As far as I know, this fighter looks very avant-garde and adopts many advanced technologies (the F-22 mainly adopts existing mature technologies). But:
1) Due to design problems, its rolling rate is not as good as that of F-22.
2) There are technical hidden dangers in aerial refueling.
3) Because its technology is too advanced, it is not very reliable.
4) A single F-22 is worth1.200 million dollars, and this guy is more expensive.
The above is the main reason for its defeat, and the following are the specific parameters (boredom)
YF-23A shows the same design concept as YF-22A, and also reflects the understanding of Northrop/McDonnell Douglas design team on future air combat requirements. ?
Overall Layout The overall layout of YF-23A largely inherits the characteristics of the conceptual design scheme of Northrop Corporation. The layout of rhombic wing and V-shaped tail is between the traditional normal layout and tail layout. Single seat, double engine, middle wing, abdominal air intake. ?
Like YF-22A, YF-23A does not adopt the duck layout that was once very popular. In fact, we can see the tendency of Americans from the fact that none of the seven companies adopt duck layout. To some extent, this is influenced by the general dynamics at the G-7 meeting a few years ago-Harry Hilllake said that "the best position of the duck wing is on someone else's plane." The author mentioned in Wings of the King that one of the reasons for rejecting the duck layout is the balance problem. If the canard is designed according to the principle of effective pitch control, then the canard cannot balance the huge bow moment generated by the wing high-lift device. If it is necessary to trim the high-lift device, then the canard must be enlarged and the downwash of the wing will be increased, thus weakening the high-lift effect. Moreover, in order to prevent deep stall, it may be necessary to increase the flat tail. On the other hand, for transonic area rule, it is difficult for canard to meet the requirements of transonic area rule, which increases the difficulty of fuselage design and supersonic drag, which is especially unacceptable for ATF (especially YF-23A) which emphasizes overflight. ?
Another important reason for rejecting duck layout is invisibility. It is difficult to unify the position, size, plane shape and stealth requirements of canards. An important principle of stealth design is to minimize (but inevitably) the discontinuity on the surface of the body (especially in the head-on direction), and it is very difficult for canards to make swords. If we want to minimize the number of main beams corresponding to the leading and trailing edges of the wing (that is, the leading and trailing edges are parallel), it will bring greater design difficulty. ?
Although according to the requirements of the US Air Force, ATF must give consideration to stealth and maneuverability, the design ideas of different companies are different, and the aircraft performance will inevitably be different. Judging from the fact that YF-23A finally chose the V-tail instead of the traditional four-tail layout, Northrop's intention to pursue stealth is quite obvious, and their design can greatly reduce the cross-sectional area of the side radar of the aircraft. Due to the reduction of a pair of tail wings, the weight and resistance of the aircraft can also be reduced, which is also helpful to improve the patrol ability. But it is followed by the efficiency of control surface and the complexity of flight control system. ?
In order to meet the requirements of "cross-theater voyage", ATF must have a large enough fuel load, and considering the stealth requirement (the aircraft cannot be externally attached to the auxiliary fuel tank), all fuel must be loaded from the internal fuel tank. Therefore, both YF-22A and YF-23A must provide enough inner product-almost twice as much as F- 15! From the perspective of fuselage size, the length of YF-23A fuselage has obviously increased, but it is still limited, so the increase of its internal area must mainly come from the increase of aircraft cross-sectional area. Considering transonic/supersonic drag, the increase of aircraft cross-sectional area is not conducive to the design of aircraft according to transonic area law. Properly lengthening the fuselage is helpful to smooth the longitudinal cross-sectional distribution of the aircraft and reduce the transonic/supersonic drag. However, the lengthening of the fuselage will inevitably lead to the increase of the longitudinal moment of inertia of the aircraft, which is unfavorable to improve the agility and precise control ability of the aircraft. The fuselage length of SUI-27 is similar to that of YF-23A. A pilot who flew over Sui -27 said that this kind of aircraft has a large control inertia and is not so good at flying. ?
In fact, the differences in design ideas between YF-23A and YF-22A can be seen only from the characteristics of fuselage design. Judging from the oil load in the engine, the oil load of YF-23A is 10.9 ton, and that of YF-22A is 1 1.35 ton. Considering that the designed bomb bay in the aircraft has the same bomb load (the design is because the battle bomb bay of YF-23A is still on the drawing), the internal volume of YF-23A will not be larger than that of YF-22A. However, the fuselage length of YF-23a is obviously longer than that of YF-22A (the actual fuselage length of YF-23A exceeds 18m due to the tail support and flat tail), which means that YF-23A can obtain a smoother cross-sectional overall cloth (that is, smaller transonic/supersonic drag) and of course a larger longitudinal moment of inertia, even if the maximum cross-sectional area of the aircraft is equivalent. It is not difficult to see that YF-23A and YF-22A are diametrically opposed to each other in order to solve the resistance problem caused by the increase of cross-sectional area. The former chooses speed performance at the expense of agility and precise control. This also reflects the positioning of the two groups for future fighters to a certain extent. In appearance, the fuselage of YF-23A is quite similar to that of Lockheed SR-7 1 Blackbird. It looks like the front fuselage and two independent engine compartments are directly embedded into an integral wing. The front fuselage is mainly equipped with radar cabin, cockpit, front landing gear cabin, avionics cabin and missile cabin. The front section of the front fuselage is approximately a hexagon with rounded corners symmetrical up and down, and then it gradually transforms into a circular section, and finally it is completely integrated with the wing in the middle section of the fuselage. The cross sections of the rear inlet and engine compartment are still trapezoidal, and they transition to the "beaver tail" of the wing or rear fuselage in a very smooth curve, which helps to reduce the interference resistance between them. As mentioned above, the Air Force canceled the requirement of using the thrust reverser, but Northrop did not modify the design, and formed a very obvious "groove" in the rear fuselage, which brought unnecessary resistance increment. ?
At high angle of attack, the strake wing layout has more advantages in lift characteristics than the canard layout, which is also one of the factors that affect Northrop's overall layout of YF-23A. As far as the traditional strake is concerned, the increase of its length (area) is obviously beneficial to improve the lift at high angle of attack. However, the greater the extension length, the greater the pitching moment at high angle of attack; Become a factor that restricts the size of the sidebar. But obviously YF-23A edging is different from the traditional edging on the third generation computers. Its three-stage linear narrow strip design is quite unique, extending from the leading edge of the wing to the top of the radome. This kind of edging is very similar to YF-22A's. ?
The strakes of YF-23A have the following functions: generating strake vortex, inducing vortex lift on the wing and improving the lift characteristics of the wing; The boundary layer energy on the upper surface of the wing is supplemented by the strake vortex to delay the stall of the wing; Play the role of pneumatic "wing knife" to prevent the accumulation of boundary layer to the tip and delay the separation of tip airflow (in fact, due to the large tip ratio of YF-23A wing, there may be an obvious trend of tip separation at high speed or high angle of attack); The separation of head vortex at high angle of attack provides better pitching and directional stability-until the third generation supersonic fighter, the asymmetric separation of head vortex at high angle of attack has not been solved, which is an important factor restricting the aircraft from entering the post-stall field. ?
However, from the traditional point of view, it is still a question whether the edge of YF-23A is too small to generate strong enough eddy current to play its due role. If so, one possibility is that the action principle of strakes is different from that of traditional strakes, and the other possibility is that there are other auxiliary measures to help improve the lift characteristics of wings. It is mentioned that "the vortex generated by the nose and the inner wing has no effect on the tail wing", which may mean that there may be some measures to generate vortex inside the YF-23A wing, which plays a role similar to the strake vortex. There are two control panels at the top of the inlet of YF-22A to control the vortex on the upper surface of the wing. YF-23A may also have a similar design-there is a bleed gap in the inlet boundary layer inside its wing, which does not rule out the possibility that the boundary layer airflow will be exhausted after acceleration, so as to improve the airflow state on the upper surface of the wing. ?
The huge diamond wing of the wing can be regarded as one of the most prominent appearance features of YF-23A. The leading edge of the wing is swept back 40 degrees, the trailing edge is swept forward 40 degrees and the dihedral angle is 2 degrees. The wing area is 88.26 square meters, the aspect ratio is 2.0, and the tip ratio is as high as 12.2. The most important factor for Northrop to choose such a dominant wing plane shape is stealth. The stealth technology of YF-23A is inherited from B-2, and they are similar-one of them is the X-shaped four-leaf reflection characteristic. In order to realize four-lobe reflection, the leading edge and trailing edge of the wing must be parallel in the horizontal plane. In this way, Northrop has no more choices: either adopt the trailing edge swept design to form a swept trapezoidal wing, which is basically similar to the wing of B-2; Or the trailing edge is swept forward to form a symmetrical rhombic wing. ?
The advantage of adopting swept trapezoidal wing is that the choice of swept angle is limited and can be optimized as needed; However, compared with triangle, the disadvantages are obvious: low structural efficiency; The internal volume is small, which has a great influence on ATF that needs to sail across the theater; Aeroelastic divergence problem is obvious; The selection of relative thickness of wing is limited, which is not conducive to choosing a smaller relative thickness to reduce supersonic drag. If the trailing edge forward-swept design is selected, when the leading edge forward-swept angle (trailing edge forward-swept angle) of the wing is small, the wing is closer to the thin wing with small sweep angle commonly used by Northrop (such as F-5 and YF- 17), and the problems it faces are the same as those of the swept trapezoidal wing-extraordinary endurance and excellent supersonic performance are huge contradictions that are difficult to solve. Symmetrical rhombic wings with large sweep angle are beneficial to stealth-the sweep angle of F-117 is as high as 66.7 degrees, in order to deflect radar waves greatly-but aerodynamic restrictions have rejected this possibility: the aspect ratio is too small and the aerodynamic efficiency is extremely low, so it is a problem whether this kind of aircraft can fly. Moreover, the trailing edge forward sweep angle is too large, which will make the efficiency of the wing trailing edge lift/control device drop sharply until it is unacceptable. ?
On the whole, only a symmetrical rhombus wing with moderate sweep angle can achieve a satisfactory balance in stealth, endurance and aerodynamics. As for why the 40-degree sweepback angle is chosen, the author thinks that the favorable interference of optimizing the strake vortex should be one of the influencing factors when other conditions are basically met. However, even so, the trailing edge forward sweep angle of 40 degrees seriously affects the efficiency of the aerodynamic device at the trailing edge of the wing: YF-23A must use a larger flap downward deflection angle to ensure the high-lift effect, but this increases the separation trend of the boundary layer on the upper surface of the wing, which not only increases the difficulty of boundary layer control, but also reduces the high-lift effect in turn. On the other hand, the aileron efficiency of YF-23A is not good, which leads to its roll rate not meeting the requirements, and finally affects the results of competitive flight test. ?
As far as the characteristics of wings are concerned, Northrop's priority is stealth, followed by supersonic speed and endurance, and finally maneuverability and agility. ?
In order to improve the lift characteristics of the wing, YF-23A adopts the design of leading edge maneuvering flap, and its span is about 2/3 of the span. It is reported that the aircraft adopts slat design, but the characteristics of slat can not be seen in the flight test photos of YF-23A. Moreover, from the stealth point of view, when the slat is extended, the slit formed will become a good reflector of electromagnetic waves, which is absolutely unacceptable to Northrop. ?
In fact, the leading edge flap still has an adverse effect on the stealth characteristics of the aircraft. The best solution is the mission adaptive wing technology verified on AFTI/F-11,which can avoid the discontinuity and slit on the wing surface, but it is a pity that this technology has not been put into practice until today. In this respect, YF-22A adopts the diamond groove design inherited from F- 1 17, which makes it a low radar reflection area when the flap is deflected. YF-23A, which strives for stealth, does not consider this detail. The only explanation is that in the typical combat state of the aircraft (overflight), the wings are symmetrical and there is no need to deflect the flaps. ?
The aerodynamic control surface located at the trailing edge of YF-23A wing is distinctive, which can be regarded as the highlight of YF-23A. Some data show that the inside of the wing is a flap and the outside is an aileron, but the actual situation is far from simple. The simple distinction between flaps and ailerons does not conform to the design idea of "one thing with multiple functions" embodied by Northrop on YF-23A. According to the flight test photos of YF-23A, the inner and outer control surfaces are involved in the lift and roll control. Therefore, the author defines it as "multi-purpose flaperon". The reason for saying "multi-purpose" is that these two pairs of control surfaces not only have the functions of traditional flaps, but also have the functions of speed brake and drag rudder. When the aileron of the inner flap deflects downwards at the same time, the wing of the outer flap tilts upwards at the same time, so as to ensure that the wing does not generate additional lift increment, and at the same time, it generates symmetrical aerodynamic drag, which plays the role of speed brake. When only one aileron tilts up/down, it will produce little symmetrical resistance and act as a resistance rudder-this must have inherited the design of B-2. This design is quite novel and effectively reduces the weight, but the complexity and development risk of the flight control system inevitably increase.
Tail wing? The design of the V-tail was not initiated by Northrop. 1956, French C.M. 175 trainer used V-tail. The same is true of Lockheed F- 1 17A (but it is special and only provides directional control). However, YF-23A takes the lead in adopting the V-tail design in future fighters that emphasize maneuverability. ?
The V-tail design of YF-23A is quite unique. In order to ensure the reflection characteristics of 4-lobe radar, the projection of the front and rear edges of the flat tail on the horizontal plane is parallel to the front and rear edges of the wing respectively. This makes the tail of the plane look quite huge. Considering that most radar reflections occur in the range of 30 degrees from the horizontal plane, YF-23A adopts the design of tilting the tail by 40 degrees to ensure that radar waves will not be reflected back to the receiver, but the corresponding tail efficiency is also reduced. In contrast, YF-22A adopts the design of 9 1 with an inclination of 27 degrees. The edge of F stealth design is the result of the comprehensive balance of stealth and maneuverability. According to the public statement, YF-23A arranged the tail at a wide distance for the requirements of maneuverability at high angle of attack, completely avoiding the vortex inside the strake and wing, thus improving the pitch, roll and yaw control in the intense maneuvering state. ?
As far as stealth is concerned, the tail design of YF-23A is obviously successful, but its aerodynamic efficiency is inevitably worrying. Yaw, pitch, roll and two-axis control are all considered. It's good to have multiple functions, but it is often overlooked that the total control ability of the tail is limited. If one axis occupies more control ability, it will inevitably weaken the control ability of other axes. When the aircraft is in a complex state, the tail of YF-23A may not be able to take care of both. Looking back at the post-stall flight test of the F-22, we can know that the control load of the control surface is quite heavy and the thrust vector control is needed. Of course, from another point of view, maybe Northrop didn't consider the control problem of super-fire attack angle flight at all. It can ensure that aerodynamic divergence does not occur in the range of high angle of attack (Northrop said that wind tunnel data show that YF-23A can fly stably at all angles of attack, but the angle of attack of YF-23A will not exceed 25 degrees in the end), which is the limit made by Northrop in this respect. After all, maneuverability is the first priority of YF-23A, not to mention post-stall maneuverability. ?
Flight control system and thrust vector control? After long-term verification, the layout with control is quite mature in ATF design stage. It is not surprising that YF-23A applies the following control layout technology and adopts fly-by-wire flight control system for this purpose. However, due to the failure of the final competition, the outside world knows little about the details of the flight control system of the aircraft. As mentioned above, YF-23A has a remarkable feature of "one thing has multiple functions" in design. Due to the reduction of control surfaces and corresponding control mechanisms, it is helpful to reduce the weight and drag of the aircraft and improve the stealth characteristics of the aircraft. However, in addition to the control surface load problem, this design is bound to face the test of the complexity of the flight control system. Of course, a similar design can be seen on the successful B-2, but it must be noted that this multi-purpose design is not a big problem for bombers that do not need complex maneuvers; However, the deflection control of fighter control surface is quite complicated even under normal circumstances, and the multi-purpose design will inevitably increase the complexity and development risk of flight control system. If unconventional flight is to be considered, the design difficulty of flight control system can be imagined. The programming of flight control software is one of the difficulties in the design of flight control system. Since the practical application of the fly-by-wire flight control system, most first-class fighters have stumbled on it. 1On April 25th, 992, YF-22A crashed into the ground due to "pilot-induced oscillation" caused by flight control software problems. Later, during the flight test of the F-22, the flight control software was continuously improved and upgraded. Even the YF-22A flight control system designed basically according to the convention has so many troubles, not to mention the unconventional design of the YF-23A flight control system. The US Air Force is relatively accurate in judging design risks. ?
If YF-23A adopts thrust vector control system, it will alleviate the control surface load problem caused by multi-purpose, and also help to improve maneuverability and agility. But Northrop finally gave up the thrust vector to ensure its primary goal-stealth ability. Because if the thrust vector control technology is to be applied, the design of the rear fuselage must be changed, which not only increases the weight of the aircraft, but also increases the radar cross-sectional area of the aircraft (mainly backward) and reduces the infrared stealth ability-because the slotted tail nozzle design must be cancelled. This is not in line with Northrop's design ideas. ?
Air intake/exhaust system? The inlet of the engine and the first stage compressor are the main sources of radar cross-sectional area in front of the jet, and a little carelessness in design may lead to all the efforts made for stealth. Aircraft flying in the middle and high altitude, such as F- 1 17 and B-2, are mainly threatened from below, so the inlet and nozzle can be placed on the upper surface of the fuselage to block the main radar reflection characteristics. But for air-to-air fighters, this threat law obviously does not apply. If the possibility of threats from all directions is equal, what principles should be used to design aircraft in this case? No one is satisfied with the answer. Judging from the design of YF-23A, in the absence of applicable stealth rules, the inlet design of YF-23A chose to follow the requirements of maneuverability and inlet. ?
Engine inlet is a cavity structure, which is a good radar wave reflector. The high-speed rotating blades of the first stage compressor of the engine are not only strong reflection sources, but also the reflected spectrum is enough to be used as the identification feature of the aircraft model. To solve the problem of invisibility, we must first solve these two troubles. One of the solutions is occlusion. The shock cone of F-11and Phantom can shield the reflected waves in the inlet and compressor to some extent, but the problem is that the shock cone itself is a strong radar scattering source. Another more commonly used way is the S-shaped air inlet, and wave-absorbing materials are laid at the air inlet. However, the S-shaped inlet is not as simple as imagined, and improper design may lead to serious total pressure loss. Without a lot of verification, the design will inevitably suffer. ?
The inlet of YF-23A is located under the wing near the leading edge, which is similar to the design of Su -27, and is obviously the consideration of inlet requirements under high angle of attack. Its cross section is trapezoidal, and it is oblique in vertical plane and slightly oblique underwater, which can improve the intake efficiency under the condition of large angle of attack and sideslip. In front of the air inlet, a porous boundary layer suction device (unpainted area on the lower surface of the wing) is designed and discharged through the upper surface of the wing. Because the air inlet is close to the leading edge of the wing and the thickness of the boundary layer is not large, it is not necessary to use a large boundary layer partition, which is helpful to reduce the radar reflection characteristics. An auxiliary intake valve (trapezoidal plate with serrated trailing edge, located near the boundary layer discharge seam) is also designed on the engine compartment surface to meet the intake needs of the engine under takeoff and landing and low speed conditions. According to the stealth principle, the inlet bends inward and upward from the inlet, and the compressor blades can't be seen from the front, so a good stealth effect can be obtained. In addition, YF-23A adopts fixed inlet design to avoid radar reflection caused by gaps and steps between adjustable inclined plates of adjustable inlet. The compression ramp is designed as a two-wave system and optimized according to the estimated cruise speed of YF-23A. ?
The engine nozzle design of YF-23A has obvious B-2 style. The grooved nozzle is located on the flat "beaver tail" between the V-shaped tails and is lined with heat-resistant materials. The top of the nozzle is hinged with a borderless adjusting plate for adjusting the size of the nozzle. Under the shield of beaver tail, V-tail and groove side wall, the hot jet from the combustion chamber is mixed with cold air in the groove section to cool down (the binary rectangular nozzle makes the jet mix with the surrounding air more easily), and then it is discharged outside the aircraft, and its infrared characteristics are obviously lower than those of conventional fighters. In addition to the stealth function, the author speculates that the nozzle design of YF-23A may also have the function of ejection and high lift, and the V-shaped tail plays a role similar to the end plate to enhance the high lift effect. However, this speculation has not been confirmed by the data. ?
Engine? Engine is the core component of aircraft, and the superior performance of YF-23A is largely based on the huge thrust of YF-119/120. Ultra-patrol capability and long-distance voyage across war zones put forward extremely strict requirements for engines. In order to meet the performance requirements, it is necessary to adopt a high-pressure compressor with a medium pressure increase ratio, a low-pressure compressor with a large pressure increase ratio, a high temperature in front of the turbine and a large thrust in the afterburner state. ?
In order to meet the requirements of afterburning thrust, GE chose variable cycle technology. Its YF- 120 engine adopts a special variable area external duct ejector, and the bypass ratio is changed by controlling the air flow rate of the internal and external ducts. Under supersonic cruise condition, YF- 120 works in a manner close to that of a turbojet engine (bypass ratio is close to zero), and only a small amount of external bypass bleed air is used for cooling; In subsonic flight, YF- 120 works as a turbofan engine (the maximum bypass ratio is about 0.3). YF- 120 is a double-rotor scheme, which adopts coaxial inversion technology, two-stage low-pressure compressor and only one stage high-low pressure turbine. Three-redundancy digital engine control module is adopted. Compared with F- 100, the number of parts is 40% less. The military thrust of YF- 120 is as high as 125 kn, even exceeding the afterburning thrust of early F- 100. ?
Pu Hui chose a relatively conservative turbofan engine scheme. Of course, the design has made remarkable progress, which makes YF- 1 19 meet the requirements of JAFE even without variable cycle technology. YF- 1 19 is also a double-rotor scheme, with three stages of low-pressure compressor, six stages of high-pressure compressor and one stage of high-and low-pressure turbine. Its afterburning thrust is obviously lower than YF- 120, only 97.9 kn. Interestingly enough, the first practical variable cycle engine J-58 (for SR-7 1) was developed by Pratt & Whitney in 1950s. Pu Hui did not give any explanation for why he gave up his original technology. Later, Ge admitted that the technology of YF 120 was somewhat advanced, and the risk was indeed higher than that of YF 1 19. ?
Weapon system? Because ATF temporarily gave up the requirement of ground attack capability, there is no ground attack weapon on the replacement weapon of YF-23A. The main air-to-air weapons originally prepared for ATF are advanced medium-range air-to-air missiles (AMRAAM, later AIM- 120) and advanced short-range air-to-air missiles (ASRAAM, later AIM- 132). Because the progress of AIM- 132 is seriously lagging behind, the US Air Force is forced to take the advanced rattlesnake modification (namely AIM-9X) as an emergency measure. Today, AIM-9X and AIM- 120 have become the main weapons of the F/A-22. ?
YF-23A inherited the design of the internal weapon cabin of Northrop's original scheme. The combat missile cabin and the main weapon cabin are arranged in series in the front fuselage. The combat missile cabin is very small and can only accommodate two AIM-9 missiles. The main weapon bay is large, which can accommodate four AIM- 120 missiles. The bomb load is the same as YF-22A. Because the wing of AIM- 120 is reduced after improvement, the main weapon bay of F/A-22 can hold six pieces. However, YF-23A arranges AIM- 120A in a staggered manner, which is different from the symmetrical arrangement of YF-22A, indicating that its main weapon bay size may be small, so it may not be able to accommodate six AIM- 120 variants. It is mentioned that YF-23A' s main weapon bay pylon can be lifted and lowered. When it is necessary to launch AIM- 120, the pylon extends out of the plane, and the missile is placed in the free stream before launching. This mode is different from the ejection mode of YF-22A, which completely avoids the possibility of abnormal state change when the missile passes through the air flow on the fuselage surface. Of course, the price of weight and inner product is inevitable. ?
YF-23A does not mention the lock/launch mode of AIM-9. But this is actually a very interesting question. Because in the closed missile cabin, it is impossible for AIM-9 seeker to capture the target. ?
On this issue, the author has had a long discussion with many colleagues, watched the video of F-22 weapon system test repeatedly, and finally reached a relatively consistent view: in the combat state, the F-22 missile cabin is in the open state, and AIM-9X is deployed to solve the problem of seeker locking. It is entirely possible for YF-23A to adopt a similar model. Combined with the launch mode of AIM- 120, the author speculates that AIM-9 may also be mounted with a lifting pylon to extend AIM-9 out of the plane by opening the hatch in combat. Because AIM-9 completely extends out of the machine, there is no side guard of the fuselage, so it can get a better view than YF-22A, and there is no need for heat insulation/flame exhaust device on YF-22A. The opening state may give people a strange feeling, but in fact, the resistance of opening the hatch to extend the missile will not be greater than that of the traditional pylon, so it will not have much negative impact on the aircraft performance. The only problem with this mode is that the radar cross-sectional area of the aircraft will increase obviously in combat. However, in the case of air combat within line of sight in the future, radar stealth is of little significance; Secondly, the combat time of modern air combat is obviously shortened, and the fire exposure time is limited, which will not pose a serious threat to YF-23A. For ATF, especially YF-23A, not entering the battle is the best tactic. ?
In addition to air-to-air missiles, M-6 1 Vulcan guns will still be used as fixed weapons of ATF. M-6 1 is not installed on YF-23A, but according to the design scheme, the machine gun will be installed on the right side of the fuselage above the main weapon bay. ?
Maintainability design, maintenance cover and hatch? ATF is the first fighter plane to put forward the maintainability index at the beginning of design, and it is also the first fighter plane to invite the maintenance department to participate in the design stage. The US Air Force attaches so much importance to maintainability, which is largely influenced by F- 15A. When the F- 15A first came into service, there were many failures and planes fell down frequently, so it was called "the queen of hangar". ?
For traditional aircraft, the coverage of the maintenance cover on the fuselage surface is an important reference index to measure its maintainability. High coverage means that airborne equipment can be well connected, and crew members don't have to spend time on useless but necessary work-most typically, in order to get close to equipment A, equipment B, C and D must be removed first. After processing, put it back in reverse order, while B, C and D are actually meaningless for the maintenance of A ...?
However, for stealth aircraft, the situation is completely different. The existence of surface waves makes it possible for any opening on the fuselage surface to seriously damage the stealth characteristics of aircraft. Therefore, "never open the fuselage surface unless necessary" is the principle that stealth aircraft must follow when designing. In this case, how to improve the maintainability of the aircraft? One way is centralized processing. Instead of opening a maintenance cover where there is equipment that needs to be approached, we should determine a centralized area, concentrate all the equipment that is most frequently approached and has the largest maintenance amount, and solve it with a large maintenance cover. The second way is based on the first way, that is, try to use the unavoidable hatch as the maintenance cover. Such as weapon bay and landing gear bay. If the equipment or interfaces that need maintenance can be concentrated in these cabins, it may not even be necessary to open other maintenance covers on the surface of the fuselage. In order to ensure the consistency of the reflected light beam, all flaps and doors on the aircraft surface must be designed in a zigzag shape, and the projection of the serrated leading edge on the horizontal plane should be parallel to the main reflecting edge of the aircraft. However, unlike what is usually imagined, the design of multi-serrated leading edge is not the best measure to control radar reflection. This design is actually the result of invisibility and folding towels with weight requirements. From the point of view of stealth, the most ideal is the single sawtooth design. However, in order to ensure the structural strength of a single sawtooth, a corresponding weight price must be paid. Under the strict weight requirements of ATF, both YF-23A and YF-22A adopt multi-sawtooth design. However, on the later F-22, we can see that with the approval of the Air Force, the number of serrations was reduced to improve the stealth characteristics.