AGK Systems - Primary Flight Controls Flashcards
What are the four primary flight controls?
Aileron
Elevator
Rudder
Roll Spoilers
Manual controls
Surfaces are mechanically connected to the control input via rods and cables
Partially Powered controls (power assist)
Controls connected to the input via rods and cables
Hydraulic pressure actuators are used to assist the pilot in overcoming aerodynamic loads
Pilot has some ‘feel’
Fully Powered controls
Signals are generated/proccessed by Flight Control Computer which command electro-hydraulic actuators to command the flight controls
Or
Mechanical inputs are transferred to Powered Flight Control Actuator which supplies hydraulic pressure to move the control surface
What is a Reversible control system?
Direct connection through the rods and cables, mean the pilot feels the aerodynamic loads during manoeuvres
What is a Irreversible control system?
No direct connection between controls and the surface
If the surface can be wiggled and no controls move, it is deemed irreversible
What does a Rudder Ratio changed do?
Limits the power of the rudder with increasing IAS as it would become too powerful
Spring Feel
Uses springs attached to the base of the control column
As the control column is deflected, one is stretched and another is compressed
Doesn’t change when TAS or altitude increases
Q Feel - Dynamic Feel
More realistic level of changing feel
By sensing dynamic pressure - usually sensed towards the rear of the a/c - routes to a feel unit
~Pilot feels resistance levels proportional too TAS and Manoeuvres
Considered ‘force feedback’
Where are PFCU or actuators located?
Pinned against the rear spear for strength and leverage
Stab Trim compromises of…
Jack-screw which is attached to a central frame connecting the left and right horizontal stabiliser
Two electric motors - redundancy
Position switches to determine the angle (in degrees) of the THS
Rudder Ratio Changer
As TAS increases the rudder becomes too powerful
So the ratio changer reduces authority as TAS increases
Blow Back Devices
If the control surface exceeds aerodynamic load, the blow back device pushes some fluid back into the return line to relieve the stress
What is the Flight Envelope Protection system?
Allows the a/c to pitch up or down in a safe manor
Are FBW systems irreversible?
Yes
Airbus control laws
Normal law - Full protection features and normal a/c operating limits
Alternate Law - basic range of capabilities with the protection lost. Speed stabilities, no AoA, pitch or roll protection
Direct Law - Any input into the side stick translates to direct movement on the control surface, no stabilities or protections
Mechanical Law - Side stick and Flight Control Computers lost; Pitch via trim wheels and yaw from rudders. Asymmetric trust may be used for limped directional control
When in a lower law, the a/c and checklists attempt to reinstate to return to NORMAL LAW!
In order for the FBW system to operate it requires…
Airspeed
Mach Number
AoA
Bank (roll)
Boeing FBW Modes
Normal Mode - Full functionality including flight envelope protection
Secondary Mode - Loss of flight envelope protection but all other aspects intact
Direct Mode - Each ACE is directly connected to the pilots input
Final Reversionary Mode - A cable run to the stabiliser and milted spoiler authority
What are control locks?
Prevent control surfaces moving in the wind etc. As this will then move the controls in the flight deck and potential damage may be caused
Only on reversible a/c
