11.9 Flight Controls Flashcards
What are the 3 primary flight controls
- aileron
- elevator
- rudder
What controls the ailerons and the elevators?
Control stick/ yoke/ wheel/ joystick
What controls the rudder?
Foot pedals/ rudder pedals
When are the inboard and outboard ailerons used?
Low speed flight
What ailerons do you use in high speed flight?
Inboard only
How do you solve the problem of negative turning moment?
Differential aileron deflection
What do elevators do?
Longitudinal control for pitch, climb and dive
Controlled around the lateral axis
What does pushing the yoke forwards do?
Lowers the nose, elevators down
What are the trim systems used for?
Added to flight control members to assist crew in controlling the aircraft and compensates for imbalances
What are the 4 trim controls?
Balance tab
Trim tab
Servo tab
Spring tab
What do trim tabs do?
Small aerobics in trailing edge of primary control surfaces
Enables pilot to trim out any unbalances without exerting pressure in primary flight controls
What is the purpose of servo tabs?
Aid in moving control surface and holding it in a desired position
What do the balance tab do?
Moves in opposite direction of primary flight controls
(Forces acting on tab assist in moving primary flight controls)
What purpose do spring tabs have?
Same purpose as hydraulic acustors
Aid the pilot in moving the primary flight control surfaces
Why do we have wing control surfaces
Improves the performance of aircraft as controls aeroelastic loads
What are the two types of active aeroelastic control techniques?
. Manoeuvre load control
. Gust load
What does the rudder do?
Directional control around the vertical axis
Nose left or right / yaw
If the left rudder pedal is pressed what way does the rudder deflect?
If left is pushed then rudder deflects left
What do spoilers do?
Assist in controlling the bank of the aircraft
When would a spoiler rise up?
On the side of the aircraft that the aileron has rises up on
What do plain flaps cause in terms of its shape?
Increases wing camber and provides greater lift
Forms trailing edge when retracted
How do slots in a wing benefit the flight?
The spanwise air allows air flow from below wing to upper surface
Hugh speed air flow mixed with boundary layer which delays boundary layer separation on the upper surface of the wing.
When do you use speed brakes and why?
It’s a secondary control surface which increases drag and reduces speed on the aircraft when flying.
Applied automatically when ground spoilers are deployed on ground.
What are control cables normally made from?
7x7 or 7x14
Flexible steel wires
How do you measure the tension places on a cable?
By using a tensiometer
Why do we use tension regulators?
Allows the cable under all conditions of temperature change and deflections to be taken in and out of each side. Remains a uniform tension
What are some disadvantages of push -pull rods?
. High weight
. Less ability to be routed without complications
When are screw jacks used?
Threaded units that convert rotary movement into linear travel
What is the main disadvantage of a screw jack?
Strong aerodynamic loads can drive the screw back backwards
What 2 operational modes does a servo control unit have?
. Damping mode
. Control/ active mode
What is damping mode?
Used as a gust damper for flight control surfaces when the aircraft is on the ground
Is PFCU reversible or non reversible?
Non reversible
What do we use pneumatic systems for?
Used as back up to essential operation services
(Landing gear, brake, nose steering - emergency’s)
Why do we prefer hydraulics over pneumatics?
As air is compressible in hydraulics
What is an advatanges of an electro hydraulic actuator?
.self contained
.saves weight
What does the fly by wire do?
Replaces manual flight control with electronic interface
What is the main advantage of fly by wire
Weight savings
How does the fly by wire operation work?
. Pilots demand sent into electrical signal in cockpit
. Sent to independent computers
. Sent to computer sample data
.processed and sent to actuator
How many gyroscopes are fitted to an aircraft?
3
One for each axis = pitch, roll and yaw
What laws can change the way in which the primary flight computers perform?
. Normal law
.direct law
What is the purpose of a yaw damper?
Damps the yawing and rolling oscillation (Dutch roll mode)
(Provides inputs to the rudders)
What is the purpose of the Mach trim system?
Trims the nose of the aircraft up as Mach tuck begins
What is Mach tuck?
Nose down as critical Mach number is reached
What do rudder limiters do?
At high speed it may exceed structural limitation on the aircraft
Therefore, rudder limiters limit the amount of rudder deflection at high speeds
What are the two ways of static balancing?
. Under balance
. Overbalance
Why do we use rigging pins?
Inserted into a control system to mobilise/ lock out a system in order to adjust the system
What is the minimum amount of hydraulic systems allowed on an aircraft?
2
When is direct law used?
. When there is a failure of three inertial reference units
. Fault in two elevators
. Flame out in two engines
What is the purpose on an electric actuator?
Controls the position of the aircraft trim systems
