What is the minimum angle between the lifting line and the horizontal that is allowed?

The minimum angle between the lifting line and the horizontal that is typically accepted in many engineering and aerodynamics contexts is 45 degrees. This angle is important because it strikes a balance between generating sufficient lift and maintaining control of the aircraft or system being evaluated. At this angle, the forces acting on the object, including lift and drag, are optimized to ensure stability and performance.

Angles below this may lead to increased drag and potential stall conditions, while angles significantly above it can compromise the control configuration and performance efficiency. Therefore, establishing a minimum of 45 degrees as acceptable helps ensure safe operational parameters while maximizing lift generation capabilities.