Only 21 Mk82s? The F-111 could carry 50 so I guess this mythical Mirage isn’t an F-111 after all.

The F-111 would carry at max 24. The load of 48 is just show-off. There seems to be a particular American affection for heavy load-outs, must be a general mentalityand obsession with “heavy-duty”: they like pick-ups, too.

OK, one more response then I promise I’ll stop dreaming about the Mirage IV.

I would be a little bit careful about the weights. At full take-off weight your delta-winged Mirage has increasing problems of leaving the runway. See the practice of B-58, which were actually fully fueled after take-off.

Field performance of delta-wing aircraft sucks hard.
Theoretical possibilities often go into the bin after some practical considerations kick in:
– is the configuration possible at an ISA+15 day?
– one engine out? that might happen quite easily, and you don’t want to scrap the entire aircraft in that case (which would certainly be the case for a fully loaded aircraft).
– combat radius (while that ain’t necessarily is an issue, see F-4s in Vietnam, which sometimes carried quite a bit of stuff, especially the ‘USMC).

The big thing about the F-111 was that it could fly lower, with more precision and make a single target pass and actually hit the target. Many other aircraft, especially aircraft like the F-105, couldn’t do that, and most times hauled bombs that finally ended up plowing the field. In 1944, 3 out of 4 B-17, flew into Germany for no particular effect (from the military point of view). That is also why a 200,000 USD GBU is cheaper than a 500lbs Mk82, at least when you consider it thoroughly.

Conclusion: many bombs don’t necessarily do many harm. The F-111 had very flexible payload configurations and could haul big payloads if needed. But it was the bigger aircraft. A Mirage IV was a “nuclear-only” aircraft.

If you do decide on the F-111F as a basis for comparison, please keep in mind that you’ll run into other problems doing an apples-to-apples comparison. You’ll be comparing early 1970s engine technology to mid-1960s technology, and the 5th iteration of the F-111 to the 2nd iteration of the Mirage IV. Feel free to do so, but I prefer to compare the best of what was offered to the RAF and RAAF in the mid-1960s, with the technology available at the time.

The TF30 advanced mainly in reliability I think, the basic performance parameters were not that much different.
The differences of the F-111 models are not that huge:
A: basic bomber
B: killed Navy model
C: for Australia with larger wings
D: “Mk2” avionic package
E: model A with some evolution
F: final version, but overall range performance probably same
FB: has more internal fuel, otherwise mainly avionics changes
Overall: range-payload wise the differences shouldn’t be that big except with the FB-111 due to more internal fuel.

The last F-111 left the factory 1976.

I do get this quite well. My point is that IF you decide to compromise on field performance, then the F-111 becomes an expensive & rather average design. The reasons for such a compromise could be many: maybe you realize that your planes are still going to be vulnerable on the tarmac, or that you simply can’t afford the extra cost, or that you’ve already compromised for the rest of your airforce (F-4 Phantom & Buccaneer). The RAF ended up canning the entire requirement – but had they compromised, then they might have ended up with a good long-ranged supersonic bomber, instead of nothing at all.

That is accepted.
While all three aircraft (Mirage IV, F-111, TSR.2) were quite heavy and expensive approaches. In the end they sticked to the Buccaneer and finally ended up having a Tornado, which is F-111 technology at Mirage IV size, with performance tailor-made for the European scenario.

– Aircraft Weight
As you pointed out, the Mirage IV is much lighter. So it’s necessary to adjust for size, as you tried to do. However, a delta is also much lighter structurally than a VG wing. It has lower loads and fewer moving parts, and also allows for a smaller, lighter fuselage since more fuel can be stored in the wing. So it simply doesn’t need to be as heavy to achieve the same payload/range specifications. Therefore, the range per flying weight benchmark is misleading, because it ignores the fact that a VG aircraft’s more efficient range per flying weight is partly/wholly canceled out by it’s higher flying weight.

No dispute. The VG additional weight must be compensated. So, the VG only justifies where very special requirements apply. the Mirage IV would be an interesting aircraft with canards and significant subsonic instability, along with leading edge slats and an internal weapons bay. Basically having it based on the Mirage 2000 instead of the III.

– Payload/Range
To guesstimate aerodynamic efficiency, it’s not very useful to compare an aircraft that has external fuel tanks with one that doesn’t. I prefer to compare two aircraft in similar same aerodynamic configurations (e.g. internal fuel only, or with an identical number of tanks). We’re not trying to figure out which aircraft is better for a given range, so I don’t mind if the ranges are slightly different. As long as the difference in range is only about 10-20%, I can assume that adding a small fuselage plug or conformal tanks would allow you to match the two aircraft’s range without fundamentally changing the aerodynamic efficiency.

We can use the F-106 and the F-14/MiG-23 as basis, and I’ll show you the big advantage for subsonic long range cruise.

– Engine efficiency
The Atar is a highly inefficient engine, with a dry SFC of 0.99kg/daN. The Spey has an SFC of 0.64, about 35% less. When comparing a vanilla Mirage IV to the F-111, you need to keep in mind this difference. That’s why I focus on the Spey Mirage, because it would benefit from this improved SFC, minus some efficiency losses due to the increased structural weight and higher drag in cruise.

The SFC disadvantage is also depending on the operating conditions. The TF scores very good in low-level cruise flight, as TJs really are wasteful here.

– Use F-111A or FB-111 as a benchmark?
Going back to the issue of aircraft weight, the F-111A is closer to the Mirage IV in terms of weights and mission requirements. The FB-111 is basically an F-111A with a more cruise-optimized wing and more internal fuel in an enlarged fuselage. It’s much more efficient in cruise than an F-111A, but is it really an apples-to-apples comparison with the Mirage IV?

I don’t have the exact figures for the F-111, only the FB-111A. It profits from more internal fuel and latest TF30 engine model.

For an apples-to-apples comparison you have to use the closest comparables in terms of range/weight/performance/payload, which IMHO are the Spey Mirage and F-111A. They are quite similar, except that the Spey Mirage gets to the same destination using ~20% less fuel. That supports my argument that the delta configuration is at least as efficient as the F-111’s VG configuration in cruise. Certainly nothing like the absolute disaster you painted. As a next step, it might be interesting to compare an F-111 with a SU-24 or F-14, because both were later, more efficient VG designs.

Don’t get me wrong. We can talk about aerodynamic and propulsive efficiency {kg/(km*t)]. And we can talk about mission efficiency [kg/km]. The latter with a fixed payload. The additional range of the F-111 can be total waste if you don’t need it. To drop a bomb 300nm from base, the Mirage 2000N beats them all.

(To compare the Spey Mirage to the FB-111, I’d want to increase its size to make its payload & internal fuel match the FB-111 better, which is too hypothetical…)

The whole point is what is the mission?
If the mission is to deliver a tactical nuclear weapon, or at least possess the ability to do so, from possibly partly disabled airfields versus a dense air defense network, over a radius of 500nm+ in Lo-Lo-Lo, you gonna end up with something like a turbo-fan equipped swing wing. If you compromise on these requirements and rather look at it “we have this aircraft, what can it possibly do?”, then the Spey’ed Mirage is possibly a good contender.
I took object on the statement that a Mirage IV will have better or similar efficiency and will overall be the more capable aircraft. That is not true, it might present a decent bang for the buck, but the F-111 is – despite being a hangar queen and very costly – a very capable aircraft. Besides nuclear attack, which it fortunately never did, it is a very powerful striker with huge payload, long radius and good chances of successful attack versus dense air defense systems (in a 1970 and 1980 environment).

1. If you have a basically sound aircraft design that still has growth margins, you can keep the same basic aerodynamic configuration and significantly upgrade/enlarge/re-engine it at very low risk. See Gripen –> Gripen NG, F-16A –> F-16C Block 60, F-8 Crusader –> Crusader III, Mirage III –> Kfir, or all the Su-27 variants.

Fraud!
The F110-GE was specifically designed to fit where the F100-PW200 was installed. That is an odd comparison.
The J-75 powering the Crusader III was the final growth version of the J-57.

Ferry range with 2x external tanks
Mirage IV: 4,000km
F-111A: 5,300km

Fuel Weight (Internal/External)
Mirage IV: 15.2T (11.2/4)
F-111A: 18,9T (15.3/3.6)

Fuel Consumption (Kg/Km)
Mirage IV: 3.8
F-111A: 3.57
–> F-111A: 6% lower fuel consumption

BUT: SFC Dry (kg/daN)
Atar: 0.99
TF30: 0.82
–> TF30: 17% lower SFC

The question is: what if the F-111 needs only to travel 4000km, I guess it can then get rid of its tanks with the according weight. And how is fuel consumption affected when the Mirage IV is pushed to 5300km.

The FB-111, a slightly modified type, is given with a 5000km ferry range on internal fuel only. It consumes 2.71 kg/km of fuel on that mission (data from the link sferrin provided).

Next thing you are missing quietly is the flying weight. That is, for the MIV something like 24t average (using 32t as take-off, and 16.5t as landing weight). The F-111 is 10t heavier.
When we discuss aerodynamic efficiency, that is a very important fact to consider, otherwise the kg/km figure is utter non-sense.

We have to look at (kg of fuel)/(km traveled * t avg weight):
F-111: 18.9t/(5300km * 33t) = .108 kg/(km*t)
M-IV: 15.2t/(4000km * 24t) = .158 kg/(km*t)

If you apply that to the FB-111A, where we have hard fact with actual fuel consumed (the example is for internal fuel only):
FB-111A: 15.2t/(5000km * 31.4t) = .086 kg/(km*t)

So, your calculation is basically cherry picking and especially misses some important facts.

I think you’re showing your bias. The Spey Mirage would have met all the same operational specifications as the TSR.2, except for the runway distance.

You’re funny! the whole point of the F-111 and TSR.2 was runway length!!!
Why don’t you get this?
For a state-of-the-art bomber for a long runway nobody had considered BLC or swing wings. It was all about field performance and having good range & good low-level speed at the same time.

Once in the air, it was squarely in the same league as the TSR.2, and based on what I’ve shown above, quite superior to the F-111 in supersonic/transonic and at least as good in cruise/low-altitude.

No, the Mirage IV was more fuel thirsty. I agree that with updated engines, and some other modifications it would come out OK, but don’t fool people by telling it was just a plug’n play modification. That is what Dassault and RR wanted to tell the British tax payer!

The runway length was a big compromise, but could be justified if it helped avoid all the design, cost and delay issues that plagued the F-111, and would have plagued TSR2 had it not been abandoned. Remember that a year or two delay in the midst of the Cold War was a long time…

If the requirement states the maximum runway length with payload, then every design must either fulfill it or is failed. If the requirements are eased, then the whole comparison is odd.

If the real Mirage IVA didn’t play in the same league, it was simply because it was a tad bit too small for its thirsty engines. That doesn’t make the fundamental design unsound – it proved to have great all-round flying characteristics and a very affordable cost, neither of which can truly be said about the F-111. The variable geometry wing didn’t really come of age until the 1970s and the F-14, which fixed a lot of the drag issues that plagued the F-111. But with the design limitations of the 1960s, a delta configuration was simpler, cleaner, and cheaper. And VG never really took off once people realized that there was no point in having better take-off/landing characteristics than your escort fighters and tankers.

I am not a big supporter of swing wings, basically due to the same problems you have listed. But one cannot escape the conclusion that it was quite a good solution for the issue. The Russians and the Tornado used it when confronted with similar mission requirements.

The Dassault Mirage IV was neither deployed in larger numbers, nor developed into anything more useful. A tailless delta with conventional static stability has a truckload of drawbacks, so that nobody used that approach after 1960. It is really only a way forward when supersonic performance is the focus, and the Mirage IV was exactly that.
If I had the option in end 1960 between an F-111 and a Spey’ed Mirage IV, I would pay considerable royalty to get the F-111.

Look, I’m giving you facts about BAC/Dassault’s proposed specifications:
– 2 foot fuselage extension to maintain required Center of Gravity
– 3 inch increase in fuselage depth applied to all fuselage frames, but general fuselage shape would stay the same
– Larger intakes to accommodate the increased mass flow
– Same wing

Using:
http://en.wikipedia.org/wiki/Rolls-Royce_Spey
The Spey seems to be 3inch wider than the Atar, so there is still some room missing (while re-arrangement of internal structure is possible, would be difficult though).

You’re countering with blanket statements. Where’s the “considerable increase in diameter”? Where’s the evidence of substantial drag penalties? I’ve already explained that the Spey Phantom drag issues aren’t directly translatable to the Spey Mirage:
– Atar is wider than the Phantom’s J79s, requiring less fuselage widening
– The Mirage IV is a bigger plane and would be lengthened, meaning fewer problems with area ruling & therefore less impact on drag
– The Mirage IV’s intakes probably need less of an enlargement than the Phantom’s due to the fact that they should already be bigger (high altitude optimization)

I would agree if we talk about an A320. But you are praising the supersonic and transonic performance, not noticing, that you enhancements would have a substantial penalty just there.
By the way, using
http://en.wikipedia.org/wiki/SNECMA_Atar
http://en.wikipedia.org/wiki/General_Electric_J79
http://en.wikipedia.org/wiki/Rolls-Royce_Spey
The diameter of the Atar is 1m, whereas the diameter of a J79 is … 1m.
The increase in engine weight of 400kg, per engine.

Deltas have less trim drag than variable geometry aircraft, due to larger Center of Gravity shifts for VG aircraft. On top of that the F-111 had unusually high drag due to its poor backend/exhaust configuration. So how exactly does that make the Mirage IV an “inefficient cruiser”? Sure it has some compromises, but compared to the F-111, it certainly wasn’t inefficient, which is why when combined with the Spey’s better SFC the Spey Mirage would have had a better tactical radius and ferry range than the F-111.

Deltas are a disaster in allowed CG range (which is very bad for a striker). The excessive shift of lift center causes massive trim counter, which cannot be generated as efficient as with all-movable tail planes.
A swing wing flies most of the time with wings swept between most forward and middle position. Here the aerodynamic efficiency is twice as good as a Delta, especially with large payloads.
Using the F-106 aerodynamic data and applying it to a Mirage IV, I get an LoD of 5 to 7 for a M0.8 at cruise altitude. A forward swept aircraft like the F-111 achieves 12-14. That is all without external payload.
And who claims the Spey to have better SFC? It uses a lower bypass ratio and is same technology era.

If your point of comparison is an A-6 or Buccaneer, then yes I’ll admit that the Mirage is an inefficient cruiser, but that’s not relevant to this discussion..

An F-111 can become an A-6 or Mirage IV. That is the whole point of the swing-wing, and in case of the requirements of the F-111, this design decision was justified.

You didn’t get my point. Of course the F-111 has better field performance than the Mirage, but given the fact that both still have to operate from the same NATO standard runways because of logistical reasons (fuel/maintenance), it’s not clear how the F-111’s short field advantage translates into a real world advantage in a Cold War scenario.

In cold war you’re hardly find a standard NATO 8000ft strip, after the second day. By chance you have a 5000ft strip, or a road section of a mile. Do you think the USAF is completely stupid? They all knew that an intact airfield would be hardly conceivable. The usage required the opponent to divert much more attention to the destruction of runways and other make-shift fields.

Once again, I am not doing all these conclusions by my own, but rather assess the apparent shortcomings by looking at the design decisions of Dassault during and after the project.
If field performance wasn’t an issue, why did they ever conduct stuff like this?
http://farm2.static.flickr.com/1356/777567246_00712ba641.jpg?v=0
And why this?
http://upload.wikimedia.org/wikipedia/commons/a/aa/Dassault_Mirage_G8.jpg

In addition, the F-111 was never an optimal design. Remember that the F-111 was not only the 1st VG aircraft, but also had to be carrier compatible (with few aerodynamic changes), and had a draggy side by side cockpit. Why is it so hard to imagine that an intrinsically lighter, less draggy design such as the Mirage IV could be slightly modified to perform better?

Few designs are optimal, the Mirage IV can’t claim to be optimal, either. It is maximum aircraft for minimum cost with minimum research requirements, basically a Mirage III with all dimensions scaled by a factor of 2.
TSR.2 and F-111 were much more sophisticated and better designs for the battlefield of the early 1970ies. Guess why they were developed?
The F-111 had severe shortcomings in terms of reliability and program performance. Avionics were a headache. Many requirements far too ambitious with negative impact on the design (Mach 2.5 requirement, Mach 1.2 cruise at tree top level). But to claim that it was inferior by airframe design is a tough call, especially when you take a delta wing. Versus the TSR.2, there are ups and downs of the F-111, but the Mirage IV didn’t even play in the same league.

Just out of curiosity, do you have similar “official” data for other aircraft, especially strike aircraft? F-111, Tornado, F-15, Jaguar, Mirage? Otherwise those numbers don’t mean much in a vacuum.

Tornado is redlined at 750KIAS as far as I know, F-111 should be the same.
F-15 is less I guess (700ish).

Anyways, a read on the Mirage IV from dassault’s website states that it is still the only European military aircraft that can sustain Mach 2 for over 30 minutes. Could the F-111 accomplish this? Aircraft from the U.S. that can do this are/were the SR-71 and B-58.

What a great achievement.
But what for?

My point is that it’s not impossible to safely exceed the limit in the manuel in some instances nor does that line automatically embue an aircraft with the given envelope. For instance one F-104 pilot mentioned flying level at Mach 2 and 73,000 feet which is WELL outside the envelope given in the manuel and it was no big deal.

Single point achievements are nice, but we have to know exactly what the external factors were. Look at SE Asia and the prevailing conditions (hot, humid, limited access to maintenance, …). The performance demonstrated on a clear day at Edwards AFB would look like a number from the moon if compared to the actual combat conditions.
While humans may get better under combat conditions (to some extent), machines normally get worse. In the end the attrition rate skyrockets, which may be acceptable for nuclear war, but not for normal missions.
So, delivering one BOMB at 650 KIAS over a distance of 1000nm, the B-58 maybe can do it. Being a fully capable (conventional) low-level attack aircraft on par with the F-111, no, that is too far stretched.

BTW this might interest you:

I owe you a beer for that!

[someone mentioned the MiG-31, I guess this thread is now doomed; how long until flight performance Über-expert bdn12 will claim the MiG-31 to be able of “supercruise”]