【By Observer Net Columnist Chen Feng】
At the 93rd military parade, people were pleasantly surprised to see the unmanned air superiority fighter (hereinafter referred to as "Wujian") unveiled. There were many new equipment displayed at the parade, and each formation was worth noting, but the appearance of Wujian was especially surprising.
As no specific model has been officially announced, we temporarily name the two types of Wujian for distinction. We call the one with a large triangular wing (or diamond-shaped wing) "Wujian-X", and the one with a Lambda wing "Wujian-Y". X and Y are placeholders for unknown models, and "Wujian" is inferred from the naming convention of the "Wuzhen" series and the "Jian" series.
The unmanned air superiority fighter displayed at the parade, the top one is "Wujian-X", and the bottom one is "Wujian-Y"
"Wujian-X" looks highly similar to the stealthy, single-engine, tailless, and without canard versions of the J-20, which would not be unexpected if it were a product of the Chengdu Aircraft Corporation. "Wujian-Y" is similar to the rumored Beijiang, which would not be unexpected if it were a product of the Shenyang Aircraft Corporation. The important thing is that they are all Chinese, and not only are they unmanned, but they are sixth-generation aircraft.
As everyone knows, compared to fifth-generation aircraft, sixth-generation aircraft will have a qualitative leap in combat performance. Traditionally, the characteristics of fifth-generation aircraft include stealth, super cruise, super maneuverability, and sensor fusion, but among these four features, only stealth is the defining feature, because other features can be achieved by fourth-generation aircraft through deep upgrades. In this sense, the F-22 is a standard fifth-generation aircraft, and the F-35 is also a fifth-generation aircraft, although its performance is somewhat reduced, it does not achieve super cruise or super maneuverability. However, the F-15EX can only be considered a fourth-and-a-half generation aircraft and cannot become a fifth-generation aircraft.
Currently, fifth-generation aircraft can only achieve forward stealth, which is effective for penetrating shallow depths, but not sufficient for deep penetration behind enemy lines. In such an environment, only omnidirectional stealth can ensure enough survivability and combat effectiveness. Although there is no consensus worldwide on the definition of sixth-generation aircraft, omnidirectional stealth and deep penetration should be the main features of sixth-generation aircraft.
In the foreseeable future, radar will still be the main means of air defense detection. There is no physically completely stealthy aircraft in the world, and the key to achieving radar stealth lies in reducing the radar cross-section. Among the current fifth-generation aircraft, the vertical tail is the largest source of side radar reflection; at the same time, in the front direction, the linear size of the vertical tail also constitutes one of the main radar reflection features. Therefore, for achieving omnidirectional stealth, the absence of a vertical tail is a necessity.
In aircraft design, the vertical tail is equivalent to a vertically placed wing, using the asymmetric pressure caused by airflow on both sides during yaw to create self-stabilization in the heading direction. The typical design principle is to ensure that the side projection area of the fuselage after the center of gravity is larger than the side projection area before the center of gravity. Including the F-22 and F-35, most fighter jets' vertical tails are mainly used to provide this side projection area, so the main part of the vertical tail is usually fixed.
The vertical tail can also be used for nose direction (yaw) control, and the control surfaces on the rear edge of the vertical tail are used for this purpose. However, during flight, the aircraft's turn is not controlled by the vertical tail surface, and forcing a turn with the vertical tail surface will only change the aircraft's longitudinal axis direction, causing the aircraft to slide sideways while continuing to move forward. The aircraft's turn is achieved by rolling the body to a certain angle, where the wings generate lateral lift.
All-moving vertical tails can reduce the passive stability effect of the vertical tail, reduce drag and side reflection area, and maintain heading stability or change the nose direction through active deflection. The J-20 and Su-57 are examples of this.
However, a tailless design means the aircraft does not even have a full-moving vertical tail. The first practical tailless combat aircraft was the B-2.
B-2 Bomber
The B-2's configuration is called a tailless flying wing. The tailless aspect is obvious, and the flying wing refers to the integration of the wing and the fuselage into one. The B-2 was the first to achieve omnidirectional stealth, which gave it the confidence to operate deep behind enemy lines.
The B-2 pioneered the use of split ailerons to control yaw. This involves dividing the original single aileron into upper and lower parts at the outer position, symmetrically opening and closing them to form asymmetric resistance on both sides, controlling yaw without creating an "unplanned" roll moment.
Due to the complex mechanical structure and high weight of split ailerons, the B-2's wing structure is relatively thick. At the same time, to reduce weight, the area of the split ailerons relative to the entire wing area is smaller. This makes the B-2 need to maintain a certain degree of openness during normal flight to ensure sufficient control sensitivity, resulting in unnecessary drag. For a stealth aircraft, the split ailerons themselves form a pair of corner reflectors in the rear direction, which is a dilemma for a tailless aircraft designed for omnidirectional stealth.
Split ailerons are also unsuitable for normal aileron use due to mechanical limitations, making it difficult to deflect the upper and lower wing surfaces in the same direction. As a result, tailless aircraft using split ailerons also need to have regular ailerons, and because the outer more effective positions must be given to the split ailerons, the area of the regular ailerons must be increased, leading to weight and drag costs.
For a long time, split ailerons have been considered a "necessary cost," whether for manned or unmanned aircraft, and almost all tailless flying wings have used split ailerons. Before the North and South sixth-generation aircraft and Wujian, tailless flying wings did not exceed subsonic speeds because of the small sweep angle and large wingspan, where the split ailerons near the wingtips required little deflection to achieve significant control moments, but this brought a common problem: the lack of length caused difficulties in pitch control moments.
Can the North and South sixth-generation aircraft and Wujian still be called flying wings? This is an academic debate, not important, not worth pursuing. What is important is that supersonic speed requires a larger sweep angle and aspect ratio, solving the issue of pitch control moments, but the problem of yaw moments arises due to the smaller wingspan. A thinner wing is also not conducive to using split ailerons.
Unmanned Air Superiority Fighters Use All-Moving Wing Tips Video Screenshot
China has taken a different approach, using all-moving wing tips, and has solved the problem thoroughly and perfectly, achieving "tailless freedom" in one step. Both the North sixth-generation and the North-South Wujian have adopted this, while the South sixth-generation uses another idea of split adjustable ailerons or vertical tails.
When the all-moving wing tip is asymmetrically deflected, it can generate a strong wing tip moment, which is obviously effective for controlling yaw. The problem is that when the all-moving wing tip is deflected, it brings unnecessary roll moment. Fortunately, regular ailerons are used for roll control, which can be used to compensate. Thus, the opposite action of the ailerons and the all-moving wing tip is equivalent to the split ailerons, but it is more mechanically advantageous and powerful, and does not form a corner reflector.
Moreover, China has already gone through a similar problem with the V-shaped all-moving vertical tail. One major problem with the V-shaped tail of the J-20 is that the deflection causes an "unplanned" roll, requiring the ailerons to compensate. Now, it's just replacing the all-moving vertical tail with the all-moving wing tip, allowing the North technology to be used by the South. Then, the all-moving wing tip returns to the "Wujian-X," and the South technology is used by the North, fully demonstrating the characteristic of "a chessboard of competition" in Chinese aviation technology.
The all-moving wing tip can be used not only for yaw control during normal flight but also for spin recovery. When a severe spin occurs, the plane's forward speed is not important, but the rapid rotation deepens the loss of control, which is very dangerous.
Tall vertical tails have the role of preventing entry into a spin and helping to recover from it. Split ailerons have little effect on spin recovery, but the all-moving wing tip has a significant advantage in spin recovery. Because it is far from the center of gravity, it can immediately stop the rotation. This means that the all-moving wing tip also has a safety net function. When using sharp, wide leading edges or equivalent nose and fuselage edges, it can boldly utilize the vortex lift effect, without worrying about the danger of nonlinear lift and asymmetric vortices causing loss of control. The Boeing F-47 uses canards, possibly considering the control of vortices to avoid asymmetric vortices causing spins. In short, without mastering China's unique secrets, it is impossible to do so.
Interestingly, the flaps on the trailing edge of the wing usually suffer from efficiency losses due to the sweep angle. When the flaps are at a non-perpendicular angle to the direction of flight, the air generates a resistance perpendicular to the trailing edge. This resistance can be decomposed into a component parallel to the direction of flight and a component perpendicular to the direction of flight. Swept-back flaps produce inward lateral components, while swept-forward trailing edges produce outward lateral components.
Normal flaps are symmetrically deflected on both wings, so the lateral components cancel each other out, which is useless, but unavoidable.
Compared to this, flaps are used for low-speed, low-altitude situations to generate additional lift, enabling early takeoff or reducing landing speed. Low-speed, low-altitude situations are particularly sensitive to drag, and thrust should not be wasted on useless work, so the inner part of the wing often reduces the sweep angle, or even becomes basically straight, which helps maximize flap efficiency. The increased root chord also benefits structural load distribution.
However, for tailless aircraft, the lateral forces caused by the sweep or forward sweep are a blessing. Therefore, "Wujian-X" has a forward-swept trailing edge, and "Wujian-Y" has a relatively large rear-swept trailing edge, without worrying about the efficiency loss and drag cost in the conventional sense.
Thus, for "Wujian-Y" with a Lambda wing, to generate a leftward yaw moment, the left flap is deflected by a certain amount, while the all-moving wing tip compensates for the roll. The yaw moment is enhanced by both the lateral force of the flap and the asymmetric resistance, achieving twice the result with half the effort.
"Wujian-X" with a diamond-shaped wing is similar, but the direction of the flap's lateral force is opposite. Whether it is the all-moving wing tip compensating for the swept-back (or forward-swept) flap, or the swept-back (or forward-swept) flap compensating for the all-moving wing tip, this is the current hot topic of the "3x8 or 8x3" issue. As long as the goal of controlling yaw without causing an "unplanned" roll is achieved, any explanation is acceptable.
Of course, the all-moving wing tip is not as simple as breaking through a layer of paper. This design changes the stress structure along the entire chord length into a single-point stress structure through the pivot. This poses challenges for structural rigidity, rotational sensitivity, stability, mechanical reliability, and durability. This technology is related to the all-moving vertical tail technology. The advantages of the all-moving vertical tail are well known worldwide, but the all-moving vertical tail is only used by the J-20 and Su-57 globally, and only the J-20 is mass-produced. There is a reason for this.
However, after solving the problem and achieving "tailless freedom," the sky becomes incredibly broad.
At the parade, CCTV deliberately pointed out that these two Wujians are "unmanned air superiority aircraft." The term "unmanned combat aircraft" (UCAV) has been around for some time, and later terms like "faithful wingman" and "unmanned wingman" have also been used, but the core is always auxiliary aircraft supporting manned fighters.
The US Air Force started with the MQ-1 "Predator A" and MQ-9 "Predator B" for reconnaissance and strike, then introduced the jet-powered but still primarily reconnaissance-oriented MQ-20 "Predator C," followed by the "external sensors and weapons bay" MQ-67, and now further developed into "collaborative combat aircraft" (CCA), currently competing between the YFQ-42 and YFQ-44. But no matter how it changes, it remains the same: these are subsonic, medium-maneuverable, medium-stealth, limited-capability auxiliary aircraft, mainly responsible for guarding posts, and at most delivering a knife when the manned lead aircraft enters combat.
The newly flown YFQ-42A has a combat capability comparable to the other two unmanned wingmen displayed at the parade
Actually, the positioning of "faithful wingman" itself indicates the problem. Traditionally, in a formation, the lead aircraft is piloted by an experienced pilot, leading the wingman in combat, mainly responsible for searching and attacking; the wingman is piloted by an inexperienced new pilot, operating under the command of the lead aircraft, mainly responsible for observing and protecting.
When there is insufficient confidence in unmanned combat aircraft, this "senior-junior order" makes sense, but it also sets a ceiling on the potential of unmanned combat aircraft from the outset. In fact, the YFQ-42 and YFQ-44 are not even qualified as "faithful wingmen." Subsonic, medium-maneuverable flight performance means they can't keep up with manned aircraft, and medium-level stealth performance can easily betray the location of stealthy manned aircraft.
The role of a "fully-fledged unmanned wingman" is still limited to guarding posts, delivering a knife when necessary, and even sacrificing itself to save the manned lead aircraft in case of danger. Undoubtedly, these tasks can be accomplished by "Wujian-X" and "Wujian-Y," but this would be a waste of their potential. It must be recognized that "Wujian-X" and "Wujian-Y" were never intended to be low-cost expendable drones, nor should they be used as such.
"Wujian-X" and "Wujian-Y" have speed, maneuverability, and stealth that meet the high standards of sixth-generation aircraft. They can serve as unmanned wingmen, but they are more adept at serving as unmanned vanguard. It can be said that Wujian is a special forces unit that goes deep behind enemy lines to listen, watch, guard, and execute missions, while CCA is just a children's militia on the village gate. This is the difference.
According to satellite imagery, the length of "Wujian-X" is 16.67 meters, and "Wujian-Y" is 14.63 meters. For comparison, the J-10C is 16.2 meters. The wingspans of the three are also similar. The maximum takeoff weight of the J-10C is 19.3 tons, and the normal takeoff weight is 14 tons. We can roughly assume that the takeoff weight of the J-10C is similar to that of the Wujian. To simplify, we assume that the maximum takeoff weight and normal takeoff weight of "Wujian-X" and "Wujian-Y" are both 20 tons and 14 tons. The reason for this assumption is to ensure the aircraft's thrust-to-weight ratio and basic flight performance are similar. Considering that both Wujian have considerable internal weapon bays, but may not have external suspension capabilities, the normal takeoff weight of 14 tons is more important than the maximum takeoff weight.
The J-10C has an internal fuel capacity of 3,860 kg, meaning a fuel coefficient of 27.6%. In fourth-generation fighters, this is moderate, not too much or too little. The Su-27 is unusually high, reaching 40%, so the original design didn't include auxiliary tanks.
Since Wujian eliminates the cockpit and pilot, systems related to the pilot can be discarded, saving a lot of weight: the average pilot weight (including gear, pistol, helmet, etc.) is calculated at 70 kg; according to the Russian K-36D, the ejection seat is 90 kg; according to the F-15C and F-16C, the canopy is 85 kg; the display, control stick, and oxygen system are 55 kg. Altogether, that's 300 kg. So, if the J-10C removes the pilot, it can add 300 kg of fuel without increasing the takeoff weight.
Because there is no concern for pilot safety, Wujian aircraft can relax requirements on structural and system redundancy. I believe that reducing 200 kg of weight should not be difficult. If you are more radical, replacing hydraulic actuators with electric actuators can save even more weight. The J-10 basic design has been around for 30 years. In 30 years, technological advancements in structures, materials, and 3D printing, along with eliminating canards and vertical tails, could potentially reduce the J-10C's empty weight by 1,200 kg.
Thus, the Wujian's internal fuel increases to 5,560 kg, with a fuel coefficient rising to 39.7%. Compared to the Su-27, theoretically, the range without refueling can reach over 3,500 km. The reduction in drag from the absence of canards and vertical tails can further increase the range, and the Wujian's range could even exceed 4,000 km.
Unmanned Air Superiority Fighters Use the WS-10 Series Engine Video Screenshot
If Wujian uses the same WS-10B (afterburning 135 kN, military thrust 89.2 kN) as the J-10C, the aircraft's thrust-to-weight ratio can reach 1.04. With good drag reduction, the aircraft's maximum speed can rise to M2.2 or even M2.5. For comparison, the Su-27 with a similar thrust-to-weight ratio reaches M2.35, and the F-15C reaches M2.5. At the same time, the Wujian's military thrust-to-weight ratio can reach 0.65, close to the F-22's 0.7. Here, drag reduction can once again play a role, making super cruise possible.
In terms of maneuverability, visually "Wujian-X" has a larger wing area than the J-10C, but "Wujian-Y" has a more favorable lift-to-drag ratio with its Lambda wing. The J-10C has a wing loading of 381 kg per square meter, comparable to the F-22's 377. There is no evidence that either of the two Wujian uses vector thrust, but considering the large control surfaces on the rear edge of the wings, ensuring the Wujian's decent maneuverability.
In summary, the above parameters mean that the Wujian is a high-performance fighter, and it has omnidirectional stealth and deep penetration capabilities. This means the Wujian is more suitable for independent operations behind enemy lines. In other words, the cooperation between the Wujian and manned aircraft will be a loose coordination.
In cooperation with sixth-generation aircraft, the Wujian will thrive and wreak havoc deep behind enemy lines; in cooperation with fifth-generation aircraft, the stealth of the J-20 and J-35 will still be sufficient in shallow depths. With the Wujian's advanced scouting and hunting, they can control a larger battlefield depth, allowing us to conduct air battles that would typically require fifth-generation aircraft against sixth-generation ones; and in cooperation with fourth-generation aircraft, the J-16 and J-10 on our side still have enough survival capability, while the Wujian can penetrate deeper into the front lines, operating freely and wreaking havoc.
In this Wujian competition, China has made promises, and China has delivered. The Wujian at the parade have even received tactical numbers. Meanwhile, across the Pacific, the United States has not even reached the stage of making promises. After the current CCA program, the U.S. Air Force plans to continue pushing the CCA Increment 2 program, which requires drones to be supersonic, highly stealthy, and highly maneuverable. However, this plan hasn't even completed its PPT. Even though the U.S. now has the Wujian as a blueprint, whether it can keep up is full of "if" scenarios.
Compared to the Air Force, the urgency is greater for the U.S. Navy. The Navy's sixth-generation plan FA-XX has been going up and down, and now needs to make way for the Air Force's F-47. Originally, the F-18E/F could handle the J-15/T, and the F-35C could counter the J-35 without a clear disadvantage. But if the Wujian is deployed on carriers, the U.S. carrier will have no chance of survival.
J-36 and J-50
Although the Wujian is not yet suitable for direct deployment on carriers, it has great potential for carrier deployment.
For unmanned combat aircraft, the biggest challenge has always been autonomous operations: identifying targets is not difficult, but distinguishing targets is. However, in the sea, the challenge of autonomously identifying targets is actually smaller. The appearance of warships is easy to recognize, and even image recognition can be used to accurately identify the type and hull number of ships, ensuring correct identification. Aircraft in the open ocean are easier to recognize. Previous civilian aircraft have ADS-B systems, and the identification of combat aircraft is simpler, as there are only a few of our own aircraft, making misfires less likely.
On the other hand, training pilots for carrier-based fighter jets is a world-class challenge, taking a long time, being costly, and requiring long-term maintenance of proficiency. Once the design and verification of the drone are complete, there are no issues with routine operational standardization and proficiency, as precise, agile, and standardized actions are what AI excels at.
Catapult takeoff is not a problem; precise landing can be achieved with cooperative landing guidance. In the U.S. Navy's pilot training, they have already considered eliminating the requirement for manual landings, as in actual use, automatic landings are mostly used.
There are many detailed issues in the operation of the deck, hangar, and elevator with manned aircraft, but there are no insurmountable technical barriers. Maintenance on the ship is no different in principle from that of manned aircraft.
This means that "Wujian-X" and "Wujian-Y" may have special advantages in carrier deployment. Of course, "Wujian-X" and "Wujian-Y" cannot simply go on board; they need to undergo carrier modifications. Dual nose wheels, tailhooks, and other are conventional adaptive modifications, none of which are insurmountable. The real challenge is the wings.
The diamond-shaped wings of "Wujian-X" and the Lambda wings of "Wujian-Y" are fine as air force aircraft, but to deploy on carriers, they need to improve low-altitude, low-speed lift characteristics. In this regard, the X-47B is a good reference. The X-47B uses a Lambda wing, with a sharp central diamond body that is beneficial for stealth and reduces drag; the relatively smaller swept-back wings on both sides provide a higher lift-to-drag ratio at low altitudes and low speeds, which is beneficial for carrier takeoff and landing, and also有利于 a longer range.
X-47B
The inherent conditions of "Wujian-X" and "Wujian-Y" are good, and they are both conducive to the modification of Lambda wings. "Wujian-Y" originally has a Lambda wing, which is relatively easy to extend the wings, or to reduce the sweep of the outer wing section while extending the wings, maintaining the lift center largely unchanged. The junction of the inner and outer wing sections is exactly the folding point of the wings. "Wujian-X" has a diamond-shaped wing, and adding a smaller-sweep outer wing section to the existing wingtip can form a Lambda wing, achieving the same purpose.
In the not-so-distant future, China's aircraft carriers might carry 12 J-35s as the basic air defense and air superiority force, 6 J-35Ss (comparable to the dual-seat J-20S) as the forward command and control and ISR nodes in the air battle, 12 J-15Ts as the basic force for anti-ship and ground attack, 6 J-15DTs as electronic warfare aircraft, 8 carrier-based Wujians as penetrating air superiority forces, 4 KJ-600s as early warning and command, and need 8 MQ-25-class refueling and anti-submarine aircraft, plus 4 tiltrotor search and rescue aircraft. Once formed, this will be a formidable ideal carrier-based air force.
The "Chinese MQ-25" is not yet seen in development, but it will exist. Using partner refueling for fighter jets only solves the issue of having or not having, but the fuel consumption is high, the refueling efficiency is low, and the transferable fuel volume is insufficient. A dedicated carrier-based refueling aircraft is needed. Perhaps we can take the "unmanned wingman" resembling "Feihong 97" seen at the parade as a starting point and scale it up. The difficulty of deploying such aircraft on carriers should be lower than that of Wujian, and it can also be a useful anti-submarine patrol aircraft and command and control relay node.
North and South sixth-generation aircraft can also be deployed on carriers, but their large size and heavy weight are disadvantages. The quantity of carrier-based aviation forces is still very important. Wujian and J-15/T, J-35/S can form a balanced and reliable maritime air force. And all of this starts with solving the flight control problems of supersonic high-maneuverability tailless aircraft.
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