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Refer to figure.
The attached graph represents a wing in two configurations: the black line in clean configuration and the blue line with a lift augmentation device extended. What type of profile does the basic wing have and what type of lift augmentation device is used?
  • A
    Symmetrical wing with flaps extended.
  • B
    Symmetrical wing with leading edge device extended.
  • C
    Asymmetrical wing with flaps extended.
  • D
    Asymmetrical wing with leading edge device extended.

Refer to figures.
SYMMETRICAL AEROFOIL

The distribution of pressure is important in aerodynamics, since it determines:
- The amount of lift generated
- Any pitching moments
- The form drag of an aerofoil section

The lift and drag forces of a wing cross-section are dependent on the pressure distribution around the wing. The pressure distribution around an aerofoil is the resultant of the angle of the aerofoil chordline to the oncoming airflow, the angle of attack.

If a symmetrical aerofoil section is in a steady airstream at zero degrees Angle of Attack, a stagnation point forms on the leading edge.

The airflow velocity above and below the aerofoil increases by an equal amount and the static pressures reduce by an equal amount. Consequently, no pressure differential exists, and no net lift is created.

CLMAX AUGMENTATION

One of the main factors which determine the CLMAX of an aerofoil section is the camber. Increasing the camber of an aerofoil section increases the CL at a given angle of attack and increases CLMAX.

TRAILING EDGE FLAPS

Aircraft are fitted with high lift devices to reduce the take-off and landing distances and when low airspeeds are beneficial. This permits operation at greater weights from given runway lengths and enables greater payloads to be carried.

Returning the flaps to their neutral position when no longer required, returns the wing to its former aerodynamic characteristics.

The increase in lift comes mainly from the variation in effective camber that occurs when the flaps are deflected.This alters the lift curve and also produces a higher maximum coefficient of lift.

In some instances, the trailing edge flaps may also increase the wing's surface area. Extending the trailing edgeflaps alters the pressure distribution around the wing.

LEADING EDGE DEVICES

Leading edge devices increase maximum value of CL and critical angle of attack. But for the constant angle of attack CL is the same or less. (Curve extends to the right and up).

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