Revision Flashcards
What is mass
Amount of matter an object contains
What force is “g”
Gravity
What is weight
Mass being acted upon by gravity
What force pushes the aircraft backwards when flying?
Drag
What force pushes the aircraft forwards?
Thrust
When thrust and drag are balanced
The aircraft moves at a constant speed or is stationary
When the resultant force is 0 what is happening with the acting forces?
They are equal
What are the 4 main forces acting on an aircraft?
Thrust, drag, lift, weight
Total weight of the airplane is called?
The All Up Weight
The centre of gravity is
The point where the weight of a body acts
What is the MTOW?
Max take off weight
What is the MATOW
Max allowable take off weight
At what point should the CG remain in the manufacturers defined limits?
All stages of flight
When might the CG move?
As fuel burns up or as parachutists leave the aircraft ect
What is wing loading?
When the lift of the wings can support the weight of the aeroplane
How do you calculate wing loading?
Weight of the aircraft / wing area
What is an aerofoil?
A surface designed to help lifting, controlling or propelling an aircraft through the airflow around it i.e. the wing
What is the boundary layer?
The layer of air a few mm thick that passes over an aerofoil
What happens if the boundary layer of air over an aerofoil moves away from the aerofoil?
At the “separation point” the airflow will become turbulent
How do you calculate constant total energy?
Pressure energy + kinetic energy
What is rho?
Air density
What happens to dynamic pressure if an objects speed increases?
The pressure increases as more air molecules are striking per second
What happens to dynamic pressure if rho increases?
It increases as more molecules will strike
What is PT?
Constant total pressure
What is V?
Speed
What happens to lift if the wing is perfectly flat (no angle of attack)
There is no lift as the air particles aren’t pushing it up or down
Why do most aircraft not have flat wings?
It causes eddying (turbulence)
What does camber mean?
Curvature
What is the mean camber line?
Line drawn halfway between the upper and lower surfaces i.e. horizontal along the wing
What is the cord line?
A straight line joining the 2 ends of the mean camber line
What is the difference between a mean camber line and a chord line called?
Camber
What is the thickness of the aerofoil ?
Greatest distance between the upper and lower surfaces
Bernoulli’s principle says that
Energy in a steady streamline flow remains constant
What is the centre of pressure?
The total reacting forces acting at a single point
What happens to the lift of the wing if the angle of attack increases?
The lift of the wing increases
What happens to the centre of pressure when the angle of attack increases?
Centre of pressure moves forward
What is the angle of attack best for lift to drag ratio?
+ 4 degrees
What is CL or C lift?
The coefficient of lift
What happens to the C lift at the angle of stall
The coefficient of lift would decrease drastically as the wing loses the ability to produce lift
Where is the centre of pressure at the stall?
The furthest point forward
What happens to the centre of pressure after the stall
It moves rearward
What is the angle of attack
Angle between the chord line and the relative airflow
The total reaction acts through
The centre of pressure
What is the angle of incidence?
The angle between the chord line and the longitudinal axis of the aircraft
What is the purpose of the tailplane?
To balance the moment created by the difference in the centre of pressure and centre of gravity
What is total drag?
The sum of all the aerodynamic forces acting in the opposite direction of flight
What is induced drag?
Drag used to produce lift
What is parasite drag?
Drag that does not directly produce lift
What is skin friction
The surface area of the aircraft producing drag
What is form drag?
The turbulent air produced by airflow separating from a surface
What is interference drag?
Drag caused by 2 parts of the aircraft joining together I.e. drag from the joint between the fuselage and the wing
What happens to parasite drag as airspeed increases?
Parasite drag invreases
What happens to drag if you double airspeed?
2^2 = 4
Parasite drag multiplied by 4
What happens to drag if you triple airspeed
3^2 = 9
Parasite drag multiplies by 9
What does a wing with high aspect ratio look like?
Long and narrow
What does a wing with low aspect ratio look like?
Short and stubby
How do you calculate aspect ratio?
Span/ chord
How do you reduce induced drag?
Have a high aspect wing
What is washout?
Where wings have a steeper angle closer to the fuselage than to the tip of the wing
What is the purpose of washout?
More lift occurs in the inner part of the wing
When is induced drag greatest?
Low airspeeds and high angles of attack
How do you calculate total drag?
Induced drag + parasite drag
When is total drag the greatest?
At high airspeeds and low angles of attack
What is minimum drag speed
When total drag is the least. This occurs when parasite and induced drag are equal
How to calculate drag using the coefficient of drag?
Drag = Cdrag x 1/2 x rho x v^2 xS
What does S mean?
Area
What aircraft design features reduce induced drag?
Washout, winglets, wing tapering
What is washout?
A reduction in the angle of incidence (and consequently the angle of attack) from wing root to wing tip
How do you calculate the lift to drag ratio?
Lift/drag
When does an aerofoil have the greatest lift ability?
Just before stall at a high angle of attack
What should your angle of attack be at low air speed
High angle of attack
What should your angle of attack be at high airspeeds
Low angle of attack
What happens to your angle of attack if you lose weight?
Angle of attack can be reduced as less lift is required to maintain level flight
What is the blade angle on a propellor
The angle of attack plus the helix angle
What slipstream affect would occur if a propellor was rotating clockwise (as viewed from the cockpit) on take off
Air would flow around the aircraft and hit the fin at the back of the plane. This would cause the tail to be pushed right
Why do some aircraft have an offset fin?
To overcome the slipstream affects of the propellor on take off
If the propellor rotates clockwise as viewed from the cockpit what will the propeller torque cause?
In high power and rpm conditions the aircraft will roll to the left. On the ground it will yaw to the left
What is the blade angle?
Angle between the chord line of the propellor blade and the plane of rotation
The blade angle is larger where?
Larger near the root and smaller near the tip
What happens to the angle of attack on a fixed pitch propellor?
It varies with speed and rpm
What happens to the rpm of you enter a dive in a fixed wing propellor?
Increased rpm
Where does lift force act?
Centre of pressure
Where does weight force act
Centre of gravity
What is a couple?
2 equal forces that cause rotation as they are acting along different axis (this is why you fly nose up or nose down)
Centre of gravity moving back and power increasing will cause what to happen to the stall speed?
Stall speed reduces
What is the purpose of a slat?
It will re-energise the airflow over the upper surface of a wing
What is wing dihedral?
The upward angle of an aircraft’s wing
What is a swept wing
Wings that are swept are used on jets and have a swept wing root to wingtip
What is the keel affect
Side force generating that stop unwanted rolling
Distance between the upper and lower aerofoil is called
Thickness
The force acting in the opposite direction to the wings in a balanced turn is the…
Total force
An aircraft returning to its trimmed position after a disturbance is a measure of its…
Dynamic stability
Why do we have differential ailerons?
To stop adverse aileron yaw as the downward aileron had increased camber and lift
Modifying what part of the aircraft would have the highest impact on induced drag?
Wing tip
What is induced drag
Drag that produces lift
Yawing is a rotation around which axis?
Normal axis
What does a slag or slot do to the coefficient of lift?
It increases the maximum coefficient of lift
What does a trail edge flap do?
Reduces the stalling angle of attack
What will happen to an aircraft with neutral dynamic stability if it is disturbed from its trimmed position?
It will oscillate with constant period and wavelength
What is VA?
Max speed that flying controls can be made without structural damage
What is the difference between a slag and a slot?
Slot is a fixed gap in the wing. A slat is a device that creates a moveable slot
What prevents flutter?
Mass balance in the controls
What is spiral instability
Weak lateral stability causing sideslip
When will a aeroplane wing stall?
At a specific angle of attack
Vertical wind sheer will cause what immediate consequence?
Change in aircraft’s airspeed
What is the normal limiting load factor in light aircraft?
+4.4
What is the difference between a slot and a slat?
Slots are fixed devices that lowers stalling speeds
Slats do the same but are opened either manually or automatically
What instrument is used to determine spin direction?
Turn coordinator
How does altitude affect stall speed?
It does not
What happens to the centre of pressure on the wing when angle of attack is increased?
The centre of pressure moves forward. When it moves in front of the wing the wing will stall
