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Good Typhoon/Rafale article


Hummingbird

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I was talking about the leading edge root extension, or wing apex strakes, whatever you want to call it. What counts exactly into the wing reference area on both aircraft isn't known. Rafale has a smoothly blended wing/body design, it is smaller and also lighter than the Typhoon. It's more about the ratios rather than the absolute numbers. That's why many people are fooled in believing a larger wing area or higher thrust means superior TWR and lower wing loading. That's only true if everything else is identical and that's not the case. The Rafale is lighter than the Typhoon and this has to be taken into account. It's called thrust WEIGHT ratio for a good reason. 

 

The FCS restrictions of the Typhoon are a result of its aerodynamic design and associated deficiencies. The proposed aerodynamic modification kit may address the extant problems adversly impacting the aircraft's performance in these areas.

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Ah didn't think yuou were talking about the LERX, well given they're deltas, and the fact the EF has dedicated vortice generators, I doubt the Rafale benefits comparatively here. (Also more sweep, more vortice generation benefits off the wing itself)

 

And yes the Rafale is lighter, but it also has quite a bit less thrust, hence the T/W is lower, and it's wing/weight (wing loading reversed) is also lower. The Rafale is also smaller, however conversely it also requires a higher Cl for the same overall lift/weight, which means more lift induced drag.

 

Now it's impossible for us to tell the precise difference between the aircraft, but I'm confident that the EF has the higher STR irrespective of altitude based on the information available (E.g. higher T/W, lower W/L), whilst the Rafale has a higher ITR thanks to a higher available Clmax (higher max lift/weight).

 

Wing ref. area is always as follows:

Wing+Reference+Area.JPGaircraft-collage-showing-wing-design-e15

 


Edited by Hummingbird
Dumb typo corrected (wing/weight vs weight/wing)
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The strakes on the Typhoon don't interact with the wings and the foreplanes doesn't to the extend close coupled canards do. The LERX directly enhance wing lift and keep the airflow attached up to higher AoA. A steeper sweep angle also produces more drag. So everything has its pros and cons and every design reflects a choice of compromises.

 

Talking about ratios, maybe we should add some numbers here.

Rafale C F2 / Typhoon Blk5

Basic Empty Weight = 9500 kg / 11150 kg

Internal fuel load = 4700 kg / 5000 kg

Static Reheat thrust = 2 x 7650 kg / 2 x 9180 kg

Wing area = 45.7 sqm / 51.2 sqm

Wing loading = 310 kg/sqm / 315 kg/sqm

TWR = 1.077 / 1.137

 

As you can see Rafale's  wing loading is in fact slightly lower. Arguably there are variations in these data. The given static thrust is uninstalled and more a thrust class. Fuel weight is dependent on density and operational empty weight is probably a better measure. Weight growth of newer build standards not accounted.

 

Anyway the two are not too far apart, albeit the devil is in the details. I wouldn't want to hazard a guess about actual lift/drag ratios which are as important for sustained turn rates as well. 

 

My take from what I know. Rafale prevails up to 20000 ft, especially below 400 kts. Above that speed both are relatively evenly matched, but the higher it goes the better gets the Typhoon. It is in the higher altitude bands where Typhoon's SEP advantage plays out. Arguably it's just a fraction of what drives the overall weapon system performance.

 

Once Typhoon would get its AMK I'd inclined to believe that Rafale will lose much of the advantages it has in terms of ITR and nose pointing authority. The long coupled foreplane configuration of the Typhoon works entirely different to the close coupled canards of the Rafale. The former are pitch control surfaces with a lever arm, the later are lift enhancing surfaces with no real controll authority. 

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8 hours ago, Spectre11 said:

The strakes on the Typhoon don't interact with the wings and the foreplanes doesn't to the extend close coupled canards do. The LERX directly enhance wing lift and keep the airflow attached up to higher AoA. A steeper sweep angle also produces more drag. So everything has its pros and cons and every design reflects a choice of compromises.

 

 Ofcourse the strakes interact with the wings, that's the point of them being there, as vortex generators to generate a vortice over the wings:

qrc56hoglq151.jpg

 

 

As for your figures, they're quite low for the Rafale, listed empty weight at Dassault is 10,000 kg, incidently the RAF lists about the same for the FGR4 Typhoon, ~10,000 kg. But let's go ahead and use empty weights of 11,000 kg for the EF and 9,850 kg for the Rafale as listed on Wiki.

 

Empty W/L:

9,850 kg / 45.7 sq.m. = 215.5 kg/sq.m.

11,000 kg / 51.2 sq.m. = 214.8 kg/sq.m.

 

Internal fuel capacity is 5,000 kg for the EF, and 4,700 kg for the Rafale:

 

Fueled W/L:

14,550 kg / 45.7 sq.m. = 318.3 kg/sq.m.

16,000 kg / 51.2 sq.m. = 312.5 kg/sq.m.

 

So the EF definitely has the W/L advantage, and the more weight you put on both, the higher the advantage gets.

 

Now for T/W

15,296 kgf (150 kN) / 14,550 kg = 1.051 kgf/kg

18,355 kgf (180 kN) / 16,000 kg = 1.147 kgf/kg

 

Fairly certain I even used a conservative AB power figure for the EF's engines here, as I believe the true figure is 91.2 kN a piece (peace time), and the variable intake lips on the EF should provide an advantage in efficiency at various flight conditions.

 

The lower W/L leads to less required Cl and thus less lift induced drag pr. G (=less thrust required to sustain said G), coupled with a higher T/W to boot this should allow the EF to maintain a higher STR irrespective of altitude.


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8 hours ago, Spectre11 said:

Once Typhoon would get its AMK I'd inclined to believe that Rafale will lose much of the advantages it has in terms of ITR and nose pointing authority. The long coupled foreplane configuration of the Typhoon works entirely different to the close coupled canards of the Rafale. The former are pitch control surfaces with a lever arm, the later are lift enhancing surfaces with no real controll authority. 

 

Here I disagree, they both act as control surfaces (hence why both aircraft deflect their canards downward when in a turn, to prevent uncontrollable pitch up [longitudinal instability]), EF's long lever arm just means less deflection required for the same applied force, which in turn means less trim drag in turns = the whole point of the long lever arm. 

 

Meanwhile the Rafale had to be carrier capable, thus a close coupled canard config was chosen as it provides a higher max Cl at low speeds where the aircraft is more stable (canards now pivot up to lift the nose).


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1 hour ago, F-2 said:

I’ve heard it *may* be part of tranche 4. The Germans seem interested. Imagine AMK and the EJ270 engines? to say nothing of that old tvc option. You’d have a real monster for sim geeks.

 

Yeah, but we won't be flying it in a sim until som 20 years later 😛

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@Hummingbird

Typhoon's fuselage strakes are a rather poor substitute for LERX. As is evident from the image you posted the strakes' vortices disperse in parallel to the wing vortices and their impact on wing lift is relatively most. If that wouldn't be the case the AMK wouldn't propose the introduction of LERX. The fuselage strake vortices first and foremost interact with the airflow around the fin to improve lateral/directional stability and to increase rudder authority in high AoA flight. 

 

The close coupled canards on the Rafale primarily act as dynamic vortice controllers. Ofcourse they deflect when the aircraft maneuvers, but their much closer position relative to the CoG limits their effectiveness as pitch control surfaces, compared to the long coupled arrangement on the Typhoon. 

 

With regard to the figures, I already made clear that there are some inaccuracies and variations. I don't pick the "best data" to make a case, but the figures that are the most reliable. Arguavly the data I have on the Typhoon are definitely more accurate. Rafale's OEW is 10220 kg acc. to data from Dassault on the F3 standard. Typhoon's OEW is around 11840 kg. That includes the pilot, gun rounds, expendables, certain store stations and consumables like oil, unusable fuel etc. Even you own figures show no notable differences in wing loading.

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Quote

As for your figures, they're quite low for the Rafale, listed empty weight at Dassault is 10,000 kg, incidently the RAF lists about the same for the FGR4 Typhoon, ~10,000 kg. But let's go ahead and use empty weights of 11,000 kg for the EF and 9,850 kg for the Rafale as listed on Wiki.

 

Empty W/L:

9,850 kg / 45.7 sq.m. = 215.5 kg/sq.m.

11,000 kg / 51.2 sq.m. = 214.8 kg/sq.m.

 

Wiki is not a reliable source and Dassault just say 10t class. The best website about the rafale give a empty mass of 9.35t for Rafale C

https://omnirole-rafale.com/performances/

 

Quote

 

 Ofcourse the strakes interact with the wings, that's the point of them being there, as vortex generators to generate a vortice over the wings:

 

Strakes are far less efficient than close coupled canard. Mirage 2000 use the same things.

 

 

Quote

The lower W/L leads to less required Cl and thus less lift induced drag pr. G (=less thrust required to sustain said G), coupled with a higher T/W to boot this should allow the EF to maintain a higher STR irrespective of altitude.

 

Typhoon has a highter sweept wing so a lower lift to drag ratio than Rafale for turning.

 


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8 hours ago, Spectre11 said:

@Hummingbird

Typhoon's fuselage strakes are a rather poor substitute for LERX. As is evident from the image you posted the strakes' vortices disperse in parallel to the wing vortices and their impact on wing lift is relatively most. If that wouldn't be the case the AMK wouldn't propose the introduction of LERX. The fuselage strake vortices first and foremost interact with the airflow around the fin to improve lateral/directional stability and to increase rudder authority in high AoA flight. 

 

The close coupled canards on the Rafale primarily act as dynamic vortice controllers. Ofcourse they deflect when the aircraft maneuvers, but their much closer position relative to the CoG limits their effectiveness as pitch control surfaces, compared to the long coupled arrangement on the Typhoon. 

 

With regard to the figures, I already made clear that there are some inaccuracies and variations. I don't pick the "best data" to make a case, but the figures that are the most reliable. Arguavly the data I have on the Typhoon are definitely more accurate. Rafale's OEW is 10220 kg acc. to data from Dassault on the F3 standard. Typhoon's OEW is around 11840 kg. That includes the pilot, gun rounds, expendables, certain store stations and consumables like oil, unusable fuel etc. Even you own figures show no notable differences in wing loading.

 

The EF doesn't need LERX to generate vortices, a wing sweep angle of over 52 deg generates strong vortices over the top of the wing. The Rafale on the other hand needs the higher swept LERX for these vortices to form. 

 

And the Rafale's canards are essential pitch control surfaces just as on the EF, no difference in that respect at all, they just have different added benefits. The close coupled canards add more to the Clmax (esp. at low speeds) as the vortices that form over the edges of the carnard start closer to the main wing. The strakes on the EF are there to achieve a similar effect, however since they are smaller & fixed they cannot add the same total increase in lift that the close coupled canards can at low speeds or very high AoA. On the other hand the closer coupled canards require more deflection to generate the same pitching moment as longer coupled ones, hence more trim drag is generated (i.e. more down trim is required in a turn), esp. in a sustained turn at speed. There is no free lunch in aero.

 

The AMK upgrade proposed for the EF is there to solve control issues at high AoA that nessicated the 25 deg limit, aiming amongst other things to make the vortices break down later in the AoA range, which in turn is going to add a lot to the total lift available. Drag is gonna go up though.


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6 hours ago, Hummingbird said:

 

 

The EF doesn't need LERX to generate vortices, a wing sweep angle of over 52 deg generates strong vortices over the top of the wing. The Rafale on the other hand needs the higher swept LERX for these vortices to form. 

 

And the Rafale's canards are essential pitch control surfaces just as on the EF, no difference in that respect at all, they just have different added benefits. The close coupled canards add more to the Clmax (esp. at low speeds) as the vortices that form over the edges of the carnard start closer to the main wing. The strakes on the EF are there to achieve a similar effect, however since they are smaller & fixed they cannot add the same total increase in lift that the close coupled canards can at low speeds or very high AoA. On the other hand the closer coupled canards require more deflection to generate the same pitching moment as longer coupled ones, hence more trim drag is generated (i.e. more down trim is required in a turn), esp. in a sustained turn at speed. There is no free lunch in aero.

 

The AMK upgrade proposed for the EF is there to solve control issues at high AoA that nessicated the 25 deg limit, aiming amongst other things to make the vortices break down later in the AoA range, which in turn is going to add a lot to the total lift available. Drag is gonna go up though.

 

I agree that everything has its price. Your statement that Rafale's LERX are necessary to build up the vortices in the first place is odd though. A 48° sweep angle is perfectly good enough. The LERX are there for the benefits they add and from which Typhoon would benefit in the same way. The results from the original strakes programme culminating in the 2007 flight trials on DA5 and the subsequent evolution towards AMK and the associated flight trials on IPA7 in 2014/2015 are a testimony of this very fact. In its current gorm the Typhoon is constrained in that field and actually non-compliant with its performance spec. The EFEM programme was launched precisely for that reason, to recover performance shortfalls which were serious enough to warrant the effort behind it, but not serious enough to become a top priority for the operators.

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There's a lot more to L/D ratio than just wing sweep mate

 

Of course but a 53 degrees swept wing is going to be more draggy than a 48 degrees swept wing anyway when turning.

 

Quote

The EF doesn't need LERX to generate vortices, a wing sweep angle of over 52 deg generates strong vortices over the top of the wing. The Rafale on the other hand needs the higher swept LERX for these vortices to form. 

 

A 48 degrees delta wing generate already a lot of vortex and the lift coeficcient of a 53 degrees swept wing is always going to be less than a 48 degrees swept wing whatever the AoA, speed and altitude.

 

 

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33 minutes ago, dontum said:

 

Of course but a 53 degrees swept wing is going to be more draggy than a 48 degrees swept wing anyway when turning.

 

 

A 48 degrees delta wing generate already a lot of vortex and the lift coeficcient of a 53 degrees swept wing is always going to be less than a 48 degrees swept wing whatever the AoA, speed and altitude.

 

 

 

Keep in mind that lift and drag go hand in hand. The advantage the Rafale has in sweep angle is mitigated by the disadvantage in W/L which means a higher required Cl pr G.

 

Furthermore the actual L/D ratio of the aircraft in various conditions depends on other factors than just the AR, as mentioned W/L, thickness ratio, trim drag, LE + TE devices etc all influence this.

 

So you cannot claim the Rafale has a higher L/D ratio under all conditions.


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12 hours ago, Spectre11 said:

I agree that everything has its price. Your statement that Rafale's LERX are necessary to build up the vortices in the first place is odd though. A 48° sweep angle is perfectly good enough. The LERX are there for the benefits they add and from which Typhoon would benefit in the same way. The results from the original strakes programme culminating in the 2007 flight trials on DA5 and the subsequent evolution towards AMK and the associated flight trials on IPA7 in 2014/2015 are a testimony of this very fact. In its current gorm the Typhoon is constrained in that field and actually non-compliant with its performance spec. The EFEM programme was launched precisely for that reason, to recover performance shortfalls which were serious enough to warrant the effort behind it, but not serious enough to become a top priority for the operators.

 

Thing is sweep angles under 52 deg don't generate particularly strong vortices by themselves, which leads to early break up. The Rafale's LERX solves this and the canards help strengthen them further when riding the lift limit. On the EF the strakes help strengthen the strong vortices already forming on the wing, however at low speed & high AoA they are not as strong in the end as on the Rafale thanks to the LERX + close coupled canards combination, hence the EF ends up with a lower max controllable AoA and thus Clmax as result. (i.e. the Rafale's tightest turn will be tighter, and it's landing speeds will be lower) However within the controllable AoA range the EF experiences lower trim drag thanks to the longer coupled canards, and since a lower Cl is required for the same G on top, this results in very high efficiency in a sustained turn where you're not riding the lift limit, but instead the Ps=0. (i.e. the EF's max STR should be higher)

 

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Keep in mind that lift and drag go hand in hand. The advantage the Rafale has in sweep angle is mitigated by the disadvantage in W/L which means a higher required Cl pr G.

 

But Rafale has also a lower wingload but wingload has nothing to do with sustain turn rate. What matter is lift to drag ratio and TWR.

 

Quote

Thing is sweep angles under 52 deg don't generate particularly strong vortices by themselves, which leads to early break up. The Rafale's LERX solves this and the canards help strengthen them further when riding the lift limit.

 

Wrong any delta wing generate lots of vortex lift especially the rafale wing with it's Leading-edge slat.

 

Dassault had a lot more experience with Delta Wing than any one in the eurofighter team.

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3 hours ago, dontum said:

 

But Rafale has also a lower wingload but wingload has nothing to do with sustain turn rate. What matter is lift to drag ratio and TWR.

 

No, the EF has the lower wing loading, esp. once you start loading up the aircraft. And wing loading certainly has something to do with sustainable turn rate as a lower W/L means less Cl required pr. G and thus less drag generated as well.

 

Remember the drag equation: 

Cdi = (Cl^2) / (pi * AR * e)

Cd = Cdo + Cdi

D = Cd * A * .5 * r * V^2

 

Now guess where most of the drag comes from in a turn?: From the lift generated, i.e. the lift induced drag (Cdi).

 

Next we got trim drag, and  sincethe EF features a longer coupled canard config it also requires less canard deflection for the same pitch moment, which in turn means less trim drag.

 

Quote

Dassault had a lot more experience with Delta Wing than any one in the eurofighter team.

 

Oh no, not this again....


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  • 2 weeks later...
On 2/10/2021 at 6:07 PM, Spectre11 said:

...

 

Once Typhoon would get its AMK I'd inclined to believe that Rafale will lose much of the advantages it has in terms of ITR and nose pointing authority. The long coupled foreplane configuration of the Typhoon works entirely different to the close coupled canards of the Rafale. The former are pitch control surfaces with a lever arm, the later are lift enhancing surfaces with no real controll authority. 

 

This I didn't know...

 

Thank you for the heads up.

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1 hour ago, Spurts said:

As it stands right now AMK is never going to happen.  No nation has requested it in their orders.  That said, yes it would eliminate many of the areas where the Typhoon gives up advantage to other types.

 

In that case that's a pity, but I fully understand the economics factor behind decisions of this nature.

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