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For interest, herewith the proposed Impala. The starboard wing is the proposed "wet" wing with supercritical airfoil and tip AAM station. The upgraded Impala lost out to being replaced by the Hawk.

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How come every time my ship comes in, I'm at the airport?

Extended range wing? Not quite, but it was an attempt to make the Impala wing supercritical. It was constrained to be a modification only forward of the front spar.

The ACW was also constrained to leave the rest of the wing behind the front spar the same.

This model of Carver was the last integrated design of the single engined version that I'm aware of. We did start experimenting with our camber design method on the same wing planform and WT tested wing alone models with our designs. We landed up with wings with a leading edge that looked bent (concave upwards) when viewed from the front. You can see similar trends in the wings of the LAVI and Eurofighter.

Based on information I have it sounds like a totally new wing design internally, to include internal wing tanks thereby increasing internal fuel capacity? All this combined with the supercritical airfoil to improve cruise speed. It sounds like it was initiated also partly due to the issues they started picking up with the Impala wing spars towards the late 80's. Double fix I guess - fix an issue while improving capability/performance.

Would these internal tanks only have been in the leading edge extension of the new wing airfoil if they kept the internal structure the same, or did the program start by keeping the same internal structure and evolved later to be a clean sheet design? It still sounds like lower drag and with more fuel it would have an increased range... Or is the "Extended range wing" term something dreamed up by someone outside the project?

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MAMBA

Keep your feet on the ground, and reach for the skies!

The Impala has no wing fuel tanks. All the fuel was in the wingtip tanks and the fuselage tanks. That doesn't mean it's impossible to include wing fuel tanks, but that wasn't really considered. The idea was simply to make a cheap modification leaving as much of the wing structure as possible the same but increasing the critical mach number by 1/10th. The wind tunnel results confirmed that, so as a design exercise it was a success.. Its a tough design challenge because modifying a wing profile ahead of a fixed point is difficult because the 2nd derivative of the profile loft line has to be smooth.

As a digression, its an aerodynamic irony is that the so called "laminar flow" NACA 6 digit profiles of the type used on the Impala and the P-51 Mustang are very good at sub-critical mach numbers, but their drag increases sharply once they go supercritical because they develope very strong shock waves. The weird thing is that the NACA 4 digit profiles of the type the spitfire used were not as low drag at low mach numbers but did behave better at supercritical mach numbers. The Spitfire had the highest achievable dive mach number of all the 2nd world war fighters. Modifying the Impala to have a supercritical wing would have made it faster.

Interesting, thanks Deltawingman

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How come every time my ship comes in, I'm at the airport?

Thanks for the information. What would the origin story then be of the ERW? It sounds very much like it would degrade the capability of the Impala instead of improving it by removing a significant amount (~1/3?) of internal fuel! An increase in cruise speed is only so helpful if you remove a chunk of fuel...

Could it be that the "wet wing" part of this design were proposed future phases and that this design as tested was first given certain constraints to see if there are gains to be made while not modifying the basic wing structure significantly?

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MAMBA

Keep your feet on the ground, and reach for the skies!

there would have been no degradation. No Impala had fuel in the wings. only in the tip tanks and fuselage tank.

I'm not sure I'm following you? How could there not be a range degradation? The ERW exchanges the tip tanks with a missile launch rail. That is a significant volume of fuel being lost with only the fuselage tank remaining if the wings were to remain dry.

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MAMBA

Keep your feet on the ground, and reach for the skies!

Oh, I see what you mean Mamba, A wingtip missile rail is a separate issue. A missile mount would make no sense to me anyway. The Impala is not a fighter so why mount a missile on it, and if someone really wanted to do that underwing mounts would do it. Compensating for lost wingtip tanks with internal wing tanks would be a major reconstruction, so much so they you may as well design a new wing from scratch instead of the relatively cheap option of modifying only the leading edge.

Thanks for clarifying. It is an interesting choice. I was under the impression this was a totally new wing instead of purely a modification to the standard wing. A self defence missile fit makes sense if you recover all the fuel and more in internal tanks with a new wing, but less sense if you are keeping a modified dry wing!

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MAMBA

Keep your feet on the ground, and reach for the skies!

Just for clarity...

Was the concave wing a later design for the Carver?
After this design on the wind tunnel model shown?
Was this concave leading edge fixed, or part of the leading edge slats?

Or are we talking about the ACW for Cheetah?

I'm only talking about design studies for a carver wing. The WT model shown was basic conical camber, (like the Mirage III, F-15 etc) have, Evidence for a computationally optimised delta wing can be seen in the Lavi and the Typhoon.

Another way of describing the front aspect of the leading edge seen here is parabolic washout. These were the sort of results we were getting so I guess we were on the right track.

The ACW was heavily constrained to keep the main wing structure untouched and only modify forward of the front spar and wingtips.


This picture of Rooivalk and the ACW test aircraft is unique in that they were flying in formation at the same speed, which I think was about 120 knots.

I think I understand.
You're saying that the wing selected for the Carver, as seen on the WT model, had basic conical camber on the leading edge, but more akin to the Mirage 2000 as opposed to the (fixed camber) Mirage III because of the moving leading edge devices.
Was a computationally optimised wing to do with varying camber as the wing sweeps away from the fuselage toward the tips?

Do you recall the wing sweep angle of the Carver wing?
I've heard it described as different (less) than the III as well as the 2000. Figure I have seen mentioned was 55 degree sweep, as opposed to the 60 degree for the Mirage III, and 58 degrees for the Mirage 2000.

Having difficulty editing my post so another question if I may:
The leading edge slats/devices on the Carver WT model seem to be quite a bit larger than the ones on the Mirage 2000, when looking at pictures of them deployed.
Is this the case?

Both Mirage 2000 and Mirage III have conical camber but Mirage 2000 has moveable leading edge slats (not slotted) as well. Slats improve manoeuvring performance in the lower speed range. At higher speeds slats are too highly loaded to be extended.

Carver was intended to have a 55deg sweep of the leading edge. Mirage III has 60 deg.

The ACW being fixed improved the manoeuvreing performance at all subsonic speeds, but had a slight supersonic penalty.