Primary Controls Flashcards by Unknown Unknown

Advantages of fly by wire

Lighter than conventional control systems
Reduces pilot workload
Offers advanced envelope protection
Even out control inputs in turbulence

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Fly By Wire

Controls inputs from pilots controls and translated to digital signals fed to series of computer that compare and make decision

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Safety Measures in FBW

Multiple Computers
Difference hardware
Different software
Different sensors

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Airbus FBW

X 3 Primary x2 secondary

Normal law - AOA protection etc
Alternate Law - x2 failures basic control law
Direct Law - Complete computer failure direct with controls
Mechanical Law - Control pitch/trim/rudder

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Boeing FBW

X 3 primary computers
Normal - full function
Secondary - loss of flight envelope protection
Direct - direct from pilots controls

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Rudder ratio changer

Protect fin from excessive rudder loads from pilot
Limited at higher speeds

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Trim Runaway Protection

Double pole trim both need to be pressed together to operate trim jack motor

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Q Feel System

Receives dynamic pressure info from pitot static system and used to control hydraulic load jack inside Q feel unit

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Spring Feel System on fully powered flight controls

Connected to the control column
When deflected one way opposite spring stretches with opposing force

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Electro-Hydraulic systems

Electro-Hydraulic Actuator (EHA) - Hydraulic pump driven by high power stepper motor. Pump electrically signalled to control operation. NO HYDRAULIC LINES

Electro-Mechanical Actuator (EMA) - entirely driven by electric motors - restricted to secondary flight controls

EBHA - Basically EHA with a back up EHA

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Manual Control

Used on light ac
Stainless steel cables run from each control via pulley wheels
Turnbuckles for tension

Reversible system

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Non reversible system

Movement of control surface cannot move control column

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Primary Controls

Elevator
Ailerons
Rudder
Roll Spoilers

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Partially Powered Controls

Hydraulic actuator attached in parallel to direct link between pilots control and control surface.

Actuator controlled by hydraulic servo linked to control system.

Reversible connection

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Fully Powered Controls

Removes direct link between control and control surface - relies on hydraulic actuator

PFCU - Power flying control unit

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Reasons for trim

Changes in CG, Changes in speed and Changes of power

Blow Back System

Blow back valve relieve excessive loads before load causes damage to controls

Rudder applied force changes with speed

Advantages of a variable incidence tailplane

Large horizontal stabiliser through very small angle to reduce drag
Elevator retains its full range of motion

Less drag in trimmed state
Trimming does not reduce range of pitch control

Fairing Role

Cover aileron actuator

Disadvantages of FBW

Sensor failure causing wrongly triggered interference of valid pilot inputs

Disadvantage of side stick controls

Make it difficult for one pilot to see and understand what other is doing. Inputs are averaged

Gust LOCK

Device that limits the movement of control surface when parked

Reasons for being trimmed in pitch

Varying CG position
Changes of speed
Changes of power

Primary stop controls

Set the range of movement of the control surface

Flutter is and preventions

Flutter of control surface is divergent oscillatory motion of control surfaces caused by natural frequency interaction of forces and stiffness of structure. Flutter occurs when external forces is applied to the ac with periodic frequency that is equal to the natural structural frequency of that ac Flutter can be avoided by remaining in flight envelope and speed limitation in turbulent conditions

Zero force position changes on

Ailerons trim Rudder trim

Zero position force does not change on

PET: Pitch controls Elevator Trim

3 ways to limit rudder deflection

Rudder ratio changer - limits deflection at high speeds Variable stops - rudder peals and rudder physically reduced Block back - applies constant movement force to rudder dictated by pedal deflection deflecting rudder depending on speed of the airflow

THS is usually controlled by

Hydraulically actuated jack

Fairings cover

Aileron actuators and flap tracks

How is redundancy achieved on fully powered primary flight controls

Duplex parallel control runs per control axis linked to control surfaces actuator which supply hydraulic systems

If failure of wiring on fly by wire ac what happens

Use a different actuator with a different computer

Rudder trim does what

Moves the rudder and the rudder pedals in the corresponding direction

Aileron trim system does what

Control wheel turns in the direction of trim

Elevator trim does what

Control column does not move - zero force position does not change

Direct Law

Pilot controls are not augmented by internal computers Exact control sent direct to hydraulic servo valves Autopilot lost Aural and visual warning will remain for over speed/stall

Trimming of aileron and rudder in an irreversible control system

Achieved by adjusting the zero force point of the feel system

Route of operation of fly by wire

Pilot operates control —— primary flight computer convert to electrical output —— actuator control electronics covert electrical signal to analogue signals —- sent to power control unit —— hydraulic actuator moves flight control surface