Basic Aerodynamic Theory Flashcards
what is static pressure?
static pressure is the prevailing pressure at any given point in the atmosphere
when there is no movement between a body and the air around it, pressure on the body is experienced (equally/unevenly)
equally
what is dynamic pressure?
the extra pressure generated by virtue of movement between a body and the air around it
when there is movement between a body and the surrounding air, the distribution of pressure around the body is (equal/uneven)
uneven
what is the equation for total (or pitot) pressure?
pitot pressure = static pressure + dynamic pressure
what is indicated airspeed (IAS)? is it corrected for anything?
indicated airspeed (IAS) is the reading on the airspeed indicator. no - instrument errors are so small they can generally be ignored
what is calibrated airspeed (CAS)? what is it corrected for?
calibrated airspeed (CAS) is IAS corrected for pressure (or position) error
what is equivalent airspeed (EAS)? what is it corrected for?
equivalent airspeed (EAS) is CAS corrected for compressibility error
what is true airspeed (TAS)? what is it corrected for?
true airspeed (TAS) is EAS corrected for density error - this fan be calculated using a nav computer
what is an aerodynamic force?
an aerodynamic force is a force generated if a solid body is placed in a moving airstream - it originates from the pressure distribution around the body
lifting capacity of large, relatively flat bodies is highest when it is (angled slightly/parallel) to the incoming airflow
angled slightly
what is an aerofoil?
a tear drop shaped surfaced designed to generate useful aerodynamic force
what is the camber of an aerofoil?
camber is the overall curvature of an aerofoil - refer to line of mean camber on the aerofoil diagram
high speed aerofoils are generally what shape?
long and thin
high lift aerofoils are generally what shape?
shorter and wider compared to high speed aerofoils
general purpose (GP) aerofoils are generally what shape?
a combination of high speed and high lift - medium length and width
whats the chord line of an aerofoil?
the straight line joining the leading and trailing edges
whats the leading edge of an aerofoil?
the edge facing the incoming airstream
whats the trailing edge of an aerofoil?
the edge facing the downstream end of the airflow - generally pointed to encourage reconnection of the airstreams
whats the chord of an aerofoil?
the distance between the leading and trailing edges, measured along the chord line
whats the angle of attack (AoA)?
the angle between the chord line and the incoming relative airflow
a higher AoA generally means a (higher/lower) amount of lift
higher, until the critical angle
whats the maximum thickness of an aerofoil?
the widest part of an aerofoil
how is lift generated?
a combination of bernoullis theorem and newtons third law - airflow remains at a constant while moving around an aerofoil, creating a pressure differential between above and below, and an upward force is created by the downward deflection of air according to newtons third law.
what is lift?
an aerodynamic force which is perpendicular to the relative airflow
what is drag?
an aerodynamic force parallel to the relative airflow, which opposes the motion of an aerofoil
what is total reaction?
total reaction is the combination of a rise in pressure under the wing and a reduction in pressure above the wing
is air an ideal fluid? why/why not?
no - air is compressible and has viscosity
wherever the speed of airflow is increased, the air gains dynamic energy and its static pressure is accordingly (increased/reduced)
reduced
what is a streamline airflow?
a flow of air in which particles follow a steady and predictable path
what is the venturi effect?
air is forced to speed up when passing through a venturi due to the bernoulli theorem - static pressure is drastically decreased at the throat of the venturi, because dynamic pressure is at its highest
whats the most effective AoA?
4 degrees
airflow above an aerofoil (speeds up/ slows down), resulting in an (increased/decreased) static pressure
speeds up, decreased
around an aerfoil, there are areas of (lower/higher) pressure, and the top area is (more/less) dramatic than the bottom area
lower, more
as AoA increases, CoP moves ___
forward until the critical angle, at which it falls backwards
general critical angle on a GP aerofoil is about ___ degrees
15
what is upwash?
the air deflected above an aerofoil
what is downwash?
the air deflected below an aerofoil
total reaction (increases/decreases) with increasing AoA until critical angle
increases
at low AoA, CoP is about ___% back from the LE
30-40
at high AoA, CoP is about ___% back from the LE
15-20
total reaction (TR) is made up of two component forces. they are:
lift and drag
