Calm down. Every fighter could be pushed to the limits. To go low at high speed for some time you are in need of a high wing load. See the special designs for that purpose. All that Mirages were designed for best performances at altitude, when in the 60s it was learned to stay low level for strikers.

As long as you go not behind Mach 0,6 at low level it is no problem for the F-15E to do so for a whole mission. When highly loaded you can go even faster for some time. But doing 600 kt on the deck for more than 5 minutes will bring the F-15E into problems. Both, the Mirage 2000N and the Rafale are kept below 500 kt on the deck with a dash of 600 kt.

While wing loading is a decent proxy for low altitude comfort, it’s not a 100% exact rule. The Mirage IV’s low level performance and gust response seem quite good, despite its delta wing, based on those quotes from RAF test pilots as well as on the fact that the Mirage IVP was used for so long as a low level striker. Similarly, some deltas such as the Rafale have a reputation for good low level gust response, while others such as the Mirage III have a very poor reputation. So unless you have data for the Mirage IV’s low level g-accelerations or speed limits, then I see no reason to doubt reliable claims that the Mirage IV was an excellent low level strike platform.

IMHO, aside from a few exceptions such as the Mirage III and F-15E, the sustained low level speed of most aircraft will be limited by fuel consumption and tactical radius considerations, not by comfort/wing loading. An F-111 or Tornado won’t be able to sustain 600kts any better than a Mirage IV, simply because it’s burning too much fuel. In fact, compared to an F-111, a Spey Mirage would have had very low drag and more efficient engines, and so I strongly believe the article’s claims that it could have sustained Mach 0.9-0.95 at low altitude in cruise, which would have been an outstanding performance.

In genenral the lower the bypass the more “oomph” the engine keeps at higher altitudes. The M53 in the Mirage 2000 is more powerful at high altitude than the F100-220 of the early F-16s for exactly that reason even though the situation is reversed at sea level.

Agree entirely. IMHO, however, the Spey’s thrust loss would have to be massive before the Atar outperformed the Spey at high altitudes, simply because the Spey was starting from a baseline 33% more static thrust than the Atar. By comparison, the gap between the M53 & F100-220 was only 15%, so the bypass ratio played a bigger role.

They were better informed than you think. The Spey was not very efficient, except at low altitude. It was definitely a bad choice for intercepting high altitude intruders. Above 35,000 feet, even the reheated Speys lost too much power. Also there were reliability issues that Rolls Royce skirted in its sales campaign.

RAF officials complained loudly about being scammed (by British politicians) into buying the F-4M with Spey turbofans and other parts made at British factories, which doubled the cost of a Phantom that gave lesser performance than a standard U.S. Navy F-4J, some of which the RAF purchased later in a separate contract.

I know the Spey-Phantom didn’t perform great at high altitude. But the Spey-Mirage would have been different. First, its primary mission would have been low altitude penetration, where the Spey excelled. Second, even at high altitudes the Spey should have been superior to the Atar:

– It offered 32% more static thrust in AB than the Atar. By comparison, the Spey only increased the F-4’s static thrust by 17%.
– The Mirage IV airframe would have accommodated the Spey with fewer of the structural changes and drag penalties that hurt the F-4K. The Atar’s diameter was about 2 inches wider than the J79, the intakes were already optimized for high altitudes so would have required less of a size increase, and the longer fuselage made area rule less of a problem.

In fact, Dassault truly believed in the Spey-Mirage, as can be seen from this quote decades later, in 1989: “Concerning the Mirage IV Spey, we lost a chance to build the most brilliant combat aircraft of this century” – General Jean Glavany, Chief Test Pilot Mirage III & Mirage IV-01 http://www.stratisc.org/ihcc_nuc1_Dassault.htm

This is from a very serious colloquium of French aerospace professionals, at a time when Dassault had moved on to the Mirage 2000 and Rafale, so hardly likely to be PR-spin. Finally, comparing Dassault’s track-record in the 1960s to General Dynamics’, there’s no reason to doubt their ability to deliver the Spey Mirage’s promised performances. Remember that the F-111 was an awful design. Here’s a quote from 1966, describing the F-111A:

“True, its prototype versions fly (they had better do so in this day and age!) but there the resemblance to the final aircraft ends. It weighs 33% more than its specification weight of 60,000lb and will weigh 50% more by the time it is operational. Its engines, as conceived, are too small and have serious compressor trouble. The intake does not work. The aircraft drag, or fuel consumption, or a combination of both, is up by 25%. No single performance figure of any significance is available, and no wonder! […] If Group Captain Harrop keeps up with the American Press he will see that the aviation writers have already detected ominous shimmerings in the vision centred over Fort Worth. That “over 4,000 mile” ferry range has already shrunk to 3,000 on closer inspection. The 100kt “over the fence” will be much nearer the 150kt which he fears. And what point in putting down on a rough and ready airfield on a blockaded island when one needs at least 30,000lb of fuel to take off for the next trip?”
R. Melling, Hawker Siddeley, in Flight International, http://www.flightglobal.com/pdfarchive/view/1966/1966%20-%200541.html

“Spey Mirage IVK” – Better than the F-111

A fighter aircraft or low level bomber normally has 700 to 800 Knots (EAS, that is, actually a bit more in real due to compressibility). Aircraft like the B-58 have lower KEAS (Knots Equivalent Airspeed), it actually is not allowed more than M0.8ish at low level. Same would apply to Mirage IV or Tu-22.

You are mistaken about the Mirage IV. Even though it was designed as a high-altitude bomber, it turned out to be a fast, stable low-level platform that could do Mach 1.1 at sea level, which is pretty good.

In fact, the UK came pretty close to ordering the Mirage IV, with Spey-engines instead of the thirsty French Atars. This would have been the ultimate Cold War bomber, mating a low-drag fuselage with powerful, efficient engines. Indeed, the “Spey Mirage” would have been superior in most respects to both the F-111A and TSR2.:eek:

Spey Mirage IV vs. F-111A
– Better lower level performance: 50% larger bomb-load for supersonic low-level penetration
– Better high altitude performance: Mach 2.5 & 20,000m ceiling vs. Mach 2.2 & 17,500m
– Longer ferry range: 5,500km vs. 5,100km
– Much easier maintenance & more reliable engines
– 33% cheaper: 2.2-2.7MM GBP vs. 3.0-3.7MM GBP

Spey Mirage IV vs. TSR2
– 33% better hi-lo-hi radius
– Similar lo-lo-lo radius, but with a larger bombload
– Better high altitude performance: Mach 2.5 & 20,000m ceiling vs. Mach 2.25 & 16,500m
– Slightly better low altitude performance: Mach 1.15 vs. Mach 1.1
– 50% cheaper: 2.2-2.7MM GBP vs. 4.7MM GBP

The “Spey-Mirage”s only real drawback was its longer take-off and landing run, due to the delta wing. But the MoD argued that the “Spey-Mirage” was a “high-risk” and inferior solution than the paper F-111A, even though it was becoming quite clear that the F-111 was turning into an expensive, high-drag pig that would never achieve its promised range/speed performance and would be delayed by several years. The argument was especially ludicrous given that the Mirage IV was already in service and that Dassault had plenty of experience grafting Rolls-Royce engines onto already proven Mirage airframes.

BAC and Rolls-Royce lobbied hard for the “Spey Mirage”, since they would have built 50-75% of it. Even Flight International editorialized in its favor, because it met the RAF’s requirements at a lower cost than the F-111 and very little technical risk. RAF pilots who evaluated the French Mirage IVAs were blown away by their sustained Mach 2 capability and also praised their low-level performance – both of which would have been improved with Spey engines. Apparently, even the RAAF’s chief was very interested, but Australia was committed to the F-111…

But the MoD ended up ordering the F-111, mostly for political and trade reasons. We know the rest of the story. The F-111 suffered big cost overruns and never met its performance goals, and the RAF canceled it. Had they chosen the “Spey-Mirage”, they would have had the best supersonic bomber in the world instead of coming empty handed. 😉

Here are some interesting what-if pictures. More here: http://www.airlinebuzz.com/forums/blog.php?b=102&goto=next

😎

A400M desperately needed in Afghanistan

What worries me most about the A400M delays is what’s going on in Afghanistan. Not to overdramatize, but Afghanistan is potentially a new Dien Bien Phu if Pakistan disintegrates.

In such an event, the Taliban could get access to portable SAMs to shut down the main Afghan airports from strategic aircraft, as well as conventional weapons (artillery, armor) to cause losses among NATO’s light infantry. Reinforcements by land would be a huge problem, and the result would be 80,000 Western troops scattered in an enclave, with no tactical initiative and hundreds of kilometers from their logistical bases. The Europeans would be in serious trouble without new tactical transports such as the A400M.

To set the tone for what an Afghan Dien Bien Phu might feel like, here’s a short history lesson in music video format.