What is the straight line from the leading edge to the trailing edge of the airfoil?

What is the straight line from the leading edge to the trailing edge of the airfoil?

• A. Span line
• B. Camber line
• C. Mean line
• D. Chord line

Answer: (D)

The straight line from the leading edge to the trailing edge is the chord line. It defines the chord, the fundamental width of the airfoil used as the reference for most geometric measurements. The airfoil’s thickness is described relative to this line, and the camber is measured with respect to it. The camber line is the curve that lies between the upper and lower surfaces and describes how much the airfoil is curved; for a symmetric airfoil the camber line is straight and coincides with the chord line. The span line, by contrast, runs along the wing from tip to tip, not across the airfoil.

The straight line from the leading edge to the trailing edge is the chord line. It defines the chord, the fundamental width of the airfoil used as the reference for most geometric measurements. The airfoil’s thickness is described relative to this line, and the camber is measured with respect to it. The camber line is the curve that lies between the upper and lower surfaces and describes how much the airfoil is curved; for a symmetric airfoil the camber line is straight and coincides with the chord line. The span line, by contrast, runs along the wing from tip to tip, not across the airfoil.