What airspeed is required for nacelle and speed modulation when airborne?

The correct airspeed for nacelle and speed modulation when airborne is 40 KCAS. This specific speed is critical for ensuring that the aircraft maintains optimal performance during flight operations that involve adjusting the nacelle position and managing speed settings effectively. At this airspeed, the aircraft has been shown to maintain sufficient control authority while allowing for safe and efficient modulation of both nacelle orientation, which is essential for vertical takeoff and landing capabilities, and the overall speed of the aircraft.

Choosing an airspeed lower than this threshold could compromise the aircraft's aerodynamic stability, while a higher speed may not provide the necessary control and responsiveness during this specific phase of flight. Therefore, 40 KCAS is established as the minimum airspeed required to safely perform nacelle and speed modulation, balancing control and performance needs effectively.