1.02.02 AIRCRAFT PRIMARY CONTROLS 1. 0 2 A I R C R A F T G E N E R A L K N O W L E D G E
CONTROLLING AIRCRAFT AIRCRAFT CONTROL SYSTEM In general, we use control inputs of the following devices in cabin: Yoke or steering column Pedals Trim knobs Flaps lever/switch
TRANSFER SYSTEMS AIRCRAFT CONTROL SYSTEM There are 3 common ways to transfer control inputs to control elements: Mechanical - by system of cables, rods, levers, chains Hydraulic by liquid under pressure (on heavy aircrafts) Electrical by electric energy, (using electric motors) Pneumatic by pressurized gas (air) Air (pneumatic systems) are not used for controlling airplane because of rough positioning of actuators. Pneumatic is used for non-precise elements like gear operation, brake system.
MECHANICAL AIRCRAFT CONTROL SYSTEM System of cables, rods, levers, chains, which allows to control aerodynamical surfaces Simple Reliable Low cost maintenance Disadvantages: Uses a lot of space inside aircraft Construction limited by size of aircrafts Limited by maximum human forces applied to controls Limited by movement range
HYDRAULIC AIRCRAFT CONTROL SYSTEM Allows control position of aerodynamic surfaces by flow of power liquid under pressure. Advantages: Passes high forces to mechanisms Gives any desired range of movement Precise and fast positioning Not restricted by mechanical configuration Disadvantages: Complicated and prone to leakage - consists of power pump, valves, reservoirs, accumulators, power lines Heavy because a lot of components and power liquid Expensive in production and maintenance Does not provide feedback force if not equipped with feedback system
ELECTRICAL AIRCRAFT CONTROL SYSTEM Electric motor actuators: Easy in construction low energy dissipation Light weight Demands less space in the aircraft, easy to mount But slow in changing position or in power (generated force) Can be used for controlling relevantly slow mechanisms, like flaps positioning system or landing gear retraction system. For example, full flaps retraction in Cessna takes about 10 seconds.
AILERONS AIRCRAFT CONTROL SYSTEM Control lateral position (bank) Aileron position controlled by yoke movement (left-right)
RIGHT BANK AILERONS While turning yoke to the right controls move ailerons: Left down (more lift) Right - up (less lift) Because of differential in generated lift forces aircraft in air banks right in result
LEFT BANK AILERONS Turning yoke to the left causes move ailerons: Right down (more lift) Left - up (less lift) Because of differential in generated lift forces aircraft in the air banks left in result
TURNS AILERONS Changing bank of aircraft will has turns in result: Total lift tilted to side (1) Lateral component of tilted fits causes aircraft turn (2) 1 2 This will be discussed in details in principles of flight part of the training course
FLAPS HIGH LIFT DEVICE Flap device mounted on trailing edge of wing which allows to change it s configuration in means of aerodynamic and therefore: Increase lift Increase drag Decrease stall speed Increased drag can be proc or cons depends of situation Flaps are used in take-off and landing configuration or to drop speed Flaps will be discusses in details in principles of flight part of the theory course
FLAPS CONTROL HIGH LIFT DEVICE Position of flaps is controlled by means of: Electric system (on light aircrafts) Mechanic system (on light aircrafts) Hydraulic system (on heavy aircrafts)
RUDDER DIRECTIONAL CONTROL Rudder is a aerodynamic surface mounted on vertical stabilizer. Rudder is used to: Maintain of directional control Correct for cross-wind on takeoffs and landing Correct for adverse yaw Recover from spin Correct asymmetrical propeller torque on single engine aircraft or on multi engine aircraft in case of asymmetrical engines power set Rudder is controlled by movement of pedals
RUDDER CONTROL INPUT DIRECTIONAL CONTROL Rudder controlled by pushing pedals: Left pedal rudder deflects left Right pedal rudder deflects right
ELEVATOR ATTITUDE CONTROL Elevator is controlled by forward-aft movement of the yoke Yoke moved forward elevator goes down (more lift on tail) Yoke moved aft elevator goes up (less lift on tail)
TRIMMERS SECONDARY CONTROLS There are trimmers on vertical and horizontal control surfaces: Rudder trimmer Elevator trimmer Trimmer tabs Trimmers are not primary control surfaces, but secondary control surfaces. Trimmers intended to eliminate aerodynamical forces on elevator, rudder and as a result, eliminate excessive control forces on the yoke
TRIMMER CONTROLS SECONDARY CONTROLS Electrical trimmer knob Trimmers could be adjustable (controllable) or preset manually. In case of controllable trimmer in can be controlled by means of Mechanical systems Electrical power Mechanical trimmer knobs
ELEVATOR TRIMMER SECONDARY CONTROLS Elevator trimmer is used for: Reducing forces on control yoke to zero to compensate changing CG (center of gravity) Allow to set desired pitch on climbing or descending Allow to set desired pitch after changing power set and flaps, chassis configuration Reduces drag on airfoils
ELEVATOR TRIMMER PITCH UP SECONDARY CONTROLS Trimming the elevator in pitch up position: 1 1. Normal position of elevator horizontal pitch 2. Elevator in pitch up - without trimming need to constantly apply control force on yoke 2 3. After trimming control force removed from yoke (elevator is balanced) 3
ELEVATOR TRIMMER PITCH UP SECONDARY CONTROLS The same but reversal for pitch down position of the elevator 1. Without trimming - need constantly apply control force on yoke 2. After trimming control force removed form yoke 1 2
RUDDER TRIMMER SECONDARY CONTROLS Two types of rudder trimmers: Fixed trim tab Controlled trim tab Fixed (preset) trim tab Controlled trim tab
RUDDER TRIMMER SECONDARY CONTROLS Rudder trimmer is used for: Reducing forces on pedals to zero to compensate lateral change of center of gravity and set pedals in neutral position Compensate yawing in case of changing propeller torque Compensate yawing in case of constant cross - wind Compensate yawing in case of asymmetric power (for multi engine aircrafts) Reduce drag on airfoil of rudder
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