A-4 Skyhawk bring back the concept for the 21st century

[H_K]

Any thoughts on a next generation, rugged, simple, and cheap A-4 type aircraft built with the same things in mind that made the A-4 so great? For the modern day add some stealth features, light weight materials, an f404 type engine, flyby wire, advanced shaping, etc.

Taking a shot at this from a slightly roundabout angle.

1) What if I started with the tiny Etendard VI, Dassault's contender for NATO's 1950s lightweight tactical strike fighter competition?
2) Replaced the Orpheus turbojet with a modern F404/M88 engine (without afterburning)... almost identical size and weight
3) Added 30 years of Dassault aerodynamic experience (delta + fly-by-wire + canards)
4) And included an optional 2nd seat trainer (as originally planned by Dassault)?

This leads to a 3.9t empty trainer / light attack fighter, optimized for low transonic drag, with a high T/W ratio (5-5.5t of dry thrust), good internal fuel fraction (1.8t of fuel), 25% reduction in fuel consumption vs. the 1950s/60s, and high maneuverability. Oddly reminiscent of the diminutive Mirage I & II. It would likely be able to supercruise (Mach 1.2?) and serve as a back-up fighter, lead-in trainer, and carry 1-2 tons of air-to-ground weapons.

Drumrole... introducing the Dassault "Zephyr":

More pics below, including comparisons to the original Etendard VI, Hawk 100 and Mirage 2000.

 

[SSgtC]

Taking a shot at this from a slightly roundabout angle.

1) What if I started with the tiny Etendard VI, Dassault's light attack contender for NATO's 1950s lightweight tactical strike fighter competition?
2) Replaced the Orpheus turbojet with a modern F404/M88 engine (without afterburning)... almost identical size and weight
3) Added 30 years of Dassault aerodynamic experience (delta + fly-by-wire + canards)
4) And included an optional 2nd seat trainer (as originally planned by Dassault)?

This leads to a 3.9t empty trainer / light attack fighter, optimized for low transonic drag, with a high T/W ratio (5-5.5t of dry thrust), good internal fuel fraction (1.8t of fuel), 25% reduction in fuel consumption vs. the 1950s/60s, and high maneuverability. Oddly reminiscent of the diminutive Mirage I & II. It would likely be able to supercruise (Mach 1.2?) and serve as a back-up fighter, lead-in trainer, and carry 1-2 tons of air-to-ground weapons.

Drumrole... introducing the Dassault "Zephyr":

More pics below, including comparisons to the original Etendard VI, Hawk 100 and Mirage 2000.

So, it's an Alpha Jet? Because the A-4 is in an entirely different weight class from this design. This could carry maybe 4,000 pounds of bombs? The Skyhawk could carry over 9,000 pounds. The A-4 also has 50% more fuel (5,400 pounds vs 3,600 pounds). It's a good design, but it's really just an advanced trainer with a secondary bet light attack role

 

[H_K]

So, it's an Alpha Jet? Because the A-4 is in an entirely different weight class from this design. This could carry maybe 4,000 pounds of bombs? The Skyhawk could carry over 9,000 pounds. The A-4 also has 50% more fuel (5,400 pounds vs 3,600 pounds). It's a good design, but it's really just an advanced trainer with a secondary bet light attack role

I’ll explain the design concept:

1) My first hypothesis is that the A-4’s role as a bomb truck is dead. The mission is no longer “plaster some jungle with bombs” but “destroy targets X, Y and Z with precision weapons”. So while in Vietnam a typical A-4 bomb load was 6-12x 250lb or 500lb bombs (3,000-5,000lb total), a modern load out would focus on small guided ordnance against 2-6 aimpoints (e.g. 2x GBU-12s, 4x SDBs, or 6x Brimstone (1,000-1,500lb total).

2) Second hypothesis is that no one has budget for a dedicated light attack aircraft. So the aircraft needs to also serve as a LIFT trainer.

3) Final hypothesis is that there is a need for increased “fighter” performance to take some load off expensive front line fighter fleets. Not necessarily for air superiority missions, but more for peacetime air patrols, red air, and more recently anti-drone intercepts.

So why not just buy a T/F-50 or T-7A, which should meet goals #1 and #3? Well I was intrigued by the idea of a smaller, cheaper aircraft, that didn’t require an afterburning F404. Something like Northrop’s N400NT, but with better transonic performance and able to make the best use of limited thrust.

And that’s when I went “aha”! Dassault spent the 1950s experimenting with lightweight, low drag, transonic Mirages and Etendards to offset the crappy engine offerings of the day. And NBMR-1 was all about cheap light attack aircraft powered by the Orpheus, which in its afterburning form turns out to be very similar in size & weight to a modern M88 or F404 without reheat. So if you take the Etendard VI designed for NBMR-1, with its low transonic drag, add a much more powerful and fuel efficient engine, and an even better delta canard planform to reduce transonic drag even further, you have a potentially good starting point.

Like I said, I took a little roundabout way to get there…

Of course it would also be possible to scale-up the basic concept with an F414 EPE, with 30-40% more power. That would be identical to the Skyhawk in size, or bigger.

 

[Scott Kenny]

Before you argue about how stealthy this thing has to be, step back and ask yourself:

Who will be using it? (Consider affordability, etc.)

Against whom? (How much stealth do you really need?)

What tasks will it be asked to perform, and what weapons will it be required to deliver? (Determinant of size, avionics.) It's clearly not going to be an air-superiority platform against a modern fighter (even F-16 era fighters will eat it for breakfast), but if what you want to shoot down is enemy COIN aircraft, helicopters, transports and the occasional maritime snooper, how much of a dogfighter does it need to be?

Who? Let's call it all of the Global South for who is using it. They can afford maybe 24-36 of these for their entire air force.

Versus? Mostly against their neighbors, maybe having to deal with a well funded Chinese-supplied opponent (still their neighbors, but a generation newer hardware)

What tasks? Basic air policing, CAS because it's about the only plane they have, if the country has a coastline this will have to be able to carry antiship missiles (so pylons capable of at least 2000lbs and 3000+ preferred). Basic air policing requires a gun to send a line of tracers past an oblivious idiot's nose to insist that they need to follow your instructions and land, I might go for the cut down M61 they're using on the FA50 or I might go for an M230 or DEFA cannon. I'd like it to have basic LO shaping but no special treatments to mess with. So it'll look more like 5thGen but have an RCS more like 4.5 or 4.75.

So, general "policing" weapons load is probably going to be gun, 2x AIM9, 2x Sparrow/AMRAAM equivalents, and 2x Exocets/Harpoons. 6000lbs or so (counting cannon ammo). Reason for the radar AAMs is bigger warhead, 4x AIM9 is also valid.

A totally crazy idea but I wonder if you were to build an A-4 today with modern composites and a fuel efficient turbofan I wonder how much improvement in weight saving, payload and range you would get?

Depends on how much you replace with composites. Composite skin? maybe 10% weight savings. Yes, the composite panels are lighter, a lot lighter, but the skin doesn't actually make all that much weight of the airframe. You'd need to replace a lot of the internal structure with composites as well to get a big weight decrease.

Should get at least 20% more range out of a modern turbofan, though. You won't save much weight going to an F404 versus a J52, however. Couple hundred pounds or so (I'm not finding an online source for an F412 or other non-afterburning F404 weight).

I think you'd be able to turn that reduced Empty Weight into additional payload.

Remember, the reason the A4 has a 10klb capacity is because it was designed around those massive 1st gen nukes. Single carried under the centerline! Which also explains the height of the landing gear. So when you're running conventional explosives you get a whole lot of bombs under the wings.

Too much of a one off. There's a reason the Strike Eagle was chosen over it. IIRC, the F-16XL was a Falcon in name only, much like the Super Hornet only looked like a legacy Hornet but was in reality a brand new plane. The same applies to the XL. If you need a strike-optimised fighter and don't care about stealth, you might as well buy either an F-15, an F/A-18 or an F-16 Block 70. All of which still have hot production lines and who's manufacturers would love to sell you a plane.

From what I remember reading, the XL was a standard F16 fuselage, with a plug added between the wheels and aft of the MLG. IIRC 4ft forward plug and 2ft aft. So a lot of the existing tooling was still usable. I'm not sure how different the forward and aft plugs were, probably new tooling there. And obviously new tooling for the wings.

 

[Foo Fighter]

Knowing what they know now from this and other developments, the XL5 could be even better.

Sorry, I shall get my coat.

I wonder if there is any Lavi tooling still around or if the PRC has it all.

 

[BlackBat242]

Should get at least 20% more range out of a modern turbofan, though. You won't save much weight going to an F404 versus a J52, however. Couple hundred pounds or so (I'm not finding an online source for an F412 or other non-afterburning F404 weight).

I think you'd be able to turn that reduced Empty Weight into additional payload.

J52:
-6A/B (early A-4E & A-6A/EA-6A): 2,056lb weight, 8,500 lb thrust.
-8A/B (late A-4E/A-4F & A-6E/KA-6D): 2,118 lb weight, 9,300 lb thrust.
-408 (A-4M & EA-6B): 2,318 b weight, 11,200 lb thrust.

F404-100D (F-117 & A-4SU*): 1,830 lb weight, 11,000 lb thrust.

F412 (A-12): 13,000 lb thrust - this was the base used for the F414 - which weighs 230lb (+/-) more than the F404. So the F412 should weigh around 2,030 +/- lb.

* Final upgrade of Singapore's modernized A-4B/Cs.

 

[H_K]

F404-100D (F-117 & A-4SU*): 1,830 lb weight, 11,000 lb thrust.

Thanks. I was having trouble finding this… eventually found GE’s old engine spec sheets archived here, with a lot of good info:

GE Aircraft Engines: Comparison Chart - Military Turbofans

So roughly 375lb / 170kg for the F404’s afterburner section…

 

[Scott Kenny]

J52:
-6A/B (early A-4E & A-6A/EA-6A): 2,056lb weight, 8,500 lb thrust.
-8A/B (late A-4E/A-4F & A-6E/KA-6D): 2,118 lb weight, 9,300 lb thrust.
-408 (A-4M & EA-6B): 2,318 b weight, 11,200 lb thrust.

F404-100D (F-117 & A-4SU*): 1,830 lb weight, 11,000 lb thrust.

F412 (A-12): 13,000 lb thrust - this was the base used for the F414 - which weighs 230lb (+/-) more than the F404. So the F412 should weigh around 2,030 +/- lb.

* Final upgrade of Singapore's modernized A-4B/Cs.

Thank you!

And oh, wow, those A-4SUs must have been hot rods! ~500lbs less engine weight than the A-4M and equivalent thrust.

 

[BlackBat242]

Thank you!

And oh, wow, those A-4SUs must have been hot rods! ~500lbs less engine weight than the A-4M and equivalent thrust.

Their airframes were lighter as well, the A-4B & C weighed 9,146 kb empty as originally equipped*, and the A-4M weighed 10,418 lb empty as originally equipped.

The upgrades (including new and more-extensive avionics) for the A-4S (and a second round for the A-4SU upgrade) did add some weight, but I cannot see that totaling more than the 1,272 lb difference of the original aircraft and the 500 lb engine weight difference combined.


* The A-4E weighed 9,624 lb empty as originally equipped.

 

[BlackBat242]

Oh, I forgot to include the engine weight for the A-4S in their original form.

J65-W-20: 2,795 lb weight; 8,500 lb thrust.

That meant a 935 lb engine weight reduction with a 2,500 lb thrust increase.

 

[H_K]

Thought I'd add a side-by-side comparison of 2 of the small light attack/trainers mentioned on this thread - the Leonardo M-346 and Aero L-159 ALCA.

As a bonus, I added my transonic delta-canard "what-if", the Dassault "Zephyr", which uses the same general dimensions as Dassault's Etendard VI and Mirage II... amazing how small those fighters were, smaller even than the 2 trainers above. It looks suitably "fighty"... I wish I could sketch it out in 3D, but that's beyond my skills!

 

[Scott Kenny]

The a-4 was absolutely loved by its pilots. Cheap and versatile (less than 600k ea when first introduced) Heinemann's hot rod was built for simplicity, ruggedness and performance. It was even more agile than the Mig-17s according to pilots. The last F404 powered version for Singapore (A-4SU) was spectacular in its performance.


Any thoughts on a next generation, rugged, simple, and cheap A-4 type aircraft built with the same things in mind that made the A-4 so great?


For the modern day add some stealth features, light weight materials, an f404 type engine, flyby wire, advanced shaping, etc. Have an air to air version, strike version and possibly a STOL version for the Marines. (I know, sounds like the JSF) BUT KEEP COST DOWN and the aircraft small like the A-4 was.

Well, the original Skyhawk was built around carrying a single nuclear bomb. A single 10,000lb bomb, because this was very early on in terms of nuclear weapons design.

Today, we have nukes that are the size of a 2000lb bomb, give or take. Some are even lighter than that, but not much smaller dimensionally. 64-71cm wide and deep (depends on which guidance package you're using) by ~4m long. Maybe a little longer to hold some missiles, so let's say 4.4m long overall. The extra length also gives you space to stagger weapons so they fit closer together without their wings interfering.

So we need a bomb bay big enough to hold a single 2000lb bomb plus some AAMs. Depending on how it all fits together, you may have space for 8x SDBs plus those two AAMs. As-is the Boeing EWP holds 6x SDB plus 2x AMRAAMs, but can't hold AMRAAMs and a 2000lb bomb. Widening that pod by ~8-10"/20-26cm to get the AMRAAMs clear of the 2000lber gives enough space to add another row of SDBs. AMRAAMs have a 53cm wingspan, but you can overlap the pieces a bit if you're sneaky. Minimum stacking distance is about 36cm (1/2 wingspan + 1/2 diameter). This gives us a bay about 1.5m wide and 4.4m long overall.

Now, the airframe.

Let's skip as much expensive and maintenance intensive RAM as possible. Shape the plane overall for radar stealth, but basically only bother with RAM-treating the canopy and inside the inlets. The canopy because the people making the canopies are mixing the RAM into the canopies already, it'll be cheaper to use RAM canopies than to have them use a custom RAM-free mix for you. Inside the inlets to mask the fan, obviously, and it's mostly protected in there.

For the engine, give me an F414 EPE. ~24,000lbs thrust. If you don't want an American engine so you can sell it to more countries, EJ240 or 270.