Primary Controls

Question 1

Elevator axis + movement

Answer 1

Lateral Axis
Pitch

Question 2

Aileron axis and movement

Answer 2

Longitudinal axis
Roll movement

Question 3

Rudder axis and movement

Answer 3

Yaw around normal axis

Question 4

Essentials req for flight control systems

Answer 4

Forces need to be balanced
Feel system (airspeed increasing etc)
Response
Movement and harmony with other axis controls

Question 5

Aerodynamic Balance - Inset Hinge

Answer 5

Reduce the distance of the moment arm

Only a small inset to around 25% otherwise behind CP can cause full selection with smaller inputs

Question 6

Aerodynamic Balance - Horn Balance

Answer 6

Extends forward of the hinge and causes drag

Usually found on elevators and rudders

Question 7

Aerodynamic Balance - Internal Balance

Answer 7

Flexible sealed diaphragm using static pressure to provide opposing hinge moment

Question 8

Aerodynamic Balance - Balance Tab

Answer 8

Small control surface tab on TE that deflects in opposite direction to control surface

Reduces control effectiveness

Question 9

Aerodynamic Balances - Anti Balance Tab

Answer 9

Tab deflects in same direction as control surface
Opposes the movement of control surface making the controls heavier.

Reduce possibility of over stressing aeroplane + light control feel at low speeds

Question 10

Aerodynamic Balance - Servo Tab

Answer 10

Pilot moves the control tab which moves the control surface via force generation

Very ineffective at slow speed due to low forces over AC

Question 11

Aerodynamic Balance - Spring Tab

Answer 11

Better version of servo tab
Prevent operation of servo tab at low speed and control directly.
High speeds spring compresses and pilot moves tab

Question 12

Why do we need mass balancing

Answer 12

To prevent flutter

Question 13

How do we avoid flutter

Answer 13

Adding mass ahead of hinge line to move CG forward of hinge line

Stay within flight envelope (reduce speed)

Question 14

Power assisted controls

Answer 14

Provide additional force to operate control surfaces
Still feedback from controls

Question 15

Full powered controls

Answer 15

Provide all power to remove control surfaces force
Via hydraulic forces
No direct connection between pilot and control surfaces
No aerodynamic feel don’t require aerodynamic balanced control surfaces

Question 16

Artificial feel system is…

Answer 16

Controls provide no natural sense of forces acting on plane therefore Q feel system added (generates force in proportions to dynamic pressure)

Question 17

Aileron controls - Up going wing

Answer 17

Deflected aileron downwards
AOA reduces on up going wing

Question 18

Aileron - down going wing

Answer 18

Aileron is deflected upwards
AOA increases on down going wing

Question 19

Ideal tailplane fin

Answer 19

Swept back and low aspect ratio
Larger stalling AOA

Question 20

Elevator controls pitch down

Answer 20

Elevator deflected down
Tailplane will pitch upwards
Nose pitches down

“Pitch down the elevator must go down”

Question 21

Elevator control pitch up

Answer 21

Elevator deflected upwards
Downwards reaction on tailplane
Nose pitches up

“Pitch up the elevator must go up”

Question 22

Stabilator

Answer 22

All moving tailplane no elevator
Angle of attack changes of elevator

Pitch down the stabilator moves up to create total reaction upwards
To move nose down

Pitch up the stabilator moves down to create downward reaction
To move nose up

Question 23

Comparison between elevator and stabilator

Answer 23

Elevator is a camber changing device where as stabilator is a AOA changing device

Better L/D ration on stabilator

Question 24

Trimmable horizontal stabiliser

Answer 24

Change angle of incidence via trim
Pitch control still controlled by elevators

Question 25

CG vs CP

Answer 25

CG is always in front of CP Forward limit CG and aft limit CG

Question 26

Downwash on pitch control T-tail vs normal

Answer 26

T-tail planes more effective as clear of undisturbed airflow Normal tails - change in relative airflow has to cope with turbulent air over TE

Question 27

Rudder Limiting Devices

Answer 27

Forces generated by tailplane could shear with high aerodynamic loads

Question 28

Main purpose of mass balancing

Answer 28

To stop control surface oscillating in front of the hinge line

Question 29

All Moving tailplane (stabilator) pitch up and down

Answer 29

Controls forward to pitch down the stabilator moves upwards Controls rearward to pitch upwards the stabilator stabilator moves downwards

Question 30

Displacement controls

Answer 30

Rudder and elevator

Question 31

Rate controls are

Answer 31

Ailerons

Question 32

Adverse Aileron Yaw

Answer 32

Increased lift produced on upgoing wing increases induced drag Reduce lift produced on downgoing wing reduces induced drag Therefore: Difference in drag between produces a moment that yaws the ac towards the upgoing wing Use rudder

Question 33

Differential Aileron

Answer 33

Up going aileron is deflected more than the downgoing wing to induce higher form drag on the down going wing to counter higher induced drag on the up going wing

Question 34

Fries Ailerons

Answer 34

Increase drag on the up going aileron to induce form drag when deflected downwards remains inside the wing

Question 35

Large A/C controls in roll

Answer 35

Outboard ailerons only used in low speed flight - flaps extended for TO/LD Lift spoilers used on upper surface with ailerons - up going aileron spoiler lifted to increase drag and reduce lift to create differential drag and yaw /roll

Question 36

Advantages/Disadvantages of spoilers

Answer 36

- Reduce overall lift + Do not suffer from flutter + No twisting moment on the wing

Question 37

Flaperons

Answer 37

Combines flaps and aileron in single control surface + Improved lateral control + Reduced weight

Question 38

Coupling Unit

Answer 38

Unit that assists pilot with rudder inputs when roll is commanded

Question 39

Ground Spoilers

Answer 39

Dump lift once on ground

Question 40

Speed Brakes

Answer 40

Increase amount of drag + reduce airspeed rapidly + increase angle of descent + increase rate of descent + control airspeed in descent

Question 41

Speed Brakes on CL/CD

Answer 41

On polar curve moves down and right Reduced L/D ratio CLMAX reduced Higher parasite drag Fuselage mounted speed brakes should have no effect on CL

Question 42

Combined Controls

Answer 42

Flaperons - flaps + ailerons Elevons - elevator + ailerons Ruddervator - rudder + elevator

Question 43

Airbus side stick

Answer 43

No direct connection Control inputs are request to computer Executed/modified or ignored No need for artificial feel system no trim Risk of loss of situation awareness pilots cannot see each others inputs

Question 44

Equilibrium is

Answer 44

Forces/Moments equal and opposite (steady flight) A/C can be in trim or out of trim in equilibrium

Question 45

Causes of out of trim forces

Answer 45

Change in thrust Change in speed Thrust asymmetry Propeller slipstream effects

Question 46

Loss of control authority

Answer 46

Pilot runs out of elevator travel - CG is too far forward or aft when flaring on landing Reduced control in one direction

Question 47

Countermeasures for a jammed THS

Answer 47

Reduce IAS if less control effectiveness needed Increase IAS to improve effectiveness of a jammed primary control

Question 48

Essential requirement for flight controls are

Answer 48

Force Feel Response

Question 49

CG forward + Nose Up trim =

Answer 49

Rotation will be normal using normal rotation technique Stabiliser is moved down to create downwards force on tailplane

Question 50

CG Aft + Nose Up Trim

Answer 50

Early nose wheel raising possible tail strikes

Question 51

CG Foward + Nose down trim

Answer 51

Rotation will require extra stick force

Question 52

CG Aft + Nose down trim

Answer 52

Rotation will be normal using normal rotation technique

Question 53

Aerodynamic balancing devices which improve control effectiveness

Answer 53

Horn balance Anti balance tab (Upforce together)

Question 54

Aerodynamic balancing devices which decrease control effectiveness

Answer 54

Balance tab Servo tab Spring tab (Move in opposite direction to control surface)

Question 55

Aerodynamic balances devices which are neutral to control effectiveness

Answer 55

Inset hinge Internal balance

Question 56

Factors that influence stabiliser position on take off

Answer 56

CG position Take off mass Flap setting