What is the term for the acute angle formed by the chord line of a wing and the relative wind?

The term for the acute angle formed by the chord line of a wing and the relative wind is known as the angle of attack. This angle is crucial because it directly influences the amount of lift generated by the wing. As the angle of attack increases, so does the lift—up to a certain point known as the stall angle, beyond which lift begins to decrease.

Understanding the angle of attack is fundamental for pilots, as it helps determine the aircraft's performance during different phases of flight, such as takeoff, cruising, and landing. It also plays a significant role in stall recognition and recovery.

In contrast, other terms like angle of incidence refer to the fixed angle of the wing's chord line in relation to the horizontal plane, rather than the relationship with relative wind. Airspeed pertains to the speed of the aircraft through the air, while lift coefficient is a dimensionless number related to the lift characteristics of a wing, which is influenced by the angle of attack but is not the definition of the angle itself. Thus, angle of attack is the most accurate term for the described relationship.