11.1 Theory Of Flight Flashcards
What movement occurs around the lateral axis
Pitch
Where’s the lateral axis located
Wing tip to wing tip
What control surface is responsible for pitch
Elevators on horiz stab
What type of movement acts on the longitudinal axis
Roll
What type of movement acts on the longitudinal axis
Roll
What control surface is responsible for roll
Aileron
What control surface is responsible for roll
Aileron
What axis is responsible for yaw
Vertical
What axis is responsible for yaw
Vertical
What control surface allows yaw movement
Rudder
What control surface allows yaw movement
Rudder
What are the primate flight controls
Rudder
Elevator
Ailerons
(Sometimes roll spoilers too)
What axis do ailerons assist to affect control around
Longitudinal
When the left aileron is deflected up and the right is deflected down which was does the aircraft roll
Left
What tends to occur when the aircraft is rolled
Sideslip
What’s the force acting on the control surface in flight a product of
Kinetic energy and surface area
How is dynamic energy calculated
1/2pV shared or 1/2 density x airspeed squared
What’s the energy in the air proportional to
The square of the airspeed
What may happen to the ailerons being moved at high speeds when being moved and why
What’s done to combat this
Can go outside it’s structural limit loads due to the forces on the surface due to high speeds
Having inboard and outboard ailerons
When are both sets of ailerons used
Take off and landing
What aileron is locked out as aircraft speeds increase
Outboard
What’s used for roll control at high speeds
Inbrd ailerons and roll spoilers
What axis does the elevators affect and what type of control on what axis
Longitudinal
Pitch control on lateral
What’s a stabilator
Controls both elevator and horizontal stab
What axis do stabilators rotate around and what movement do they affect
Vertical and affect pitch
What’s usually installed in conjunction with a stabilator
Anti balance tab
What are stabilators used for
Enhanced speed and rapid manoeuvrability
What problem can occur with stabilators at high speed transonic flight
Surface can be rendered In effective due to a shockwave for,ed at the hinge line
What are variable incidence stabiles/ THS used for
Pitch trimming
What advantage does the variable incidence stabiliser/THS have
Reduced requirement for elevator deflection due to less drag
What direction does the nose go when the angle of attack of the THS increases
Nose down
Where are the horizontal control surfaces of canards located
Front of aircraft ahead of the main wings
How can canards fwd position improve the aircraft’s natural stability
By providing a nose down force
What are benifits of canards
Enhance aircraft’s stall resistance
Increase manoeuvrability ( as canard will stall first and cause a nose down pitching moment to help recover the stall )
Control redundancy (fallback/back up)
What’s the rudder used for
Directional or Yaw control
What direction does the aircraft go if the left rudder pedals pressed down
Left
What does the rudder limiter do
Restricts the amount of rudder deflection with increasing airspeed
What’s used to assist ailerons in a roll movement
Rudder
What are Frise ailerons
Differential ailerons
What are methods of the uneven drag on wings caused by aileron deflection
Frise ailerons
Differential ailerons
Spoilers
What affects can happen as a result of a high vertical stabiliser
Adverse roll
What systems in place r help overcome adverse roll
Aileron-rudder interconnect system
What system is used correct osicillations of Dutch roll
Yaw damping system
What aircraft dome have horizontal stabilisers
Delta-wing
What movement do you get on a elevon when they are moved in opposing directions
Aileron/roll
What way do the rudder gator control surfaces move to pitch the aircraft down
Ruddervator down together
Where are slots primarily located on the wing
Outboard leading edge
What’s the purpose of slots
Allows high energy air to accelerate through to the top of the wing and reenergise the boundary layer to prevent flow seperation
What’s the purpose of slots
Allows high energy air to accelerate through to the top of the wing and reenergise the boundary layer to prevent flow separation and stalls
Allowing aircraft to fly at slower speeds and higher aofa
Do slots give lift
No just re energise boundary layer
What’s a disadvantage of slots
Give drag
How do slats increase lift
By increasing the camber
What control surface can be used as a stall prevention in flight
Slats
What’s a downside of flaps
Increased drag
What can happen as flaps are deployed (negatives)
Aerodynamic force moves the wings centre of pressure rearwards causing a nose down pitch tendency
What way will the nose pitch when the flaps are being PUT IN
Nose up
How much % lift do the plain flaps provide
50-55
What’s a benifit of split edge flaps
Avoids boundary layer separation ivermectin the upper surface
What % lift does the split flap provide
60-65
What percentage of lift does the slotted flap provide
70-75
What does the fowler flap design do the chord of the wing
Increases
What does the fowler flap design do the chord of the wing
Increases
What percentage of lift does the fowler flap provide
Up to 95
What do Krueger flaps help to do
Carry out low speed handling
What are the two functions on spoilers
Assist ailerons in a roll
And to increase drag
When can full deflection of spoilers be achueved
On ground
What’s the main point of ground spoilers
To improve efficiency of the landing gear brakes by dumping the lift generated by the wing so forcing that weight into the landing gear
What’s the main point of ground spoilers
To improve efficiency of the landing gear brakes by dumping the lift generated by the wing so forcing that weight into the landing gear
What effect does spa wise flow have on the boundary layer
Thicken it
What happens to the distance between the c of g ans the c of p when both wing tips stall at the same time,
They get closer
How do sawtooth leading edges work
Creates a small vortex that limits the boundary layer outflow and redirects spanwise flow
How are vortex generators installed
In pairs so the vortices mix
What are stall strips made of
Alluminium
What are trim tabs used for
Compensate for imbalances of aircraft
Where are trim tabs usually positioned on light aircraft
Rudder
What way do trim tabs deflect in relation to the flight control surface
Opposite direction to the direction the flight control has been deflected to
This assists to keep the flight control in the desired position
What direction does the balance tab move in relation to the control surface and why
Opposite
Creates a force on the flight surface which assists the movement
Disadvantage of the balance tab
Reduces efficiency of surface
What direction does the anti-balance tab move in relation to the flight surface
Same direction but deflects to a greater angle than control surface
What’s a disadvantage of an anti balance tab
More effort required to deflect these
What direction does the servo tab move in relation to the Scot roll surface
Opposite
What way does a spring tab deflect in with the control surface
Opposite
What can happen if the c of g of a control surface is aft of the hinge line
Can cause an inertia to be felt and an ossicillation/flutter to follow
How can torsional aileron flutter be prevented
Mass balancing so that the c of g is on or slightly ahead of the hinge line
What’s the speed of sound at sea level
340 m/s
How’s the Mach number calculate
The velocity of object (v) / speed of sound (a)
Where are the sound waves if the objects travelling at low speeds
Ahead of the object
What speeds does subsonic flight occur in
0-0.8 mach
What speeds does transonic flight occur at
0.8-1.2 Mach
What issue can occur with stability of flight in transonic region
Airflow separation due to shockwave
What speeds are supersonic
1.2-5
What happens to density and pressure at supersonic flight
Slight changes in pressure and no changes in density
At what stage of flight is air compressible
Supersonic
What happens to the coefficient of lift and coefficient of drag in the supersonic range
Reduction in coefficient of lift
Increased coefficient of drag
What Mach number is airspeed considered compressible
0.4 Mach
When does a normal shockwave formation take place
In transonic range at the Mcrit and will form at right angles to the path of the airflow
What happens to the position of the shockwave as the mach number increases
Grows ans moves rearwards
What happens to the speed of the airflow after it’s passed through the shockwave
Decelerates to a subsonic speed
What happens to kinetic energy as it goes through a shockwave
Coverts to heat energy and temp rises
What’s wave drag
Wave drag is the proportion of total drag which is due to shockwaves
What’s the two ways to reduce wave drag
Using vortex generators
Area rule
Generally what’s the position of the centre of lift on a circular arc wing type if the airflow on the wing is supersonic
50% of the chord
Why’s it important that the aircraft is arranged so that the cross sectional area is as smooth as possible from nose to tail
To ensure volume distribution which minimises wave drag
Why’s it important that the aircraft is arranged so that the cross sectional area is as smooth as possible from nose to tail
To ensure volume distribution which minimises wave drag
What’s the sear hack body shape
The body with the lowest theoretical wave drag in supersonic flow
What can be done to the shape of the aircraft to get volume distributions
Flattening the sides of the fuselage below a bubble canopy and at the tail surfaces to compensate for their presence.
When’s an expansion wave formed
When supersonic airflow changes direction around a curve or corner away from the proceeding flow direction
What happens to the static pressure, Density, temp, useful energy and total pressure when a expansion wave occurs
Stat pres,dens, temp decrease
Useful energy and total press stay same
When’s aerodynamic heating significant
At supersonic speeds
What happens to velocity and temp as if flows over an aerodynamic surface
Velocity decrease
Temp increase
What’s Areodynamic heating also known as
Friction heating
What percentage of strength does aluminium alloy lose as 250 degrees celsius
80%
Why’s alluminium commonly used in some military aircraft (heat)
Lightweight and low coefficient of thermal expansion
What’s the limit that gte compressors take axial velocities
Not much more than 0.4 Mach regardless of aircraft speed
What does a normal shock diffuser inlet do
Employs a single normal shock wave at the inlet to slow the air to subsonic velocity
What does a normal shock diffuser inlet do
Employs a single normal shock wave at the inlet to slow the air to subsonic velocity
Why’s a normal shock diffuser inlet not used at higher-supersonic speeds
Bc the normal shockwave is strong and will cause a great reduction in total pressure recovered by the inlet
Why’s a normal shock diffuser inlet not used at higher-supersonic speeds
Bc the normal shockwave is strong and will cause a great reduction in total pressure recovered by the inlet
What’s the single and multiple oblique shock inlet do
Uses a series of very weak oblique shockwaves to gradually slow to the flow before a normal shock wave can occur. Slowing it before reduces the strength of a normal shockwave
Leads to a least waste in energy and highest pressure recovery
How does the variable supersonic inlet work
When below Mach 1 - Inlet fully open and ac fly at high aofa
When just above Mach 1 - inlet closes slightly to employ single shockwave
When at high Mach numbers - close more so 3 oblique shockwave occur then 1 normal shock wave
What’s a way to reduce profile thickness of the wing and it’s critical Mach number
Aero Swept wings
How’s profile thickness calculate
Actual thickness / chord length
What sweep angle do most modern jet ac have
30 degrees
Bc ur reduces prof thickness and increases crit mach number
What disadvantage do swept wings have
Increased spanwise flow
This can cause stagnation in boundary layer and wing tip stall
What disadvantage do swept wings have
Increased spanwise flow
This can cause stagnation in boundary layer and wing tip stall
What’s bigger inbrd or outbrd ailerons
Outbrd
When can fixed trim tabs be adjusted
Only on the ground
