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In the recent Sino-foreign joint exercise, our army actually began to test a "little-known" small domestic reconnaissance and strike drone that can drop six grenades at a time, and even brought it abroad for foreign troops to use. This drone is different from the common multi-rotor drones. It uses a coaxial twin-propeller aerodynamic layout. It looks small, but it can carry six grenades, which can be said to be very powerful.

This brings up a question: Why would the Chinese military deploy a coaxial twin-propeller mini-bomber? Compared with the common multi-rotor drones we have, what advantages does it have?

This controversy has actually always existed in the history of helicopter development. Russia's Ka-52 series is considered to be the representative of coaxial twin-rotor helicopters, but the US military still chose the single-rotor solution. The controversy here is that the use of coaxial twin-rotor helicopters has both advantages and disadvantages. The coaxial twin-rotor helicopter uses two coaxially arranged propellers with the same diameter on the helicopter, cancels the tail rotor, and uses two rotors to rotate in opposite directions to provide lift and maintain the stability of the flight posture in the air. Because there is no tail rotor, the coaxial twin-rotor helicopter has a higher hovering efficiency, which is 17% to 30% higher according to Russian statistics. The second advantage of the coaxial twin-rotor helicopter is that it is relatively short, with a longitudinal dimension of only about 60% of that of a single-rotor helicopter. Because the structural weight and load are concentrated, this type of helicopter has good acceleration performance and outstanding high-speed flight characteristics.

However, the reason why the United States does not use this method is that coaxial helicopters have a series of problems such as complex mechanical structure, the risk of blade striking during high maneuvers, taller fuselage and high cost.

So why did the special operations team of the Chinese army choose the coaxial twin-propeller mini bomber? The most important reason is that the drones of this type currently equipped by China are all controlled by motors, which fundamentally solves all the shortcomings of coaxial twin-propeller aircraft, such as complex structure, high cost and hidden dangers of propeller failure. At the same time, it also has a series of advantages such as small size, easy to carry, strong load capacity, flexible use, good silent performance and low cost. Whether compared with large reconnaissance and strike drones or cheap multi-rotor drones, coaxial twin-propeller drones have the following advantages:

1. Powerful vertical take-off and landing capability. In the case of the same size, the coaxial twin-propeller UAV has higher flight efficiency and larger payload, and has excellent load capacity and endurance. It stands to reason that it is impossible for such a large UAV to carry 6 grenades and perform long-term cruise missions, but it is possible with the coaxial twin-propeller solution.

Second, it is possible to achieve high-precision balance control and maintain stability under various flight conditions. The motor drive solution can better achieve precise control of the propeller, and its flight speed is high and its ability to adapt to strong winds is quite strong.

3. Low noise and energy saving: When the payload is the same, the coaxial twin-propeller drone has a lower rotor speed, less noise, and is more difficult to detect. Its pitch and roll control does not require the main rotor to accelerate or decelerate, so the energy utilization efficiency is higher.

In general, with the rise of China's unmanned combat forces, the coaxial twin-propeller aerodynamic layout will surely shine because of its natural advantages. In the future, relevant manufacturers can launch larger coaxial twin-propeller drones to cooperate with ground armored forces to perform a series of combat tasks such as reconnaissance, strikes, and firepower strike effect evaluation. Compared with multi-rotor drones, this type of drone has an important disadvantage that the cost may be more expensive, but as long as the equipment scale is large enough, its cost-effectiveness is still very attractive. The route of China's drone technology needs to be flourishing, so as to promote the PLA's combat to stride forward in the direction of unmanned operations.