What is defined as the acute angle between a line parallel to the wing chord and the longitudinal axis of the aircraft?

The term that describes the acute angle between a line parallel to the wing chord and the longitudinal axis of the aircraft is indeed the angle of incidence. This angle is significant because it affects the performance characteristics of the aircraft, particularly in terms of lift generation.

The angle of incidence is usually fixed at the design stage and represents the angle at which the wing is mounted relative to the aircraft's longitudinal axis. It plays a critical role in establishing the aircraft's stall characteristics and overall aerodynamic efficiency. A well-designed angle of incidence ensures optimal airflow over the wing at various angles of attack, thus contributing to stable flight and improved performance.

Understanding the angle of incidence helps in comprehending the relationship between the wing's design and the aircraft's flight dynamics, which is vital knowledge for anyone involved in assembly and rigging of aircraft.