F-35 Lightning II vs Dassault Rafale

The F-35 compared with other modern jets.
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dwightlooi

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Unread post04 Jan 2008, 01:34

LowObservable wrote:Whoa.
Missing element here is that the payload-range performance (along with the fuel burn, ELP) is determined by MTOW (thrust/aerodynamics), L/D (wing design, and yes, external stores if carried, and until jetissoned), SFC (engine cycle mostly) and fuel fraction (internal and external and related to clean MTOW).
JSF with internal only weapons (and DL, you should really specify "eight very small bombs") doesn't have the drag of external tanks or weapons; but to do this it carries an extra two tons of metal, all the time; and it is fatter, all the time; and A and B have the little wing demanded by the B.
It's also a mistake to assume that JSF-A can carry all that internal fuel, internal weapons AND a Typhoon/Rafale-like external load. It doesn't have the hardpoints or the lift to do that.


(1) The F-35A/B does not have a tiny wing. It has a wing size that is quite optimal. It has in fact a slightly larger wing per unit weight than say an F-16. In addition, the body of the F-35 also generates a lot of lift – probably more than enough to keep the aircraft aloft even if you remove the wings entirely when it is moving higher subsonic speeds. Do not underestimate bodylift. Even an F-15 can not only fly but LAND with one wing totally removed.

(2) The extra enveloped volume it takes to enclose the additional internal fuel and weapons will never result in drag that is anywhere near that generated by those stores carried externally. The reason is two fold. Firstly, the shaping is much more cohesive from an aerodynamics standpoint than external pylons and a collection of cylindrical ogives. Secondly, the wetted surface area is much lower. The having about 6 to 8 empty pylons in the air stream may in fact incur just as much drag as the F-35 does with its bulked up fuselage that holds those additional fuel and weapons bays.

(3) Finally, the F-35A does actually match the approximate total ordnance carrying capacity of the EF and the Rafale – both in weight and in space. The F-35A will carry a total of 7.2 tons of ordnance in addition to 8.4 tons of fuel. The EF will lug 7.4 tons of ordnance and 4.5 tons of fuel (2-seaters carry less gas). The Rafale M carries 9.6 tons of ordnance with 4.9 tons of fuel.

(4) Let’s put it this way. If you are carrying 6 x 2,000 pounders plus 4 AAMs, that’s “only” about 5.9 tons. Each of those huge 600 gallon ferry tanks are about 2 tons. Carry two of those huge 2300 liter tanks, 6 x 1000 lb bombs and 2 AAMs and that’s about 7.2 tons. In short all these aircraft can lift just about ANYTHING you can sling on those pylons. Space, not load is usually the limiting factor.

(5) The F-35A has enough “space” for a load such as 2 x AIM-120C/Ds + 2 x 2,000 lbs JDAMs internally. Plus, enough external “room” for 8 x 1000 pound bombs or 4 x 2,000 lbs bombs + two more AAMs. While carrying all of these and no external tanks, it is already carrying the equivalent of a Typhoon or a Rafale’s total fuel load with two ferry tanks, or if you want you can sling two massive tanks on the inner two underwing hardpoints rated for 5000 lbs.
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elp

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Unread post04 Jan 2008, 04:29

Hi DW. Hope you had a good holiday!

Consider right now that external tanks for the JSF are off the SDD schedule.

Be interesting to see what they come up with in this area post SDD. Same tank? Different design?
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dwightlooi

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Unread post04 Jan 2008, 06:38

elp wrote:Hi DW. Hope you had a good holiday!

Consider right now that external tanks for the JSF are off the SDD schedule.

Be interesting to see what they come up with in this area post SDD. Same tank? Different design?


Not in the SDD doesn't mean it's not part of the F-35 ordnance set. It just mean that its not a priority to be integrated by IOC (circa 2011) Remember that this aircraft essentially has the ferry range of fighters like the Typhoon with just its internal fuel.

Image

The F-35 tanks as disclosed in the 2005-2006 briefs are "only" 1620 liters or about 1.3 tons of fuel each. They should weigh in at about 3000~3200 lbs of which about 2850 lbs is the fuel. The inner hard points under the wings are good for 5000 lbs so they are not maximizing the carrying capacity of the airframe. The tanks however are heavily area ruled and do not appear to be ferry tanks but rather supersonic tanks. Like the Raptor tanks, it appears that the "pylon" is integrated into the tank's structure and not a separate component. It is prudent to assume that the F-35 will drop the pylon along with the tank to revert back to its stealthy configuration.

Image
F-22 dropping its tanks and pylons.
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Corsair1963

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Unread post04 Jan 2008, 15:30

At what point is the AIM-9X suppose to be intergraded to fit the internal bays of the F-35. As I can't see US Versions flying around with the ASRAAM............... :doh:
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dwightlooi

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Unread post04 Jan 2008, 16:47

Corsair1963 wrote:At what point is the AIM-9X suppose to be intergraded to fit the internal bays of the F-35. As I can't see US Versions flying around with the ASRAAM............... :doh:


That is not a priority right now. That is to say the F-35 will fly with only internal AMRAAMs at IOC (2011). The problem is NOT the F-35. The problem is the AIM-9X, which at this time needs to be launched off a rail. ALL the internal positions on the F-35, including the ones on the inner bay doors are not rails, they are ejectors. So what needs to happen is the creation of an AIM-9X variant that accommodates ejector launch.

On a rail, the missile lights its motor leaves horizontally. On an ejector, the missile is jettisoned vertically an lights its motor after it has been released. The data receptable on the AIM-9X -- like those on earlier AIM-9s -- are designed solely for horizontal severance and the programming on the missiles are for ignitiion on launch not after.
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Pilotasso

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Unread post04 Jan 2008, 17:00

I think the stealth profile in the F-35 is meant to be used for AG missions with minimal AA self defense only. Remenber its not an F-22 and it still remains well above average AA platform with Sidwinders externaly. You cant have the best of both worlds without paying a premium for it. ;)
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elp

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Unread post04 Jan 2008, 17:13

dwightlooi wrote:Not in the SDD doesn't mean it's not part of the F-35 ordnance set.


Well, that chart is about all anyone has. The upper right hand corner states the purpose of the chart. When funds in the form of a contract appear for the drop tanks... then we will know.
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Smithsguy

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Unread post04 Jan 2008, 21:24

dwightlooi wrote:That is not a priority right now. That is to say the F-35 will fly with only internal AMRAAMs at IOC (2011). The problem is NOT the F-35. The problem is the AIM-9X, which at this time needs to be launched off a rail. ALL the internal positions on the F-35, including the ones on the inner bay doors are not rails, they are ejectors. So what needs to happen is the creation of an AIM-9X variant that accommodates ejector launch.


Dwight,

Two questions:
1, isn't there going to be an "internal" version of the ARL for the bay AA positions?
2, and is the proposed trapeze for the AG positions connected to a rail or an ejector?

Either would allow AIM-9Xs in the bays, correct?

Ciao,
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LowObservable

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Unread post04 Jan 2008, 21:53

Coupla points...

Negatory on the body lift. If you want to get into an F-35 modded with explosive bolts that chop off the wings in level high-subsonic flight, let me know and I'll video it for YouTube and the Darwins.

The wing loading comparison between the F-35 and other aircraft gets interesting because of the F-35's wide body. Unless there is seriously useful and efficient body lift (and a Tooth Fairy) the classic geometrical comparison tells only half the story. In fact, there's a very clear benchmark: the Super Bug. It's about the same size as the F-35C, meets about the same approach speed criteria - but the F-35C needs (in classic geometric terms) more than one-third more wing area. So where's your body lift?

My guess is that the F-35A will max out with standard internal load, 425 USG tanks (when and if they are restored to the program), 4 x 1000 lb bombs on the mid pylons and SRAAMs outboard. Anything more and take-off velocities are going to get exciting.

There are times when internal fuel and weapons do generate more drag than external; to wit, when the weapons are expended and tanks dropped, or when they're not required. Also, I'd ask you seriously whether semi-conformal AMRAAMs, for instance, are less efficient in weight and drag terms than AMRAAMs in an internal bay. I would bet not.

On the JSF tanks: I don't think they're area-ruled. I think they're diameter-constrained at the mid-wing point to stop them being toasted by the roll post nozzles.
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dwightlooi

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Unread post04 Jan 2008, 22:47

Smithsguy wrote:
dwightlooi wrote:That is not a priority right now. That is to say the F-35 will fly with only internal AMRAAMs at IOC (2011). The problem is NOT the F-35. The problem is the AIM-9X, which at this time needs to be launched off a rail. ALL the internal positions on the F-35, including the ones on the inner bay doors are not rails, they are ejectors. So what needs to happen is the creation of an AIM-9X variant that accommodates ejector launch.


Dwight,

Two questions:
1, isn't there going to be an "internal" version of the ARL for the bay AA positions?
2, and is the proposed trapeze for the AG positions connected to a rail or an ejector?

Either would allow AIM-9Xs in the bays, correct?

Ciao,
Smithsguy


No, the internal positions are all ejectors. The two door mounted AMRAAMs or ASRAAMs will be ejected not rail launched. Whether you put single bombs, 4 x SDBs, an AMRAAM or two on the "A2G" station these are all ejected not rail launched. The same can be said of the F-22's underside bays. The F-22 however uses rails on the sidebays specifically for the Sidewinders.

In short the only way to put AIM-9Xs inside an F-35 is to create an ejector compliant AIM-9X. This is also the simplest solution.
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dwightlooi

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Unread post05 Jan 2008, 00:55

LowObservable wrote:Coupla points...
The wing loading comparison between the F-35 and other aircraft gets interesting because of the F-35's wide body. Unless there is seriously useful and efficient body lift (and a Tooth Fairy) the classic geometrical comparison tells only half the story. In fact, there's a very clear benchmark: the Super Bug. It's about the same size as the F-35C, meets about the same approach speed criteria - but the F-35C needs (in classic geometric terms) more than one-third more wing area. So where's your body lift?


There the larger wing is probably needed to meet approach speed requirements. And approach speeds are VERY slow. You need to be going notably faster than near stall speed to have effective body lift. When the Israeli F-15 landed with one wing, it touched down at nearly 260 knots! Thats unsafe for landings but it is actually half as fast as the speed at which an F-15 cruises.

So we know that at about 260 knots the F-15 makes enough body lift to do more than the job of one entire wing and keep the aircraft level and aloft. We also know for instance that even Another thing is that body lift becomes a much larger lift component at high AoA during hard maneuvering. In fact, due to flow separation on the wings it can account for 40~60% of the lift at high AoA.

In otherwords, body lift is much more useful at high speed cruise and flight as well as during hard maneuvering than for lowering landing speeds.
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sprstdlyscottsmn

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Unread post06 Jan 2008, 15:25

Well put, but another point to concider in the Super Bugs favor is that the massive LERXs are NOT counted in wing area yet I guarentee they provide a LOT of lift at all speeds (as they themselves have camber and are in effect low AR wings). The LERXs also allow for more efficient lift through vortex generation. While this is most prevalent at high AOA (20-40) it plays a small role at landing AoA (~8?) as well. The Super Hornet also has lower wing sweep wich allows for higher lift values. You could pnly match the approach speed of a Super Hornet with a 1000ft^2 wing if it had too much sweep.

In short, the Lightning II is a drastically advanced weapons delivery system where the whole is far greater then the sum of the parts. Sadly, however, we still have 6 years or so to see them opperational.
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Scorpion82

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Unread post06 Jan 2008, 20:05

sprstdlyscottsmn wrote:In short, the Lightning II is a drastically advanced weapons delivery system where the whole is far greater then the sum of the parts.


That is true for most modern fighters such as Rafale, Eurofighter, F-22A, probably F/A-18E/F Block II or even newest Russian designs. Avionics networking and sensor fusion are the key to that.
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dwightlooi

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Unread post06 Jan 2008, 21:20

sprstdlyscottsmn wrote:Well put, but another point to concider in the Super Bugs favor is that the massive LERXs are NOT counted in wing area yet I guarentee they provide a LOT of lift at all speeds (as they themselves have camber and are in effect low AR wings). The LERXs also allow for more efficient lift through vortex generation. While this is most prevalent at high AOA (20-40) it plays a small role at landing AoA (~8?) as well. The Super Hornet also has lower wing sweep wich allows for higher lift values. You could pnly match the approach speed of a Super Hornet with a 1000ft^2 wing if it had too much sweep.

In short, the Lightning II is a drastically advanced weapons delivery system where the whole is far greater then the sum of the parts. Sadly, however, we still have 6 years or so to see them opperational.


I think that what most people fail to grasp is that wing loading means very little if anything in modern fighter aircrafts. First, there is the problem of what wing area is. It is the leading and trailing edges of the main wing extended to the center line. It neither accurately reflects the actual size of the "wing" or the actual amount of lift the aircraft can produce in flight. Second, the actual wing itself is no better than the fuselage past a reasonably low AoA. Take a "wing" and place it 45 degrees or even 20 degrees through to the oncoming air stream and basically the unsides deflect air and the upper sides is a turbulent mess of separated flow. All "wings" are not created equal. A long slender wing remains more effective as a "wing" up to a higher AoA than a wide chord wing like Deltas. By "wing" I mean a device which produces lift via the airfoil effect. In other words, at attitudes where hard maneuvering is done, the total surface planar area of the aircraft is more reflective of how well it can turn than how big a wing it carries. Of course things like vortice(s) from LEXes, canards, intake lips, noses, etc all affect the total lift available.

At a fast enough speed wings are in fact a liability. The ASRAAM and some other AAMs are essentially "wingless" save for the small fins in the rear for steering purposes. At ~Mach 2 for instance, essentially near zero AoA already produces sufficient body lift to keep the missile aloft. When maneuvering the wingless ASRAAM rapidly pulls 50Gs, limited by the airframe structure and not the availability of lift. Wings in fact contribute mostly to drag and reduces the kinematic range of the missile.
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Unread post07 Jan 2008, 16:23

I'm waiting to see wing fences show up on the JSF someday. :lol:
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