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
In general, we use control inputs of the following
devices in cabin:
Yoke or steering column
Pedals
Trim knobs
Flaps lever/switch
AIRCRAFT CONTROL SYSTEM
TRANSFER SYSTEMS
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.
AIRCRAFT CONTROL SYSTEM
MECHANICAL
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
AIRCRAFT CONTROL SYSTEM
HYDRAULIC
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
AIRCRAFT CONTROL SYSTEM
ELECTRICAL
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.
AIRCRAFT CONTROL SYSTEM
AILERONS
Control lateral position (bank)
Aileron position controlled by yoke
movement (left-right)
AIRCRAFT CONTROL SYSTEM
RIGHT BANK
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
AILERONS
LEFT BANK
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
AILERONS
TURNS
Changing bank of aircraft will has turns in
result:
Total lift tilted to side (1)
Lateral component of tilted fits causes aircraft
turn (2)
This will be discussed in details in “principles of
flight“ part of the training course
AILERONS
1
2
FLAPS
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
HIGH LIFT DEVICE
FLAPS CONTROL
Position of flaps is controlled by means of:
Electric system (on light aircrafts)
Mechanic system (on light aircrafts)
Hydraulic system (on heavy aircrafts)
HIGH LIFT DEVICE
RUDDER
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
DIRECTIONAL CONTROL
RUDDER CONTROL INPUT
Rudder controlled by pushing pedals:
Left pedal – rudder deflects left
Right pedal – rudder deflects right
DIRECTIONAL CONTROL
ELEVATOR
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)
ATTITUDE CONTROL
TRIMMERS SECONDARY CONTROLS
Trimmer
tabs
There are trimmers on vertical and horizontal control
surfaces:
Rudder trimmer
Elevator trimmer
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
Trimmers could be adjustable (controllable)
or preset manually. In case of controllable
trimmer in can be controlled by means of
Mechanical systems
Electrical power
SECONDARY CONTROLS
Electrical
trimmer knob
Mechanical
trimmer knobs
ELEVATOR TRIMMER
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
SECONDARY CONTROLS
ELEVATOR TRIMMER – PITCH UP
Trimming the elevator in pitch up position:
1. Normal position of elevator – horizontal pitch
2. Elevator in pitch up - without trimming need to
constantly apply control force on yoke
3. After trimming control force removed from yoke
(elevator is balanced)
SECONDARY CONTROLS
1
2
3
ELEVATOR TRIMMER – PITCH UP
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
SECONDARY CONTROLS
1
2
RUDDER TRIMMER
Two types of rudder trimmers:
Fixed trim tab
Controlled trim tab
SECONDARY CONTROLS
Controlled
trim tab
Fixed (preset)
trim tab
SECONDARY CONTROLSRUDDER TRIMMER
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
Thank you!Please visit Q/A section to prepare to the theory examination
PPL THEORY
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