B1-11a Flight Controls

Knowledge Levels

• Basic knowledge levels for aircraft maintenance licences are indicated by levels 1, 2, or 3 depending on the subject.
• Category C applicants must meet either B1 or B2 basic knowledge levels.

Level 1 Objectives

• Familiarity with the basic elements of the subject
• Able to give a simple description using common words and examples
• Able to use typical terms

Level 2 Objectives

• General knowledge of theoretical and practical aspects
• Able to apply that knowledge
• Able to understand the theoretical fundamentals
• Able to give general subject descriptions with examples
• Able to understand sketches, drawings, and schematics
• Able to apply mathematical formulae with physical laws
• Able to apply knowledge practically using detailed procedures

Level 3 Objectives

• Detailed knowledge of the theoretical and practical aspects
• Able to combine and apply separate elements logically and comprehensively
• Able to know the theory of the subject and interrelationships with other subjects.
• Able to provide detailed subject descriptions using theoretical fundamentals and specific examples.
• Able to understand and use mathematical formulae related to the subject.
• Able to read, understand, and prepare sketches, drawings, and schematics
• Able to practically apply knowledge using manufacturer's instructions
• Able to interpret results from various sources/measurements and apply corrective action.

Aeroplane Axes and Primary Flight Controls

• An aircraft rotates around three axes passing through the center of gravity (CG).
• CG is the theoretical point where the entire weight of the aircraft is concentrated.

Longitudinal Axis

• Straight line from nose to tail known as the roll axis.
• Ailerons and roll spoilers control roll, also called lateral control.

Lateral Axis

• Straight line through CG at right angles to longitudinal and vertical axes.
• Rotary motion is called pitching.
• Elevators control pitch, also called longitudinal control.

Vertical Axis

• Straight line through CG at right angles to longitudinal and lateral axes.
• Rotary motion is called yaw.
• Directional control comes from the rudder.

Flight Control Systems

• Primary flight control surfaces are the main control surfaces.
• Secondary flight control surfaces are auxiliary.

Flight controls

• Flight controls modify the camber or aerodynamic shape of the surface.
• Changes in camber create changes in lift and drag, which result in rotation about an axis.

Primary Flight Controls

• Aeroplanes control by rotating about three axes.
• Ailerons control roll through longitudinal axes.
• Elevators control pitch through lateral axes.
• Rudders control yaw through the vertical axes.

Roll Control

• Ailerons and flaps are on wing's trailing edges.
• Ailerons are outboard of the midpoint of each wing.
• Ailerons move in opposite directions.
• Control wheel movement moves ailerons in the cockpit.
• Flaps use a switch or handle.

Aileron Drag

• Aileron displacement causes aileron drag.
• Downward moving ailerons have a big impact on drag.
• Wingtip drag pulls the nose opposite the turn, also known as adverse yaw.
• Aileron drag is a problem because wings producing lift also produce a horizontal component, displacing the nose
• Aileron movement creates drag and pulls the nose to the left.

Differential Ailerons

• Adverse yaw is minimized using differential ailerons.
• Upward moving ailerons travel greater distances than downward moving ones.
• Extra upward travel creates parasite drag, counteracting induced drag from lowered aileron.

Frise Ailerons

• Adverse yaw is minimized using Frise ailerons.
• Extending up-aileron's leading edge below the wing creates additional parasite drag, counteracting increased induced drag.

Roll Spoilers

• Hinged surfaces ahead of flaps on wing's upper surface to assist roll control.
• Roll spoilers lie flush with the wing surface.
• Roll spoilers connect to aileron controls; spoiler raises when aileron moves up past a certain angle.
• Up-moving aileron's wing's roll spoilers automatically deploy, decreasing lift.
• Additionally, extra parasite drag overcomes adverse yaw.
• Spoilers can account for up to 80% roll rate
• Transport-category aircraft use spoilers as a secondary flight control system or to increase/decrease lift.

Pitch Control

• Elevators are movable horizontal control surfaces on the tail, rotating about its lateral axis.
• When the control wheel is pulled back, elevators move upwards, deflecting the airstream upwards and rotating the nose upwards.
• When the control wheel is pushed forward, elevators move downwards, pushing the tail up and lowering the nose.
• Elevator movement is intuitive

Stabilator

• The stabilator, or all-moveable tail, has no fixed stabiliser but has an anti-balance tab on its trailing edge.
• The anti-balance tab decreases sensitivity and moves in the same direction as the surface.
• Leading edge movement downward increases force of the tail, rotating the nose up.
• Leading edge movement upward decreases tail load, rotating the aeroplane down.

Variable Incidence Stabiliser Pitch Trimming

• Stabiliser is adjustable to maintain a balance of forces, preventing undesired rotation along the pitch axis.
• A downward force is caused by gravity.
• An equal upward force comes from lift.
• The CG position is not fixed and depends on: Amount of fuel, number of passengers, amount/distribution of cargo
• Lift is applied to the wing's pressure point.
• The pressure point is not a fixed point - depending on airspeed, it moves backward when airspeed increases.
• Combination causes aircraft's nose movement: upwards or downwards rotation along the pitch axis
• Stabilizer creates opposite force via screw spindles driven hydraulically, electrically, or both to adjust in relation to airflow.
• Pitch trim wheel or trim switches in the cockpit operate the trim actuator.
• Variable incidence horizontal stabilisers are used in high-speed aeroplanes.

Drag Reduction

• Forces of elevator/adjustable stabiliser reduce drag.
• Trimmable stabiliser reduces amount of parasite drag generated

T-Tail Configuration

• Horizontal tail surfaces are mounted on top of vertical surfaces and used with fuselage/tail-mounted engines.
• Positions horizontal tail surface at the verical structure.

Canards

• Any aircraft with two lifting surfaces can be classified as a canard
• Canard is the forward surface
• The aircraft regains full lift, the nose returns while aileron controls remain available.
• Canards virtually eliminate the chance of an inadvertent stall/spin accident.

Yaw Control

• The rudder is on back of a vertical stabiliser moving the nose of the aircraft left and right when used with ailerons.
• Applying pressure deflects the rudder into the airstream.
• Aeroplane rotates about its vertical axis, called yawing
• Only used at the beginning of the turn, for crosswind conditions, and one-engine operations.
• Left rudder pressure moves the rudder left, generating a force towards the right of the fin.
• Connected rudder to aileron controls make the rudder move in the correct direction
• Movement of nose or tail wheel is incorporated in the rudder for operator to steer during taxi on ground

Rudder Limiters

• Controlled by the pedals.
• Limits rudder deflection, as a function of speed
• Limitations applied, keeps loads below maximum allowance, to enable trimming throughout flight’s envelope.
• Achieved by two units installed at the Pedal travel and rudder travel limitation units.
• As airspeed increases, airspeed data feed it to digital controllers energizing electric motors.
• Motors rotate jack screws, the nuts move with them & position movable stops limiting the inputs.
• Feedback transmitted to controllers and duplicated for redundancy.

Elevons

• Aircraft like the Concorde use Elevons as control surfaces, which combine both ailerons and elevators in the absence of a tail.
• Elevons act as elevators by backward & forward movement of control columns.
• Elevons act as ailerons by rotating the control wheel.

Ruddervators

• Aircraft with tail empennages use Ruddervators that angle upwards and outwards from the aft fuselage in a V configuration.
• Two surfaces act as horizontal and vertical stabilisers
• Movement inputs two surfaces in the same direction for pitch control, but in opposite directions for yaw control.

High-Lift Devices

• Flaps and slats help modify aerodynamics to increase stability, maneuverability, higher cruising speeds, and lower landing speeds
• Primary controls enable rotation about axes, while secondary modify effects of primary
• Secondary flight controls are extended when needed.
• Modifying aerofoil section changes the lift by using flaps & slots to increase camber & change trim
• This creates four basic types of secondary flight controls

High-Lift Device Objectives

• Modify amount of lift of a surface, especially high-lift devices, on trailing edges & leading edges
• Change amount of force needed to operate primary controls
• Control the aircraft's balance
• Induce drag

Trailing Edge Flaps

• Change the cambers for lift and drag for different attacks.
• Allow landing at slower speeds
• Selected at differing configurations
• Airflow is lost with the flap so lead edge slots and slats are often used

Types of Trailing Edge Flaps

• Plain Flaps
  • Sections of the wing's trailing edge.
  • Deflected so that it increases angle of attack and wing chamber, and total drag, only used on low-speed aircraft
• Split Flaps
  • Portion of the lower surface
  • Produces much more drag at low lift coefficients.
• Slotted Flaps
  • Increases lift coefficient more than the simple type
  • Utilises a duct to help air flow back over the top of the flap at high-pressure
• Fowler Flaps
  • Constructed lower part of wing's trailing edge that rolls back on a track
  • Initially improves wing area
  • wing angle of attack, camber & drag are increased as it continues.
• Slotted Fowler Flaps
  • Fowler with single, double and triple slots
  • Used for reasonable takeoff
  • Negates disadvantages of Fowler by incorporating slots
• Flaperons
  • Combines aspects of ailerons & flaps
  • Differential movement, while collective movement produces the same effect as flaps.

Leading Edge High-Lift Devices

• Some high performance aircraft use edge flaps to increase a camber.
• They extend forward and downward.
• High-lift reduces peak of pressure at the higher angles of attack.

Krueger Flaps

• Used to increase a wing camber and lift - especially needed at slow speeds by turbine aircraft's swept wings.
• They are hinged to leading edge, which extends down to alter wing profile.
• Controlled by trailing edge's movement.

Drooped Leading Edge Flaps

• Uses jack-screw arrangement and droops the edge with a hinge
• This leads to increases of camber

Slots

• Designed to improve airflow when attacking at slow speeds.
• Located on the leading edge, built to increase a stall angle through deflection.
• Increase in drag due to turbulence

Slats

• Used to boost low pressures over wings at attack angles
• Increases drag, moving the slate until it gives less drag.
• Made through actuators.

Effect of Flaps and Slats on Stall Angle

• Decreases stall-angle to decrease stall-speed
• Increased camber at flap moves separation point forward.
• Deploying slats restores and exceeds the no-flap position due to slots
• Angle of attack decreases with the leading edge
• Increases the coefficient which leads to a Transport Category craft

Effect of Flap Deployment on Pitch

• Bulk of lift moves to trailing edge of wing location of the flap
• Leads to nose-down movement

Drag-Inducing Devices

• Disturbs pattern of smooth airflow and produces increment of drag

Two devices used are Drag-Inducing

• Wing-installed to increase drag and reduce lift
• Fuselage increases drag

Drag used in the following maneuvers

• Approach & Rapid Descent- Commanded by speed brakes to decrease glide ration
• Landing - Arming Ground - automatic with landing gear legs compression.

Spoilers

• Spoilers control device to kill portions of wing and lift
• Allows for rapid rates of descent while maintaining overall-control
• Become ground spoilers when raised on the ground to increase tire contact with the ground

Effect on spoiler

• Turbulent airflow will result, reducing the lift while increasing drag
• Must keep spoiler retracted if flaps are in very slow mode

Speed Brakes

• Installed to reduce airspeed while allowing steep descents
• Speed brakes are known as spoilers
• Lift Reduction -
• Ground Spoilers
• Used on weight to slow aircraft and reduce landing when weight is on the landing gear

Boundary Layer Control

• The region of air that flows immediately adjacent to the surface of the airfoil.
• Designed to delay airfoil.
• Separation of boundary causes winng stalls.

Not only attack cause boundary layers, but so do shock waves, separation boundary also increases drag

• Wing Fences
• Dog Tooth leading Edges
• Vortex Generators
• Stall Wedges

Wing fences

• Boundary layers are a fixed vane extend across the wing of a swept wing aircraft
• Air will now flow to prevent it for moving to the wingtip to reduce separation or stall.

Saw, cut, Dog -Tooh and Leading Edges.

• On swept will it can occur towards tips to pitching
• Effect reduced is reduces by a cut or tooth each generates s strong vortex to control that boundary layer

Vortex Generators

• To prevent or delay separation of airflows from airfoils
• Reinvigorate it and towards surface they are installed where separation occurs
• The tip vortexes pulled down there helps prevent separation.

Stall Strips

• Strips provide air disturbances to push of aeroplane and provide pilot with stall predetermination
• Used on both small and larger that will have horizontal stabilizer, produces a small vortex toward stabilizer

Flight Control Tabs

• Allows aircraft to move high speeds when needing to maintain control
• Types
  • Trim Tab - small movable surface and separate control with the cockpit
  • Balance - a balance tab and linkage allow for the position of the tab to be changed

Control Surface Bias Ground-Adjustable Tab (Fixed Tab)

• Fixed to the surface for certain conditions
• Surface is bias the opposite the tab is deflected too

Control Surface type balance

• Helps to move the control surface depending on the pressure in surface

Two Type of Control Surfaces Balancing:

• Mass balance- Prevents 'flutter' of controls during flight
• Aerodynamic balance- Assists pilot to move controls

Control Surface Mass Balance:

• Flutter occurs at high speeds and causes vibrations in frame
• Flutter is the oscillation of control as structure gets bend
• If CG IS behind hinge, inertia will cause it to isolate in its hinge with structure Distorts
• Flutter is eliminated by static balance and weights.

Aerodynamic Balance

• Control that is on the surface due for speed and are of control surface
• It is there are for often aero dymanically balanced to help pilot

Horn Balance

• Elevator is where the balance is achieved where the horn extends away from the surface
• And use as the airflow to aid with surface

Supplemental media

• How Flex and spoilers work during landing?

High–Speed Flight Learning Objectives

• Describe Local speed and effect Local sound
• Describes the transition of all flights
• Mach Number and effect on flight
• Compressibility in Mach Number and compression.

SubSonic Transonic and Supersonic Flight

• At low speeds small speeds air negligible but approaches sound with its mark to effect streamline patterns
• It causes a problem in transonic ranges
• Flow of wing can be predictable but behaviors require the design to compensate
• At low speeds, that change in pressure density
• Is incompressible to study

Standard Atmosphere

• At standard speeds = travel and high speeds as air enters or compressed
• Changes and high energy requires more changes in density requires that high speeds all these changes should be accounted

Doppler Effect

• Standing at object, disturbances occurs and travels at low speed
• Hear higher quickly but then at lowers speed
• Pressure waves changes

Mach Number

• Travel speeds a local speed

Pitch trimming

• The purpose to adjust balance
• Aircraft forces includes by the pull of the ground force which equals if during lift

Vertical Axis

• The force for CG will be affected by
• Amount of fuel
• Number of Passengers
• Amount and Distribution of cargo
• Lift point is affected to as that is dependent on air speed

Drag Reduction

• Stabilized Air on elevators will reduce to drag but the stabilize correct to instead reduce drag

High Lift (11.9)

• Primary effects including all device such as
• Elevator, Ailerons,

Flight Controls Systems and Device

• Devices do know more than modify cambers or aerodynamic of the surface of which it has been attached
• Primary flight
• Secondary flight
• Hight control warning system

Active Load Control

• Flight causes many movement to increase in wing bending that decrease aircraft life time that will Alleviate Load
• One active method used by aircraft for movements to system that will be done from Turbulence in System