Flight Controls Flashcards
Primary Controls
Controls aircraft around its three axis.
Causes changes in aircraft’s flight path or attitude.
Axis and functions
Roll - Longitudinal
Pitch - Lateral
Yaw - Normal/Vertical
Mechanical Control Systems
System of cables, rods, levels and chains
Hydraulic Control Systems
Moved by hydraulic power but control valve may be operated mechanically
Electrical Control Systems
Cockpit controls send signal to control surface.
Manual Controls
Reversible, no artificial feel
Power Assisted Aontrols
Reversible, if loads are large enough, would give natural feel at high loads.
No artificial feel.
Fully Power Operated
Irreversible, no natural feel. Require artificial feel.
Manual Controls - Pitch Control
Cables can’t be pushed.
Therefore a system of 2 cables exists, one for up, one for down.
Cables must be set to the correct tension.
When are the outboard ailerons locked?
Upon flap retraction, where only the inboard ailerons are used.
Adverse Aileron Yaw
Yawing moment opposite to the rolling moment.
Preventing Adverse Aileron Yaw
Differential Ailerons
Frise Ailerons
Aileron-rudder coupling
Differential Ailerons
Spoilers are used.
Downgoing wing will have an increase in drag.
Frise Ailerons
Protruding up-going aileron on downgoing wing causes high drag. This will balance the adverse yaw out.
Aileron-rudder coupling
Aileron and rudder are connected automatically to counter adverse yaw
Effect of Temperature on Tension of Control Cables
Temperature increases, tension increases.
This is because the aircraft fuselage extends, therefore cables tense up more.
Hinge Moments
Force x Distance.
Distance is from control surface centre of pressure.
Duplicate Inspections
Any work performed on the flight controls must be inspected by an independent individual who is properly qualified.
Set Back Hinge Line
Reduce Hinge Moment
Reduces effort you need.
Doesn’t reduce effectiveness.
Horn Balance
No control loss effectiveness, overall moment reduces.
Balance Tab
1) Control moves surface which drives a balance tab
2) Balance tab moves in opposite direction to control surface
3) Applied to TRAILING EDGE of surface
Some reduction in control effectiveness
Servo Tab
Moving tab
Tab moves opposite direction to control surface
Ineffective at low speeds
Spring Tab
Maximum assistance when stick forces are greatest (high speeds)
Reduce control loads at high airspeed
Anti-balance Tab
Opposes control surface, tab will move in same direction.
Increase Control Effectiveness.
Disconnect levers
Reduces rate of control output
Protection against jamming of controls
Shear rivets can be used to allow remaining ailerons to be used following a seizure.
Hydraulic Q feel
Takes pitot and static pressure, and the output of this is used to operate a Q feel actuator. The actuator then applies a force to the controls that is proportional to the dynamic forces.
Trimmable hydraulic stabiliser (THS).
Less trim drag
What does the RAT power
Flight controls
Where are flight controls attached to?
The rear spar
How can we reduce adverse aileron yaw?
Frise ailerons, differential ailerons, rudder-aileron coupling
Fly By Wire System
Reduces weight, easier maintenance, prevents from exceeding flight envelope. Multiple layers of redundancy, and reversion to normal, alternate, direct modes.
Flap Operation on Large Aircraft
Hydraulically Powered, electrical backup
Auto slats
Extend when a certain AoA is exceeded
