AGK Systems - Primary Flight Controls

Question 1

What are the four primary flight controls?

Answer 1

Aileron

Elevator

Rudder

Roll Spoilers

Question 2

Manual controls

Answer 2

Surfaces are mechanically connected to the control input via rods and cables

Question 3

Partially Powered controls (power assist)

Answer 3

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’

Question 4

Fully Powered controls

Answer 4

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

Question 5

What is a Reversible control system?

Answer 5

Direct connection through the rods and cables, mean the pilot feels the aerodynamic loads during manoeuvres

Question 6

What is a Irreversible control system?

Answer 6

No direct connection between controls and the surface

If the surface can be wiggled and no controls move, it is deemed irreversible

Question 7

What does a Rudder Ratio changed do?

Answer 7

Limits the power of the rudder with increasing IAS as it would become too powerful

Question 8

Spring Feel

Answer 8

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

Question 9

Q Feel - Dynamic Feel

Answer 9

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’

Question 10

Where are PFCU or actuators located?

Answer 10

Pinned against the rear spear for strength and leverage

Question 11

Stab Trim compromises of…

Answer 11

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

Question 12

Rudder Ratio Changer

Answer 12

As TAS increases the rudder becomes too powerful

So the ratio changer reduces authority as TAS increases

Question 13

Blow Back Devices

Answer 13

If the control surface exceeds aerodynamic load, the blow back device pushes some fluid back into the return line to relieve the stress

Question 14

What is the Flight Envelope Protection system?

Answer 14

Allows the a/c to pitch up or down in a safe manor

Question 15

Are FBW systems irreversible?

Answer 15

Yes

Question 16

Airbus control laws

Answer 16

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!

Question 17

In order for the FBW system to operate it requires…

Answer 17

Airspeed

Mach Number

AoA

Bank (roll)

Question 18

Boeing FBW Modes

Answer 18

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

Question 19

What are control locks?

Answer 19

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