Primary Flight Controls

Question 1

Examples of secondary controls

Answer 1

Leading edge flaps and slats

Trailing edge flaps

Spoilers used as speed brakes

Question 2

Different flight control systems

Answer 2

Mechanically - cables and rods, levers and chains

Hydraulically - moved y hydraulic power but control valve may still be moved mechanically

Electrically - cockpit controls sends signal to control surface - electrical signal is amplified - computer decides what you get - hydraulically control jack moves control surface

Question 3

Different ways of operating flying controls and artificial feel req

Answer 3

Manual controls - reversible - natural feel - no artificial

Power assisted - hydraulic assists the input - reversible - if loads are large enough - will give feel - no artificial

Fully power operated - irreversible- no natural feel so req artificial

Question 4

A reversible system - controls

Answer 4

Transmits forces and movements of control surfaces to pilot controls

Question 5

An irreversible system - controls

Answer 5

Transmits no aerodynamic forces in the control surface to pilot controls

Question 6

Manual control system

Answer 6

Cheap, simple and reliable

Stainless steel cables run from each control via a pulley wheels - control movement through a bell crank at control surface

Allows aerodynamic feel at the control column - provides natural protection against over stressing

Question 7

Fairleads

Answer 7

Keep the cables from rubbing on the airframe - direct the cables

Question 8

Methods to reduce adverse aileron yaw

Answer 8

Differential ailerons

Frise ailerons

Aileron - rudder coupling

Use of roll ailerons - down going wing = more drag

Question 9

Backlash

Answer 9

Free or ineffective movement of the cockpit control when the direction is reversed

May indicate worn or broken controls

Question 10

Purpose of primary stops

Answer 10

Near the control/on the control surfaces - adjustable - controls the range of movement

Bellcrank/quadrant gets stuck on these - can’t move any further

Question 11

Purpose of secondary stops

Answer 11

Near the control column - limits the range of movement for the column

Will have a gap for thermal expansion

Question 12

Temperature compensation - controls

Answer 12

Increase in ambient temp will make the aluminium frame expand - pulls the cables - increases tension - makes the controls stiffer

Automatic temp compensator - fitted to maintain correct tension for temp changes

Question 13

Duplicate inspection of flying controls

Answer 13

Anything to do with flying controls needs to be inspected twice by someone who isn’t to do with the job and certified for that a/c

Question 14

Turnbuckle

Answer 14

Locks the tension in the cable

Question 15

Hinge moment

Answer 15

Aerodynamic force x distance from the hinge to the control surface centre of pressure

Cockpit control load will be effected by this

Question 16

Aerodynamic balances designed to reduce the hinge moment

Answer 16

Set back hinge

Horn balance

Internal balance

Question 17

Set back hinge

Answer 17

Reduces the moment by reducing the distance between the hinge and the centre of pressure - force still remained the same

Does not reduce the effectiveness of the controls

Question 18

Internal balance

Answer 18

Works on the same principle as the set back hinge but the balancing area is inside the wing

Question 19

Balance tab

Answer 19

Makes it easier to control the control surface

Stick moves the control surface - balance tab moves in opposition - creates a force opposing the control surface force

Reduces the control effectiveness

Question 20

Servo tab

Answer 20

Pilot controls the tab - no direct movement of the control surface

When stick moves the tab - force directs the control surface - makes it easier to control the control surfaces

Useless at low speeds, more drag, possible to think that you have control of the a/c with control locks still in

Question 21

Spring tab

Answer 21

Modification of the servo tab - proportional to the applied stick forces

Max assistance is therefore obtained when the stick forces are greatest

Reduces control loads at high airspeeds

Question 22

Anti balance tab

Answer 22

Tab moves in the same direction as the control surface

Increases control effectiveness

Will increase the hinge moment - give heavier stick forces