Primary Flight Controls Flashcards
Vertical axes
Vertical axes always point to the earth surface perpendicolour
Normal axes is perpendiclour to the longitudinal and lateral axes
Fully powered
Mechanical input transfers to a powers flight actuator which supplies hydraulic pressure ,so there is no manual reversing
A fly by wire is a fully powered system by defintion
Turnbuckles
Cables that get adjusted for tension due to temp differences
Partially powered sys
Syst have manual sys at the core but augmentted by the main hyd sys of the a/c.
Control cables is connected to a powered flying control actuator which hyd sys pressure.
When a demand is placed on the sys ,hyd pressure assists the pilot in deflecting the control surface and manoeuvring the aeroplane .
Each control surface will have multiple actuators which are connected to different hydraulic supplies for redundancy.
Still feel a good amount of forces
Torque tube
Ensures full control in the unlikely event of cable breakage or jamming.
Each control column is connected via the torque tube
Should control coloumn jam ,pilot can exert a force on both cloumn to shear the torque tube and regain authority over the reaminng operational colomuun
Partially powered control actuator
Pilot commands control the available hyd pressure assist in moving the control surfaces.
In the unlikely event if hyd loss ,the pilot can still commmand movement of the control syrface.
Partially manual reversible.
Is like the system is in parallel
Fully powered sys
Input force may be transmitted:
~mechanically attached via cables ,rods and levers
~electriccally connected via electrical cables in a FBW sys
No manual reversible.
Is like the sys is in series.
In case of a failure a piston allows the free movement of the hyd liquid preventing hydraulic lock
Feel system for fully powered sys
An artificial feel system is incorporated in to the system wich make the controls feel heavier as TAS manouvres increase.
~Spring feel syetem (doesn’t change with tas)
~q feel system»sensing dynamic pressure
Primary controls stops
The PFCU or actuator is pinned against the rear spar for strenght and leverage.
~to limit the range of movemnt availble on the control surface .primary control stops are fitted
~these are mechanical stops that are adjusted to provide a maximum limit to the range of movemnt
Should a primary stop fail ,a secondary stop is fitted in parallel
Trimming a/c to be neutral
An a/c is trimmed when all input forces are neutral.
Typically the ailerons are the ones that requires the least amount of trim
Stab trim
~jack screw
~two electric motors
~position switches to determine in the angle
Electric motors are most used
And in Boeing they use two switches to operate the stab to reduce the chance of runaway
Rudder ration changer
As TAS increases the rudder limit reduces
Blow back devices
A Basic of protection device is the blow back system
A pressure relief valve fitted within the actuators allow the fluid in the actuator to be return to reservoir as the control surface is pushed back by aerodynamic load.This also employed on a secondary flight controls
Fly by wire
Additional ,flight protection and speed protections are now controlled by dedicated computers.
Reduce ilot work load.
Main reasons was to save weight over convection systems
AIRBUS LAW
~NORMAL LAW»FULL SUITE PROTECION FEATURE AND NORMAL A/C OPERATING LIMITS .ANLGE OF ATTACK ,ROLL AND PITCH LIMITS ,OVER AND UNDER SPEED PROTECTION
~ALTERNATE LAW»_space;BASIC RANGE OF STABILITIES WITH THE PROTECTIONS LOST.SPEED STABILITIES ,NO AOA,PITCH OR ROLL PROTECTION
~DIRECT LAW»ANY INPUT THE SIDESTICK TRANSLATE TO DIRECT MOVEMNET ON THE CONTROL SURFACE ,NO STABILTIES OR PROTECTIONS
~MECHANICAL LAW»_space;SIDE-STICK AND FLIGHT CONTROL COMPUTER LOST,PITCH VIA THE TRIM WHEELS AND YAW FROM RUDDERS.ASYMMETRIC THRUST MAY BE USERD FOE LIMITED DIRECTIONAL CONTROL.
WHEN IN A LOWER LAW IT WILL TRY TO RETURN TO THE NORMAL LAW
