Module 11.9 Flight controls Flashcards
Secondary control surfaces are used for what?
Changer lift and drag characteristics
What is THS a type of?
Long term pitch control device
Spring tabs serve as what after a certain speed?
Servo tabs
How are the primary control surfaces moved?
Hydraulic actuators
Lateral and directional trim is controlled through what?
FCU
When may directional trim be used?
In the event of single engine failure the directional trim will yaw the aircraft to maintain heading
Pitch attitude is controlled by what type of trimming?
Longitudinal
What shows the correct stabiliser position for take off?
A green band on the indicator
What are the two fly-by-wire functions added to modern aircraft?
- Manoeuvre Load Control (MLC)
- Gust Load Alleviation (GLA)
What does the MLC do?
Uses ailerons to move the centre of lift inboard to the root. This is to reduce wing structural loading, wing tip bending moment
What does the MLC help to alleviate?
Reduces load at the outboard section of the wing
How does a GLA help to alleviate loads?
Gust computer measures acceleration of aircraft and compares this to the pilots inputs. Feedback loops add correction signal to counteract the acceleration caused by the gust
What control surface are used in the MLC and GLA?
Ailerons
What detects active load alleviation?
Wing tip accelerometers
What 3 types of uses do spoilers have?
- Ground spoilers
- Flight/roll spoilers
- Speed brakes
Automatic deployment of spoilers occurs when what conditions are met?
- Lever armed
- Weight on wheels
- Airspeed
- Throttle idle
Manually operated systems to control primary control surfaces are used when?
Older aircraft and small aircraft
What is the purpose of a fairlead?
Prevent damage to structure, limit vibration and give the gable guidance
Fairleads must never be used as what?
Pulleys to change the direction
How is cable tension checked?
Tensiometer
Why is a cable tension regulator necessary?
Varying operating temps lead to expansion and contraction
When do push pull rods have strength?
Pull, tension
What do witness holes verify in push pull rods?
Thread engagement
What is the purpose of a bell crank?
Change direction, transmit a force and can give mechanical advantage
When are torque tubes used?
Linear to rotational
What are torque tubes often used to actuate?
- Ailerons
- Flaps
- Slats
When might a screw jack be used?
Extreme aero loads
- THS
- Leading edge flaps
- Trailing edge flaps
What would the nut on a screw jack be attached to in the empanage?
Attached to the THS
Hydraulic systems are classed as what, due to the system providing feedback?
Reversible
What do cable tension regulators help to maintain?
Uniform
What are the two primary redundancy means for hydraulics systems?
- Multiple system
- Multiple pressure sources
What is power control unit?
A unit that assists the pilot with moving control services. Servo servo with actuator
What does the piston create?
- Two chambers by which the piston is actuated. Depending on which chamber is pressurised moves the rod back and forth
What are the names for the two chambers?
- Extension chamber
- Retraction chamber
How does the pilots input affect the PCU?
The pilots input moves a servo valve which directs hydraulic fluid into either the extension or retraction chamber
Where would a PCU be found?
Near the control surface
The servo control unit is divided what two sections?
- Power section
- Distribution
After total electric failure in an electrically controlled hydraulically actuated system, what surfaces are available to control?
- THS
- Rudder
What are the main components of a power section?
- Cylinder
- Piston
- Piston rod
What are the main components of the distribution?
- Bypass valve
- Control valve
What are the two servo control units modes?
- Control/active mode
- Damping mode
In the damping mode what state is the servo unit mode in?
De-pressurised
What occurs when the pistons are moved by external forces?
Hydraulic fluids move from one chamber to the next via the bypass valve
In damping mode the chambers are interconnected by what valve?
Bypass valve
In the damping mode what occurs when a gust moves the control surface?
The damping mode allows the surface to be moved, meaning it will not be broken as easy.
The damping also slows the movement under wind
How is the actuator slowed after a gust in the damping mode?
Restrictor lines
What is responsible for the initial deflection in a power assisted system?
The pilot is responsible for the initial deflection
Is the fully powered system reversible?
No, it is irreversible
In a fully powered system are the pilot controls and the control surface connected mechanically?
No, they are not
What flight control system requires additional feel?
Fully-powered
What are the two types of artificial feel?
- Fixed
- Variable, Q pot system
What is the disadvantage of fixed feel system at a high speed?
The aircraft gets over controlled
Where would the artificial feel unit be found?
In between pilot control and PCU
How is the feel changed with airspeed on Q pot feel system?
The increased airspeed increases the pitot pressure which compresses the diaphragm more
Artificial feel system wants to return controls to what position?
Neutral
How is the servo valve controlled in a electronically controlled PCU?
The servo valve is controlled by two solenoids which move the valve back and forth.
Electrical signals
What position is the mode valve spring loaded to?
Neutral
What side is the movement of the mode valve influenced from?
Left side
The servo valve can be positioned to what 3 modes?
- Normal
- Bypass
- Damping/blocked
How is the ElectroHydraulic Servo Valve (EHSV) positioned?
The servo valve is controlled by two solenoids which move the valve back and forth.
What does the EHSV do?
Takes pilot inputs and translates them into servo valve movement to control the control surface
What positions does the EHSV allow the servo valve to be in?
- Active
- Damping
- Bypass
Also anything in between
When does the bypass mode occur?
Single hydraulic or electrical failure on the PCU
What is the Linear Variable Differential Transformer (LVDT) signal proportional to?
Surface deflection
What can the LVDT be used for?
- Surface deflection monitoring
- Flight crew feedback
What is the major advantage of Fly-By-Wire (FBW)?
Weight saving
How is stability maintained in FBW?
3 gyroscopes, one for each movement: Yaw, Pitch, Roll. Movement results in signal generation to move the relevant actuators
What is flight control law in FBW?
Algorithm that translates pilot input into actuator movement
What are the flight control laws of FBW?
- Normal
- Alternate
- Direct
When would a law be downgraded?
Failure of a system, i.e. an actuator
What is another name for yaw damper?
Dutch roll damper
What happens when dutch roll is detected?
The device increases directional stability by moving the rudder
What is the yaw damper?
A device that communicates with the rudder PCU and actuates it
How many yaw dampers would be needed in a split rudder?
2 would be needed, upper and lower
What happens when mach tuck is detected?
The computer will either move the elevators or THS up. This action is called mach trim
What is and when would mach tuck occur?
It is a nose down movement
It occurs in the transonic region
What is the purpose of the rudder limiter?
It limits the deflection of the rudder at higher speeds to prevent structural damage
When may gust locks be used?
In aircraft with mechanically driven systems when they are parked
Where may gust Locks be found?
- Interior, i.e. locking flight control stick
- Exterior, locking control surface to structure that does not pivot, i.e. wing and aileron.
How may gusts locks be identified?
By remove before flight tags
What is static balance?
Tendency of an object to remain stationary when supported by its CofG
If a control surface is statically balanced then what position will the control surface be in?
Neutral
What is dynamic balancing?
In a rotating body, all rotating forces are balanced so no vibration
What are the 3 types of rebalancing a control surface?
- Calculation method
- Scale method
- Balance beam method
What is the benefit of the calculation method?
The control surface does not require removal
What is the scale method?
Use of a scale
\what does rigging involve?
Adjusting of flight control surfaces so that it is aligned with the flight control stick
What are the 3 steps of checking range of movement?
- Lock flight deck control
- Adjust tension
- Adjust control stops
How is the aircrafts Angle of Attack (AoA) determined?
AoA vanes
What does the vane inform the crew of?
difference between max AoA and current AoA
When will a stall occur?
When the AoA exceeds the aircraft critical AoA
Would the flight crew be able exceed the critical AoA?
No, there a systems preventing this
What will give the flight crew warning on the yoke of an impending stall?
Stick shaker
Can the flight crew overcome the input of the stick nudger/pusher?
Yes they can
