Basic Aerody Flashcards
What is kinetic energy?
Energy an object possesses due to its speed
What is potential energy?
Energy an object possesses due to its height.
Gravitational potential energy
In a loop, when will an aircraft have its maximum kinetic energy?
Before entering and just after exiting
In a loop, when will an aircraft have its maximum potential energy?
At the top of the loop
What are the two types of pressure?
Static Pressure (Ps) and Dynamic Pressure (Pd)
What is static pressure?
The pressure caused by gravity pulling air molecules down toward the centre of the Earth
What happens to static pressure as altitude increases?
Decreases - due to air being less dense at higher altitudes
How does pressure move?
High to low
What is dynamic pressure?
Kinetic energy to motion
What is the formula for dynamic pressure?
Pd = 1/2 rho v^2
What is Bernoulli’s Theorem?
Total pressure does not change.
I.e. Pt = Pd + Ps
What is the Coanda effect?
The tendency of the airflow to follow a surface with gentle curvature rather than continue its original path until the stalling angle is reached
What does the air do as a result of the Coanda effect?
Results in the air being deflected downward after it leaves the trailing edge of the wing
What is an aerofoil?
Any surface which is designed to provide an aerodynamic force when interacting with a moving stream of air
What is the chordline of an aerofoil?
The straight line joining the leading edge to the trailing edge
What is the mean camber line of an aerofoil?
The line drawn an equal distance from the upper and lower surfaces
What is the thickness of an aerofoil?
The distance between the upper and lower surfaces
What is the camber of an aerofoil?
The curvature of an aerofoil
What is a well-cambered aerofoil used for?
Typical high-lift, low speed wing
What is a symmetrical aerofoil used for?
Typical horizontal stabiliser
What is aspect ratio?
It is span divided by chord
What does a wing with high aspect ratio bring?
Can reduce induced drag
What is Relative Airflow (RAF)?
Airflow in the opposite to the direction of the path of the aircraft
What is angle of attack (AoA)?
The angle between the chordline and relative airflow
What is the centre of pressure (CoP)?
A point on the top surface of an aerofoil which the total reaction of all lifting aerodynamic forces is said to act
Where is the high pressure around an aerofoil?
Underneath
Where is the low pressure around an aerofoil?
On top
What is the effect of flap?
Causes a greater increase in drag than lift
What is induced drag?
Drag created when creating lift
What is the equation of lift?
L = C(L) 1/2 rho v^2 S
What is C(L) in the equation of lift?
Coefficient of lift, made up of AoA and Wing Shape
What is S in the equation of lift?
Surface area
How can we increase C(L)?
Increase AoA
Increase camber
Deploy flap
Increase thickness/chord ratio
What is the thickness/chord ratio?
Is an aerofoils relative thickness
What are the two types of drag?
Induced drag and Parasite drag
What is parasite drag made up of?
Skin friction
Interference drag
Form drag
What is skin friction?
Exists between an object and the air in which it is moving through
What is interference drag?
Air mixing at junctions creates turbulence in the region of the joint
How is interference drag reduced?
With the use of fairings
What is form drag?
Results from airflow separation
How is form drag reduced?
Reduced by using streamlined parts
Which fineness ratio produces the least drag?
Large fineness ratio
What happens to parasite drag as airspeed increases?
Parasite drag increases
What happens to induced drag as AoA increases?
Induced drag increases
When causes induced drag to be greater?
The greater the pressure difference between the bottom and top surface, the greater the induced drag
Why does a slower aircraft produce more induced drag?
The slower the aircraft flies, the more time air has to spill over the wing tip
Where is induced drag produced?
At the wingtip as air spills over from high to low pressure
What increases the pressure difference over an aerofoil?
Aircraft weight
AoA
Aspect ratio
What happens to induced drag as airspeed increases?
Induced drag reduces
What is total drag?
Total Drag = Parasite Drag + Induced Drag
What point is the min drag point?
The best glide speed
What is the drag equation?
D = C(d) 1/2 rho v^2 S
What is C(d) in the drag equation?
The coefficient of drag
What impacts on the C(d)?
The AoA and wing shape
What is wake turbulence?
A result of air spilling around the wingtip due to the high pressure below the aerofoil and lower pressure above
What happens to wake turbulence as AoA increases?
Wake turbulence increases
What happens to wake turbulence as IAS decreases?
Wake turbulence increases
What happens to wake turbulence as weight increases?
Wake turbulence increases
What happens to wake turbulence as aspect ratio increases?
Wake turbulence decreases
What happens to wake turbulence if you increase the dissipating time?
Wake turbulence decreases
When are wingtip vortices at their greatest strength?
When an aircraft is heavy, slow with gear and flaps up
When is wake turbulence strongest?
Just prior to take-off
Where should you fly to avoid wake turbulence?
Upwind and above
When taking off after a large aircraft takes off, where should you aim to rotate?
Aim to lift off well before the larger aircraft’s rotation point and climb above their flightpath
When taking off after a large aircraft has landed, where should you aim to rotate?
Aim to lift off well after its touchdown point or wait for it to dissapte
When landing after a large aircraft lands, where should you approach and aim to land?
Approach above it’s flight path and aim to land well beyond it’s touchdown point
When landing after a large aircraft takes off, where should you aim to touchdown?
Aim to touchdown well before its point of rotation
Where should you aim to land when a large aircraft lands on a crossing runway?
Plan to cross above the larger aircraft’s flightpath and touchdown well beyond the runway it has landed on
Where should you aim to land when a large aircraft takes-off on a crossing runway? (Consider both pre/post intersection departure)
If the rotation is beyond the intersection then land before the intersection.
If the rotation is before the intersection, then go around unless the landing can be completed before the intersection
How fast does wake turbulence sink?
400-500 fpm
How far does wake turbulence extend?
2 wingspans horizontally and 1 wingspan vertically
How do you avoid wake turbulence en-route?
Aim to fly 200ft above or 1000ft below
How long can vortices persist for at altitude and on the ground?
5 mins at altitude
3 mins on the ground
If a heavy aircraft conducts a go around, what should you do?
Assume the entire runway could be a hazard and delay or discontinue the approach
Do helicopters produce wake turbulence?
Yes, known as rotor downwash
When is a helicopters wake turbulence greatest?
When a helicopter is operating at lower speeds
How far can helicopter wake turbulence be hazardous for?
Up to a radius of approximately 3x rotor diameter
What is equilibrium?
Forces acting on an object are in balance and there is no acceleration
What is a moment?
Force x Arm
What is inward spanwise drift?
Air on the top of the wing moves inwards
What is outward spanwise drift?
Air on the bottom of the wing move outwards
