What combination must remain above the low speed boundary for the conversion protection system to allow forward nacelle conversion?

The correct answer is based on the operational principles of a conversion protection system, which is designed to ensure safe transitions between different flight modes, particularly in aircraft with variable geometry wings or tilt-rotor capabilities.

For the conversion protection system to enable forward nacelle conversion, it is essential that the combination of nacelle angle and airspeed maintains a safe operating margin above the low-speed boundary. This boundary is critical because if the aircraft operates below this threshold, it may encounter control issues or insufficient lift, which could jeopardize safe flight. Maintaining an appropriate nacelle setting while ensuring the airspeed is above the specified low-speed limit helps prevent aerodynamic stall and ensures the aircraft remains controllable during the transition phase.

Inadequate altitude or speed alone does not specifically address the unique requirements of the nacelle's positioning relative to airspeed for safe operation during conversion. Similarly, considerations of power to weight ratio or velocity regarding drag do not directly link to the specific spatial and airflow dynamics involved in flying with the nacelle set for conversion. Therefore, the relationship between nacelle configuration and airspeed is paramount for safe conversions.