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The Centre of Pressure of a biconvex symmetrical aerofoil, with the angles of attack within its normal operating limits…
  • A

    Moves nearer the leading edge.

  • B
    Needs to be offset from the CG line of the rotor blade for control purposes.
  • C
    Moves very little.
  • D
    Moves nearer the trailing edge.
Refer to figure.

The sum of all the reactive aerodynamic forces is known as the Total Reaction, which acts through the Centre of Pressure (CP).

Alternatively, it is defined as the point on the chord line where the resultant of all the aerodynamic forces acts.

"Bi-convex" or "Double wedge" is a category of airfoil shape, which is symmetrical and with very sharp leading and trailing edges, thus, preventing the formation of shockwave in front of the airfoil, as it travels through the air.

On a symmetrical airfoil, the position of the CP remains relatively unchanged at about 25% of the chord line with the change in Angle of Attack, provided that the angle of attack remains within its normal operating limits.

Whilst, on a cambered airfoil, the CP varies with the Angle of Attack and moves progressively forward to about 15% of the chord line.

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