11.1 Theory Of Flight Flashcards
What are the 3 main aircraft axis’s?
Longitudinal
Lateral
Vertical
What axis would pitch be controlled by?
Lateral axis
What axis would roll be controlled by
Longitudinal
What movement would be had from the vertical axis
Yaw
What type of stability would be around the vertical axis
Directional
What are the 3 primary flight controls
Ailerons
Elevators
Rudder
What axis would be controlled by the rudder
Vertical
What axis would be controlled by the ailerons
Longitudinal
What are the secondary flight controls
Slats
Flaps
Spoilers
Trim systems
On larger aircraft what would be added to increase the efficiency of an aileron
Flight spoilers
Are roll spoilers on both large and small aircraft?
Usually only large
What type of ailerons would be used on larger aircraft during flight at high speed
Inboard
If the outboards are used it would cause damage to the aircraft of flying control
What is done to the outboard ailerons during flight at high speed
Aileron lock out.
To prevent from being used
If the elevators are deflected downward what way will the nose point
Down
What is a stabiliser sometimes referred to
The all moving tail
What are the two types of stabiliser is used on a/c?
Fixed and trimmable
What is the name for the two types of canards
Lifting cannard and control cannard
Why are canards used
Located forward to the main wing to provide longitudinal stability and control.
Are canards always fixed.
No, they are fixed, movable or variable geometry.
Do control canards contribute to lift.
Not really, they are predominantly used for pitch control during manoeuvres.
Usually at zero angle of attack
What speeds and angle is full rudder travel permitted?
30 degrees and speeds up to 150 KTS
What speeds and angle is intermediate rudder travel permitted
15 degrees and 150-200KTS
What speeds and angle is minimum rudder travel permitted
Angle of 5.7 degrees and speeds above 200 KTS
What is a ruddervator
A combination or a rudder and elevator
Why is the V-tail said to be weight saving
As there is no vertical stabiliser needed
What are the disadvantages of the V-Tail
- The control surfaces must be larger
- No full rudder or elevator deflection at the same time
- Control surface adjustment is more complicated
On what type of aircraft would elevons be found
Delta and fighter aircraft
What surfaces do elevons combine
Elevator and ailerons
What are secondary flight controls used for
Lift, drag and trim
What secondary flight controls are found on the leading edge
Slats
What do drag devices include
- Speed breaks (Air breaks)
- Spoilers
When are the flaps primarily used
On landing to increase lift and drag as speed is reduced.
They are also used on take off to increase lift
What happens to the wing profile when the slats and flaps are extended
The chord line changes
What type of flap gives the most lift
Fowler flaps 95%
What are the 4 types of flap on aircraft
Plain
Split edge
Slotted
Fowler
How much do slotted flaps increase lift by
Approx 70%
What are the benefits of slotted flaps
The slots allow air from the lower side of the wing to the upper side to prevent early flow separation
Where are spoilers located
Upper surface of the wing towards the trailing edge
What is the purpose of spoilers
To reduce lift and increase drag
What is spanwise flow
Air particles flow over the wing and split in 2 directions
One at right angles to the leading edge and the other follows the leading edge
What is used to reduce the effect of spanwise flow
Wing fences
Why does spanwise flow do to the boundary layer
Thickens the boundary layer towards the wing tip, especially during high speeds with a high angle of attack
What are wing fences also called
Boundary layer fences
What is a vortex generator used for
To improve boundary layer control
What does the vortex generator do to the air
It takes high energy air from the outside boundary layer and mixes it with low energy air in the boundary layer
What does the number and location of vortex generators depend on
Depends on flight test investigation
What are stall wedges or strips
They are small triangular devices located on the leading edge and at high angles of attack help the wing root to stall before the tip
What do trim systems compensate for?
Aerodynamic imbalance on the a/c
How does aerodynamic imbalance occur
If any forces around aircraft axis are not equal
What systems do pitch systems help with
Ailerons
Elevators
Rudder
What 3 categories do all flight control systems get divided into
- Control inputs
- Control transmissions ( control runs which transmit through the airframe)
- Control surface outputs
What is the control column used to operate
The elevators
What do the control wheels (yolk) operate
Ailerons and roll spoilers
What mechanical cockpit control would control the rudder
The rudder pedals
What do ruddervators need to assist with control inputs
Mixer units
How are the pilots inputs (control inputs) connect with the flight control outputs?
Through control runs
The control runs connect the pilots inputs to the flying control system
They are known as transmissions
What are the flaps controlled by?
The flap lever
What are the 3 transmission control run methods from flight deck to control surface
Mechanically
Electrically
Hydraulically
What are the main components in a mechanical control run?
Rods and cables
This is the simplest form - usually on small a/c
How do hydraulic controls in a control run work
Hydraulic components convert input signals from a mechanical control run into a hydraulic output to drive the control surface
What do hydraulic systems use for control runs
- Mechanical components (rods and cables)
- hydraulic components
What do electrical control runs do
Includes an Imput from the flight deck via a flight control computer, which turns an electrical imput, via an electrohydraulic valve into a hydraulic output
What components would electricical control transmissions use?
- Mechanical components
- Electrical components
- Hydraulic components
What is an aerodynamic horn balance
Part of the surface that is located forward of the hinge line and moves into the wind during deflection aiding movement
What is a balance tab?
Assists deflection of control surface
Disadvantage - reduces effectiveness of control surface
What is the balance panel?
A plate connected to the leading edge of the control surface
What is the anti-balance tab?
Increases efficiency of control surface
Disadvantage - more effort needed to deflect control surface
What is the purpose of a trim tab
To compensate for imbalance of the aircraft
How are the trim tabs operated from the cockpit
Via a cable system, screw jack and trim rod
What is the trim position
When the trim tab is deflected the control surface is repositioned to a new neutral position
How is the speed of sound defined
The distance travelled per unit of time by a sound wave as it propagates through an elastic medium
What is the speed of the speed of sound?
In dry air at 20 degrees Celsius the speed of sound is 343.2 m/s
What are the 3 speed regions for aircraft
Subsonic
Transonic
Supersonic
What happens to the air in the supper sonic region
Shock waves are formed and there are large pressure changes and changes in density
What region is air incompressible
Subsonic
How is the Mach number worked out
Speed of sound
What does the term ‘local Mach number’ mean
An example - the air over the top of the wings could be travelling at the speed of sound when the rest of the air is moving below
What is the critical Mach number
The highest Mach number achievable before reaching the speed of sound
At what Mach number does a shock wave begin to form
Mach 1.2
What is wave drag
The drag caused by shock waves
What is a vortex generator
Transfers high energy to the boundary to reduce flow separation
They also produce an oblique shock wave inside the supersonic flow
What is the sweep angle on most modern jet aircraft
30 degrees
Increases critical Mach
How are swept wings prone to wing tip stall in their original form
The shape of the wing channels air to the tip creating a thicker boundary layer and then flow separation
How is wing tip stall prevented on swept wings
With wing fences and saw tooth
What type of wing performs well in the transonic region
The transonic profile
What are the 3 main characteristics of the transonic profile wing
- Flatter upper surface
- More curved leading edge
- Thinner trailing edge
What is a wing with a transonic profile also called
A rear loaded wing
What manufacturing advantages do transonic profiles provide?
Transonic wing profile uses the entire entire skin as the torque box which allows for thinner and lighter material to be used
What can be done to compensate for the tuck under effect
The horizontal stabiliser must increase the downward acting force
What flying control is it dangerous to use to compensate for tuck under
The elevator
When supersonic airflow passes through a shock wave what happens to density, pressure, temperature and velocity?
Pressure - increases
Temperature - increases
Density - increases
Velocity - decreases
What type of energy do shock waves waste
Energy is lost through heat
What are the main forms of waves created in supersonic flow
- Shock waves
- Expansion waves
What are the two types of shock waves
- Normal shock wave
- Oblique shock wave
What happens to the air when it passes through a normal shock wave
No change in direction but it is slowed from supersonic to subsonic
Temp, density and static pressure increased a lot
Total energy greatly reduced
Does an oblique shock wave consume more or less energy than a normal shock wave
Less than a normal
What are the two supersonic profiles?
- The double wedge profile
- The circular arc profile
On a circular arc profile where is the centre of life with supersonic airflow and subsonic airflow?
- Supersonic airflow centre of lift around 50% back
- Subsonic airflow centre of lift around 25% back
What kind of air speeds can be entered into the inlet of a jet engine?
Must be subsonic
What are the most important characteristics of a supersonic inlet?
Must slow the air down but minimise energy losses due to temperature
How much of aluminium strength is lost at what temperature?
80% if the temperature reaches 250 Celsius
