Aircraft Fundamentals Flashcards
What control surface is used to change the pitch of the aircraft?
Elevators (movable part of the tailplane)
What is the main purpose of the tailplane on an aircraft?
Pitch stability
By what aerodynamic mechanism do control surfaces change the orientation of an aircraft/
Control is achieved by changing the lift on the relative surface to create a moment about the appropriate axis with respect to the centre of gravity
What control surface controls yaw motion?
Rudder (Mounted on trailing edge of fin)
How is roll achieved on an aircraft?
Rotation about longitudinal axis controlled by differential deflections of ailerons
In what direction does the lift force act?
Right angle to direction of flight
What are the 4 primary forces acting on an aircraft?
Lift, Weight, Thrust, Drag
Define the angle of attack of an aerofoil
Angle between chord line and direction of airflow
What distance on a aerofoil corresponds to the chord length?
Distance of the straight-line between the leading edge and trailing edge
Define what is meant by a camber or the mean line of an airfoil?
Line that is always midway between the upper and lower surfaces of the wing
In words, what is the equation for the aspect ratio of the wing?
Span divided by mean chord
Does a short stubby wing have low or high aspect ratio?
Low
What is sideslip?
Aircraft moving in a sideways direction as well as into the oncoming airflow
Define the true airspeed of an aircraft?
Speed relative to the air
Define the equivalent airspeed of an aircraft
airspeed at sea level that would give the same dynamic pressure as the true airspeed at the actual altitude the aircraft is flying
What is free stream
The air far upstream of the aircraft which has not yet been disturbed by the aircraft
What is the general equation for lift? Define the meaning of each term in the equation.
0.5rhoV^2SCl
Rho - Air density
V - True Airspeed
S - Wing surface area
Cl - Coefficient of lift
What is bernoullis equation? Define each term
0.5Rhov^2 + p = po
Rho - Airdensity
V - True airspeed
p - static Pressure
po = total pressure
Is the actual lift force produced by the difference in static pressure or dynamic pressure on a aerofoil?
Static Pressure
For low angles of attack what is the relationship between lift coefficient and angle of attack for a general airfoil?
linear relationship
How does camber of the airfoil affect the relationship between lift coefficient and angle of attack?
camber increases the coefficient of lift for a corresponding angle of attack.
How is a stall reflected in the curve of lift coefficient versus angle of attack?
Sudden drop in Cl
What is the physical mechanism that results in a boundary layer?
Air flowing past a surface tries to stick to it and speeds up as it gets further away from the surface.
Briefly describe the behaviour of air flowing over a wing in a laminar boundary layer?
Air flows smoothly in a streamlined manner
What is the equation of reynolds number? Define all the terms
rhovl/mu
rho - air density
v - true airspeed
l - a characteristic length
mu - dynamic viscosity of air
Why is the reynolds number important?
Used to characterise and predict airflow. Predict transition from laminar to turbulent flow
In terms of airflow over a wing, which type of airflow corresponds to stall?
turbulent
How do flaps temporarily increase the lift on a wing?
Increases the camber on the wing which increases the coefficient of lift curve
What is the general equation for drag? define meaning of each term
0.5rhov^2scd
rho - air density
v - true airspeed
s - wing surface area
cd - coefficient of drag
what are the 3 types of parasitic drag?
Form drag
Skin friction drag
Interference drag
What is the commonly used relationship between the drag coefficient and the lift coefficient also called the drag polar.
cd=a+bcl^2
what is a shockwave?
abrupt changes in airspeed, temperature and pressure
Define mach number
true airspeed/ speed of sound
What values of mach number correspond to transonic flow and explain the meaning of transonic flow
0.7 < 𝑀 < 1.4 – transonic flow, compressibility becomes important, some locally supersonic airflow around the aircraft
What is the purpose of swept wing?
reduce the effect of high speed flow
