|Comparing stealth fighters|
|送交者: 2016年10月14日04:53:38 于 [世界时事论坛] 发送悄悄话|
Comparing stealth fighters
A Christmas / New Year present for all of you.
This article will compare “stealth” fighters, regardless of wether they are in service. Aircraft compared are as follows: F-22, F-35, T-50 / PAK FA, J-20 and J-31. Following article will form a basis for comparision:
Radar will be ignored for two reasons: its nature as an active sensor makes it tactically irrelevant in air-to-air combat even between conventional aircraft, and even if used, low RCS of fighters being compared means that IRST will still have far longer detection range.
It should be noted that this comparision includes test and development prototypes, and as such cannot be truly accurate due to lack of data and changes to the final version. US T&D prototype of the F-22 – YF-22 – was (rightly) called “paint job with shape of the F22″.
Impact on pilot’s skill
As stated, pilots should fly at least 30-45 hours per month. Neither the F-22 or the F-35 fulfill that requirement (F-22 can offer 15 hours per month at maximum), and no other stealth fighter on the list is likely to fulfill it either. If anything, PAK FA and J-20/31 are likely to have worse record than the F-22, if standard pattern is followed.
Numbers in the air
Again, no precise comparision is possible due to the lack of information.
F-22A has unit flyaway cost of 273 million USD, mission avaliability of 55,5% and sortie rate at 1 hour per sortie of 0,52 sorties/day/aircraft. Assuming 20 billion USD cost, this gives 73 aircraft flying 21 sortie per day. (Another figure I found that is unconfirmed, 70,6% avaliability, would allow it 27 sorties per day).
F-35A has unit flyaway cost of 145 million USD, mission avaliability of 35% and sortie rate (at 1 hour per sortie) of 0,53 sorties/day/aircraft. Assuming 20 billion USD cost, this gives 138 aircraft flying 26 sorties per day.
T-50 has an expected unit flyaway cost of 50-100 million USD, though real figure will likely be higher (up to 150 million USD). As it is a stealth fighter with RAM coating, it is likely to have avaliability similar to the F-22, as well as relatively low sortie rate. Assuming 45-65% mission avaliability and 0,4-0,6 sorties/day/aircraft, it can provide 133-200 aircraft and 24-78 sorties per day for 20 billion USD procurement cost.
J-20 is expected to cost cca 80 million USD, though it will likely end up costing cca 150 million USD. Again, assuming 45-65% mission avaliability and 0,4-0,6 sorties/day/aircraft, it can provide 133 aircraft and 24-52 sorties per day.
J-31 will likely cost cca 80 million USD. Assuming 45-65% mission avaliability and 0,4-0,6 sorties/day/aircraft, it can provide 250 aircraft and 45-98 sorties per day.
(It should be noted that all these aircraft will have exorbant prices when development costs are included, as these tend to be multiple times higher than for 4th and 4,5th generation fighter aircraft. They are also hard to maintain and unreliable – no exceptions).
For comparision, Rafale C has a unit flyaway cost of 90 million USD, demonstrated mission avaliability of 100% and sortie rate (at 1 hour per sortie) of 2 sorties/day/aircraft. Assuming 20 billion USD cost, this gives 222 aircraft flying 444 sorties per day (a 17:1 advantage over the F-35). If mission avaliability is reduced to 90%, it still gives 200 aircraft flying 400 sorties per day, a 15:1 advantage over the F-35 and at least a 4:1 advantage over the J-31.
Quick response to attacks and on-ground survivability
F-22 has an approach speed of 155 knots. Wing span is 13,56 meters and takeoff distance is 480 meters. While takeoff distance is acceptable, wing span is well above 10 meter maximum allowance for adequate road basing capability.
F-35s high wing loading and weight result in high minimum approach speeds. Even the F-35C, with its comparably low wing loading (compared to other two F-35 variants – F-35Cs wing loading is similar to the F-22s) has to deflect flaps to 30 degrees in order to meet maximum approach speed limit of 145 kts, resulting in poor handling qualities. Its sink rate of 21 feet per second is considerably higher than the typical 10 fps sink rate. It also has a wing span of 10,7 meters, which is just above themaximum 10 meter wing span allowable for optimal road basing capability. Takeoff distance for air defense is 183 meters for C.
T-50 will likely have approach speeds on order of 150 knots. It also has a very robust undercarriage with large low pressure tires, allowing excellent STOL and likely dirt strip capability. Takeoff distance is around 458 meters, though values of 300-400 meters have also appeared. Road basing capability is limited by wing span of 13,95 meters.
J-20 is estimated to have a takeoff distance of 470 meters, but 13 wingspan meter limits road basing capability.
J-31 has a takeoff distance of 400 meters and a landing distance of 600 meters. Wingspan of 11,5 meters however limits its road basing capability.
Ability to achieve surprise bounces without being surprised
F-22 does not have an IRST, which means that it has to use radar to engage the enemy at beyond visual range. This, combined with its large size (18,9 m length, 13,56 m wingspan, 5,08 m height) and high IR signature, severely limits its ability to achieve surprise bounces. In terms of avoiding surprise it is no better: while limited rearward visibility is somewhat compensated for by high cruise speed of Mach 1,7, its high IR signature despite some IR signature reduction measures means that it will be easily noticed (engine IR signature reduction measures seem incidental, just a byproduct of having to combine thrust vectoring and all-aspect radar stealth, but they exist – which is far more than can be said for any other fighter discussed here. More specifically, flat engine nozzle helps cool the air, and nozzles themselves are hidden by tail booms).
Due to severe transonic buffeting, wing roll-off and low acceleration, F-35C is essentially a subsonic aircraft in both air intercept and ground attack missions. Even other two variants, though capable of limited supersonic flight, can not achieve supercruise as typically defined (sustaining speeds above Mach 1 without afterburner). All F-35 variants also have very high IR signature due to hugely powerful engine (with no IR signature reduction measures) required to push its brutal shape through the air, unaerodynamic airframe and lack of IR signature reduction measures. Problem is made worse by the fact that the F-35 has very limited rearward visibility, making surprise bounces from rear quadrant a certainity. Depending on amount of data Chinese have stolen, it might be possible for them to render F-35s sensors worthless by feeding them false information. Only advantage that the F-35 has over the F-22 is presence of IRST, but “IRST” in question is basically an in-build Litening pod, being optimized for the ground attack, and so has limited air-to-air performance (limited ability to detect targets at higher altitude than the F-35, limited range and resolution). As limited as it is, it still allows the F-35 to detect and attack the enemy without need to use radar, and thus to achieve surprise.
T-50 has a frontal IRST, as well as a rearward–facing IRST. This provides it with good sensors coverage, and allows it to detect and possibly engage rear-quadrant threats well out to beyond visual range, though its own engines’ exhaust might mask targets directly to the rear. Having IRSTs also allows it to engage the enemy completely passively, thus maintaining surprise for longer (assuming that it uses QWIP technology, OLS 50 could track a subsonic fighter at 130 km via its engine exhaust, and likely at 80 km from front). High cruise speed of Mach 1,6 allows it great freedom of choosing when and how to engage and also reduces the possibility of suffering a rear-quarter bounce while increasing the possibility of achiveing the same bounce against most other fighters. However, inadequate rearward visibility will still make it vulnerable to surprise bounces in within visual range fight, and engines have no IR signature reduction measures.
J-20 is a large aircraft (20 m length, 13 m wingspan, 4,45 m height). As a result, its ability to achieve surprise bounces is rather limited. As with the F-22, it has to rely on high cruise speed (Mach 1,4-1,6) to avoid rear-quadrant attacks due to high IR signature and bad rearward visibility. While it does have an IRST, which will enable it to attack the enemy aircraft completely passively (a crucial element in achieving surprise), location and shape of its IRST suggest that it is similar in purpose and capabilities to the F-35s EOTS – in other words, it is not a fully developed IRST, but is instead a built-in IR targeting pod optimized for ground attack. Its canopy and cockpit design seems to provide barely adequate rearward visibility. Engines have no IR signature reduction measures.
J-31 is 16,9 m long and has a wing span of 11,5 m, which indicates moderate IR signature. It is expected to have an IRST of similar type as the J-20, though its smaller size will help in achieving surprise, especially if it turns out to be capable of supercruise. However, it is still very vulnerable to surprise bounces due to inadequate rearward visibility. Engines have no IR signature reduction measures.
F-22 has combat weight of 24.883 kg, a wing loading of 317,4 kg/m2, thrust-to-weight ratio of 1,35, and span loading of 1.835 kg/m. Wing sweep is 42*, and engine has a power-to-frontal area ratio of 26,82 N/cm2. As a result, the F-22 will have good instantaneous turn rate, sustained turn rate and acceleration, while its weight harms transient performance; it also uses thrust vectoring to improve high-speed high-altitude performance. However, low fuel fraction of 0,29 will limit endurance.
F-35A has combat weight of 18.270 kg, a wing loading of 427,9 kg/m2, thrust-to-weight ratio of 1,07 and span loading of 1.707,5 kg/m. Wing sweep is 34*, and engine has a power-to-frontal area ratio of 17,86 N/cm2. As a result, the F-35 has very bad instantaneous and sustained turn rates (50% of the F-22s sustained turn rate, or ~14 deg/s) as well as bad acceleration, while its weight still harms the transient performance. Inefficient aerodynamics and powerplant will also limit combat endurance despite excellent fuel fraction of 0,38.
T-50 has a typical combat weight of 21.500 kg, a wing loading of 272,8 kg/m2, thrust-to-weight ratio of 1,39 and span loading of 1.541 kg/m. At heavy combat weight (50% maximum internal fuel capacity) of 23.150 kg, it has wing loading of 294 kg/m2, thrust-to-weight ratio of 1,3 and span loading of 1.659 kg/m. Wing sweep is 46,5*, and engine has a power-to-frontal area ratio of 22,85 N/cm2. Aircraft itself also has very small frontal area, about half of the F-22s. Result is that T-50 will have excellent instantaneous turn rate as well as very good sustained turn rates and acceleration, but its weight harms transient performance (though it will still be better than the F-22s). It also has a very good fuel fraction of 0,36, indicating good combat endurance. Overall it adheres very closely to Boyd’s energy-maneuverability requirements.
J-20 has an estimated combat weight of 26.422 kg, a wing loading of 339 kg/m2, thrust-to-weight ratio of 0,95 (possibly 1,1, but lower value is more likely as J-20 uses Russian AL-31F and will continue to do for forseeable future, until Chinese manage to copy it) and span loading of 2.032 kg/m. Wing sweep is 43* and engine has a power-to-frontal area ratio of 19,02 N/cm2. As a result it will have adequate instantaneous turn and climb rates, but limited acceleration and sustained turn rates, while transient performance will be very limited. Lack of horizontal tail will reduce interference drag and improve cruise speed and sustained turn rate, while canards will improve pitch/turn onset and instantaneous turn rates. Fuel fraction is very good at 0,35, indicating good combat endurance. Low wing loading and usage of canards combined with large LERX indicates greater focus on high-speed high-altitude performance, including maneuvering combat, of long arm canards as opposed to close-coupled ones indicates a focus on high-altitude interception. However, location of landing gear (center of gravity is always slightly in front of main landing gear) indicates that center of gravity is in front of centre of lift, or at least not far behind, thus indicating either stable or very slightly unstable aircraft. (Compare to Rafale).
J-31, at least its pre-production variant (production variants will be heavier), has a combat weight of 17.600 kg. As a result, it will have a wing loading of 440 kg/m2, thrust-to-weight ratio of 1,13, and span loading of 1.530 kg/m. Wing sweep is 35*. This means that it will have very bad turn instantaneous and sustained turn rates, though its sustained turn rate and cruise speed will be better than the F-35s due to flatter, more aerodynamic fuselage resulting from not having a STOVL variant.
(ability to achieve quick kills, vulnerability to countermeasures, ability to maintain surprise, and number of onboard kills)
In terms of kill probability, revolver and linear action guns have Pk of 0,31, rotary guns of 0,26, IR WVR missiles of 0,15, IR BVR missiles of 0,11 and RF BVR missiles of 0,08. BVR missiles’ Pk falls by 25% compared to values listed when actually used at beyond visual range.
F-22 uses the M-61 gun as well as AIM-9 Sidewinder WVR missile and AIM-120 BVR missile. As the M-61 needs 0,25 seconds to spin up to full rate of fire, and gun doors require 0,5 seconds to open, it will fire 37 projectiles weighting 3,77 kg in the first second. Missile bay doors also require 0,5 seconds to open. While both gun and IR missiles may allow it to surprise the enemy within visual range, it uses radar-guided BVR missiles which destroy surprise even when fired by using data from offboard sensors or RWRs, and are comparably unreliable and easy to decoy, jam, confuse or evade. That being said, AIM-9X Block III entering service in 2022 may have a range of up to 60 km. With standard loadout of 13 gun bursts, 2 WVR IR and 6 BVR RF missiles, it has a total of 4,16 onboard kills.
F-35 uses the GAU-22/A gun as well as AIM-9 Sidewinder WVR missile and AIM-120 BVR missile, though only the latter will be typically carried. GAU-22/A needs 0,4 seconds to spin up to full rate of fire and gun doors require 0,5 seconds to open. Thus, in the first second it will fire 16 projectiles weighting 2,94 kg. Again, usage of radar guided missiles does not allow it to surprise the enemy at beyond visual range, and unlike the F-22, it can only carry an IR missile at wingtip stations, thus negating its radar stealth. With standard loadout of 11,3 gun bursts and 4 RF BVR missiles, it has a total of 3,26 onboard kills.
T-50 uses the GSh-301 gun as well as R-73 WVR and R-77 BVR missile. GSh-301 achieves its maximum rate of fire of 1.800 rpm instantaneously, and thus can fire 15 projectiles weighting 5,79 kg in first 0,5 seconds. If standard Russian practice is followed, its BVR missiles will have RF, AR and IR variants; PAK FAs RF variant uses an AESA seeker, thus reducing the probability of seeker getting jammed or loosing track of the target. Presence of IR and AR BVR missiles allows, when combined with presence of the IRST, a completely passive engagement at beyond visual range. Assuming 12,5 gun bursts, as is standard for the Flanker family, as well as 2 IR WVR and 6 RF BVR missiles gives it a total of 4,67 onboard kills. If RF BVR missiles are replaced with IR BVR missiles, total number of kills increases to 4,84. It is also capable of carrying Kh-58UShE anti-radar and RVV-BD air-to-air missile, both with 200 km range. This indicates that SEAD/DEAD and AWACS elimination are also important missions for the T-50.
J-20 does not seem to have a gun, and it might carry 4 BVR and 2 WVR missiles. This gives it a total of 0,62 – 0,74 onboard kills, depending on wether BVR missiles are of the RF or IR variety. As with the T-50, it has an avaliable selection of RF, IR and AR BVR missiles, which increases probability of kill for a salvo as each type of missiles behaves differently.
J-31 can carry 4 BVR missiles. If it does not have a gun, this translates into a total of 0,32 – 0,44 onboard kills, depending on wether missiles are of the RF or IR variety.
F-22 has two closely packed engines, similar to the F-15. Its wings are also capable of carrying 4-g loads even after some combat damage. Fuselage fuel tanks are designed to be empty by the point 60% fuel capacity has been reached, thus avoiding possible fuel ingestion by the engine. However, at longer combat radiuses the F-22 will carry external fuel tanks, which means that possibility of ingestion is present, and there are still fuel tanks at sides of the engines. Hydraulic and electric systems are redundant. However, both main hydraulic pumps are placed near the centerline, close enough for a high single hit-kill probability. Tail actuator bay has no fire protection, potentially leaving the aircraft uncontrollable if damaged. Aeliron actuators and flight control avionics are very close to flammable hydraulic liquid. Hit into a missile bay is likely to take out the entire aircraft, a vulerability shared by all stealth fighters. A hit on gun ammunition will disable the gun but will not result in loss of the aircraft. While two engines are thought to provide an increased survivability, some failure modes (e.g. a disk burst, uncontained engine fire) will result in loss of both engines. Also, both engine control units are located at the bottom of the aircraft, as are all engine accessories.
F-35 is far worse when it comes to damage tolerance than any other fighter listed. Both A and C variants have massive quantities of fuel surrounding the engine inlet. This fuel will be at an elevated temperature during flight, and especially during combat, as it is used as a heat sink. Same fuel is used in aircraft’s hydraulic system, including the system used to swivel the F-35Bs vectoring nozzle. A hit from a 30 mm HEI round (as used by most Russian and Chinese fighters as well as Dassault Rafale) is almost certain to ignite the fuel and catastrophically destroy the aircraft, and engine is likely to ignite it even if the hit itself doesn’t. Even 25 mm and 20 mm shells or .50 cal and 7,62 mm bullets, as well as fragments from SAMs and MANPADS can cause a loss of aircraft. And since the F-35 is primarily a ground attack aircraft, it is likely to be fired at from below – which is a problem as its primary avionics bay is located in the lower front fuselage, an area most likely to be hit by the AAA fire. Engine inlet and air intakes are also surrounded by fuel. This lack of damage tolerance is compunded by the fact that the F-35s pilot may not be capable of bailling out due to ill designed cockpit and ejection seat.
F-35B has a lift fan which is untested against combat damage. It also melts asphalt, spalls concrete and crumbles flight decks with high-temperature Mach 1 exhaust. This means that the F-35B could damage (or, if unlucky enough, destroy) itself while landing, and will be an operational nightmare due to extreme airfield maintenance requirements.
T-50 has two widely spaced engines whose thrust lines are canted outwards at 2-3 degrees. As a result, it can fly with only one engine active, and any hit is less likely to take out both engines. Flip side is that it increases roll inertia somewhat, increasing probability of damage, though usage of independently vectored thrust might compensate for that somewhat.
J-20 has an advantage over all other fighters mentioned in that it has additional control surfaces in canards, leading to increased redundancy.
J-31 has an advantage over the F-35 in that it does not have a STOVL variant, as well as having two engines.
Ground attack performance
(important points: gust sensitivity, radar stealth, payload, combat radius)
F-22s all aspect radar stealth and supercruise speed mean that it can comparably easily avoid most typical air defense systems and take out high value targets, without need for low altitude flight. Requirement for rear aspect stealth has been achieved at cost of nozzle design that is both heavy and causes some thrust loss. It has a maximum combat radius on internal fuel of 1.166 km and internal payload of 900 kg (2×450 kg JDAM or 8×110 kg SDB).
F-35 has limited side and rear stealth and no supercruise capability. This is because it is meant for low-altitude penetration, where its high wing loading reduces its gust sensitivity and allows it to achieve higher speeds than typical low wing loading aircraft could achieve. It has a maximum combat radius on internal fuel of 1.082 km and internal payload of 900 kg; however, effectiveness of delivery compared to the F-22 is impeded by the lack of the supercruise (though it is compensated for by lower aircraft cost). It should be effective in SEAD: as its radar was capable of jamming the F-22s radar in tests, it should also be capable of jamming modern frequency-agile X-band SAMs (but not VHF SAMs). However, radar can only jam targets in front of the aircraft, and F-35 has no internal jammer to compensate for compromised rear aspect radar stealth.
T-50 is not as good as the above two in ground attack due to nonstealthy engine nozzles, lower and aft fuselage as well as a gap between air intakes; it also does not use saw tooth design. Further problems are caused by protrusions outwards of engines, intended to house WVR AAMs. As a result, it does not have as good deep penetration capabilities at high altitude as the F-22 does, and low wing loading limits its ability to hide below the radar coverage. Some info suggests that gaps are to be covered with net that has openings of less than 1/4 of wavelength of typical radars, and thus acts as a solid plate towards the radar. However, combination of high cruise speed and altitude might reduce SAM effective range so much that rear aspect stealth won’t matter anyway (specifically, to less than 1/5th of stated maximum range), and production engines might increase its rear aspect stealth (though it is also possible that Russians will opt for retaining 3D TVC nozzles over improving stealth). Production variant is also unlikely to retain current spherical IRST. It has a maximum combat radius on internal fuel of 1.250 km (est.) and internal payload of >=2.600 kg. It might be able to carry two 1.500 kg anti-ship bombs
J-20 uses a stealthy design, and stealth coatings probably based on the F-117 (after Serbs shot down the F-117, Croatian intelligence services noticed Chinese agents buying parts of the downed F-117 from local farmers) and possibly the F-35 (project’s rather porous information security was consistently penetrated by Chinese hackers). However, its round engine nozzles mean that it does not have as good stealth performance as the F-22, though it is likely better than the T-50 due to the more even underside. It should be noted that canards are not actually a stealth penalty: a Lockheed Martin engineer who worked on the F-35 has stated that early canarded configuration was not any less stealthy than later wing-tail configuration (due to aircraft always flying at angle of attack, tail will not be masked by the wing except for a short time and only if aircraft radiating is at higher altitude than stealth aircraft; against ground radars, horizontal tail is as much of a penalty as canards). It likely has a maximum combat radius on internal fuel of cca 1.800 km and internal payload of cca 3.000 kg. It utilizes glide bombs, meaning that it can release its payload outside the radar detection range, possibly even taking into account increased RCS due to open weapons bay doors, and use supercruise to defeat rear-quadrant SAM shots.
J-31 is mostly similar to the J-20, and it also has a high wing loading similar to the F-35, allowing it better low-level performance. New J-31 demonstrator also has a saw-tooth nozzle, showing greater focus on penetrating air defenses. It has a combat radius on internal fuel of 1.250 km and maximum internal payload of cca. 2.270 kg.
However, if enemy uses VHF and HF radars, value of stealth is heavily reduced if not eliminated alltogether – as shown by the F-117, shot down only 18 seconds after getting discovered by the VHF radar, and another F-117 that got mission killed. In such situation, none of the “stealth” fighters are much better than the conventional ones.
Combat radius also has implications for basing survivability. Most if not all of these fighters will require large and vulnerable air bases to functions; these have to be located outside the range of most prevalent threats. Since evolved Scud missiles may have range of up to 1.100 km, T-50, J-20 and J-31 have the adequate combat radius, while F-22s is borderline adequate and F-35s is completely inadequate.
All fighters discussed have low frontal RCS and thus improved ability to destroy AWACS. Ideal scenario however would require a fighter to sneak up to within its longest missile range (preferably within half of it) without being detected by AWACS. Characteristics required are thus low frontal RCS and high cruise speed as well as air-to-air missile range.
AWACS used for comparision will be E-3 Sentry with 400 km detection range vs 5 m2 RCS aircraft, and 855 kph maximum speed. Radar range calculation is (RCS1/RCS2) = (R1/R2)^4, where RCS = radar cross section, while R=range. Speed of sound at 30.000 ft is 1.091 kph.
F-22 has 0,0001-0,0014 m2 frontal RCS (average RCS is 0,3-0,4 m2). Its longest-ranged missile is AIM-120D with 180 km range. Thus it will get detected at 27-52 km, well within half-range of the AIM-120D.
F-35 has 0,00143-0,006 m2 frontal RCS. Its longest-ranged missile is AIM-120D with 180 km range. Thus it will get detected at 52-74 km, well within AIM-120Ds half-range. Export F-35 has an RCS of 0,25 m2 and will get detected at 190 km, just outside the AIM-120Ds maximum aerodynamic range. To cover remainig 100 km to AIM-120Ds half-range it will require 346 seconds (5,8 minutes) at cruise speed of Mach 0,95 or 206 seconds (3,4 minutes) at maximum speed of Mach 1,6.
T-50 has 0,006-0,015 m2 frontal RCS (average RCS is 0,5 m2). Its longest-ranged missile is R-77 with 110 km range. Thus it will get detected at 74-94 km and to cover remaining 19-39 km it will need 40 to 81 seconds at cruise speed of Mach 1,6 or 31 to 64 seconds at maximum speed of Mach 2,0. (Most likely RCS is 0,013 m2). However, its R-37 missile (not yet in service but likely will enter service by the time T-50 does it as well) has a range of 400 km, allowing it to easily take out AWACS.
(Previous RCS figures are estimates from official releases, J-20 figure is APA estimate
J-20 has 0,001-0,1 m2 frontal RCS. Its longest-ranged missile is PL-12 with 70-100 km range. Thus it will get detected at 48-150 km, which in best case is just within the PL-12s half-range.
Overall PAK FA is the best and F-35 is the worst stealth fighter, where air superiority is concerned. Rating would go roughly T-50 > F-22 > J-20 > J-31 > F-35. T-50 and F-22 seem to be air superiority fighters and interceptors, though PAK FA shows greater focus towards air superiority than the F-22. J-20 is primarly a bomber/transport interceptor, while both J-31 and F-35 are primarily (if not solely) ground attack aircraft. F-35s air combat capabilities were intentionally limited in order to prevent it from replacing the F-22. Still, F-35s purpose is often misunderstood – it is not, and never was, an F-16 replacement. While the F-16 was the top dogfighter in the US air fleet, F-35 is optimized for strikes against fixed targets and deep incursions.
This shows different Russian and Chinese approaches. While PAK FA (T-50) is optimized to shoot down US fighter aircraft (primarily F-22 and F-15), J-20 is more optimized for shooting down US AWACS, transport and tanker aircraft, thus neutralizing its relatively short-range fighters without having to engage them in combat at all. F-22 is a compromise between two roles. T-50 seems to be the only stealth fighter made with actually realistic approach to aerial combat, in particular focus on maneuverability, passive sensors and on-ground survivability and ability to operate without large air bases (which will get destroyed), while J-20 is meant to avoid aerial combat, though it should be capable of handling itself if it comes to that.
What is also important is that US are the only country planning to replace all fighters with stealth variants. Both Russians and Chinese seem to be planning to use their stealth fighters to supplement conventional forces, to be used for highly specific missions such as AWACS hunting, tanker destruction and strikes against heavily defended targets (especially air bases and command and control facilities), while other aircraft establish air superiority (though T-50 seems to be meant to destroy other stealth fighters as well). This strategy targets precisely the most vulnerable parts of US air power structure. US, despite experience with stealth, have not – unlike Europe, Russia and China – taken many steps to counter stealth aircraft. IR sensors still seem to be considered primarly ground attack additions, and there is little in way of development and production of counter-stealth (VHF, HF, passive) radars, unlike in China, Russia and Europe.
Missile guidance types:
RF – active radar
IR – infrared
AR – anti-radiation