Avon engines

kaiserbill

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Hi all

I've done quite a bit of searching on the net, but cannot seem to find details on all the Avon series engines with physical characteristics and timelines. Any pointers would be much appreciated.

On this topic, I've seen the Mirage III originally touted for Australia was fitted with an "Avon 67" of 7200kg thrust. Does anyone know what this engine is, as info is scarce. Is it an Avon 300 series engine? What were the performance figures of the Mirage when fitted with this engine over the Atar?

Lastly, am I right in assuming the Avon was a more modern engine in concept than the Atar? I've read that the Atar has it's roots firmly in WW2. This being the case, why wasn't the Avon more successful on the world market? Apart from Sweden, it doesn't appear to have been used by non-British manufacturers....
Surely something like the Mirage F1 could have benefitted from some of the later, more powerful Avon types, like the RM6C that pushed out 5800kg/8000kg.

Was there anything inherently wrong with the Avon? Weight/throttle-ability/thirst?
 
They are pretty much contemporaries. Avon development started in 1945.

Avon was more ambitious than the Atar, initially aiming for a pressure ratio about 8:1 (eventually 10:1) as opposed to 5:1 (eventually 6.5:1). All things being equal, this meant more thrust and/or better fuel economy, at a cost in complexity, cost and potentially additional weight. Thrust to weight appears to have similar in practise though. Avon SFC (specific fuel consumption) was noticably lower than the Atar.
 
Thanks Overscan. Any idea what the weight of the Avon 300 series were? Or the RM6? I know the Atar 9K50 was about 1580kg and almost 6 meters long, which is big for an engine pushing out 5000kg thrust dry. Mind you, the later model J-79's were also big beasts at around 1700kg and over 5 meters for 10% more thrust than the 9K50.
 
pr: on the AF RR point, I doubt this was an evil plot. Until 6/2/1987 (BA)/5/87 (RR) the fond British taxpayer owned, thus picked up the losses of, both BA and RR. So, BA "chose": 757-200(RR), 767-300ER(RR), 747-200B(RR), -400(RR), L-1011s, not DC-10s. Free to use its best judgement, BA chose GE/SNECMA in 1991 for 777 (for the second buy RR learned and sharpened their pencil). SNECMA+AF were/are synonymous with French National Interest, so were expected to employ voters. (I think) SNECMA has made chunks of all AF power since JT8D Mercure (Air Inter)/737-200.

ATAR was German-inspired/influenced (so was AJ65, to be Avon). RR became miffed over RAAF rejection of Avon, for ATAR, in Mirage IIIO, though no doubt pr's point rules - that Installation Development messed up the $. In Oct.1966 RR bought BSEL, in part to kill Pratt/BSEL/SNECMA JT9D competition to RB207/211. No RR offer to SNECMA to join RB211 (though such an offer was made to Allison). So GE leapt in with CF6, which led to CFM56...on...and on. Unintended consequences.
 
Found this in Flight Jan 1961 article

RB.146 Avon 300. The improved
economy of this engine confers an appreciable increase in range,
and its great thrust (13,2201b dry, 17,4201b with reheat) improvest
the Mirage's already outstanding rate of climb and altitude performance.

As a side note, which I had not heard of before, in relation to the RAAF Mirage IIIO - the article also states -
The
French Mirage is equipped with the Cyrano, produced by CSF,
who on December 20 announced in Paris that the RAAF aircraft
"will be equipped with CSF airborne fire-control radar . . . the
Australian industry . . . will participate in the project." As we
go to press this decision could not be confirmed; the main
competitor is the Ferranti Airpass 2

What is the Ferranti Airpass 2? and what other fighters was it employed in?

if guns are to be fitted they are likely
to be Adens, and not the French DEFA.


Can anyone elaborate whether the RAAF seriously looked at fitting Aden 30mm cannons??

On a final note, does anyone know were I can get a profile drawing of the prototype Avon-powered Mirage IIIO, that Dassault built and tested?

Regards
Pioneer
 
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Pioneer said:
What is the Ferranti Airpass 2? and what other fighters was it employed in?

This isn't the AI-23B as used in the EE Lightning F3 is it?

Sounds as though with the Avon, AIRPASS radar and Adens, they looked to make essentially an Anglicised Mirage III. I wonder if plans were also afoot to equip it with British A-A missiles?

Regards,

Greg
 
Not so much Anglicised as follow-on to CAC production (Avon), and RAAF operational familiarity (ADEN) on CA-27 Sabre. Marcel Dassault did a good job in selling near-standard product (the only Oz-ments were in the cockpit, for inventory standardisation). Ferranti A.I.23 Airborne Intercept Radar and Pilot's Attack Sight System (apologies for dredging that out of memory).
 

Developed as a private venture, Airpass II provides largely for automatic navigation and weapon-aiming by day or night on interception, ground support or long-range strike missions, yet the size and weight are little more than those of Airpass I, which is purely an interception system. The pilot's attack sight is identical in both instances and the Airpass II radar has many features similar to those of Airpass I.

An interchangeable nose-pack is retained, thus saving weight and simplifying front-line servicing.

Ferranti tried selling Airpass II to the Swiss (Mirage) and more generally to French and German industry.
 
alertken said:
Not so much Anglicised as follow-on to CAC production (Avon), and RAAF operational familiarity (ADEN) on CA-27 Sabre. Marcel Dassault did a good job in selling near-standard product (the only Oz-ments were in the cockpit, for inventory standardisation). Ferranti A.I.23 Airborne Intercept Radar and Pilot's Attack Sight System (apologies for dredging that out of memory).

Just came across this thread searching for other stuff. Marcel Dassault (actually it was Benno Claude Vallières who was president of GAMD at the time who ran the Mirage III sales campaign) did not try to sell the RAAF on the Atar powered Mirage IIIO. Quite the opposite. Dassault wanted the Mirage with R-R Avon because not only would it apparently fly better but they saw such an equipment fit as much better for export. They and the French Government saw the British and RAAF common (sort of) equipment, especially the engine, as important for the customer. They were also planning on this new IIIO (Avon powered, nose and front guns being to customer preference) standard to be the export standard for Mirage IIIs. Remember at this time (1960-61) the Mirage III had only been ordered by France, South Africa and Israel. And the latter two were at this time more of an albatross than an endorsement for wider export orders. Also beside the Australians the next two interested customers were the Swiss and Indians who were both Avon users and interested in the same performance and commonality gains that were motivating the RAAF to look at the Avon.

The issue for the engine for the Mirage IIIO was not down to the cost of integration because when approving the acquisition of the Mirage III in late 1960 the Cabinet of the Australian Government had done so on the proviso that they wanted a comparison of the Atar and Avon powered options to be considered at the contract stage (along with various local production and other equipment issues) by the Government’s Air Board (that managed the RAAF). The cost of the actual integration ended out being very small as GAMD did the engineering in 28 days though there would be later additional costs as the Avon powered Mirage IIIO would became effectively a separate aircraft to the Atar powered Mirages and GAMD’s ongoing costs as OEM of the Mirage III would no longer be carried by the French Air Force.

SNECMA did near to nothing to sell the engine and had been warned off by the French Government as they saw the Avon as an important part of not just selling the Mirage III to Australia but the rest of the world. The only people pushing the Atar where Pratt & Whitney who owned 20% of SNECMA and did their best to sell the engine to the RAAF. But as the time frame was compressed (northern Spring 1961) and the RAAF too professional these sales efforts meant little.

The main reason the RAAF didn’t select the Avon (Mk 67, aka RB.146) to power the Mirage IIIO was that the new Atar 9C (not the 9K but it was known about) in the Mirage IIIE (with extra avionics weight close to the RAAF’s eventual avionics requirement) performed very well. It was judged by the RAAF team that the Atar 9C was better for the Mirage IIIE than the Avon Mk 67. The performance advantage of the Avon Mk 67 at take off, climb and range was not seen as being much better than the Atar 9C. Whilst at over 40,000 feet the Atar 9C performed better. Plus the growth options of the Avon Mk 67 were limited and to go to the next Avon would require a wider exhaust pipe countering improvements in performance. The RAAF assessed that if growth was needed the Atar 9K would be much better in a Mirage IIIE than a more powerful Avon RB.146. The Atar was also lighter, cheaper and more rugged than the Avon and with all the benefits of commonality with the French Mirage III through the life of the aircraft.

So the Air Board decided in May 1961 to select the Atar 9C and hold an option up until September to go with the Atar 9K. This option lapsed as there had been no 9K testing by then and it was seen as too risky. Though this would be a very interesting What If… The RAAF Mirage III team had also looked at changing the armament from the French standard to either Ferranti Airpass or Hughes TARAN systems. But recommended against it. These armament options were considered in whole with associated missiles. I don’t have data on the weapons but I would assume since the Cyrano was linked to the Matra R.530 medium range missile (AIM-9Bs were also to be carried under the outer wings) that such missiles would be the Red Top and AIM-4 Falcon. In which case the high weight of these missiles would have been significantly disadvantageous.

My primary source for the above is The RAAF Mirage Story’s “French Connection” chapter written by AVM Ron Susans, CBE, DSO, DFC who at that time was Senior Air Staff Officer at WRE (RAAF Edinburgh, Woomera Weapons Range) who ran the Mirage III evaluation program.

A persistent story is that SNECMA won the Mirage IIIO engine because they had confused the exchange rate difference between the Australian Pound and the Pound Sterling. I have found no evidence of this and since SNECMA sent an executive team to Australia to provide briefs to support the Air Board consideration of the engine options it is hard to believe they didn’t notice the difference in currency and values. The Atar was a cheaper engine because it was lighter, simpler and easier to manufacture.

I think the persistent stories that the RAAF and the world missed a great option with the Avon Mirage III and that SNECMA only won thanks to fortunate foolishness can be attributed to the ever vocal British aviation press. Who always have a good yarn, many of them are even true, as to why Britain no longer rules the air.
 
Just found this interesting snippet piece of information, which I think IMO would support the notion that the Avon-powered Mirage III for the RAAF would have been superior -


“However, when Australian operations required the addition of two supersonic external fuel tanks and two Sidewinder missiles, plus the Matra, a lack of available power was apparent. As a result, the RAAF Mirage 111O was underpowered in the configuration required for our conditions. This would have been a definite handicap if offensive air interceptions had been required.”
(Source: http://www.raafa.org.au/mirage)



Regards
Pioneer
 
I too have a copy of The RAAF Mirage Story, and the “French Connection” chapter states that the Hughes TARAN radar (paired with the Sparrow, not the Falcon) was actually the main competitor to the Cyrano - for the same reason that the Avon was being pushed.

The Swiss were getting ready to buy the Mirage III, and they had expressed a strong preference for the Avon/TARAN combination (and had done extensive studies on the TARAN/Sparrow combo), but were unwilling to be the sole operator of such a variant. The RAAF's evaluation team even sent 4 of its members to Berne to consult with the Swiss Air Force, and they reported favorably on both options.

This would have meant 2 reliable and substantial operators with Avon/TARAN Mirage IIIs, which would have created a good support base for those variants.

In the end, the promise of the Atar 9K* was the deciding factor in the choice against the Avon (which was seen as being at the end of its development potential), and an option to substitute the -9K for the -9C was included in the contract... only to see that engine not enter production until 1968/69, keeping it from ever being fitted in any of the RAAF's Mirages.

Likewise, the lower cost of keeping the French radar carried the day over the US radar-missile combo.
The Swiss, however, did fit the TARAN - but with Falcon missiles, so I wonder if the mention of Sparrow on page 8 was an error.

I have seen the cost differential for the initial 30-aircraft contract as being A$44.9 million for Atar vs A$46.9 million for Avon.


* Atar 9C [9,430 lbs thrust (13,670 lbs w/reheat)]
Atar-9K [11,023 lbs thrust (15,870 lbs w/reheat)]
RB146 Avon 67 12,100 lbs thrust (15,715 lbs w/reheat)
 
Hi all, on the Avon engine, I've got a few models of Avon engines that I'm having trouble finding info/aircraft usage on. Does anyone have more info on any of the following Avon models:
  • Avon RA.3 Mk.104
  • Avon RA.7R Mk.108
  • Avon RA.21 Mk.113
  • Avon RA.25 Mk.505
  • Avon RA.26 Mk.524
  • Avon RA.29/1 Mk.524B
  • Avon RA.29/6 Mk.530
  • Avon RA.29/6 Mk.532R-B
  • Avon RA.29/6 Mk.533R-11A

And some Mk. or RA numbers missing:
  • Avon RA.16, RA.17, RA.18, RA.20, RA.29/5, RA.30 & RA.50 (no applications known) - anyone know the Mks. for these models?
  • Avon RA.24 used in the Lightning protoype - anyone know the Mk. for this model?
  • Avon RA.28-49 used in the X-13 - anyone know the Mk. for this model?
  • Avon RA.28R used in the BAC 221 - anyone know the Mk. for this model?
  • Avon Mk.51 used in the Entendard IVB prototype - anyone know the RA number for this model?

Thanks,
Nathan

P.S. I'm finally updating my database again, so there will be lots more posts like this on other engine models!
 
Any particular reason why you did not post this in the Propulsion section?
 
Hi all, on the Avon engine, I've got a few models of Avon engines that I'm having trouble finding info/aircraft usage on. Does anyone have more info on any of the following Avon models:
  • Avon RA.3 Mk.104
  • Avon RA.7R Mk.108
  • Avon RA.21 Mk.113
  • Avon RA.25 Mk.505
  • Avon RA.26 Mk.524
  • Avon RA.29/1 Mk.524B
  • Avon RA.29/6 Mk.530
  • Avon RA.29/6 Mk.532R-B
  • Avon RA.29/6 Mk.533R-11A

And some Mk. or RA numbers missing:
  • Avon RA.16, RA.17, RA.18, RA.20, RA.29/5, RA.30 & RA.50 (no applications known) - anyone know the Mks. for these models?
  • Avon RA.24 used in the Lightning protoype - anyone know the Mk. for this model?
  • Avon RA.28-49 used in the X-13 - anyone know the Mk. for this model?
  • Avon RA.28R used in the BAC 221 - anyone know the Mk. for this model?
  • Avon Mk.51 used in the Entendard IVB prototype - anyone know the RA number for this model?

Thanks,
Nathan

P.S. I'm finally updating my database again, so there will be lots more posts like this on other engine models!
According to the RRHT Hucknall book, Mk 108/RA7R (6,675 lbf dry thrust, 8,950 lbf reheat) was production engine for Swift. Similar to Mk 105 but with intake hot-air anti-icing. Same source has Mk 113 as RA.7 (7,250 lbf) with increased NGV area, production for Hunter and RA.21 (7,815 lbf) as Mk 115, similar to Mk 113 but with increased NGV area and other mods, also for Hunter.
 
Checking out Bill Gunston's World Encyclopaedia of Aero Engines (4th Ed, Patrick Stephens, 1998).
The RA3 100 series were first in service. It was not a particularly outstanding engine.
"It really became competitive when in December 1952 it was redesigned as the 200-series with a much better compressor whose first 4 stages followed the aerodynamic design of the Sapphire, and a cannular combustor."
The Sapphire design had itself started during WWII, as the Metrovick F.2, and was later passed on to Armstrong Siddeley. So it made no difference on that score which engine Hawker put in each Hunter version, you would end up with much the same compressor.

In the 'sixties a version of the Avon was launched for maritime and industrial use. It was outstandingly successful, especially in industry, and as far as I can tell is still being (made and?) sold by Siemens. Here is some R-R puff dating from 2007.
 
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Hi
there were bits of Metrovick jet engines and an Avon at the Museum of Science and Industry, (SIM), in Manchester last time I went in, just pre-Covid.

G
 
They are pretty much contemporaries. Avon development started in 1945.

Avon was more ambitious than the Atar, initially aiming for a pressure ratio about 8:1 (eventually 10:1) as opposed to 5:1 (eventually 6.5:1). All things being equal, this meant more thrust and/or better fuel economy, at a cost in complexity, cost and potentially additional weight. Thrust to weight appears to have similar in practise though. Avon SFC (specific fuel consumption) was noticably lower than the Atar.
I'd really like to see a more comprehensive comparison of the four major western turbojet fighter engines of the 1950s and 60s, the Rolls-Royce Avon, General Electric J79, Pratt & Whitney J57, and the SNECMA ATAR. I have generally gotten the perception that the Atar was inferior to its contemporaries in terms of thrust to weight and sfc, I'd like to see if this perception is rooted in reality or if the Atar was as good as its contemporaries.
 
ATAR's virtues were:

Cheap
Simple to build and maintain
In theory, lighter (though figures don't support this)
Good thrust at high speeds and altitudes (due to low pressure ratio)

Its vices were:
Poor SFC (due to low pressure ratio)
Relatively lower thrust at takeoff, lower speeds and altitudes

It is most similar in terms of layout to the British Gyron or Russian R-15-300. Avon is the closest in timing and design but was generally superior to ATAR in all time periods.

J-57 and J-79 are conceptually a generation ahead of either, though Rolls-Royce squeezed a lot out of the Avon family.
 
SNECMA did near to nothing to sell the engine and had been warned off by the French Government as they saw the Avon as an important part of not just selling the Mirage III to Australia but the rest of the world. The only people pushing the Atar where Pratt & Whitney who owned 20% of SNECMA
And the reason for that in the first place had been the need for J75s for what was to be the definite Mirage IV: NOT the Vigilante-size Mirage IVA, but a B-58-size beast called the Mirage IVB, dated 1959.
SNECMA was to build a 12 tons thrust "Super Atar" for it but failed, and so foreign engines were examined with the company to take a licence. They were the RB.141 Medway, Olympus, (that one got its revenge three years for Concorde, the irony !) Orenda Iroquois (and thus Dassault became part of the Avro Arrow lore and myth) and Pratt's J75, which carried the day but not for long as the Mirage IVB was canned for a host of reasons.

Later (1963) that share of Pratt into SNECMA was revived to get JTF10 & TF30 licences, first for the VSTOL Mirage, then for the F2 & F3 and finally, for the Mirage G. The final result in 1969 was the TF306E with 10.3 tons of thrust, for nothing as the M53 was prefered as a national development.
 
Checking out Bill Gunston's World Encyclopaedia of Aero Engines (4th Ed, Patrick Stephens, 1998).
The RA3 100 series were first in service. It was not a particularly outstanding engine.
"It really became competitive when in December 1952 it was redesigned as the 200-series with a much better compressor whose first 4 stages followed the aerodynamic design of the Sapphire, and a cannular combustor."
The Sapphire design had itself started during WWII, as the Metrovick F.2, and was later passed on to Armstrong Siddeley. So it made no difference on that score which engine Hawker put in each Hunter version, you would end up with much the same compressor.

In the 'sixties a version of the Avon was launched for maritime and industrial use. It was outstandingly successful, especially in industry, and as far as I can tell is still being (made and?) sold by Siemens. Here is some R-R puff dating from 2007.
I worked on one of those industrial Avons in the Gulf in the 90s and it was pretty much as it came out of the aircraft.
 
ATAR's virtues were:

Cheap
Simple to build and maintain
In theory, lighter (though figures don't support this)
Good thrust at high speeds and altitudes (due to low pressure ratio)

Its vices were:
Poor SFC (due to low pressure ratio)
Relatively lower thrust at takeoff, lower speeds and altitudes

It is most similar in terms of layout to the British Gyron or Russian R-15-300. Avon is the closest in timing and design but was generally superior to ATAR in all time periods.

J-57 and J-79 are conceptually a generation ahead of either, though Rolls-Royce squeezed a lot out of the Avon family.
The Avon 301R was lighter than the ATAR 09C, at least according to wikipedia, it lists the dry weight of the Avon as 1,310kg and the ATAR as 1,456kg. Are these figures accurate or is the Avon's figure the weight of an RB.146 without the afterburner? I'm trying to get an idea of how much better, if at all, the performance of the Avon-powered Mirage IIIO proposed for Australia would have been compared to the baseline Mirage IIIE with ATAR 09C.
Also, what about the American engines sets them apart from their European counterparts? In terms of thrust to weight, the J79 is only marginally better than the ATAR. Another question I have is why the French settled with the ATAR's mediocre performance and never tried to improve it more drastically or develop a clean-sheet engine. Honestly I am surprised to a degree, considering France's political standing at the time, that a domestically designed, 100% French, replacement for the ATAR (which was originally designed by BMW engineers) wasn't created in a spate of nationalistic fervor. Was it really just down to economics or was there something else at play at SNECMA?
 
Also, what about the American engines sets them apart from their European counterparts? In terms of thrust to weight, the J79 is only marginally better than the ATAR.

Higher pressure ratio, which translates to lower fuel consumption.

Another question I have is why the French settled with the ATAR's mediocre performance and never tried to improve it more drastically or develop a clean-sheet engine. Honestly I am surprised to a degree, considering France's political standing at the time, that a domestically designed, 100% French, replacement for the ATAR (which was originally designed by BMW engineers) wasn't created in a spate of nationalistic fervor. Was it really just down to economics or was there something else at play at SNECMA?

ATAR 9K90 is pretty far developed from original ATAR. For a basic fighter air defence mission, where range isn't a priority, lower SFC isn't that important compared to other factors.

France played around with license-built TF30s in the late 60s / early 70s, but for the fighter mission, TF30s aren't great. Better SFC is more critical to long range strike. TF30 is reasonably heavy, complex, and costly, plus you have to pay royalties.

It isn't until F100 and F404 era that you can get decent SFC, high T/W and good all-round performance in one engine.

SNECMA built up capability with civil engine collaboration. ATAR was eventually replaced by M53, and with M88 SNECMA essentially reached world class in fighter class engines.
 
I'm trying to get an idea of how much better, if at all, the performance of the Avon-powered Mirage IIIO proposed for Australia would have been compared to the baseline Mirage IIIE with ATAR 09C.
Also, what about the American engines sets them apart from their European counterparts? In terms of thrust to weight, the J79 is only marginally better than the ATAR. Another question I have is why the French settled with the ATAR's mediocre performance
This is covered in the RAAF Mirage Story. Simple answer is the Avon wasn’t nearly as good as it was marketed and the extra performance edge was not always obvious.

See pages 8-10:

'Thus by early May, it was apparent that the expected advantages in take-off performance, rate of climb and range for the Mirage III with the Avon Mk67 engine were not a significant improvement over the Mirage IIIE, whereas overall performance at altitudes above 40,000ft was somewhat inferior, although the Avon version was able to achieve higher speeds without afterburner at altitudes below 45,000ft. On the other hand, the development potential of the Avon Mk67 engine was limited to the fitment of a larger tail pipe (36" diameter as opposed to 28.8" in the standard engine) and the expected benefits to thrust and fuel consumption were not comparable with those available from the Atar 9K. The Atar engine offered additional important benefits, being lighter and cheaper than the Avon and was perceived to have benefits due to ease of manufacture and servicing together with simplicity of operation associated with design for military operation exclusively.

(…) When the Avon/Mirage trials were complete and the data studied by Darling and members of the staff, it was clear that the only advantage, and this was marginal, that the Avon enjoyed over the Atar was in dry power at low altitude. It was also thought that the Atar was a more rugged engine and therefore more suitable for fighter operations. At altitude, and with afterburner at any height, the Atar was superior and when this was considered against the background of the risks inherent in going non standard with the Mirage as developed by the French, the decision to recommended the fitment of the Atar in the Australian aircraft was made.


 
@Yankee_Aviator Also see what I posted on the Etendard IVB in the thread 'Dassault Etendard Prototypes and Projects':
https://www.secretprojects.co.uk/threads/dassault-etendard-prototypes-and-projects.11138/post-425831

There were actually 2 Avon Etendard proposals. The first Avon proposal was based on the Avon Mk 203 powering the Hunter. It had "similar thrust" to the Atar, which makes sense as the Hunter F.4 had 10,000 lbf (4,500 kgf), so very close to the Atar 8's 9,700 lbf (4,400 kgf).

The Avon Mk 203 installation was expected to be 100kg heavier. The larger diameter required the removal of the rearmost fuel tanks (2x 120L), reducing fuel capacity by ~8% to 3,000L. As a result, there would be no gain in range despite the Avon's lower fuel consumption.

The second Avon proposal was based on the "Avon 51" (11,200 lbf (5,080 kgf), which I believe was a non-reheat variant of the RA28R that equipped the Lightning. This more powerful Avon was ~300kg heavier than the Atar 8 (1,350 vs. 1,050 kg), with 12.5% lower fuel burn at sea level / 350 knots and 4.5% lower fuel burn at 36,000ft / M.085. So the improvement in range, if any, must have been minimal (given the 8% lower internal fuel capacity). However, overall performance improved slightly (Mach 1.07 level speed at 36,000ft, 6m15 climb to 43,000ft).
 
Pl;ease remember that the Atar 9K50 was not certified for production until 1968... so the ONLY Atar numbers that could honestly be compared with the Avon 67 is the 9C.

There is a major difference in their performance, not a "marginal" one...

Atar 9C (1960): 9,430 lb (13,670 lb) “Overspeed” provides 14,110 lb.s.t. @ 36,000+’ & mach 1.4+

Avon 301 (1960): 12,100 lb (15,715 lb)
Avon 302 (1961): 12,690 lb (16,360 lb)
Avon 67 (the only place I have found numbers for the mk 67 is with the Swedish version - Svenska Flygmotor RM6C (RA.29)) (1961): 12,690 lb (17,640 lb)
 
Pl;ease remember that the Atar 9K50 was not certified for production until 1968... so the ONLY Atar numbers that could honestly be compared with the Avon 67 is the 9C.

There is a major difference in their performance, not a "marginal" one...

Atar 9C (1960): 9,430 lb (13,670 lb) “Overspeed” provides 14,110 lb.s.t. @ 36,000+’ & mach 1.4+

Avon 301 (1960): 12,100 lb (15,715 lb)
Avon 302 (1961): 12,690 lb (16,360 lb)
Avon 67 (the only place I have found numbers for the mk 67 is with the Swedish version - Svenska Flygmotor RM6C (RA.29)) (1961): 12,690 lb (17,640 lb)
What is interesting here is that the Australian comparative flight test programme conclusively proved these numbers to give the wrong answer. Such figures as these do not detail little things like altitude, airspeed or ambient temperature, never mind how long the engine will last at said thrust level.
The RAAF Mirage Story explicitly states that you could not "sell" a plane to Australia, they "bought" what they needed. They were especially unimpressed by American sales efforts to muscle in on the engine replacement. In the present case, they went to the trouble of conducting a fly-off. They would have been equally unimpressed by the figures just given - and, frankly, so am I. As the great JW Dunne once said, "But the aeroplane does do these things. And if the theory does not give warranty to the practice, then it is the theory which is wrong".
 
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F100-PW-220 engine has a slightly higher bypass ratio than optimal for a fighter and an overly ambitious pressure ratio resulting in an engine that is fuel efficient at subsonic cruise but also a little sensitive to disturbed air and burns fuel at a high rate in afterburner as well as being a bit of a maintenance hog in its earlier days. F404 was a little more conservative in design, and with a lower bypass ratio it burns fuel faster in subsonic cruise, but in afterburner it is less thirsty than the F100. Which engine is "better" for your fighter entirely depends on the mission you select.

Even a simple point like which engine is cheaper to run depends not just of fuel efficiency but cost of engine maintenance. A fuel efficient engine that requires 50% more maintenance probably won't pay for itself in fuel cost savings.

Typically a lot of care is taken to integrate the powerplant, intake and airframe in an aircraft design. Swapping out an engine requires a redesign, which may not be as optimised for the new engine.

In the early 60s, when the Mirage evaluation was done, it was all about high speed and altitudes. By its low pressure ratio, the ATAR is better optimised for supersonic conditions. If that is your yardstick, then of course ATAR is better.

I'd love to see how often the RAAF Mirage actually flew supersonically, let alone at Mach 2. I doubt it was very often.
 
it was clear that the only advantage, and this was marginal, that the Avon enjoyed over the Atar was in dry power at low altitude
the expected advantages in take-off performance, rate of climb and range for the Mirage III with the Avon Mk67 engine were not a significant improvement over the Mirage IIIE, whereas overall performance at altitudes above 40,000ft was somewhat inferior
This is actually really surprising, the Avon 67 was producing 3,000 lbf more thrust dry and in afterburner than the Atar 09C, at least on paper. I wonder if it was the additional weight, speaking of, how much heavier was that engine? According to Wikipedia, the Avon (RB.146) is in fact lighter than the Atar (09C), I know Wikipedia isn't the most reliable source of information, so I'm wondering now if the figure given is the weight of an Avon without the afterburner.
 
F100-PW-220 engine has a slightly higher bypass ratio than optimal for a fighter and an overly ambitious pressure ratio resulting in an engine that is fuel efficient at subsonic cruise but also a little sensitive to disturbed air and burns fuel at a high rate in afterburner as well as being a bit of a maintenance hog in its earlier days. F404 was a little more conservative in design, and with a lower bypass ratio it burns fuel faster in subsonic cruise, but in afterburner it is less thirsty than the F100. Which engine is "better" for your fighter entirely depends on the mission you select.

Even a simple point like which engine is cheaper to run depends not just of fuel efficiency but cost of engine maintenance. A fuel efficient engine that requires 50% more maintenance probably won't pay for itself in fuel cost savings.

Typically a lot of care is taken to integrate the powerplant, intake and airframe in an aircraft design. Swapping out an engine requires a redesign, which may not be as optimised for the new engine.

In the early 60s, when the Mirage evaluation was done, it was all about high speed and altitudes. By its low pressure ratio, the ATAR is better optimised for supersonic conditions. If that is your yardstick, then of course ATAR is better.

I'd love to see how often the RAAF Mirage actually flew supersonically, let alone at Mach 2. I doubt it was very often.
So was there an engine out there that would have (in hindsight) been more practical for the Mirage III? Or was the Atar really the optimal engine for it because of the Mirage's airframe being designed around it?
 
SNECMA built up capability with civil engine collaboration. ATAR was eventually replaced by M53, and with M88 SNECMA essentially reached world class in fighter class engines.

SNECMA was created in 1946 by amalgmation of many ruined engine makers. Back in 1939 Gnome&Rhone and Hispano Suiza were lagging behind at many levels, with dramatic consequences in May-June 1940. French pilots had to fought with 860 hp against 109Es at 1100 hp.
SNECMA probably stayed too long with the Atar but at least squeezed every single ounce of performance out of the thing.
1943: BMW 003, thrust: 780 kg
1948: Atar 01, thrust: 1700 kg
1968: Atar 9K50, thrust: 7200 kg.
They squeezed 10x thrust in 25 years, not bad.
But I agree they stuck with it for too long, to Dassault dismay.


Note that in the 1950 they developed the Vulcain, but it went nowhere. Second atempt was the "Super Atar" also went nowhere, although because the Armée de l'Air kept shifting requirements and got its budget cuts. SNECMA unlike Dassault was a public company so at the mercy of government shifts - and from that regard, between 1946 and 1958 the 4th Republic remarquably got 25 governments in 12 years: one every six months. It gave Italy, Belgium or Israel political instability a run for their money.

But SNECMA did tried to get out of its Atar mono-culture many times in the 1950's, to no avail.

By 1959 they got in touch with Pratt to get J75s or JTF10 / TF30s 4 years later (1963) and by 1969 got 10300 kg thrust out of the TF306E - to no avail.

The M53 was average, the real problem was that SNECMA could not get it above 8500 kg of thrust in the 1970's without enlarging the diameter and as such it wouldn't fit a Mirage F1 rear end. This until the P2 update in the early 1980's that finally got a power boost without being enlarged.

My understanding is that SNECMA was weak at combustion chambers and other "hots" parts, and the solution was their partnership with General Electric over the CFM56. That way they snatched the F101 core, and it probably helped a lot when making the M88.
 

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...at least on paper.
That was exactly what the Australians didn't trust.

So was there an engine out there that would have (in hindsight) been more practical for the Mirage III? Or was the Atar really the optimal engine for it because of the Mirage's airframe being designed around it?
The Australian investigations revealed that there was not, at least not in the Western sphere. The Avon could be substituted easily enough (Dassault took only a few weeks to swap one in for the Aussie trials) but was better optimised only for lower and slower missions. If you wanted the Mirage for ground attack it would have been a good choice, but the airframe was not optimised for that role so that was not a viable proposition anyway. The American engines would have required much redesign of the rear fuselage; the Aussies' opinion of them was not overly high in other respects.
 
...at least on paper.
That was exactly what the Australians didn't trust.

So was there an engine out there that would have (in hindsight) been more practical for the Mirage III? Or was the Atar really the optimal engine for it because of the Mirage's airframe being designed around it?
The Australian investigations revealed that there was not, at least not in the Western sphere. The Avon could be substituted easily enough (Dassault took only a few weeks to swap one in for the Aussie trials) but was better optimised only for lower and slower missions. If you wanted the Mirage for ground attack it would have been a good choice, but the airframe was not optimised for that role so that was not a viable proposition anyway. The American engines would have required much redesign of the rear fuselage; the Aussies' opinion of them was not overly high in other respects.

IAI Kfir readily agrees ! What the israelis found was that the J79 put a lot more heat than Atar, and they had to put a small (air & cooling ?) scoop at the base of the fin to help.
Note that the basic Mirage airframe got the following engines rammed into it, along the years (and from the top of my head)
- Avon (Mirage III-O)
- J79 (Kfir)
- TF104 /106 (Mirage III-T)
- Orpheus (Balzac V, also with a whole bunch of RB.108 lift jets)

Funnily enough it never got a M53 - although a case could be make the F1 basic airframe minus the wings and tail was a close derivate from the Mirage V. At least the M53 was a smoother fit than either J79 in Kfir or TF104/106 in the Mirage III-T.

Never got a Spey either, although it was not for lack of projects (III-K and naval F1s).

The Mirage III-T really pushed the airframe limits, never got faster than Mach 1.4 with the correct intakes, and it suffered from severe bouts of compressor stalls (welcome to the F-111 and Tomcat worlds !).
Compressor stalls in french are called "pompage" (as in a pompe = pump) and according to those whose watched the III-T struggling with them over Melun-Villaroche and Istres in 1964-66, it made a truly awful noise - not unlike that 75 gun of WWI fame. https://en.wikipedia.org/wiki/Canon_de_75_modèle_1897

MirageIII-T.jpg


It uncannily looks like a Mirage 2000, from that angle...

... it survived many compressor stalls and the airframe still exists today, at Rochefort military base.


http://bdd.deltareflex.com/cns_affiche.php?image=11211 (the much enlarged rump is clearly visible).
 
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The American engines would have required much redesign of the rear fuselage; the Aussies' opinion of them was not overly high in other respects.
I'm aware that the Kfir suffered from stability (aft CG) issues due to the J79 being shorter and heavier (more weight positioned further aft in the fuselage) and the additional cooling equipment required for it ate into the performance advantages the J79 offered. At this point I just want to know if there's anything SNECMA could have done to improve the ATAR's thrust output without increasing its weight, I want to know if they could have done anything to improve the Mirage III/F1's thrust to weight ratio.
 

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