1 Flashcards
What are the 3 primary axes in flight?
- Longitudinal
- Lateral
- Vertical
What are the 3 movements about the axes?
- Roll
- Pitch
- Yaw
What movement is about the vertical axis?
Yaw
What movement is about the lateral axis?
Pitch
What are the primary flight controls?
- Rudder
- Aileron
- Elevator
What happens when the aileron deflects upwards?
Decrease in lift
What is the equation for dynamic energy?
= 1/2 x Density x Velocity Squared
What occurs to the outboard aileron at high speeds?
Locked
What aileron is used at high speeds?
Inboard aileron
What is the purpose of roll/flight spoilers on an up-going aileron of a rolling aircraft?
Supplement aileron control by reducing lift
What is the differential operation of flight spoilers linked to?
Aileron control system
Roll spoilers have two purposes what are they?
- Execute accurate turn
- Reduce need for large aileron deflection at high speeds
Why is the elevator at the position furthest away from the C of G?
Greater leverage
What are stabilators?
Dual purpose control surface
Where are stabilators used?
High speed military aircraft
When a shockwave forms on the hinge line of an elevator the control surface is ineffective what is the solution to this?
Stabilators
THS is also known as what?
Variable incidence stabilisers
THS are only used for what purpose?
Pitch trimming
What is the advantage of the THS?
Reduced drag due to reduced requirement for elevator deflection
What does the trim angle account for?
- Weight distribution
- Fuel consumption
- Flap and engine settings
Which way is the trim wheel movement for nose down?
Spin wheels forward
What are Canards?
Flight control system forward of the wings
How Canard config influence the flight control system?
- Lift and trim
- Pitch control
- Stability
- Stall prevention
- High A of A manouvuers
- Control redundancy
What is the purpose of a rudder limiter?
Limits rudder movement at high speeds
What is side slip?
Yaw in the direction of the roll movement
Elevons are a combination of what controls?
Elevators and ailerons
Ruddervators are a combination of what controls?
Rudder and elevator
What is adverse yaw?
Yaw in the opposite direction to roll
How is adverse yaw prevented?
- Aileron differential
- Frise aileron
- Spoilers
Frise ailerons increase drag how?
Has a leading edge that protrudes into airflow
What direction is roll in adverse roll?
Opposite to yaw
What do slots do?
Do not increase lift but they energise the boundary layer to delay separation
What is the disadvantage of slots?
Fair amount of drag
What is the main difference of slots and slats?
Slats are moveable
What does a slat produce?
Lift due to camber increase
Flap extension has what effect on the nose?
Pitch it down
Which flaps produce the least lift increase?
Plain flaps
What are the leading edge droops designed to improve?
Improve airflow over wings at high A of A
What do Kruger flaps result in when extended?
Blunt leading edge leading to better lower speed handling
Where may leading edge flaps be found?
Large aircraft at wing root
What are flaperons?
Aileron that can also act as a flap
When would a flaperon be used?
Take-off/landing
What are the 3 types of spoilers?
- Flight
- Ground
- Roll
When would flight spoilers be used?
Too slow the aircraft inflight, max deflection is not used.
- Only a few spoilers used not all
When would ground spoilers be used?
Rejected take off or landing
What happens when roll spoilers are deployed?
Only a few spoilers deployed on the wing of the direction you want to turn in
When can speed brakes be used?
- Final approach to touchdown
- Landing
What do speed brakes not have an affect on?
Lift
What affect does span wise flow have on the boundary layer?
Makes it thicker and at the wing tip
What is the danger of swept back wings?
Tip stalls first
What do wing fences do?
Delay onset of boundary layer separation at wing tip
What does a saw tooth leading edge do?
Creates a small vortex that limits boundary layer outflow and redirects span wise flow
Where are vortex generators placed?
Trailing edge of the wing
How and why are they installed like this? (Vortex generators)
They are installed opposite so that the vortices mix
Where would a stall strip be installed?
Leading edge at wing root
What do stall strips encourage?
Encourage the root to stall before the wing tip
Where would a trim tab be found?
Trailing edge of primary control surface
Besides anti-balance what direction are the trim tabs moved?
opposite to the control surface
What is the purpose of the trim tabs?
Reduce the load for the pilots by making it easier to move the control surface
A trimmed aircraft has what?
0 aerodynamic moments
What is the disadvantage of a balance trim tab?
Reduces efficiency of the control surface
How does a pilot operate the control surface with a servo tab?
By moving the tab not the control surface
What is a spring tab?
A spring tab is like a servo tab however it only moves at a certain load
- High speed only
When would an anti balance tab be used?
Used when input off control is too sensitive and needs some resistance
What is a disadvantage of anti balance tabs?
More effort to deflect
When does mass balance flutter occur?
C of G of control surface aft of hinge line
What is control surface bias?
Control surfaces set at a slight angle from neutral to create a continuous aerodynamic force to offset forces during flight
What is a horn balance?
A weight placed forward of the hinge line on a control surface
What is an insert hinge?
An insert hinge is where the hinge line is moved back
How does a balance panel work?
Creates a chamber of higher and lower pressure and uses this to help move the control surface
What is the equation for mach number?
Velocity/Speed of sound
What are the 3 speed ranges?
- Subsonic <0.8 mach
- Transonic 0.8 to 1.2 mach
- Supersonic >1.2 mach
Is the local airspeed of airflow over the wing greater or less than true speed?
Greater than
What range can local airflow be in if true speed is in transonic?
Supersonic
Is air incompressible or compressible at supersonic?
Compressible
Describe the pressure waves of transonic?
Piled up
Describe the pressure waves of Subsonic?
Equally spaced
Describe the pressure waves of Supersonic?
Intersecting
What is the critical mach number?
The min true speed that will result in local air speed being the speed of sound
Air is considered compressible at what speeds?
Mach 0.4 and above
What problems occur when a shock wave is formed?
- Reduce lift
- Increase in drag
- Buffeting
- Control problems
- Uncommanded changes in trim and stability
Normal shockwaves occur at what angles to the airflow?
90 degrees
What direction do shockwaves move if the speed is increased?
Aft towards trailing edge
What happens when supersonic airflow passes through a shockwave?
- Velocity decrease
- Density and pressure increase
- Temperature increase
What angles do oblique shockwaves occur to the airflow?
Not 90
What happens to the airflow speed when passing through an oblique shockwave?
Slightly reduced
When is an expansion wave formed?
When a supersonic airflow changes direction around a curve or corner
What occurs to the airflow of an expansion wave?
- Increase in velocity
- Decrease in pressure, density and temp
What does the wave profile on a flat plate profile look like?
Positive AoA
Leading edge:
- Underside oblique wave
- Top expansion wave
Trailing edge:
- Underside expansion wave
- Top oblique wave
As the speed increases, where does a shockwave occur?
Underside of the wing
What occurs to the flow after the shockwave?
Turbulent flow
What are the two supersonic wing profiles
- Double wedge
- Circular arc
Where is centre of pressure located on a wing if the airflow is supersonic?
50% aft of Chord line
Where is centre of pressure located on a wing if the airflow is subsonic?
25% aft of chord line
What can be said about the expansion wave on a circular arc profile?
Continuous
What is the benefit of vortex generators?
They create a small oblique shock wave when airflow is supersonic, this reduces the normal shock. This means less flow separation and reduced wave drag
What is the body type with the lowest theoretical wave drag?
Sears-Haack body
To ensure volume distribution, what can be done to the fuselage at the wing attachment position?
Narrowed/ waisted fuselage
What is aerodynamic heating caused by?
Friction from the air
What can be done to supersonic aircraft to eliminate aluminiums strength problem at high temperature?
Use of titanium alloys
How does a normal shock diffuser inlet slow air to subsonic speeds?
Normal shock wave
What speed is a normal shock diffuser suitable for?
Low supersonic
In a single/ multiple oblique shock inlet, oblique shock waves reduce what?
The strength of the normal shockwave
How does a variable supersonic inlet work?
Actuators move a panel to change the size of the inlet. This affects the normal shock and at high speeds moves further to create oblique shockwaves to reduce the normal shock strength
What happens in a divergent intake of a subsonic engine?
- Velocity decrease
- Pressure and density increases
When a wing is swept back what can be said for the thickness?
Reduced profile thickness
Profile thickness = Actual thickness/ chord length
What is the most common angle for swept wings?
30 degrees
What do swept wings reduce?
- Critical mach no.
- Profile drag
- Improved stability laterally
- Overall frontal area
What is the drawback of sweptback wings?
- Tip stalls first
- Increased span wise flow
