Deck 1 Flashcards
What are the 3 zones of the atmosphere we consider when speaking about aircraft
Troposphere
Tropopause
Stratosphere
What is the height of the Troposphere
11km
At what rates do temperatures drop when ascending through the atmosphere
2 degrees Celsius per 1000ft
6.5 degrees Celsius per 1000m
What are the ISA values for temperature, pressure and density
15 degrees Celsius
1013.2 millibar
1.226kg/m cubed
What is the definition of viscosity
A fluids resistance to internal friction
How are the AoA and AoI measured
AoA - angle between the chord line and relative air flow
AoI - angle between chord line and datum line
What is the aspect ratio and how is it calculated
The ratio of span to chord
Span / chord
Span^2 / area
What is wash out and wash in
Wash out - Decrease in AoI towards the wing tip
Wash in - Increase in AoI towards the wing tip
What is upwash and down wash
Upwash - Upwards flow of air before reaching the aerofoil
Downwash - Downwards flow of air after passing aerofoil
What are the 4 main aerofoil planforms
Rectangular - simplest to manufacture and use
Tapered - Chord length changes from wing root to wing tip
Swept - can be both forward and back swept
Delta - fighter jet
What are the 2 equations relating to subsonic flow
Bernoullis equation
Conservation of mass flow equation
What does the conservation of mass flow equation state
The mass of air at any point entering, passing through or leaving a pipe must be constant
What does bernoullis equation state
P1 + 1/2 pv1^2 =1 P2 + 1/2pv2^2
What happens to air when is passes through a Venturi
Velocity will increase, pressure will drop
What is the total reaction
The resultant force of the drag and lift
What happens to the CoP and AoA increases
Will initially move 20% forward along the chord line, then move 30% backwards
What is free stream flow
Air unaffected by the passage of aircraft through it
What is a streamline
The path traced by a particle in a steady fluid flow
What is the boundary layer
A thin section of slow moving air surrounding an aircraft, typically 0.1-0.2mm in thickness
What is the separation point
Where turbulent flow separates from the aerofoil shape
What happens to the fineness ratio when and aerofoil is streamlined
The fineness ratio will increase
What is stall defined as?
When an increase in AoA no longer produces an increase in lift
What is the standard stall angle
15-16 degrees
What is the stalling speed
The slowest an aircraft can fly to produce sufficient lift to overcome its weight
What is spanwise drift
The movement of air laterally from wing root to tip or vice versa
What 6 factors affect the total reaction
Density
Air velocity
Wing area
AoA
Surface finish
Aerofoil shape
What are the equations for the Coefficient of lift and drag
1/2pv^2 x S x C (L/D)
What is the most effective AoA in straight and level flight
4 degrees
What are the 3 aerofoil classes
High lift
High speed
General purpose
What are the 4 leading edge lift augmentation devices
Slots
Slats
Krueger flaps
Droop nose
What are the 3 trailing edge lift augmentation devices
Single, double or triple slotted fowler flaps
Plain flaps
Split flaps
What 2 sections make up total drag
Lift dependant
Non lift dependant (parasite)
What 3 sections make up lift dependant drag
Form Drag
Skin friction
Induced drag
What 3 sections make up non lift dependant drag
Form drag
Skin friction
Interference drag
What 3 methods are used to control the boundary layer
Vortex Generators
Blowing
Suction
What are the effects of ice forming on aircraft
Aerodynamics will be affected
Weight increase
Vibration on moving parts
Controls stiff
Pressure instruments incorrect
Comms degraded
Vision impaired
Undercarriage locked
Engine intakes blocked or restricted
What parts are most vulnerable to ice formation
Areas with a thin cross section
Where and how does packed snow form
Leading edges, nose and air intakes
Forms on non streamlined sections below 0 degrees when flying in or underneath snow clouds
What is hoar frost and how does it form
Light icing
Forms on clear nights, rapid descent from cold air into moist air
Take off on a frosty morning climbing into moist air
What is the basic stalling speed
The speed below which a clean aircraft with the engines throttled back cannot maintain straight and level flight
What conditions must be met to perform a maximum radius turn and minimum radius turn
Wing load must be as low as possible
Air must be as dense as possible
What does the manoeuvre envelope show
Comparisons of capabilities of aircraft
Performance of products
Design requirements for new aircraft
What are the axis labelled on the manoeuvre envelope
Vertical axis - load factor
Horizontal axis - EAS
What are the G limits for training, fighter and transport aircraft
Trainer and fighter - +7 -> -3.5
Transport - +2 -> -0.5
What is the safety factor on velocity
5-10%
What is the safety factor on load factor
50%
What information can you gather from the manoeuvre envelope
Basic stalling speed
Load factor at any height and speed
Max EAS at any height
Stalling speed at any height and load factor
What is positive stability (stable)
When an object will return to its original position
What is negative stability (unstable)
When an object will never return to its original position
What is neutrally stable
What an object will not return to, nor carry on away from its original position
Around which axis is the rolling motion
Longitudinal axis
Around which axis is the pitching movement
Lateral axis
Around which axis is the yawing motion
Normal axis
What methods can be used to increase lateral stability
Dihedral (upwards angled wings)
High fin
High wing
Sweep back
What 3 devices give control of rolling pitching and yawing
Rolling - Ailerons
Pitching - Elevators
Yawing - Rudder
What ways are there to overcome adverse aileron yaw
Coupled controls to the rudder
Differential ailerons
Frise ailerons
What methods are there to overcome high speed ailerons reversal
Wing strengthening
Inner and outer wing aileron sets
Spoilers on down going wing
What 4 methods are used to assist the pilot in moving the flight controls
Horn balance
Inset hinge
Balance tab
Spring tab
What is flutter
The rapid violent oscillation of the aerofoil
How can flutter be countered
Using weights to bring the CoG forward of the hinge line
Air is deemed incompressible at what air speed
150m/s
What is the total pressure
The dynamic and static pressure added together
Where is spanwise drift the weakest
At the root of the wing
The size of the vortex will depend on what
The size of the wing tips
How do you increase directional stability
Make fuselage longer
Make the fin taller
Ventral fin
Dorsal fin
How would you increase longitudinal stability
Make Horizontal stabilisers larger or love them rearward
How would you increase lateral stability
High fin
High wing
Dihedral
Sweep back
