Which statement defines the coefficient of lift (CL)?

• A. The ratio between lift pressure and dynamic pressure.
• B. A true course corrected for variation and deviation errors.
• C. A small circle graduated in 360° increments, to show direction.
• D. An aircraft with retractable landing gear, flaps, and a controllable-pitch propeller.

Answer: (A)

The coefficient of lift is a dimensionless factor that connects the lift the wing generates to the air’s dynamic pressure and the wing area. It’s defined by the relationship L = CL × q × S, where L is lift, q is dynamic pressure (q = ½ ρ V²), and S is wing area. So CL equals L divided by (q × S). In practical terms, CL tells you how effective the wing is at producing lift for a given airspeed and density, independent of size or speed.

The statement describing CL as the ratio between lift per unit area (lift pressure) and dynamic pressure matches this concept because lift per unit area is essentially the lift pressure, and dividing by dynamic pressure yields the dimensionless CL value. The other options refer to navigation corrections, a compass instrument, and aircraft configuration, which are not related to the definition of CL.