Which of the following is NOT a method to stop the tail rotor from spinning?

Blowing air with a fan is not a suitable method to stop the tail rotor from spinning because a fan is an ineffective and impractical means of providing sufficient resistance or obstruction to the rotor's movement. Tail rotors require substantial force to halt their operation due to the high rotational speeds at which they typically operate.

Other methods such as using the bristle end of a broom or fresh water stream are more effective as they can create direct physical resistance or cooling effects that can help in reducing the rotor's speed. Towing the aircraft out of the wind can also reduce the effectiveness of the wind on the rotor, allowing it to slow down naturally due to decreased airflow. Therefore, using a fan does not provide the necessary force or interference to effectively stop the tail rotor, making it the incorrect choice in this context.