11.1.1 - Aerodynamics and Flight Controls Flashcards
Name thr Primary Flight Controls
Ailerons
Rudder
Elevator
Which control surface is used to control an aircraft longitudinally about the lateral axis?
Elevator
What is the purpose of a variable incidence stabiliser?
Angle of Incidence is the angle between chord line of wing and longitudinal axis of aircraft.
variable incidence stabiliser means that the full stabiliser can be moved to change the angle of incidence.
It is usually for the horizontal stabiliser and the elevator is still part of it.
Used for trimming purposes
What is a canard?
Any aircraft that has the equivalent of two lifting surfaces, instead of the conventional horizontal stabiliser that provides a down load, can be classified as a canard.
The canard is the forward surface, and frequently is also a control surface.
Where does an aircraft get it directional control from?
Directional control is achieved by the rudder.
Directional control about the vertical axis
What is a Ruddervator?
V-Tailfin
The two fixed surfaces act as both horizontal and vertical stabilisers, while also the movable surfaces are connected through a mixing-type linkage that allows in and out movement of the control wheel to move both surfaces together
The rudder pedals move the surfaces differentially.
What are the 2 ways of controlling spoilers?
- Arm the spoilers with the lever (cockpit)
- When flaps retracted, the side stick will move them to roll the aircraft instead of the ailerons
What is the purpose of a slot?
To improve the airflow conditions at high angles of attack and slow speeds
A slot is fixed
What effect does extending the slats/flaps have on angle of attack?
Changes the chord line decreasing angle of attack
(approx normal 16/17 degree to 25 degree)
Briefly explain ‘‘Adverse Yaw’’
The movement of the nose in the wrong direction at the beginning of a turn is called adverse yaw
Adverse yaw is the natural and undesirable tendency for an aircraft to yaw in the opposite direction of a roll. It is caused by the difference in lift and drag of each wing
Describe breifly the purpose of a stall strip (stall wedge) and its operation
It is extremely important that an aircraft wing stall progressively from the root out to the tip, so the ailerons will be effective throughout the stall.
If a wing does not naturually have this stall progression characteristic (washout), it is possible to place stall wedges on the leading edge of the wing in the root area.
Explain the operation of a Servo Tab
- How operated
- Movement relative to control surface
- Purpose
A Servo tab is integrated into the flight control
It moves in the Opposite direction to the control surface
Assists or provides the force for moving a primary flight control. Aerodynamically positions control surfaces that require too much force to move manually.
What are anti-servo tabs (anti-balance tabs)?
Moves in the same direction as the control surface
Increases force needed by pilot to change flight control position. De-sensitizes flight controls.
What is the purpose of a spoiler mixer?
Takes 2 inputs
- aileron
- (spoiler) lever position in cockpit
determines what overall spoiler position should be
Explain how a vortex generator operates?
Small Venturi like system on top of wing at transition phase.
Vortex generator re-energises airflow to keep laminar flow for longer
What is the purpose of a trim tab?
(how Controlled?
What direction relative to control surface?
also purpose)
It is independently controlled linkage system set from the cockpit
Moves in the opposite direction as the control surface deflection
Reduces the force needed to move a primary control surface (Allows for ‘‘hands off’’ flight)
What will happen to control surface whose CG is behind the hinge line during flight?
Control surface will move ‘arse-down’
Will pivot it down where the CG is (will create a tendency about the hinge line)
The aileron that moves upwards travels a _____ distance than the aileron that moves downward.
Greater
Large transport aircraft have two ailerons on each wing. For high-speed flight the _____ aileron is locked in place and does not move
outer
When the ailerons of a large transport airplane are deflected, the flight spoilers on the wing with the ____ (up or down) aileron extend automatically.
Up
Flight spoilers may be extended the same amount on each wing to act as ______
Speed brakes
The movable control surfaces on a V-tail airplane act as both elevators and rudders. These surfaces are called ______
Ruddervators
In a conventional airplane using horizontal stabilator and elevators mounted on the tail, the normal aerodynamic force acts _____ (Upward or downward)
Downward
A canard surface has an angle of incidence that causes it to stall ____(Before or after) the main wing stalls
before
The angle of incidence of the canard is greater than that of the main wing, so it will stall first
The type of wing flap that produces the greatest amount of increase in lift with the minimum change in drag is the _____ flap
Fowler
A leading edge flap _____ (increases or decreases) the camber of the wing
increases
Slats extend from the leading edge of the wing to ______ (increase or decrease) the wing camber
increase
A trim tab ______ (does or does not) move relative to the control surface on which it is installed as the surface is moved in flight
does not
A balance tab moves in the _______ (same or opposite) direction as the control surface on which it is mounted
opposite
The type of tab that is controlled from the cockpit to produce an aerodynamic force that moves the primary control surface is called a/an _____ tab
servo
(The cockpit control is attached to the servo tab so that it moves in the direction opposite that desired for the primary surface. Deflection of the servo tab produces an aerodynamic force that deflects the primary surface, which in turn rotates the airplane about the desired axis
A servo tab moves in the _____ (same or opposite) direction as the control surface on which it is mounted
opposite
A spring tab automatically deflects when the control forces are _____ (high or low)
high
A spring tab is used on high-performance airplanes that, under high-speed conditions, develop aerodynamic forces so great that assistance is needed to help the pilot move the controls
An anti-servo (anti-balance) tab moves in the ______ (same or opposite) direction as the control surface on which it is mounted
same
What is a stabilator? (pitch control)
-location of pivot point
This is a single piece horizontal surface that pivots about a point approximately one third of the way back from the leading edge.
A stabilator does not replace elevator, it just gives the ability of trim
The rudder is used only at the ______ of the turn to overcome the adverse yaw
beginning
(differential aileron is used to combat A.Y primarily)
Many large jet transport aircrafts have two ailerons on each wing and flight spoilers to assist in roll control.
The _______ ailerons are locked in their faired or streamline, position when the ____ _____ ___ are up
outboard
trailing edge flaps
Describe what flight spoilers do when ailerons are deflected.
When the ailerons are deflected, the flight spoilers on the wing with the up-aileron automatically extend to decrease the lift on the wing that is moving down and to produce additional parasite drag to overcome any adverse yaw
The movement of the nose in the wrong direction at the beginning of a turn is called ____ ___
adverse yaw
What happens to the CG (Centre of Gravity) during flight?
During flight , the centre of gravity will move slowly in the direction of the nose of the aircraft, as a result of fuel consumption.
On which axis do the following control surfaces act?
(a) Rudder
(b) Elevator
(c) Aileron
(a) Rudder is about the vertical (normal) axis
(b) Elevator is about the lateral axis
(c) Aileron is about the longitudinal axis
What are flight control trim systems used for?
A trim tab is controlled from the cockpit and used to alter the camber of the surface and create an aerodynamic force that will hold the control surface deflected.
Allow for ‘‘hands off’’ flying
What kind of high lift devices are used on modern jet airliner aircraft?
Slats
Leading edge flaps (Kreugor flaps)
Trailing Edge flaps
Explain the relationship between high lift devices and the angle of attack
High lift devices increase the angle of attack at which an aircraft will stall (16/17 ^ -> 25^) while flying at low speeds
Explain the function of:
(a) Servo tab
(b) Trim tab
(a) The servo tab assists or provides the force for moving a primary flight control
(b) The trim tab reduces the force needed to move a primary control surface
What type of actuators are included in the cable trim systems?
electrical actuators
The following situations require trimming from what control surface:
- A change of position of the centre of gravity and the centre of pressure
- When there is an uneven thrust of the engines
- When there is a fuel imbalance
- Adjustible stabiliser (Stabilator)
- Rudder
- Aileron
Roll trimming is usually a result of ______ ______
Fuel imbalance
In modern passenger aircraft, an ____ ______ is installed in the cable system between the pedals and the _____ ______ of the steering units
Electric actuator
Control valves
The purpose of slats may be as much to _____ _____ at low speeds by curing any tendencies towards ____ ____ ____ as it is to augment the lift coefficient
improve control
wing tip stalling
Whenever the slat is open, at even moderate angles of attack, the _____ ____ can penetrate further aft along the chord thus reducing the thickening effect and delaying ______ and resulting in a stronger _____ ______ than that obtained from a wing without slats.
Boundary layer
Separation
Pressure distribution
What is the approximate stall angle with slats extended?
25 degrees
(Normal stall angle is 16/17 degrees)
What type of flap setting is used for take off?
For take-off, an intermediate flap setting is used.
What type of aircraft is the plain flap used on?
The plain flap is only used on low speed aircraft.
Why are stall strips used?
It is extremely important that an aircraft wing stall progressively from the root out to the tip, so the ailerons will be effective thoughout the stall
An artificial feel system gives the pilot resistance that is proportional to the flight loads on the surfaces.
The control forces are too great for the pilot to manually move the surfaces, so, in the event of a hydraulic system failure
They are controlled with ___ tabs
Servo
