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F-35 reality check

Discussion in 'The Americas' started by Picard, Jul 17, 2015.

  1. Picard

    Picard Lt. Colonel RESEARCHER

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    CLAIM: F-35 can supercruise

    Incorrect. F-35 can achieve and maintain speeds just above M 1 though usage of minimum afterburner. “Supercruise” claim can be discounted by comparing the F-35A with F-16A.

    F-16A has a 40* wing sweep with a laminary wing profile designed for supersonic flight. Its engine has a frontal area of 6.082 cm2 while providing 64,9 kN dry (uninstalled) thrust, giving 10,67 N/cm2. F-16A also has wing loading of 338,5 kg/m2 at combat weight, span loading of 947,2 kg/m and TWR of 0,7 at combat weight and dry thrust.

    F-35A has a 33* wing sweep with a supercritical wing profile designed for transonic flight. It also has frontal area about as large as the F-18s. Its engine has a frontal area of 10.715 cm2 while providing 124,5 kN dry thrust, giving 11,62 N/cm2. F-35A has wing loading of 427,9 kg/m2 at combat weight, span loading of 1.698 kg/m and TWR of 0,7 at combat weight and dry thrust.

    F-16s higher wing sweep and supersonic wing profile means that it will suffer slower drag increase past transonic speed. This is compounded by F-16s lower wing loading which means that the F-16 has to maintain lower angle of attack in order to achieve level flight, and lower span loading leading to lower vortex drag in level flight. F-35 also has twice the frontal area, which cancels out its double amount of dry thrust. F-35s only (minor) advantage is in engine dry thrust to frontal area ratio. As the F-16 can achieve Mach 1,1 with two wingtip missiles and 50% fuel at 40.000 ft, which is just out of its transonic region, F-35 will be limited to subsonic to low transonic speeds (drag coefficient nearly doubles between M 0,8 and M 1,0, and due to the F-35s lower wing sweep it will have larger transonic region than the F-16).

    [​IMG]
    [​IMG]

    In level flight, thrust to weight ratio of the aircraft is inverse of its lift to drag ratio – lift counters weight and thrust counters drag. Ergo, aircraft with better lift-to-weight ratio – lower wing loading for aircraft with similar aerodynamics – will need lesser 0* AoA thrust-to-drag ratio to achieve a certain speed.

    While many aircraft were or are capable of supercruise – English Electric Lightning, Mirage IIIO, F-104, F-16, Gripen, Rafale, Typhoon, F-22 – all of them had their maximum speed limited by engine pressure recovery limit and not by thrust-to-drag limit, and so could achieve top speeds of at least Mach 1,8. F-35 on the other hand has dash speed of Mach 1,67, which is thrust-to-drag limit.

    This can also be confirmed with following:

    “What we can do in our airplane is get above the Mach with afterburner, and once you get it going … you can definitely pull the throttle back quite a bit and still maintain supersonic, so technically you’re pretty much at very, very min[imum] afterburner while you’re cruising,” Griffiths said. “So it really does have very good acceleration capabilities up in the air.”

    Further, F-35 was said to be capable of maintaining Mach 1,2 for 150 miles. F135 will, at maximum dry thrust and at test bench, produce 12.700 kgf of thrust while consuming 11.089 kg/h. 150 miles at 30.000 ft and Mach 1,2 would take 13,27 minutes. F-35 has 8.280 kg of internal fuel. Assuming that it can consume 68-82% of the fuel (allowing supercruise but nothing else) would give it 30,46 – 36,74 minutes of cruise. Assuming allowance of 35% of the fuel for supercruise (which would also allow extended subsonic cruise) would allow it to supercruise for 15,78 minutes. This means that it should be capable of covering at very least 178 miles, and more likely 344 to 415 miles. (Note that it will consume less fuel in flight than these values suggest, as both thrust and SFC values are from the test-bench and not in-flight testing, and total fuel consumption will be less in an actual flight).

    There are several explanations for the F-35s inability to achieve even minimum treshold. One is that “supercruise” is achieved at a favorable altitude, with limited fuel onboard. In that scenario, F-35 would use afterburner to go through transonic region and burn most of the onboard fuel before switching to dry thrust and slowing down to Mach 1,2. However, when combined with the quote provided above, more likely explanation is that it has to stay in low afterburner in order to maintain supersonic flight. It is also possible that both explanations are true – F-35 needs low afterburner to achieve supercruise early on, but can achieve supercruise at dry thrust after it has already spent most of its fuel.

    Whichever is true, it is obvious that the F-35 is not truly capable of supercruise. Above performance can be compared with other aircraft. Rafale C has two M88-2 engines providing a total of 9.952,8 kgf of dry thrust, and 4.750 kg of internal fuel. Typhoon has two EJ200 engines providing a total of 12.236 kgf of dry thrust, and 4.940 kg of internal fuel. Gripen E will have a single F-414G engine providing a total of 5.894 kgf of dry thrust, and 3.130 kg of internal fuel.

    Rafale C will consume 7.808 kg/h in dry thrust. Using same percentages as for the F-35, it can be seen that it can stay at maximum dry thrust for either 12,78, 24,82 to 29,93 minutes. As it can supercruise at Mach 1,4 with 6 AAM, it can cover 196,8 to 460,8 miles. Typhoon will consume =<9.936 kg/h in dry thrust. This would allow it to stay at maximum dry thrust for 10,44 to 24,46 minutes, which at Mach 1,5 gives 172,2 to 403,5 miles. Gripen E will consume 4.855 kg/h in dry thrust, allowing it to stay at maximum dry thrust for 13,54 to 31,72 minutes. As it can achieve Mach 1,2 supercruise with 2 IRIS-T, 4 AMRAAM and centerline tank at 25.000 ft, supercruise speed without centerline tank is likely to be around Mach 1,3. This will allow it to cover 203,2 to 476,0 miles.

    For comparison, F-22 can cover a maximum of 0,04 miles per pound of fuel at 45.000 ft and Mach 1,5. As the F-22 has 18.000 lbs of internal fuel, it can cover 252 to 590 miles at Mach 1,5. Using dry thrust comparison, F-22 will consume 19.936 kg per hour with 21.319 kgf of dry thrust and 8.200 kg of internal fuel. This would give it 8,64 to 20,24 minutes at maximum dry thrust, which at Mach 1,7 allows it to cover 161,5 to 378,4 miles. F-22s combat radius is is 400 nm with 100 nm supercruise; this means that it uses 5.000 lbs of fuel for supercruise and 8.600 lbs for subsonic cruise. As the F-22 has 18.000 lbs of internal fuel, 13.600 lbs of fuel would equalize 76% of the onboard fuel, with just supercruise requirement accounting for 28% of the onboard fuel. This would suggest that, even if it is capable of supercruise, F-35 can only achieve it with most of the fuel burned off, as it has significantly higher fuel fraction than the F-22.

    Similarly, Typhoon is stated to have a two-way supercruise capability of 250 nm on internal fuel. This may provide an indication of actual cruise distance of other fighters, as fuel consumption values used are for sea level and engine on test bench, and will be lower in flight (and increases the difference between the F-35s actual supersonic endurance and one it should be able to achieve were it really capable of supercruise). It is interesting to note relation between cruise distance and fuel fraction (F-22: 0,29, Typhoon: 0,31, Rafale C: 0,33, Gripen E: 0,31) as well as beneficial impact of a single-engined configuration on supercruise range and endurance. Even if the F-35s supercruise performance claim is correct, it can be seen that its range at supercruise is significantly inferior to all aircraft compared here, as is its claimed supercruise speed.

    Supercruise altitude is assumed to be cca. 40.000 ft for all aircraft (F-22 achieves Mach 1,725 at that altitude), except Gripen E for which supercruise altitude is known (and in Gripen’s case, actual speed is likely to be higher at 40.000 ft).

    F-35 has a very draggy design even in subsonic flight. Rafale C has combat radius of 925 km on internal fuel and with 6 missiles, with fuel fraction of 0,33 and internal fuel capacity of 4.750 kg, depsite being a twin-engined design and thus comparably fuel-inefficient. F-16A has combat radius of 925 km – identical to Rafale – with fuel fraction of 0,31 and internal fuel capacity of 3.160 kg. F-35A, despite having fuel fraction of 0,39 and internal fuel capacity of 8.280 kg, only manages a combat radius of 1.082 km. F-22, with far lower fuel fraction of 0,29 and almost identical fuel capacity of 8.200 kg has maximum combat radius on internal fuel of 1.166 km – and this despite its engines being optimized for supersonic cruise as opposed to the F135s optimization for subsonic cruise performance.
     
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  2. Picard

    Picard Lt. Colonel RESEARCHER

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    CLAIM: F-35 is designed to outturn and outaccelerate the F-16

    Partly true. F-35 is indeed designed with a requirement to out- -turn and -accelerate the F-16 in mind. What is typically unstated is that this is only for air-to-ground mission: that is, both aircraft are expected to carry bombs. Acceleration part can be seen below:

    [​IMG]

    While the differences are not large, it can be seen that the F-16C with 6 missiles has better subsonic acceleration than any F-35 variant. In fact, the F-16C with 2 external fuel tanks has subsonic acceleration comparable to the F-35B, and superior to the F-35C. It should be noted that the F-35 in the above comparison does not even have a full internal fuel load; if both aircraft have similar fuel fraction, F-16 will have even better comparative performance than it achieved in graph.

    In terms of transonic acceleration, F-35A takes 63 seconds to accelerate from M 0,8 to 1,2 @ 30.000 ft, compared to 40 seconds for F-16A and 43 seconds for F-16C (clean F-16 needs ~20 seconds to pass transonic region, which for the F-16 is ~M 0,9 – M 1,1). F-16s acceleration is comparable to that of clean F-35A only if the F-16 is carrying two supersonic fuel tanks (~60 s w/ 2 EFT + 4 AMRAAM). [Note here; according to Stevenson, 2006, F-16s acceleration values given above are achieved at 40.000 ft; at 30.000 ft F-16C would need 28 seconds, which is less than half of time that the F-35A needs.] Both F-35B and especially F-35C can be expected to have significantly inferior acceleration performance as compared to the F-35A.

    In air-to-air combat, F-35A should have ITR corner speed of 9 g @ 370 kts and 15.000 ft and STR of 4,95 g @ M 0,8. This translates into ITR of 26,6 deg/s and STR of 10,8 deg/s. F-16A has corner speed of 350 kts for 9 g instantaneous turn, which results in ITR of 28,1 deg/s. I don’t have such data for the F-16C but known figures list 26 deg/s ITR and 18 deg/s STR, which fits due to the F-16Cs increased weight (and thus wing loading). In either case it is clear that the F-35A is inferior turner when compared to the F-16A and is comparable to the F-16C in terms of instantaneous turn rate but significantly inferior in terms of the sustained turn rate. Main reason why the F-35A manages to match or surpass the F-16Cs turn rate despite latter’s somwehat lower wing loading (425,5 vs 392 kg/m2) is that the F-16 can only achieve angle of attack of 25,52 degrees, while to achieve maximum lift it needs to reach 32* AoA. (This limit is a consequence of USAFs insistence on larger nose for the F-16 compared to the YF-16 prototype, which allowed BVR radar but also decreased directional stability at high angles of attack). F-35 on the other hand can surpass its maximum lift AoA by a wide margin, with operational AoA limit of 50* and maximum aerodynamic AoA of 110*. Due to its inability to retain or recover the energy, it has to shoot down the F-16 within first few turns – it is almost impossible for the F-35 to win in a protracted dogfight against the F-16A or C due to the F-35s high energy bleed rates and inability to recover the lost energy.

    Overall, F-35 can neither outturn or outaccelerate the F-16 in air-to-air configuration. F-35 can match F-16s acceleration capability if latter is carrying two external supersonic fuel tanks, and can surpass F-16s turn and acceleration capability if both aircraft are in air-to-ground configuration. This comparison is based on the F-35s standard (stealth) air-to-ground configuration, which consists of two AIM-120 and two air-to-ground weapons. F-16s standard air-to-ground configuration includes two external fuel tanks, two AIM-120, and 2-4 air-to-ground weapons, plus a targeting pod. This configuration is comparable to the F-35s stealth configuration (F-35 has an inbuilt targeting pod in form of EOTS and far greater internal fuel fraction), and can be surpassed by the F-35 via external carriage.

    This is confirmed with following statement:

    Eglin F-35 initial cadre starts transition training - The DEW Line

    “A combat-configured F-16 is encumbered with weapons,external fuel tanks, and electronic countermeasures pods that sap the jet’sperformance. The F-35′s acceleration is “very comparable” to a Block 50 F-16. “Again, if you cleaned off an F-16 and wanted to turn and maintain Gs and[turn] rates, then I think a clean F-16 would certainly outperform a loaded F-35,”Kloos says. “But if you compared them at combat loadings, the F-35 I thinkwould probably outperform it.” ”

    While fuselage lift is often given as an excuse for the F-35s high wing loading, F-16 also has major amount of fuselage lift when turning (45%, same as the F-35). Main difference is that the F-35 also has comparably high fuselage lift at low angles of attack, allowing it to carry greater payloads.

    Assuming that reports are correct, then a mock dogfight has proven that clean F-35A cannot outmaneuver F-16D even when latter is lugging around two external fuel tanks. F-35 “remained at a distinct energy disadvantage in every engagement” which “would increase over time”, had “insufficient pitch rate” and “The flying qualities in the blended region (20–26 degrees AoA) were not intuitive or favorable.”. F-16 easily dodged F-35s attempts at gun shots, while the F-35 could not escape the F-16s own gun tracking. Literally the only way F-35 could shoot down the F-16 was to perform a post-stall maneuver (by its description, it is similar to Herbst maneuver or a Cobra); but this maneuver is a last-ditch option for one-on-one fight, leaving jet “dead in the air”. In many-on-many fights, it is suicidal, and even in one-on-one, the F-35 is dead if it does not work. This performance may or may not be suggestive of inferior instantaneous turn performance, but clearly shows inferior ability to retain and/or recover energy during the dogfight (that is, inferior sustained turn rate and acceleration, which is in line with the assessment in previous parts of this section). Lack of cockpit visibility and shitty overall cockpit/canopy design allowed the F-16 to easily sneak up onto the F-35. Pilot has also mentioned that the F-35 is inferior to the F-15E in close dogfight.
     
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  3. Picard

    Picard Lt. Colonel RESEARCHER

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    CLAIM: F-35 can outmaneuver Eurocanards

    When it comes to maneuverability, important factors are turn and roll onset rates, instantaneous turn rate, acceleration and sustained turn rate.

    Turn and roll onset rates cannot be clearly compared with avaliable data. However, some points have to be made. Since all aircraft in question are unstable, they have center of mass relatively far aft. This means that canards have moment arm advantage over horizontal tail when initiating a turn. Close coupled canards also affect wing lift, with canard movement providing a momentary increase in wing lift forward of the neutral point. Strong vortices produced by close coupled canards not only improve wing lift, but also delay stall to higher angles of attack and energize wing, improving control surface effectiveness and wing response to same at all angles of attack. Unlike LERX and “chimes” used on the F-35, canards energize outboard as well as inboard portion of the wing. All of this points to close coupled canard configuration having significantly superior overall transient performance when compared to conventional aft tailed configuration.

    F-35 also has disadvantage of inertia. Combat weight is 18.270 kg for F-35A, 14.539 kg for Typhoon, 12.597 kg for Rafale C and 8.779 kg for Gripen C. Even if the F-35 is reduced to 15% fuel fraction (similar to Eurocanards), it has combat weight of 16.477 kg. This reduces its ability to quickly transit from one maneuver to another. Inertia is also important in roll performance; all other things being equal, aircraft with lower wing span will have quicker roll onset. F-35A has wing span of 10,7 m, compared to 10,95 m for Typhoon, 10,8 m for Rafale and 8,4 m for Gripen C. Combined with canard influence outlined in the previous section, it can be seen that while the F-35 may be capable of achieving better roll performance than Typhoon, it has no hope of surpassing either Rafale or Gripen.

    Instantaneous turn rate can be compared with wing loading. Wing loading figures are 428 kg/m2 for F-35A, 276 kg/m2 for Rafale C, 291 kg/m2 for Typhoon and 293 kg/m2 for Gripen C. However, there are some caveats. First, during turn onset both horizontal tail and horizontal control surfaces reduce lift as opposed to adding to it (which they do during turn itself). Second, canards actually add to lift during turn onset while being neutral during sustained turn. Third, close-coupled canards improve wing lift and lift-to-drag ratio during turn onset, instantaneous and sustained turn. I have no data about aft control surfaces so I will not include subtraction. However, while Typhoon’s canards have no influence on wing lift, Gripen’s and Rafale’s canards can be expected to improve it by cca 10% (real value will likely be at least 50% higher due to Rafale having LERX and Gripen’s canards being comparatively large). Canards also add their own lift; canard area is 3,6 m2 for Rafale C, 2,4 m2 for Typhoon and 4,5 m2 for Gripen C. All said and done, effective wing loading for turn onset is 428 kg/m2 for F-35A, 234 kg/m2 for Rafale C (53,87 m2), 277 kg/m2 for Typhoon (52,4 m2) and 234 kg/m2 for Gripen C (37,5 m2). All aircraft except possibly Typhoon also have large amount of body lift, thanks to the wing-body blending. In case of Gripen and Rafale, some canard lift “spill” causes an increase in forward fuselage lift at high angles of attack. Rafale also has LERX on the wings (these are planned as an upgrade to Gripen and Typhoon). F-35 has no LERX but rather stealth-friendly “chimes”. Chimes are fixed, and so cannot adjust themselves to different flight conditions. Further, there is adverse interaction between chime and wing root vortices, which causes them to burst well forward of the tail, and thus reduces maximum avaliable lift.

    [​IMG]

    During sustained turn, both Eurocanards’ trailling edge control surfaces and F-35s horizontal tail (11,8 m2) will add to lift, while canards will typically be in lift-neutral position to minimize drag. Close coupled canards will still improve wing lift-to-drag ratio, but may not improve lift due to lower angle of attack. Consequently, effective wing loading for sustained turn is 335 kg/m2 for F-35A, 276 kg/m2 for Rafale C, 291 kg/m2 for Typhoon and 293 kg/m2 for Gripen C. Span loading also influences sustained turn as higher span loading means more drag. Span loading is 1.707 kg/m for F-35A, 1.166 kg/m for Rafale C, 1.328 kg/m for Typhoon and 1.045 kg/m for Gripen C. Even if F-35s tail span is counted in, its span loading is still 1.138 kg/m.

    This can be confirmed with known turn performance data. F-35A has ITR corner speed of 9 g @ 370 kts and 15.000 ft and STR of 4,95 g @ M 0,8 at same altitude. This translates into ITR of 26,6 deg/s and STR of 10,8 deg/s. Rafale C has ITR corner speed of 330 kts for 11 g instantaneous turn (altitude unknown) and 350 kts for 9 g sustained turn at 25.000 ft, translating into instantaneous turn rate of 36,4 deg/s and sustained turn rate of 28,1 deg/s; at 15.000 ft, sustained turn rate at least should be even higher. Typhoon should have comparable STR and slightly lower ITR when compared to Rafale. Since two degrees per second turn rate difference allows pilot to dominate adversary in dogfight, it is clear that the F-35 is seriously outmatched in dogfight against both twin-engined Eurocanards, and quite certainly against Gripen as well.

    In terms of acceleration, F-35s acceleration when clean is inferior to Eurocanards’ acceleration with combat load. This can be seen from speed limits. Clean F-35 is limited to Mach 1,6, which is a thrust-to-drag limit. All Eurocanards can reach Mach 2,0-2,1 in afterburner. Moreover, M 2 is not a thrust-to-drag limit but rather engine pressure recovery limit. Had Eurocanards used F-15-style multi-shock inlets, their top speeds would have been significantly higher. Similarly, while F-35 has a cruise speed of M 0,95 on dry thrust (and slightly above Mach 1 with low afterburner), all Eurocanards can fly above Mach 1 at dry thrust – M 1,15 for Gripen C with 6 AAM, M 1,3 for Gripen E with 6 AAM, M 1,4 for Rafale with 6 AAM and M 1,5 for Typhoon with 6 AAM.

    Gripen A can accelerate from M 0,5 to M 1,1 in 30 seconds with 6 missiles. F-35A takes 63 seconds to accelerate from M 0,8 to 1,2 while Rafale C accelerates from M 0,8 to M 1,2 in 26 seconds with 4 MICA and 50% fuel. Part of this is due to Eurocanards’ superior aerodynamics and engines, while part of it is simply due to the F-35s large frontal area, as can be seen below.

    [​IMG]

    From all of the above, it is clear that the F-35 cannot outmaneuver any of Eurocanards in air-to-air configuration. This claim likely does hold true in air-to-ground configuration. But, just like with the F-16, that is a problem: F-35 is intended to replace the F-16 and F-18, both of which are primarily air superiority fighters. Countries that buy only the F-35 will have to rely on it for all missions – air-to-air and air-to-ground. But the F-35 cannot adequately perform air-to-air missions, while all Eurocanards have excellent air-to-air and adequate air-to-ground performance.
     
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  4. Picard

    Picard Lt. Colonel RESEARCHER

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    CLAIM: F-35 uses nontraditional wing and body geometry

    It is true that the F-35 uses extensive wing-body blending to increase amount of lift at high angles of attack. But this does not give it much of an advantage, because (nearly) everybody else does it as well. While claim that it can completely compensate for high wing loading is easily discounted by looking at the figures previously posted, here I will go more into an aerodynamic part of things.

    Wing-body blending is advantageous because it provides a continuous upper surface, which then provides lift. While non-blended wide body aircraft also can have some body lift, it will not be as much as in blended configurations. In this regard, it is a large advantage for any aircraft that have it compared to aircraft that don’t. But it is not large advantage for the F-35, for one very simple reason: almost everybody does it. First Western fighter which consciously used wing-body blending was the F-16, though the F-14 and F-15 already had massive amount of body lift. In fact, body lift was 40% of the total lift in the F-14 and 45% in the F-16. Since then, it has been used in most modern fighters: F-22, F-35, Rafale, Gripen, Su-27/30/35, MiG-29/35, with Rafale and Gripen in particular being similar to the F-16 in terms of wing-body blending (but otherwise far more aerodynamically advanced). Sole exceptions to this are Mirage variants and Eurofighter Typhoon, designs optimized for supersonic interception at the expense of dogfight performance. In fact, Typhoon is aerodynamically more or less identical to Mirage, a design which first flew in 1955 (only exceptions being air intake locations and addition of canards; though Mirage IIIRS had canards, these were of close-coupled variety).

    Wing-body blending does not make “wing loading” metric irrelevant. In fact, it makes it more relevant, as traditional wing loading metric also includes major body surface area in the calculation, as can be seen below:

    [​IMG]

    And while top view comparison of the F-16 and F-35 might suggest that F-35s body isn’t very wide, this is an incorrect impression as F-16 has large LERX surfaces and very flat top body. Frontal comparison shows the F-35 to be far “fatter” than either F-16 or Rafale (Rafale’s body is about as wide, but much flatter).
     
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  5. Picard

    Picard Lt. Colonel RESEARCHER

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    CLAIM: F-35 is stealth aircraft

    Answer: it depends, but most of the time, it is not.

    F-35 does have extensive radar signature reduction measures. But these are only effective against active X-band radar emitters that are more or less level with the F-35. As soon as it banks, it will reveal its presence. They are also rather limited in effectiveness against long-wavelength radars. While the F-35 will still have lower radar cross section in VHF band when compared to the legacy aircraft, difference will not be large as its tail and wing surfaces will either resonate with radio waves, scatter them or both. When wavelengths are comparable to shaping features (wings, stabilizers), resonance occurs, creating electrical charge and increasing RCS; if wavelengths are larger than shaping features, scattering occurs (same scattering that is responsible for the sky being blue). In HF band (over-the-horizon radars), wavelengths are comparable or larger than the aircraft itself; as a result, HF radars render any and all RCS reduction measures superfluous.

    [​IMG]

    [​IMG]

    [This also suggests that the best planforms for radar stealth would be tailless canardless delta/trapezoid with high amount of wing-body blending, or a flying wing.]

    Its IR signature reduction measures are rather less impressive, and are mostly an afterthought. Its nozzle is coated in ceramics and has serrated shape which helps, to an extent, mixing of hot exhaust plume with the ambient air. But ceramic coating was placed to reduce nozzle wear due to extremely hot exhaust gasses, while serrations are there primarily to reduce aft RCS. It does help that its engine is a high-bypass turbofan, but it is also the hottest-running engine on the market; again, bypass ratio was chosen to improve low level performance and not to reduce IR signature. F-35 also uses its own fuel as a coolant, which has a possibility of significantly raising aircraft’s thermal signature as aircraft heats up during a long mission while quantity of fuel to store excess thermal energy in gets ever lower. Its inability to supercruise means that it has to choose between a heavy speed disadvantage and massive IR signature penalty of afterburner – and supercruising fighters can match or surpass the F-35s dash speed of Mach 1,6 with far less IR signature increase due to either not having to use afterburner or at least not having to use full afterburner to achieve speeds of >= M 1,6.

    Due to combat radius of 830 – 1.100 km (depending on a variant), F-35 will in many situations have to use external fuel tanks. Aside from reducing its already low maximum cruise speed, external tanks will also increase aircraft’s IR signature and significantly increase its RCS, even if “stealth” tanks are desiged (due to interaction between airframe and external stores, total RCS will be higher than additive RCS of airframe and said stores, unless conformal or internal carriage is used; conformal/wingtip carriage can only be done with missiles).

    It is true that it will be extremely hard to find. This has nothing to do with stealth, however. Rather, its huge price tag and maintenance downtime will lead to very sporadic appearance over enemy skies. At price of 120-145 million USD per aircraft, and sortie rate of one sortie per every two to three days, it will produce 2-4 sorties per every billion procurement USD. Compare to Rafale C’s 22 sorties per every billion procurement USD, F-16Cs 15-20 sorties per every billion procurement USDs and Gripen Cs 44 sorties per every billion procurement USD. This sortie rate is what will make it truly stealthy, both in terms of enemy’s (in)ability to find it as well as in terms of its combat contribution.

    Further reading:

    Stealth in the air « Defense Issues

    Value of stealth aircraft « Defense Issues

    How stealthy is the F-35 « Defense Issues
     
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  6. Picard

    Picard Lt. Colonel RESEARCHER

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    CLAIM: F-35 has the advantage of flying clean

    While it is definetly correct when it comes to air-to-ground missions, it may or may not be correct in air-to-air configurations. As it can be seen from image below, “clean” F-16 has two wingtip AAMs.

    [​IMG]

    “Clean” configurations are as follows: 8 AAM for F-22, 4 AAM for F-35, 4 AAM for Typhoon, 2 AAM for Rafale (with additional two avaliable on low-drag pylons), 2 AAM for Gripen, 2 AAM for F-16.

    Further, air-to-air missiles can have a decisive impact on aircraft performance only when aircraft compared have very similar (almost identical) performance when flying clean. This is nowhere near the case in the F-35 vs Eurocanard comparison. As can be seen from data provided up to now, clean F-35 is still significantly inferior to loaded Eurocanards.

    CLAIM: F-35 is a multirole aircraft

    [​IMG]

    As it can be seen from the above, F-35 is a specialized ground attack aircraft for environments heavily infested with X-band SAMs. It is optimized for air-to-ground lethality, with air-to-air being a secondary concern. (In fact, F-35s air-to-air capability was at first considered purely in terms of self-defense during strike mission, hence all comparisons with other aircraft in strike configurations). It is a strike fighter, similar to the F-18E.

    Even discarding the above, F-35s design is that of a ground attack aircraft. It has high wing loading, providing low gust sensitivity and thus facilitating high-speed low-level flight, but at expense of maneuverability. Sunk cockpit reduces drag but also reduces situational awareness. Large internal bays improve range and performance with air-to-ground munitions but at the expense of kinematic performance. Single-channel midwave IRST under the nose provides excellent resolution and all-weather performance at the expense of detection range at higher altitudes and inability to detect threats above the aircraft. Its turbofan engine, with comparably high bypass ratio and low thrust-to-weight and thrust-to-frontal-area ratios, is similarly optimized for ground attack performance (particularly subsonic endurance) over air-to-air performance.

    CLAIM: F-35 is designed to defeat today’s most advanced air and ground threats

    Wrong. In reality, F-35 was designed to fly ground attack missions deep in the Warsaw Pact territory (deep interdiction, deep strike, SEAD, DEAD). For this reason, it was designed with all-aspect radar stealth, advanced air-to-ground avionics (including radar and internal targeting pod) and capability to carry heavy munitions internally. It was never expected to fight enemy air threats – it would operate alongside the F-22 which would take care of the enemy air threats, leaving the F-35s free to focus on air-to-ground work. Even if the F-35s got caught by the enemy fighters, they only had to keep enemy busy until supercruising F-22s could arrive.

    As it can be seen from one of previous points, it can be detected by ground VHF radars. It can also be detected by over-the-horizont radars, as well as detected and engaged by ground SAM systems using IRST/FLIR as a primary sensor.

    In short, F-35 is designed to defeat 1980s-1990s era threats, and exclusively those of ground variety. Its air-to-air capability always was and will be extremely limited, barely sufficient for self defense.

    CLAIM: F-35 is one aircraft replacing X different aircraft

    While the F-35 is intended to replace the F-16, F-18 and AV-8B aircraft, it is not one aircraft with three variants. Rather, the F-35 is a family of aircraft composed of three dissimilar types. Part commonality is around 25-30% across all three “variants, compared to the initial requirement for 70-80% commonality across three variants. Another 29-41% parts are “cousin” to each other, while 20-43% of parts are completely unique.

    There are some differences that are obvious at the first glance, at either aircraft itself or its specifications. F-35A and C have identical engine, while F-35B has a lift-fan variant which produces less thrust in flight but allows it to land vertically (it cannot take of vertically in combat configuration). On the other hand, F-35A and B have identical wing, while F-35C has a far larger wing as dictated by its carrier requirements. F-35C has a tail hook, and stronger undercarriage when compared to A and B variants, again due to its carrier requirements.

    CLAIM: F-35s namesake, Lockheed Lightning, was the first modern fighter of its day

    How the F-35 Got its Name · Lockheed Martin

    In reality, P-38 Lightning had its first flight in 1939, and entered service in 1940. Supermarine Spitfire entered service in 1938, Messerschmitt Bf-109 entered service in 1937, Bf-110 entered service in 1937. As a result, not only Lightning was not the first modern fighter of its day, it was not even the first modern twin-engined fighter of its day. Only in exclusively US context can the P-38 be considered the first modern fighter, with P-40 entering service in 1940, P-39 in 1941, P-47 and P-51 in 1942.

    Even forgetting such bragging rights reward statements, P-38s combat performance is nothing to be proud of. In Europe, it proved slow, unmaneuverable, and extremely vulnerable to German single-engined fighters. Consequently, its fighter variants were withdrawn from the ETO, while it did continue in photo-reconnaissance and ground attack role. In Pacific, it had higher cruise speed than Japanese Zero, allowing it to achieve surprise attacks despite its large size, and avoid maneuvering combat. As a consequence, it performed relatively well. But P-38s main utility in Pacific theatre was its long range, and the F-35 is no better than other fighters of its weight class in that respect.
     
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  7. BMD

    BMD Lt. Colonel ELITE MEMBER

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    The F-35’s Race Against Time

    The F-35, while not technically a "supercruising" aircraft, can maintain Mach 1.2 for a dash of 150 miles without using fuel-gulping afterburners.

    Also consider the affect of straighter wings on lift and the affect of high BPR engines on subsonic thrust.
     
  8. Picard

    Picard Lt. Colonel RESEARCHER

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    Which can mean two things. Either it uses minimum afterburner for that, or it can do it with extremely limited fuel load (and likely no weapons). Otherwise, considering its fuel fraction and total fuel capacity, it should have been able to supercruise for far longer - even using static sea-level fuel consumption figures, 150 miles uses up less than a third of F-35s internal fuel load, and fuel consumption in installed engine at altitude will be one third to a half of that on sea level.
     
  9. somedude

    somedude Captain FULL MEMBER

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    It means it uses afterburners to go supersonic, and then it merely maintains supersonic speed for a short while.
     
  10. BMD

    BMD Lt. Colonel ELITE MEMBER

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    Which makes it little different to a Gripen or Rafale.
     
  11. somedude

    somedude Captain FULL MEMBER

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    Reaching supersonic speed without afterburners is very different from being only able to stave off decelerating below it for a short while.
     
  12. BMD

    BMD Lt. Colonel ELITE MEMBER

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    Yes and neither the Gripen nor Rafale can do it with a realistic weapons load.

    UK Armed Forces Commentary: Eurofighter Typhoon

    "AFM understands, however, that the evaluation, which was the first time Typhoon had flown outside Europe (redeploying together with a VC10 air tanker), was a resounding success. Though BAE and Eurofighter will not confirm any details, it is believed that the two aircraft (they were RAF T1 fighters) flew 28 missions, totalling 35 flying hours, during the course of which the aircraft convincingly demonstrated its air-to-air capabilities, first against a pair of F-16s and then against a package of six F-5S and F-16C/D aircraft. It also demonstrated its ability to 'supercruise' (fly supersonically without reheat), achieving Mach 1.21 on a normal, hot Singapore day. This impressed the Singaporeans - and Typhoon's rival bidders, whose aircraft require reheat for supersonic flight.
    "They didn't wait for the cool evening, they didn't wait for a cooler day - they just went out and did it in a hot, daytime, tropical environment," one Rafale programme insider told AFM, with grudging admiration.
     
  13. Picard

    Picard Lt. Colonel RESEARCHER

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    Rafale and Gripen can sustain supercruise with air-to-air load.
     
  14. vstol jockey

    vstol jockey Colonel MILITARY STRATEGIST

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    Regarding Gripen, I have my doubts. Gripen does it only in combat weight unlike Rafale, Typhoon and F-22. Moreover mach 1.2 is transonic regime. It is not supersonic regime.
    Infact very few people know that HF-24 used to hit Mach 1.02 Mach with 50% fuel in clean configuration at 36k feet.
     
  15. BMD

    BMD Lt. Colonel ELITE MEMBER

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    Rafale and Gripen both need drop tanks for any realistic mission profile though, especially the Gripen, which has an internal fuel fraction of 29% and is hugely affected by any load. M1.1 with just AAMs is hardly true supercruise performance because as soon as the weather changes, you're back subsonic. Even an F-16 has marginal supercruise with just AAMs but marginal isn't what this is about.
     

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