Helicopter tail rotor problem!

Your picture is the so-called X tail rotor, and its blades are installed on the hub like the letter "X". Compared with the common symmetrical tail rotor, the main advantage of the X-type tail rotor is to reduce the aerodynamic coupling of the tip vortex of each pair of adjacent blades. Therefore, when the main parameters of this kind of tail rotor are the best value and the best combination, it has higher efficiency and less noise than ordinary tail rotor.

Ducted tail rotor is a cylindrical duct made of vertical tail. Tail blades and tail rotor hub are installed in the duct to generate additional aerodynamic force. The tail rotor and the tail rotor hub of the tail rotor are directly installed in the vertical stabilizer and do not need to be moved out, which has the following advantages: the harmful windward resistance of the helicopter is reduced, the tail rotor can be prevented from hitting the ground objects when the helicopter maneuvers at ultra-low altitude, and people working beside the helicopter on the ground are prevented from being injured. However, compared with ordinary tail rotor, this kind of tail rotor needs much more power. Of course, in addition, there are those without tail rotor, such as the Oka series and so on. The red circle is the transmission system of the tail rotor.