What does the angle of incidence refer to in aviation?

The angle of incidence is defined as the angle formed between a line parallel to the wing chord of an aircraft and a line parallel to the longitudinal axis of the aircraft. This angle is a critical design parameter for aircraft wings because it affects the aerodynamic characteristics and performance of the wing.

Proper angle of incidence ensures that the wing can achieve sufficient lift at different speeds and configurations. A positive angle of incidence usually means that the wing is slightly tilted upwards relative to the aircraft's body, facilitating lift generation during flight. When considering aircraft design and performance, it is essential to understand this relationship, as it directly influences factors like stall characteristics and overall stability.

In contrast, the other options refer to different aspects of aviation. The angle between the wing chord and the horizontal surface relates more to the aircraft’s orientation on the ground or during a specific flight condition. The steepness of the descent angle during landing and the angle of elevator deflection during flight pertain to different aerodynamic and control surface dynamics rather than the incidence of the wing itself. These distinctions clarify why the angle of incidence is vitally important within the context of aircraft performance and aerodynamics.