Final answer:
The rotor brake should not be applied when the engine(s) are operating and the rotor is turning, except during an emergency situation.
Step-by-step explanation:
The statement provided in the question refers to the operation of a rotor brake in certain conditions. According to the question, the rotor brake should not be applied when the engine(s) are operating and the rotor is turning, except during an emergency situation. The maximum rotor speed for emergency rotor brake applications is determined as a percentage of the normal rotor speed or NR.