The YF-23 lost out to the F-22 in the competition and is definitely not in service in the US. The prototype is probably a research piece for the next generation of fighters, or it's in an aviation museum somewhere.
From what I understand, this fighter is very avant-garde in appearance, and utilizes a lot of advanced technology (the F-22 utilizes mostly existing mature technology). But:
1) It has less roll rate than the F-22 due to its form factor. 2) There are technical pitfalls in aerial refueling. 3) It is so far ahead of its time due to the technology it uses that it is not too reliable. 4) The F-22 is worth 120 million dollars per unit, this guy is more expensive.The above are the main reasons for its failure, here are the specific parameters (rather boring)
The YF-23A demonstrated a completely different design concept from the YF-22A, and reflected the Northrop/McDonnell Douglas design team's understanding of the future requirements of air warfare.
The overall layout of the YF-23A is largely inherited from the Northrop concept. Its diamond-shaped wing + V-shaped tail layout, between the traditional normal layout and the lame tail layout. The single-seat, twin-engine, center-monoplane, ventral air intake. Like the YF-22A, the YF-23A did not ultimately adopt the once-popular duck layout. In fact, the American preference can be seen in the fact that none of the seven companies' proposals adopted the duck layout. To some extent, this was influenced by General Dynamics' comments at the G7's powwow a few years ago - Harry Hillaker said "The best place for a duck wing is on somebody else's airplane." As the author mentioned in Wings of the King, one of the reasons for rejecting the duck layout was the leveling problem. If the duckwing is designed according to the principle of water capable of effective pitch control, then the duckwing will not be able to level the large low head moment generated by the wing's augmentation devices. If leveling is required, the duckwing must be enlarged and the downwash on the wing increased, which in turn weakens the lift effect. And to prevent deep stalls, it may be necessary to add a flat tail. On the other hand, in terms of the transonic area law, a large duck wing is difficult to meet the requirements of the transonic area law, which increases the fuselage design difficulty and supersonic drag - this is especially difficult to accept for the ATF (especially the YF I-23A), which emphasizes supersonic patrol. And another important reason for rejecting the duck layout was stealth. It is difficult to harmonize the position, size, and planform of the duck wing with stealth requirements. An important principle of stealth design is to minimize (but unavoidable) airframe surface (especially the head-on direction) of the discontinuity, and the duck wing is difficult to do exactly this sword. The desire to minimize the number of main beams corresponding to the leading and trailing edges of the wing (i.e., parallel leading and trailing edges) would present even greater design difficulties. While the ATF necessarily balances stealth and maneuverability according to USAF requirements, the design thinking of each company is different, and the performance bias of the aircraft is bound to be different. From the YF-23A ultimately chose a V-shaped tail instead of the traditional four-tail layout, Northrop's intention to pursue stealth is quite obvious, and their design can greatly reduce the aircraft's lateral radar reflection cross-sectional area. By reducing the pair of tail fins, the weight and drag of the aircraft can also be reduced, which will also help to improve the over-travel capability. However, the efficiency of the maneuvering surfaces and the complexity of the flight control system are also issues. In order to meet the requirements of "cross-theater range", the ATF must have a sufficiently large fuel capacity, and considering the stealth requirements (the aircraft can not be attached to the external tanks), all fuel must be loaded from the internal tanks. Therefore both the YF-122A and YF-123A must provide enough airframe volume - almost twice that of the F-115! In terms of fuselage dimensions, the YF I-23A's fuselage length has increased significantly, but is still limited, so its increased internal volume must come mainly from the increase in the airplane's cross-section. If considered in terms of trans/supersonic drag, the increase in aircraft cross-sectional area is not conducive to designing the aircraft in accordance with the trans-sonic area law. Appropriate elongation of the fuselage can help to smooth the longitudinal cross-sectional area distribution of the airplane and reduce the trans/ supersonic drag. However, fuselage lengthening inevitably leads to an increase in the longitudinal rotational inertia of the aircraft, which is unfavorable to the improvement of aircraft agility and precise control. The Su-27's fuselage length is similar to that of the YF-23A, and pilots who have flown the Su-27 say that the aircraft's maneuvering inertia is large and not so good. In fact, just from the characteristics of the fuselage design, we can see the difference in design thinking between the YF-23A and the YF-22A. In terms of fuel capacity, the YF-23A carries 10.9 tons of fuel, while the YF-22A carries 11.35 tons of fuel. Considering that the bomb bay is designed to carry the same amount of fuel (I say designed because the YF-23A's fighting bomb bay is still on the drawing board), the YF-23A's internal volume will not be larger than the YF-22A's. The length of the fuselage of the YF-23A is significantly longer than that of the YF-22A (the latter's tail strut and the flat tanks are not as long as the YF-22A's). (the latter's actual fuselage length is more than 18 meters due to the tail struts and flat tail), which means that even when the maximum cross-sectional area of the aircraft is comparable, the YF I-23A gets a smoother cross-sectional area distribution (i.e., less transverse/hypersonic drag), and, of course, a larger longitudinal moment of inertia. It is easy to see that in order to solve the drag problem caused by the increased cross-sectional area, the YF I 23A and the YF I 22A are diametrically opposed to each other, with the former choosing speed performance at the expense of agility and precise control. To a certain extent, this also reflects the positioning of the two groups for future fighters. Externally, the YF-23A's fuselage is a bit like that of the Lockheed SR-71 Blackbird, in that it looks as if the forward fuselage and two separate engine nacelles have been nested directly into a single wing. The front fuselage contains the radar bay, cockpit, front landing gear bay, avionics bay and missile bay. The forward fuselage section approximates a rounded hexagonal shape with symmetry at the top and bottom, then gradually transitions to a rounded cross-section, and finally merges completely with the wing at the mid-fuselage section. The rear air intakes and engine nacelles remained trapezoidal in cross-section and transitioned to the wing or rear fuselage's "beaver tail" in a very smooth curve, which helped to minimize interfering drag. As mentioned earlier, the Air Force eliminated the requirement for a thrust reverser, and Northrop did not modify the design to create a very pronounced "groove" in the rear fuselage that would have created an unnecessary drag increment. The side-strip side-strip wing layout has a greater advantage in lift characteristics than the duck layout at large angles of approach - one of the factors that influenced Northrop's choice of the YF-23A's overall layout. In the case of conventional sidebars, the increase in their spread (and also in their area) has a clear benefit in improving lift at large angles of approach. However, the larger the spread, the larger the upward pitching moment generated at large angles of approach; this becomes a factor that restricts the size of the sidebar. However, it is obvious that the YF-23A's side strips are different from the traditional side strips on the third generation aircraft. It has a three-section straight narrow side strip that extends from the leading edge of the wing all the way to the top of the radome. The strip is similar to that of the YF-22A.The YF-23A's side strips have several functions: generating vortices, inducing vortex lift on the wing and improving the wing's lift characteristics; utilizing the vortices to replenish energy for the wing's upper surface surface layer, delaying the wing's stall; and acting as an aerodynamic "wing knife" to prevent the surface layer from accumulating toward the wing tip, delaying the wing tip airflow separation (in fact, due to the YF-22A's narrow side strip design, it is quite similar to the YF-22A's side strip). Separation (in fact, due to the large root/tip ratio of the YF-23A wing, there may be an obvious tendency of wingtip separation under high speed or large angle of approach); separation of nose vortex under large angle of approach to provide better pitch and directional stability - Until the third generation of supersonic fighters, the problem of asymmetric separation of nose vortex under large angle of approach has not been solved, which is one of the limitations for the airplane to enter the field of overstall. aircraft from entering the realm of overstall.?
But if you look at it from a conventional point of view, it's doubtful that the YF-23A's sidebars are too small to generate a strong enough vortex to do what they're supposed to do. If it does, then one possibility is that the side strips work differently from conventional side strips, and another is that there are other aids to help improve the wing lift characteristics. It has been mentioned that "the vortices generated by the nose and inboard wing have little effect on the tail", which could mean that there may be some measure of vortex generation on the inboard side of the YF-23A wing, similar to the vortex of the side strips. There are two control panels at the top of the inlet ducts of the YF-22A to control vortices on the upper surfaces of the wing, and the YF-23A may have a similar design - there is a venting slit in the inboard side of the wing for the inlet deck, so we can't rule out the possibility that the airflow is accelerated from this deck to improve the airflow on the upper surfaces of the wing.The huge diamond-shaped wing can be considered one of the most prominent features of the YF-23A. One of them is the X-shaped four-flap reflection feature. To achieve quadruple flap reflection, the leading and trailing edges of the wings had to be parallel in the horizontal plane. This left Northrop with no more options: either a trailing edge swept-back design with a swept-back trapezoidal wing, essentially similar to the B-1/2's, or a trailing edge swept-forward design with a symmetrical diamond-shaped wing.
The advantage of using a swept-back trapezoidal wing is that the choice of swept-back angle is less restricted and can be optimized as needed, but the disadvantages compared to a delta wing are obvious: lower structural efficiency; smaller internal volume, especially for ATFs with cross-theater ranges; more pronounced aeroelastic dispersion; and a limited choice of relative thickness of the wing, which does not allow for the choice of smaller relative thicknesses to reduce supersonic drag. . If the trailing edge swept forward design is chosen, when the wing leading edge swept back (trailing edge swept forward angle) is small, this wing is closer to Northrop's usual small swept back thin wing (typical such as the F-5, YF-17), and faces the same problems as the swept back trapezoidal wing - extraordinary range and excellent supersonic performance is a huge contradiction that is difficult to be solved by this kind of wing. A symmetrical diamond-shaped wing with a large swept-back angle would be advantageous in terms of stealth - the F-117 uses a swept-back angle of up to 66.7 degrees in order to deflect radar waves dramatically - but aerodynamic constraints have already vetoed this possibility: the aspect ratio is too small, and aerodynamic efficiency is extremely low. was so small and aerodynamically inefficient that it was questionable whether such an airplane could be built to fly. And too much trailing-edge swept angle would dramatically reduce the efficiency of the wing trailing-edge lift/maneuvering mechanism to an unacceptable level. On balance, a symmetrical rhombic wing with a medium swept back angle was the only way to achieve a more satisfactory balance of stealth, range, and aerodynamics. As for why the 40-degree swept-back angle was chosen, I believe that the optimization of the favorable interference of the vortex of the sidebar should be one of the influencing factors, while other conditions are basically satisfied. However, even so, the 40-degree trailing edge swept angle also seriously affects the efficiency of the aerodynamic device at the trailing edge of the wing: the YF-23A must use a larger flap downward deflection angle to ensure the lift effect, but this in turn increases the tendency of the upper surface of the wing to separate from the appendage layer, which not only increases the difficulty of appendage layer control, but also reduces the lift effect in turn. On the other hand, the aileron efficiency of YF-23A was also poor, resulting in a roll rate that did not meet the requirements, which ultimately affected the results of the competition test flights. In terms of wing characteristics, Northrop prioritized stealth first, supersonic speed and range second, and maneuverability and agility last. In order to improve the wing lift characteristics, the YF I-23A adopts a leading edge maneuvering flap design with a spread of about 2/3 of the wingspan. Some sources claim that the aircraft adopts a slit-wing design, but the slit-wing feature cannot be seen on the YF-23A test flight photos. Moreover, from the stealth point of view, when the slit wing is extended, the slit formed will be a good reflector of electromagnetic waves, which is absolutely unacceptable to Northrop. The fact is that leading edge flaps still have a detrimental effect on the stealth characteristics of the aircraft. The best solution is the mission-adaptive wing technology validated on the AFTI/F-111, which avoids discontinuities and slits on the wing surface, although unfortunately this technology has not been put into practice until today. In response, the YF-22A adopts the diamond-shaped slot design inherited from the F-117, which makes the area a low radar reflection area when the flap is deflected. The YF-23A, which is a stealthy aircraft, does not take this detail into account, and the only explanation for this is that in the aircraft's typical operational state (over-travel), the wings are symmetrical and do not need to be deflected for the flaps. The design of the aerodynamic maneuvering surfaces located on the trailing edge of the YF I-23A's wings is quite distinctive and can be considered the highlight of the YF I-23A. Some sources say that the inner part of the wing is the flap and the outer part is the aileron, but the reality is far from that simple. The simple distinction between flaps and ailerons is not in line with Northrop's "multi-purpose" design concept embodied in the YF-23A. According to the test flight photos of YF-23A, both the inner and outer control surfaces are involved in lift and roll control. Therefore, the author has positioned the YF-23A as a "multi-purpose flap and aileron". The reason why I say "multi-purpose" is that these two pairs of control surfaces, in addition to the functions of traditional flaps, also have the functions of deceleration plate and drag rudder. When the inner flap is deflected downward at the same time, and the outer flap is deflected upward at the same time, it can generate symmetric aerodynamic drag and play the role of deceleration plate while ensuring that the wing does not generate additional lift increment; when only one side of the flap is upward, it can generate symmetric aerodynamic drag and play the role of deceleration plate. When only one side of the flap adopts upward/downward deflection, it generates small symmetrical drag and acts as a drag rudder - this must have been inherited and developed from the design of the B-1/2. This design was quite innovative and effectively reduced weight, but the complexity of the flight control system and the development risk inevitably increased.Tailplane?The V-shaped tailplane design was not a first for Northrop; it was adopted on the French C.M.175 trainer in 1956. So did Lockheed's F-117A (though it was more specialized, offering only directional control). But the YF-23A is the first to use a V-tail design on a future fighter that emphasizes maneuverability.?
The v-shaped tail design of the YF-23A is quite unique. In order to ensure the 4-wavelength radar reflection characteristics, the projection of the leading and trailing edges of the flat tail in the horizontal plane is parallel to the leading and trailing edges of the wing respectively. This makes the tail look quite huge. Considering that most of the radar reflection occurs within ±30 degrees from the horizontal, the YF-23A adopts a 40-degree outward tilt of the tail to ensure that the radar waves will not be reflected back to the receiver, but accordingly, the efficiency of the tail is also reduced. In contrast, the YF-22A adopts a 91-degree design with a 27-degree tilt, which is at the edge of the F stealth design and is the result of a combination of stealth and maneuverability trade-offs. According to public statements, the YF-23A has a wide-pitch tail arrangement for large-angle maneuverability, which completely avoids the side strips and inboard vortex, thus improving pitch, roll and yaw control under severe maneuvering conditions. The YF-23A's tail design is clearly a success as far as stealth is concerned, but its aerodynamic efficiency is not without concern. Yaw, pitch, roll, two-axis control all wrapped up. Multi-purpose is good, but an important but often overlooked point is: the total control capability of the tail is limited, a certain axis occupies more control capability, will inevitably weaken the control capability of other axes. When the airplane is stuck in a more complicated state, the YF-23A's tail may not be able to take care of both. Just look at the later F-122's overstall test flights, the control load on the maneuvering surfaces is quite heavy, and you have to add thrust vectoring control to make it work. Of course, thinking about it another way, it's possible that Northrop didn't even consider the control issues of overfire heading angle flight. Can ensure that the large angle range without aerodynamic dispersion (Northrop said, wind tunnel data show that the YF-23A can be stable flight in all the angle range, but the YF-23A test flight angle eventually did not exceed 25 degrees), is the limit of Northrop in this regard. After all, maneuverability is not the first priority of the YF-23A, not to mention overstall maneuverability. The flight control system and thrust vectoring?The YF-23A's follow-me layout has been proven over time to be quite mature during the ATF design phase, and it's not surprising that the YF-23A would apply the follow-me layout technology, and for that reason adopt the fly-by-wire control system. However, due to the failure of the final competition, the details of the flight control system of this aircraft are not well known to the outside world. As mentioned earlier, the YF-23A has a distinctive "multi-purpose" design. The reduction of maneuvering surfaces and the corresponding control mechanisms helped to reduce the weight and drag of the aircraft, and was also quite beneficial to the improvement of the stealth characteristics of the aircraft. However, in addition to the load on the maneuvering surfaces, one of the inevitable tests of this design is the complexity of the flight control system. Of course, in the already successful B1-2 can also see a similar design, but it must be seen that, for the bomber does not need to carry out complex maneuvers and account for this kind of multi-purpose design is not a big problem; however, even in the conventional conditions of the fighter aircraft maneuvering, its manipulation of the surface of the deflection control is also quite complex, multi-purpose design will inevitably increase the degree of complexity of the fly-control system and the risk of research and development. If we also consider the super routine flight, the design of the flight control system is difficult to imagine. The preparation of flight control software is one of the difficulties in the design of flight control system. Since the practical use of fly-by-wire flight control system, most of the first-class fighters have fallen into this. 25 April 1992, YF-22A because of the flight control software problems caused by "pilot-induced oscillations", crashed into the ground and was destroyed. Later, the F-22 flight control software was continuously improved and upgraded during the test flight phase. Even the YF-22A flight control system, which is basically designed according to the conventional design, has so many troubles, and the YF-23A flight control system, which is not designed according to the conventional design, is even more difficult to say. The USAF is still relatively accurate in its judgment of design risk.
If the YF-23A had adopted a thrust vectoring control system, the control surface loading problems associated with multi-purpose use would have been mitigated, and there would have been benefits in terms of improved maneuverability and agility. But Northrop ultimately abandoned thrust vectoring to ensure its primary goal, stealth capability. The reason was that applying thrust vectoring would have required changes to the aft fuselage design, which not only increased the weight of the aircraft, but also led to an increase in the aircraft's radar-reflected cross-sectional area (mainly rearward) and a reduction in infrared stealth capability - because that fluted tail nozzle design would have to be eliminated. This is not in line with Northrop's design thinking. Intake/exhaust system? The intake and engine stage pressurizers are the main source of radar-reflected cross-sectional area at the front of the jet, and the slightest miscalculation in their design can result in a total loss of stealth efforts. Normally, the main threat to aircraft flying at medium and high altitudes, such as the F-117 and B-2, comes from below, so intakes and nozzles can be placed on the upper surface of the fuselage to shield the main radar-reflecting features from the fuselage. However, for air control fighters, this law of threat clearly does not apply. If the threat is equally likely in all directions, on what basis should an aircraft be designed in such a case? There is no satisfactory answer for everyone. The YF-23A design, in the absence of applicable stealth rules, chose to follow maneuverability and air intake requirements for its air intake design. The engine intake is a cavity structure, itself a good reflector of radar waves. The high-speed rotating blades of the engine primary pressurizer are not only a strong reflection source, but their reflected wave spectrum is even enough to become an identifying feature of the aircraft model. To solve the stealth problem, we must first solve these two troubles. One of the ways to solve the problem is to mask the F-111, Mirage kind of ternary air intakes, its surge cone can be to a certain extent masked inside the intake channel and the reflections of the pressurizer, but the problem is that the surge cone itself is a strong radar scattering source. The other and more common route is the S-shaped inlet with wave-absorbing material inside the inlet. However, the S-shaped inlet is not as simple as one might think, and improper design can lead to severe total pressure loss. Without a lot of validation, the design is not without pain. The YF-23A's air intake is located under the wing near the leading edge, similar to the design of the Su-27, which is clearly a consideration for air intake requirements at large head-on angles. Its cross-section is trapezoidal, and in addition to the diagonal cut structure in the vertical plane, there is also a slight diagonal cut in the underwater plane, which can serve to improve the efficiency of air intake under the conditions of large angle of approach and sideslip. In front of the air inlet, there is a porous surface layer suction device (unpainted area on the lower surface of the wing), and it is discharged through the upper surface of the wing. Since the air inlet is close to the leading edge of the wing, the thickness of the surface layer is not large, so it is not necessary to use a large surface layer partition, which helps to reduce the radar reflection characteristics. An auxiliary intake door (a trapezoidal plate with a serrated trailing edge located next to the appendage discharge slit) is also designed on the engine nacelle dividing surface to fulfill the engine's air intake needs during takeoff and landing and at low speeds. According to the principle of stealth, the intake channel is curved inward and upward from the intake port, so that it is impossible to see the pressurizer blades from the front, and a better stealth effect can be obtained. In addition, the YF-23A adopts a fixed inlet design to avoid radar reflections from the gaps and steps between the adjustable inlet's regulating ramps. The compression ramp is a two-wave system design, optimized for the YF-23A's projected cruise speed. The YF-23A's engine nozzle design is distinctly B-2 in style. The fluted nozzles are located on a flat "beaver tail" between the V-shaped tail fins and are lined with heat-resistant material. The top of the nozzle is hinged with an infinitely shaped adjustment plate to adjust the size of the nozzle. Shielded by the beaver tail, the V-shaped tail, and the grooved sidewalls, the hot jet from the combustion chamber mixes with cold air in the grooved section to cool down (the binary rectangular nozzles make it easier for the jet to mix with the surrounding air), and then is discharged out of the aircraft, with the infrared signature significantly reduced compared to that of conventional fighters. In addition to stealth, I speculate that the YF-23A's nozzle design may also have the role of the pilot lift, V-shaped tail plays a similar role as the end plate, to enhance the effect of the lift. However, this speculation has not been confirmed by the information.Engine? The engine is the centerpiece of the aircraft, and much of the YF-23A's superior performance is based on the massive thrust of the YF-119/120. The over-travel capability and cross-theater range place extremely stringent demands on the engine. To meet the performance requirements, a high-pressure pressurized engine with a medium boost ratio, a low-pressure pressurized engine with a large boost ratio, higher pre-turbine temperatures, and a large unboosted state thrust are required.
To meet the unboosted thrust requirements, GE chose variable cycle technology. A special variable-area outer culvert pilot is used on its YF-120 engine to change the culvert ratio by controlling the inner and outer culvert air flow. In supersonic cruise, the YF-120 operates as a near turbojet engine (with a culvert ratio close to 0), with only a small amount of outer culvert induced air used for cooling; when flying at subsonic speeds, the YF-120 operates as a turbofan engine (with a maximum culvert ratio of about 0.3).The YF-120 is a twin-rotor scheme, with coaxial reversing technology, two low-pressure pressurized stages, and only one stage of both the high/low-pressure turbine. The YF-120 is a twin-rotor program with coaxial reversing technology, two-stage low-pressure compressor and one-stage high/low pressure turbine. Compared with the F-100, it has 40% fewer parts. And the YF-120's military thrust is up to 125 kN, even exceeding the earlier F-100's added thrust.? Pratt & Whitney, on the other hand, opted for a relatively conservative turbofan engine scheme, but of course there were significant design advances that allowed the YF-119 to meet JAFE requirements even without variable cycle technology.The YF-119 was also a twin-rotor scheme, with a 3-stage low-pressure pressurizer, a 6-stage high-pressure pressurizer, and one stage of each of the high/low-pressure turbines. Its unboosted thrust is significantly lower than the YF-120, at 97.9 kN. Interestingly enough, the first practical variable cycle engine, the J-58 (used in the SR-71), was developed by Pratt & Whitney in the 1950s. There was no explanation from Pratt & Whitney as to why they abandoned their first technology. GE later admitted that the YF120 was a bit ahead of its time and was indeed riskier than the YF119.? Weapons systems? There were no ground-attack weapons on the YF-23A's options, as the ATF dropped the requirement for ground-attack capability for the time being. The primary air-to-air weapons initially intended for the ATF were the Advanced Medium Range Air-to-Air Missile (AMRAAM, later AIM I-120) and the Advanced Short Range Air-to-Air Missile (ASRAAM, later AIM-132). Serious delays in the progress of the AIM-132 forced the USAF to use the Advanced Rattlesnake variant (i.e., the AIM-9X) as a contingency measure. Today, the AIM-9X and AIM-120 are the primary weapons of the F/A-22.? The YF I-23A inherited the internal weapons bay design from Northrop's original program. The combat missile bay and main weapon bay are arranged in tandem in the forward fuselage. The combat missile bay is small and can only hold two AIM-9 missiles. The main weapons bay is larger and can hold four AIM-120 missiles. The load capacity is the same as that of the YF-22A. Due to the reduced wing size of the modified AIM-120, six AIM-120 missiles can be accommodated in the main weapon bay of the F/A-22. However, the way the YF-23A arranges the AIM-120A is staggered from top to bottom and front to back, which is different from the symmetrical arrangement of the YF-22A, indicating that the size of its main weapon compartment may be smaller, and therefore may not be able to accommodate six AIM-120 variants. It has been mentioned that the YF-23A's main weapon bay mounts can be raised and lowered. When the AIM-120s need to be launched, the mounts are extended out of the aircraft, placing the missiles in the free stream before firing. This method, unlike the YF-22A's ejection launch, completely avoids the possibility of the missile's status changing abnormally as it traverses the airflow over the fuselage's surface. Of course, the cost in weight and airframe volume is unavoidable. There is no information mentioning the lock/launch mode of the AIM-9 on the YF-23A. But this is actually an interesting question. Because it is impossible for the AIM-9's guide head to capture the target in a closed missile bay.? On this issue, the author and many of his colleagues had a long discussion, repeatedly watched the video of the F-22 weapon system test, and finally formed a more consistent view: F-22 in the fighting state, fighting missile compartment is in the open state, the AIM-9X will be stretched out to solve the problem of the guide head locking. YF-23A is entirely possible to use a similar mode. Combined with the launch mode of the AIM-120, I speculate: the mounted AIM-9 may also be elevated mounts, the fighting state of the open hatch will AIM-9 out of the aircraft. Since it is fully extended out of the aircraft, there is no fuselage side shielding, the AIM-9 can get a better field of view than on the YF-22A, and there is no need for the heat insulation/flame evacuation device on top of the YF-22A. The open hatch status may give a rather odd appearance, but in fact the drag from opening the hatch to extend the missile is no greater than that of a conventional external mount, and therefore doesn't negatively affect the performance of the aircraft too much. The only problem with this mode is that the radar reflection cross-sectional area of the aircraft will be significantly larger in the fighting state. However, radar stealth is not significant in the future in the case of air combat into the line of sight; secondly, the modern air combat fighting time is significantly shortened, and the exposure time of open fire is limited, so it does not pose a serious threat to the YF I 23A. For the ATF, especially the YF a 23A this li aircraft, do not enter the fight is the best tactics. In addition to the air-to-air missiles, the M-61 Vulcan cannon will remain as a fixed weapon for the ATF. the YF-23A does not have the M-61 mounted on it, but as designed, the cannon will be mounted on the right side of the fuselage, above the main weapons bay.? Maintainability Design - Maintenance Port Cover - Hatch?The ATF was the first combat aircraft to propose maintainability targets at the outset of its design, and the first fighter to invite the involvement of the aircrew during the design phase. The U.S. Air Force attaches so much importance to maintainability, to a large extent by the influence of the F-15A - F-15A has just been in service, failures are endless, the aircraft is often lying down, known as the "Queen of the Hangar". For traditional airplanes, the coverage of the maintenance port cover on the surface of the fuselage is an important reference indicator to measure its maintainability. High coverage means that the onboard equipment is accessible and the flight attendants don't have to spend their time on useless but necessary tasks - the most typical being that in order to get to equipment A, you have to remove equipment B, C, D...; and then put it back in the reverse order when you are done with it, whereas B, C, and D are actually meaningless for the maintenance of A.In the traditional aircraft, the cover on the fuselage surface is an important indicator of maintainability. s maintenance is meaningless.?
However, for stealth airplanes, the situation is completely different. The presence of surface waves makes any opening in the surface of the fuselage can seriously damage the stealth characteristics of the aircraft. Therefore, "never open the fuselage surface unless necessary" is a principle that must be followed in the design of stealth airplanes. In this case, how to improve the maintainability of the aircraft? One way is centralization. No longer where there is a need to approach the equipment where to open the maintenance port cover, but to determine a centralized area, the most frequent approach to the largest amount of maintenance equipment to all centralized there, with a large maintenance port cover to solve. Route 2 is built on the basis of route 1, that is, try to utilize the aircraft necessary to set up the hatch that can not be omitted as a maintenance port cover. Examples include the weapons bay and landing gear bay. If the equipment or interfaces that need to be maintained can be centralized in these compartments, it may not even be necessary to open other maintenance covers on the fuselage surface. In order to ensure the consistency of the reflected beam, all covers and hatches on the surface of the aircraft must be of a serrated design, with the projection of the serrated leading edge in the horizontal plane parallel to the main reflective edge of the aircraft. However, contrary to what is commonly thought, a multi-serrated leading edge design is not the best measure for controlling radar reflections. This design is the result of a compromise between stealth and weight requirements. From a stealth perspective, a single-tooth design would be ideal. However, in order to ensure the structural strength of a single serration, a corresponding weight cost must be paid. Under the ATF's stringent weight requirements, the YF-23A and YF-22A were both multi-tooth designs. However, on the later F-22, we can see that the number of serrations was reduced, with the agreement of the Air Force, to improve stealth characteristics.