rotor system allows for two differentmovements, flapping and feathering. This system isnormally comprised of two blades, which are rigidlyattached to the rotor hub. The hub is then attached tothe rotor mast by a trunnion bearing or teetering hinge.This allows the blades to see-saw or flap together. Asone blade flaps down, the other flaps up. Feathering isaccomplished by the feathering hinge, which changesthe pitch angle of the blade.RIGID ROTOR SYSTEMThe rigid rotor system is mechanically simple, butstructurally complex because operating loads must beabsorbed in bending rather than through hinges. In thissystem, the blades cannot flap or lead and lag, but theycan be feathered.ANTITORQUE SYSTEMS
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发表于 2009-3-20 23:42:21
TAIL ROTORMost helicopters with a single, main rotor systemrequire a separate rotor to overcome torque. This isaccomplished through a variable pitch, antitorque rotoror tail rotor. . You will need to vary thethrust of the antitorque system to maintain directionalcontrol whenever the main rotor torque changes, or tomake heading changes while hovering.FENESTRONAnother form of antitorque rotor is the fenestron or“fan-in-tail” design. This system uses a series of rotating blades shrouded within a vertical tail. Because theblades are located within a circular duct, they are lesslikely to come into contact with people or objects.NOTAR®The NOTAR® system is an alternative to the antitorquerotor. The system uses low-pressure air that is forcedinto the tailboom by a fan mounted within the helicopter. The air is then fed through horizontal slots, locatedon the right side of the tailboom, and to a controllablerotating nozzle to provide antitorque and directionalcontrol. The low-pressure air coming from the horizontal slots, in conjunction with the downwash from themain rotor, creates a phenomenon called “CoandaEffect,” which produces a lifting force on the right sideof the tailboom. LANDING GEARThe most common landing gear is a skid type gear,which is suitable for landing on various types of surfaces. Some types of skid gear are equipped withdampers so touchdown shocks or jolts are not transmitted to the main rotor system. Other types absorb theshocks by the bending of the skid attachment arms.Landing skids may be fitted with replaceable heavyduty skid shoes to protect them from excessive wearand tear.Helicopters can also be equipped with floats for wateroperations, or skis for landing on snow or soft terrain.Wheels are another type of landing gear. They may bein a tricycle or four point configuration. Normally, theTail Rotor Thrustto Compensate for TorqueTorqueTorqueBlade RotationFigure 1-3. The antitorque rotor produces thrust to opposetorque and helps prevent the helicopter from turning in theopposite direction of the main rotor.Figure 1-4. Compared to an unprotected tail rotor, the fenestron antitorque system provides an improved margin ofsafety during ground operations.1-3nose or tail gear is free to swivel as the helicopter istaxied on the ground.POWERPLANT
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发表于 2009-3-20 23:42:29
A typical small helicopter has a reciprocating engine,which is mounted on the airframe. The engine can bemounted horizontally or vertically with the transmission supplying the power to the vertical main rotorshaft. Another engine type is the gas turbine. This engine isused in most medium to heavy lift helicopters due to itslarge horsepower output. The engine drives the maintransmission, which then transfers power directly to themain rotor system, as well as the tail rotor.FLIGHT CONTROLSWhen you begin flying a helicopter, you will use fourbasic flight controls. They are the cyclic pitch control;the collective pitch control; the throttle, which isusually a twist grip control located on the end of thecollective lever; and the antitorque pedals. The collective and cyclic controls the pitch of the main rotorblades. The function of these controls will be explainedin detail in Chapter 4—Flight Controls. Figure 1-5. While in a hover, Coanda Effect supplies approximately two-thirds of the lift necessary to maintain directionalcontrol. The rest is created by directing the thrust from thecontrollable rotating nozzle.Main RotorWakeRotatingNozzleDownwashAirJetLiftAir IntakeMainRotorMainTransmissionAntitorqueRotorEngineFigure 1-6. Typically, the engine drives the main rotor througha transmission and belt drive or centrifugal clutch system.The antitorque rotor is driven from the transmission.CyclicThrottleCollectiveAntitorquePedalsFigure 1-7. Location of flight controls.1-42-1There are four forces acting on a helicopter in flight.They are lift, weight, thrust, and drag. Liftis the upward force created by the effect of airflow as itpasses around an airfoil. Weight opposes lift and iscaused by the downward pull of gravity. Thrust is theforce that propels the helicopter through the air.Opposing lift and thrust is drag, which is the retardingforce created by development of lift and the movementof an object through the air.AIRFOILBefore beginning the discussion of lift, you need to be
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发表于 2009-3-20 23:42:41
aware of certain aerodynamic terms that describe anairfoil and the interaction of the airflow around it.An airfoil is any surface, such as an airplane wing or ahelicopter rotor blade, which provides aerodynamicforce when it interacts with a moving stream of air.Although there are many different rotor blade airfoildesigns, in most helicopter flight conditions, all airfoilsperform in the same manner.Engineers of the first helicopters designed relativelythick airfoils for their structural characteristics.Because the rotor blades were very long and slender, itwas necessary to incorporate more structural rigidityinto them. This prevented excessive blade droop whenthe rotor system was idle, and minimized blade twisting while in flight. The airfoils were also designed tobe symmetrical, which means they had the same camber (curvature) on both the upper and lower surfaces.Symmetrical blades are very stable, which helps keepblade twisting and flight control loads to a minimum. This stability is achieved by keeping thecenter of pressure virtually unchanged as the angle ofattack changes. Center of pressure is the imaginarypoint on the chord line where the resultant of all aerodynamic forces are considered to be concentrated.Today, designers use thinner airfoils and obtain therequired rigidity by using composite materials. In addition, airfoils are asymmetrical in design, meaning theupper and lower surface do not have the same camber.Normally these airfoils would not be as stable, but thiscan be corrected by bending the trailing edge to producethe same characteristics as symmetrical airfoils. This iscalled “reflexing.” Using this type of rotor blade allowsthe rotor system to operate at higher forward speeds.One of the reasons an asymmetrical rotor blade is notas stable is that the center of pressure changes withchanges in angle of attack. When the center of pressurelifting force is behind the pivot point on a rotor blade, ittends to cause the rotor disc to pitch up. As the angle ofattack increases, the center of pressure moves forward.If it moves ahead of the pivot point, the pitch of therotor disc decreases. Since the angle of attack of therotor blades is constantly changing during each cycleof rotation, the blades tend to flap, feather, lead, andlag to a greater degree.When referring to an airfoil, the span is the distancefrom the rotor hub to the blade tip. Blade twist refers toa changing chord line from the blade root to the tip.Figure 2-2. The upper and lower curvatures are the same on asymmetrical airfoil and vary on an asymmetrical airfoil.AsymmetricalSymmetricalLiftWeightDragThrust
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发表于 2009-3-20 23:42:55
Figure 2-1. Four forces acting on a helicopter in forward flight.2-2Twisting a rotor blade causes it to produce a more evenamount of lift along its span. This is necessary becauserotational velocity increases toward the blade tip. Theleading edge is the first part of the airfoil to meet theoncoming air. The trailing edge is the aftportion where the airflow over the upper surface joinsthe airflow under the lower surface. The chord line isan imaginary straight line drawn from the leading tothe trailing edge. The camber is the curvature of the airfoil’s upper and lower surfaces. The relative wind is thewind moving past the airfoil. The direction of this windis relative to the attitude, or position, of the airfoil andis always parallel, equal, and opposite in direction tothe flight path of the airfoil. The angle of attack is theangle between the blade chord line and the direction ofthe relative wind.RELATIVE WINDRelative wind is created by the motion of an airfoilthrough the air, by the motion of air past an airfoil, or bya combination of the two. Relative wind may beaffected by several factors, including the rotation of therotor blades, horizontal movement of the helicopter,flapping of the rotor blades, and wind speed and direction.For a helicopter, the relative wind is the flow of air withrespect to the rotor blades. If the rotor is stopped, windblowing over the blades creates a relative wind. Whenthe helicopter is hovering in a no-wind condition, relative wind is created by the motion of the rotor bladesthrough the air. If the helicopter is hovering in a wind,the relative wind is a combination of the wind and themotion of the rotor blades through the air. When thehelicopter is in forward flight, the relative wind is acombination of the rotation of the rotor blades and theforward speed of the helicopter.BLADE PITCH ANGLEThe pitch angle of a rotor blade is the angle between itschord line and the reference plane containing the rotorhub. You control the pitch angle of the bladeswith the flight controls. The collective pitch changes eachrotor blade an equal amount of pitch no matter where it islocated in the plane of rotation (rotor disc) and is used tochange rotor thrust. The cyclic pitch control changes thepitch of each blade as a function of where it is in the planeof rotation. This allows for trimming the helicopter inpitch and roll during forward flight and for maneuveringin all flight conditions.ANGLE OF ATTACKWhen the angle of attack is increased, air flowing overthe airfoil is diverted over a greater distance, resultingin an increase of air velocity and more lift. As angle ofattack is increased further, it becomes more difficult for
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发表于 2009-3-20 23:43:09
air to flow smoothly across the top of the airfoil. At thispoint the airflow begins to separate from the airfoil andenters a burbling or turbulent pattern. The turbulenceresults in a large increase in drag and loss of lift in thearea where it is taking place. Increasing the angle ofattack increases lift until the critical angle of attack isreached. Any increase in the angle of attack beyond thispoint produces a stall and a rapid decrease in lift.Angle of attack should not be confused with pitchangle. Pitch angle is determined by the direction of therelative wind. You can, however, change the angle ofattack by changing the pitch angle through the use ofthe flight controls. If the pitch angle is increased, theangle of attack is increased, if the pitch angle isreduced, the angle of attack is reduced. Axis-of-Rotation—The imaginaryline about which the rotor rotates.It is represented by a line drawnthrough the center of, and perpendicular to, the tip-path plane.Tip-Path Plane—The imaginarycircular plane outlined by therotor blade tips as they make acycle of rotation.Aircraft Pitch—When referencedto a helicopter, is the movement ofthe helicopter about its lateral, orside to side axis. Movement of thecyclic forward or aft causes thenose of the helicopter to move upor down.Aircraft Roll—Is the movement ofthe helicopter about its longitudinal, or nose to tail axis. Movementof the cyclic right or left causes thehelicopter to tilt in that direction.Figure 2-3. Aerodynamic terms of an airfoil.TrailingEdgeChordLineAngleofAttackFLIGHT PATHRELATIVE WINDUpperCamberLowerCamberLeadingEdgeAxis of RotationReference PlanePitchAngleChordLineFigure 2-4. Do not confuse the axis of rotation with the rotormast. The only time they coincide is when the tip-path planeis perpendicular to the rotor mast.2-3LIFTMAGNUS EFFECTThe explanation of lift can best be explained by lookingat a cylinder rotating in an airstream. The local velocitynear the cylinder is composed of the airstream velocityand the cylinder’s rotational velocity, which decreases
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发表于 2009-3-20 23:43:30
with distance from the cylinder. On a cylinder, which isrotating in such a way that the top surface area is rotatingin the same direction as the airflow, the local velocity atthe surface is high on top and low on the bottom.As shown in figure 2-7, at point “A,” a stagnation pointexists where the airstream line that impinges on the surface splits; some air goes over and some under. Anotherstagnation point exists at “B,” where the two airstreams rejoin and resume at identical velocities. Wenow have upwash ahead of the rotating cylinder anddownwash at the rear.The difference in surface velocity accounts for a difference in pressure, with the pressure being lower on thetop than the bottom. This low pressure area producesan upward force known as the “Magnus Effect.” Thismechanically induced circulation illustrates the relationship between circulation and lift.An airfoil with a positive angle of attack develops aircirculation as its sharp trailing edge forces the rearstagnation point to be aft of the trailing edge, while thefront stagnation point is below the leading edge.BERNOULLI’S PRINCIPLEAir flowing over the top surface accelerates. The airfoilis now subjected to Bernoulli’s Principle or the “venturieffect.” As air velocity increases through the constrictedportion of a venturi tube, the pressure decreases.Axis of RotationReference PlanePitchAngleChordLineAngleofAttackRELATIVE WINDFigure 2-6. Angle of attack may be greater than, less than, orthe same as the pitch angle.Figure 2-5. As the angle of attack is increased, the separationpoint starts near the trailing edge of the airfoil and progresses forward. Finally, the airfoil loses its lift and a stallcondition occurs.LIFTSTALL8°12-16°Figure 2-7. Magnus Effect is a lifting force produced when arotating cylinder produces a pressure differential. This is thesame effect that makes a baseball curve or a golf ball slice.B AIncreased Local Velocity(Decreased pressure)Decreased Local VelocityDownwash UpwashFigure 2-8. Air circulation around an airfoil occurs when thefront stagnation point is below the leading edge and the aftstagnation point is beyond the trailing edge.Leading EdgeStagnation PointTrailing EdgeStagnation PointBASteady-State Flight—A conditionwhen an aircraft is in straightand-level, unaccelerated flight,and all forces are in balance.2-4ward. According to Newton’s Third Law of Motion,“for every action there is an equal and opposite reaction,” the air that is deflected downward also producesan upward (lifting) reaction.Since air is much like water, the explanation for thissource of lift may be compared to the planing effect ofskis on water. The lift which supports the water skis(and the skier) is the force caused by the impact pressure and the deflection of water from the lower surfacesof the skis.Under most flying conditions, the impact pressure andthe deflection of air from the lower surface of the rotorblade provides a comparatively small percentage of thetotal lift. The majority of lift is the result of decreasedpressure above the blade, rather than the increasedpressure below it.WEIGHTNormally, weight is thought of as being a known, fixedvalue, such as the weight of the helicopter, fuel, andoccupants. To lift the helicopter off the ground vertically, the rotor system must generate enough lift toovercome or offset the total weight of the helicopterand its occupants. This is accomplished by increasingthe pitch angle of the main rotor blades.The weight of the helicopter can also be influenced byaerodynamic loads. When you bank a helicopter whilemaintaining a constant altitude, the “G” load or loadfactor increases. Load factor is the ratio of the load supported by the main rotor system to the actual weight ofthe helicopter and its contents. In steady-state flight,the helicopter has a load factor of one, which means themain rotor system is supporting the actual total weightof the helicopter. If you increase the bank angle to 60°,while still maintaining a constant altitude, the load factor increases to two. In this case, the main rotor systemhas to support twice the weight of the helicopter and itscontents. Disc loading of a helicopter is the ratio of weight to thetotal main rotor disc area, and is determined by dividing the total helicopter weight by the rotor disc area,which is the area swept by the blades of a rotor. Discarea can be found by using the span of one rotor bladeas the radius of a circle and then determining the areathe blades encompass during a complete rotation. Asthe helicopter is maneuvered, disc loading changes.The higher the loading, the more power you need tomaintain rotor speed.Leading EdgeStagnation PointB
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