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# 直升机飞行力学 Helicopter dynamics chapter 2

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Helicopter Dynamics

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• Correction of previous comments: 6th line "without the knowledge "of" itsts

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• Advise for helicopter mechanics to learn helicopter aerodynamics so that they can realize the stressed impose on the aerodynamic surfaces and rotary components during flight and accordingly they can do maintenance on the helicopter components. If a mechanic do maintenance work in helicopters without knowing the role of the component in helicopter flying,he is just doing the job like a blind man. As a matter of fact, the mechanic do maintenance work in helicopter without the knowledge its function in the air, he is more hazardous than an unserviceable components.Please be awre of yourself and know your capacity .

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### 直升机飞行力学 Helicopter dynamics chapter 2

1. 1. Helicopter Flight Dynamics Chapter 2: Helicopter Flight Controllers
2. 2. Topics <ul><li>External forces acting on helicopter </li></ul><ul><li>Control manners of helicopter </li></ul><ul><li>Control systems and their mechanical characteristic </li></ul><ul><li>The Development of helicopter controllers </li></ul>
3. 3. External Forces Acting on Helicopter V V
4. 4. Aerodynamic Forces of Main Rotor Thrust: T Hind force: H Side force: S Anti-torque: M k Hub moments: M Gx , M Gz
5. 5. Aerodynamic Forces of Tail Rotor Thrust: T T Anti-torque: M kT V V
6. 6. Aerodynamic Forces of Fuselage Drag: Q f Lift: Y f Side Force: S f Roll Moment: M xf Yaw Moment: M yf Pitch Moment: M zf V V
7. 7. Aerodynamic Forces of Horizontal Tail Drag: D h Lift: Y h V V
8. 8. Aerodynamic Forces of Vertical Tail Drag: D v Lift: Y v V V
9. 9. Helicopter Control Manners <ul><li>Control manners of helicopter with main rotor and tail rotor </li></ul><ul><li>Control manners of twin rotors helicopter </li></ul><ul><li>Control manners of tilt-rotor aircraft </li></ul><ul><li>Other control manners </li></ul>
10. 10. Helicopter Types
11. 11. Control of Fixed-wing Aircraft aileron rudder elevator aileron
12. 12. Control of Fixed-wing Aircraft M Y Rudder Paddle Yaw F Stick + Throttle Altitude Indirect Control Direct Control S Stick + Paddle Sideward M X Aileron Stick Roll M Z Elevator Stick Pitch T Thrust Throttle Forward Control Forces Aerodynamic Surfaces Cockpit Control Unit Degree of Freedoms
13. 13. Control of Helicopter Main Rotor Tail Rotor Engines Control System
14. 14. Control of Helicopter with Main & Tail Rotors Main rotor is the lift surface to produce the lift of helicopter. On the other hand, it is the control surface to produce the forces or moments of heaving, pitching and rolling. Furthermore, it is the propeller to make helicopter to fly in any directions. T T Tail rotor Rudder Heading Yaw S, M Gx Rotor Stick Rolling, sidestep Lateral H, M Gz Rotor Stick Pitching, Forward & backward Longitudinal T Rotor Collective stick Altitude Vertical Control Forces Aerodynamic Surfaces Cockpit Control Unit Motions Degree of Freedoms
15. 15. Comparison of Control Between helicopter and Fixed-wing Aircraft S Collective + stick + Rudder Sideward H Collective + stick Forward Indirect Control T T Tail rotor Rudder Yaw S, M Gx Rotor Stick Roll H, M Gz Rotor Stick Pitch T Rotor Collective Altitude Direct Control Helicopter Fixed_wing Aircraft M Y Rudder Paddle Yaw F Stick + Throttle Altitude Indirect Control Direct Control S Stick + Paddle Sideward M X Aileron Stick Roll M Z Elevator Stick Pitch T Thrust Throttle Forward Control Forces Aerodynamic Surfaces Cockpit Control Unit Degree of Freedoms
16. 16. Control Manners of Twin Rotors Helicopter Configuration Tandem rotors Control Side by side rotors Single rotor Co-axis rotors Vert. Lon. Lat. Yaw Anti- Torque Balance
17. 17. Control Tandem Helicopter
18. 18. Control of Tilt-rotor Aircraft Pitch Thrust Roll Side Force Yaw Helicopter Mode Fixed-wing Mode
19. 19. Control of Tilt-rotor Aircraft Helicopter Airplane <ul><li>Thrust /power level controls Collective pitch and throttles </li></ul><ul><li>Acts as altitude control </li></ul><ul><li>Thrust /power level controls blade pitch and engine throttles </li></ul><ul><li>Acts as altitude control </li></ul>Thrust/power Control
20. 20. Control of Tilt-rotor Aircraft Helicopter Airplane Forward longitudinal cyclic pitch elevator <ul><li>Proprotor discs tilt forward </li></ul><ul><li>Aircraft assumes nose-down altitude </li></ul><ul><li>Airspeed increases </li></ul><ul><li>Elevator deflects downward </li></ul><ul><li>Aircraft assumes nose-down altitude </li></ul><ul><li>Altitude decreases </li></ul><ul><li>Airspeed increases </li></ul>Forward Stick Control
21. 21. Control of Tilt-rotor Aircraft Helicopter Airplane elevator Backward longitudinal cyclic pitch <ul><li>Proprotor discs tilt backward </li></ul><ul><li>Aircraft assumes nose-up altitude </li></ul><ul><li>Airspeed decreases </li></ul><ul><li>Elevator deflects upward </li></ul><ul><li>Aircraft assumes nose-up altitude </li></ul><ul><li>Altitude increases </li></ul><ul><li>Airspeed decreases </li></ul>Backward Stick Control
22. 22. Control of Tilt-rotor Aircraft Helicopter Airplane differential collective pitch and lateral cyclic pitch flaperon <ul><li>Right proprotor increase collective pitch </li></ul><ul><li>Left proprotor decrease collective pitch </li></ul><ul><li>Proprotor discs tilt to left </li></ul><ul><li>Aircraft rolls to left </li></ul><ul><li>Right flaperon deflects downward </li></ul><ul><li>Left flaperon deflects downward </li></ul><ul><li>Aircraft rolls to left </li></ul>Left Stick Control
23. 23. Control of Tilt-rotor Aircraft Helicopter Airplane differential collective pitch and lateral cyclic pitch flaperon <ul><li>Left proprotor increase collective pitch </li></ul><ul><li>Right proprotor decrease collective pitch </li></ul><ul><li>Proprotor discs tilt to right </li></ul><ul><li>Aircraft rolls to right </li></ul><ul><li>Left flaperon deflects downward </li></ul><ul><li>Right flaperon deflects downward </li></ul><ul><li>Aircraft rolls to right </li></ul>Right Stick Control
24. 24. Control of Tilt-rotor Aircraft Helicopter Airplane Differential longitudinal cyclic Rudder <ul><li>Left proprotor disk tilts forward </li></ul><ul><li>Right proprotor disk tilts backward </li></ul><ul><li>Aircraft yaws to left </li></ul><ul><li>Rudder deflect to left </li></ul><ul><li>Aircraft yaws to left </li></ul>Left Pedal Control
25. 25. Control of Tilt-rotor Aircraft Helicopter Airplane Differential longitudinal cyclic Rudder <ul><li>Left proprotor disk tilts backward </li></ul><ul><li>Right proprotor disk tilts forward </li></ul><ul><li>Aircraft yaws to right </li></ul><ul><li>Rudder deflect to right </li></ul><ul><li>Aircraft yaws to right </li></ul>Right Pedal Control
26. 26. Direct Control Manner In the early time, The small helicopter was controlled by directly rotating the rotor shaft. Advantages: structure simple Disadvantages: too large control forces and difficult to control precisely Status: Still be used now by Gyroplane
27. 27. Control by Hiller Bar <ul><li>Two Heller bars forms the control rotor (teetering rotor) </li></ul><ul><li>The control rotor is connected directly to swashplate. </li></ul><ul><li>The flap motion of bar adjust the blade cyclic pitching angles of main rotor. </li></ul><ul><li>Advantages: </li></ul><ul><ul><li>Small control forces and air loads. </li></ul></ul><ul><ul><li>Large aerodynamic damping, good stability (stable hover) </li></ul></ul><ul><li>Disadvantage: delay of response </li></ul><ul><li>Status: Used by most of model helicopter </li></ul>Hiller B ar
28. 28. Control by Servoflap <ul><li>There is a flap at the blade trail edge. </li></ul><ul><li>Pilot controls the deflection angle of servoflap. </li></ul><ul><li>The blade pitching angle is achieved with the blade torsional deflection </li></ul><ul><li>Servofalp has been successfully used on the Kaman helicopter </li></ul>
29. 29. Controller and Mechanical Features <ul><li>Swashplate </li></ul><ul><li>Typical Controller of Helicopter </li></ul><ul><li>Mechanical Feature of Controller </li></ul><ul><li>Other Controller </li></ul>
31. 31. Helicopter Typical Controller
32. 32. Mechanical Feature of Controller <ul><li>Gradient of Stick Force </li></ul><ul><li>Breakout Forces </li></ul><ul><li>Limited Control Forces </li></ul><ul><li>Cockpit Control Free Play </li></ul>The movement and load ranges of cockpit controllers shall be suitable to the pilot physiological characteristics. The mechanical features directly affect the control precision and pilot workloads.
33. 33. Gradient of Stick Force <ul><li>The relationship between stick force and displacement should be monotonous, continuous, primarily linear and symmetry to center point. </li></ul><ul><li>The magnitude of stick forces gradient shall be suitable to control the helicopter precisely. The adjust system for trimming stick force is needed. </li></ul>Ideal Stick force vs. displacement real Stick force vs. displacement Forward Force Backward Force Backward Position Forward Position Forward Force Backward Force Breakout Force Trim Free Play Friction band Forward Position Backward Position
34. 34. Breakout Forces <ul><li>Breakout forces, including friction, preload, etc., refer to the cockpit control force required to start movement of the control surface in flight. </li></ul><ul><li>In some cases, the engineers intently increase the friction to prevent from the slippage of stick position so that the pilot can remove his hands from the stick for a short time to do something. </li></ul>Forward Force Backward Force Breakout Force Trim Free Play Friction band Forward Position Backward Position
35. 35. Cockpit Control Free Play <ul><li>The free play is that any motion of the cockpit control does not move the appropriate moment - or force - producing device in flight. </li></ul><ul><li>The free play is caused by clearance. </li></ul><ul><li>In design, the engineers will do their best to keep the free play as small as possible. </li></ul>Forward Force Backward Force Breakout Force Trim Free Play Friction band Forward Position Backward Position
36. 36. Limited Control Forces <ul><li>Too large limited control forces will make the pilot tired and difficult to control the helicopter precisely. </li></ul><ul><li>Unless otherwise specified in particular requirements, the maximum control forces required shall not exceed the given value. </li></ul><ul><li>The value of limited control forces is given by the specification of flight qualities. </li></ul>
37. 37. The Development of Controller <ul><li>Fly-by-Iron </li></ul><ul><ul><li>This controller was very common in the early time. It is still used in the small helicopters. </li></ul></ul><ul><ul><li>Advantages: simple, direct and reliable </li></ul></ul><ul><ul><li>Disadvantages: large stick force, dithering of stick, free play and friction hurting the flight qualities </li></ul></ul><ul><li>Fly-by-Oil </li></ul><ul><ul><li>Combination of fly-by-iron and hydraulic system , stick control the hydraulic actuator which move the swashplate. </li></ul></ul><ul><ul><li>Advantages: large control power, no stick dithering, easy working with SCAS </li></ul></ul><ul><ul><li>Disadvantages: complicated structure, heavy, need of backup for safety </li></ul></ul>
38. 38. The Development of Controller Stick inputs commands into computer with redundant technology. The computer controls the actuators (electric or hydraulic) Advantages: small, light, good flight qualities (insured by computer software), high reliability (redundant, self check) Disadvantages: electromagnetic effects (such as thunder) Fly-by-Wire
39. 39. The Development of Controller Fly-by-Light Signals is carried by optical fiber, the others is the same as fly-by-wire. There is no electromagnetic effects. It is still under the development. Sidestick Controller Developed for fly-by-wire or fly-by-light. It located on the right side of pilot. The command signals are forces. Advantages: small size, big cockpit room. One hand and foot of pilot are free. Status: Installed on RAH-66 helicopter
40. 40. The Development of Controller Smart Control System Ambient disturbance Information from navigation sys. Commands from pilot Airborne Computer Helicopter flight dynamic model Actuators Sensors Helicopter