Subsonic Airflow Flashcards
Aerofoil
A shape capable of producing lift with relatively high efficiency
Chord Line
A straight line joining the centres of curvature of the leading and trailing edges of an aerofoil
Chord
The distance between the leading and trailing edges measured along the chord line
Angle of Incidence
The angle between the wing root chord line and the longitudinal axis of the aircraft. This angle is fixed for the wing
Mean Line or Camber Line
A line joining the leading and trailing edges of an aerofoil, equidistant from the upper and lower surfaces
Maximum Camber
The maximum distance of the mean line from the chord line. Max camber is expressed as a % of the chord, with its location as a percentage of the chord aft of the leading
edge.
- camber line lies above the chord line Positive
- camber line is below the chord line Negative
- A symmetrical aerofoil has no camber
Thickness/Chord Ratio
The maximum thickness or depth of an aerofoil section expressed as a percentage of the chord.
Thickness / chord line length
determines the shape of a wing and his AERODYNAMAL PROPERTIES
Extrados
Upper wing surface
Intrados
Lower wing surface
Positive Camber
The camber line is located ABOVE the chord line
Negative Camber
The camber line is located BELOW the chord line
Symmetric
no Camber
LEADING EDGE RADIUS
The radius of the front edge
of the wing (the first meets the relative airflow)
RELATIVE WIND
Speed with which the air flows over the wing
• V relative wind is = to the V of the airplane BUT OPPOSITE DIRECTIONS!
• Relative wind is the consequence of a wing moving through air, but when studying the wing, it looks as
if the air is moving over the wing
Pressure on wind
When a wing is moved through the air, lowered/
reduced static pressure is created ABOVE the wing
NEGATIVE AOA Positive Camber
equal decrease in Ps above and below the wing
• The resulting pressure differential is ZERO
• This means that NO AERODYNAMICAL FORCE is
developed
AOA ZERO Positive Camber
there is a higher decrease in static pressure above the wing, compared to below the wing
• The resulting pressure differential is ZERO
• This means that there is a SMALL UPWARD AERODYNAMICAL FORCE being developed
AOA Positive Camber (from 0 to 12-
16° for most types
there is a significant decrease in static pressure above the wing and an increase in static pressure below the wing
• The resulting pressure differential is POSITIVE (Lift)
• INCREASING UPWARD AERODYNAMICAL FORCE
Critical AOA from 12 - 16 + Camber
there is a sudden/significant drop in the decrease in static pressure above the wing
• There is an increase in the Ps below the
wing, but the resulting pressure differential is
NEGATIVE
• sudden/violent reduction in the AERODYNAMICAL FORCE being developed (STALL)
Lift generation
Upwing 2/3
downwing 1/3
