Aerodynamics Flashcards
What is an aerofoil?
A body shaped to produce an aerodynamic reaction (lift) perpendicular to its direction of motion, for a small resistance (drag) force in that plane.
What is an aerofoil chordline?
A straight line from the leading edge to the trailing edge of an aerofoil.
What is the mean chordline?
Wing area/Wing span
What is the mean chamberline?
An equidistant line from the leading edge to the trailing edge of an aerofoil
What is the angle of incidence?
The angle between the aerofoil’s chordline and the aircraft’s longitudinal datum
What is the angle of attack?
The angle between the aerofoil’s chordline and the relative airflow.
What is washout on the wing?
Washout is a decrease in the angle of incidence from the wing root to the tip.
This delays the onset of a stall due to higher levels of loading experienced at the wing tips.
What is the coefficient of lift (CL)?
The lifting ability of a particular wing. It depends on both the shape of the wing section and the angle of attack.
What is the centre of pressure?
A single point acting on the wing chord line at a right angle to the relative airflow, through which the wing’s lifting force is produced.
High lift devices
- Trailing edge flaps (Fowler): increase lift at lower angles of deflection
- Leading edge flaps (Kruger): increase lift by giving a lonfer wing chordline, camber and area
- Slots: Prevent/delay separation of the airflow boundary layer (increasing CL)
High drag devices
- Trailing edge flaps (in high-drag, low-lift position)
- Spoilers (in flight detent as a speedbrake, or on the ground used as lift dumpers)
- Landing gear
- Reverse thrust
- Braking parachute
Wing-tip vortices
Created by spanwise airflow over the upper and lower surfaces of a wing/aerofoil.
Increases drag, reduces aileron efficiency and increases likelihood of wing-tip stall due to the disturbed airflow.
Creates: drag, turbulence and affacts longitudinal stability.
Prevented by:
Fences - reduces the reverse spanwise airflow on the upper wing from reaching the wing tips.
Vortex generators - disturbs and creates a denser airflow perpendicular to the leading edge to increase effectiveness of controls.
What is compressibility?
The effect of air being compressed onto a surface resulting in an increase of air density and an increase of dynamic pressure above its specific value
Why does an ineffective tailplane make an aircraft unable to recover from a stall condition?
Because the low-energy turbulent air passing aft will immerse the high-set tail, causing the aircraft to lose its pitching capability which is what is required for the aircraft to recover from its stall
