Alternative RAAF fleets.

[NOMISYRRUC]

Note the engine names in italics... you put Goblin in one place where it should have been Ghost, and the Gnome is a late-1950s turboshaft that went in the Sea King.

Venoms (and Vampire FB.1) had Ghosts (4,400 lb.s.t. to 5,300 lb.s.t) - Goblins only produced 2,700 lb.s.t to 3,350 lb.s.t..

Nenes produced from 4,600 lb.s.t.* to 5,400 lb.s.t..


* This was the version in the Vampire F.2.

As you're criticising my poor proof reading skills. To my knowledge there wasn't a Vampire FB.1.

 

[Rule of cool]

I wonder if the evaluation of the F4, Lightning, F5 and Drakken were left and right of arc. The Mirage III and F104 were pretty much middle of the road for high end fighters in 1961. Going anything different would be an outlier decision.

 

[BlackBat242]

As you're criticising my poor proof reading skills. To my knowledge there wasn't a Vampire FB.1.

Over 10 years ago (more like 15) I had saved the data from this website: https://jet-engine.net/miltfspec.htm
It showed the following lines:

de Havilland Ghost 48 Aquilon 4,850 - - - - 1 - - 1C 1 - - - Notes - - -
de Havilland Ghost 50 XJ 29 4,400 - - - - 1 - - 1C 1 - - - - - -
de Havilland Ghost 101 Vampire FB.1/NF.2/NF.3/FB.4 5,060 - 1.020 - 87 4.5 - - 1 - - 1C 1 - - - Notes - - -
de Havilland Ghost 103 Venom FB.1, Venom NF.2/NF.2A 4,850 - - - - 1 - - 1C 1 - - - - - -
de Havilland Ghost 104 Venom NF.3, Sea Venom F(AW).20/F(AW).21 4,950 - - - - 1 - - 1C 1 - - - - - -
de Havilland Ghost 105 Sea Venom F(AW).22/F(AW).53 5,300 - - - - 1 - - 1C 1 - - - - - -

I just went back to the website, to find there have been several edits - with engine variants and designations changed... and none of the Ghost versions list "Vampire" as an application. Ah, well... that's the problem with internet sources.

Note: grey - denotes optional engine selection or no nominal application for engine, and I had deleted those in my copy.





For comparison, here are my copy of the Goblin entry and the current one:


de Havilland Goblin DGu.1 Meteor prototype, Meteor F.2, F.9/40 2,700 - - - - 1 - - - - - Notes - - -
de Havilland Goblin DGu.2 Vampire F.1/F.3/FB.5/FB.9/NF.10/FB.20 3,100 - - - - 1 - - - - - - - -
de Havilland Goblin DGu.3 D.H. 108, Meteor F.2, Vampire FB.5/FB.6/FB.50/FB.52/FB.53, G.80-1B/-2B/-3B 3,350 - - - - 1 - - - - - - - -

 

[NOMISYRRUC]

Everybody loves the Avon Mirage, but trials showed that it did not come with any significant performance benefit over the Atar 9C, was more expensive, heavier and didn't fit the Mirage as well the Atar which the Mirage was designed around. What's more the cost was initially calculated incorrectly as British pounds with 20 shillings instead of Australian pound with 16 shillings, wen this was corrected the Avon 'became' 20% more expensive.

What the RAAF was interested in was the Atar 9K(-10) which was to be fitted to the Mirage IV bomber, which had the performance offered by the Avon without the risk. However this engine wasn't available in time for the RAAF decision so Mirage IIIO were fitted with Atar 9C.

Rolls Royce Australia lobbied the Government, which was felt by the RAAF assessment team in France, but to no avail.

FWIW Gunston wrote that the Avon increased the ferry range by 600 miles (which allowed it to fly from Darwin to Singapore) and increased the gun-firing height by 10,000ft.

He also wrote:

Harker thinks the French underpriced the Atar aircraft by quoting prices in Australian Pounds (which were 20 per cent cheaper than Sterling).

That's the opposite of the above on two counts. That is: The Atar version was incorrectly priced, not the Avon version; and it calculated incorrectly in Australian Pounds instead of Pounds Sterling rather than vice versa.

He continued.

The clincher, he says, is that some nit in Derby refused to supply a more powerful afterburner at the original price, reasoning that "it wouldn't be economic for a batch of only 30 aircraft". So the one good R-R re-engining effort came to nothing. Of course, the 30 Atar-engined Mirage III fighters for the RAAF was just for starters; successive batches brought their total up to 100 aircraft, and there is not the slightest doubt that the all-round superior performance of the Avon-Mirage would have seen it sold in the place of the Atar in a high proportion of today's 1,410 similar aircraft.

However, it may be him that's got it the wrong way around rather than you. I simply don't know.

 

[NOMISYRRUC]

Link to Post 43.

I suspect that Vampire FB.1 was a typo for Venom FB.1.

FWIW these are the engines for the Vampire and Venom according to the specification tables on Pages 108 & 109 of Postwar Military Aircraft: 5 Vampire, Venom and Sea Vixen by Philip Birtles.

​

 

[Rule of cool]

FWIW Gunston wrote that the Avon increased the ferry range by 600 miles (which allowed it to fly from Darwin to Singapore) and increased the gun-firing height by 10,000ft.

He also wrote:That's the opposite of the above on two counts. That is: The Atar version was incorrectly priced, not the Avon version; and it calculated incorrectly in Australian Pounds instead of Pounds Sterling rather than vice versa.

He continued.However, it may be him that's got it the wrong way around rather than you. I simply don't know.

I don't have access to sources anymore so that maybe correct, certainly Darwin to Singapore ferry range sounds familiar.

However the RAAF preferred the Atar after comparing it to the Avon and despite political pressure from Rolls Royce Australia, so I'd take the claims with a pinch of salt.

Further, the whole Australian to British pounds thing shows how tight the budget was, which makes more expensive aircraft like the Lightning less likely contenders even if it was supported wholeheartedly by Britain.

 

[GTX]

I don't have access to sources anymore so that maybe correct, certainly Darwin to Singapore ferry range sounds familiar.

However the RAAF preferred the Atar after comparing it to the Avon and despite political pressure from Rolls Royce Australia, so I'd take the claims with a pinch of salt.

Further, the whole Australian to British pounds thing shows how tight the budget was, which makes more expensive aircraft like the Lightning less likely contenders even if it was supported wholeheartedly by Britain.

From here:



We have the following:

 

[Rule of cool]

I have that, but I don't have access to the Defence library service like I used to.

 

[GTX]

Try also looking up "Comparison of Atar 9C and Avon mark 67 for Mirage IIIC for installation" in the National Archives. A full scan of the file is available online.

 

[Scott Kenny]

Go the whole hog and order the Phantom in 1960 (instead of the Mirage III) to replace the Sabre and buy the leased F-4Es in 1973 as attrition replacements. I appreciate that the Phantom was more expensive.

IIRC about twice the price of Mirage III, so Aus would either be buying about 15 birds or spending twice as much (edit) for the initial buy. And there just wasn't the budget space for that. Sadly.

Because it would have been pretty amazing for Aus.

 

[Rule of cool]

Try also looking up "Comparison of Atar 9C and Avon mark 67 for Mirage IIIC for installation" in the National Archives. A full scan of the file is available online.

I had a look at that document, it appears that the Avon would have provided a fatter performance envelope. That said it wouldn't be a straight forward swap, development work would have to be done on the 36" afterburner and to fit the starter fluid which might be problematic.

Interestingly, even the more expensive (up front) Avon Mirage was cheaper than the F104.

 

[NOMISYRRUC]

IIRC about twice the price of Mirage III, so Aus would either be buying about 15 birds or spending twice as much. And there just wasn't the budget space for that. Sadly.

Because it would have been pretty amazing for Aus.

The eventual total was 116 Mirage III so it would either be buying about 58 aircraft or spending twice as much. But point taken.

 

[Rule of cool]

I doubt the 1959-60 RAAF 'evaluation' of the F4 was particularly serious, it certainly wasn't flown in the way the Mirage III and F104 were.

The first real opportunity for the RAAF to get the F4 was when the Hancock mission looked at the F4C, RA5C and Mirage IV in late 1963 as a replacement for the Canberra. For that role it was found unsuitable due to the lack of range; IIRC 627 miles against the RA5Cs 1000+miles and a fully developed buddy tanking system.

The leased Phantoms were returned to the US in 1973 rather than purchased because the RAAF didn't want their purchase to interfere with the Mirage IIIO replacement, which they wanted sooner rather than later.

 

[Rule of cool]

Possibly more interesting to me than the fighters and bombers are the helicopters. The RAAF was commanded by bomber pilots in the early Cold War and were closely integrated into the RAFs FEAF so had little to no interest in Army cooperation and therefore little to no interest in acquiring helicopters.

The big buys were 27 Wessex by the RAN, 47 H-13 for the joint Army-RAAF 16 AOP Flight (became Army 1st Avn Regt in 1966) and 42(?) UH1 for the RAN (7) and RAAF.

However, the RAN also received 2 Westland Scout (1963) for Hydro Survey and the RAAF 3 Alouette III (1964) for Womera rocket range work. It'd be cool to see more of either of these types instead of the later batches H-13s, they could do good work in Vietnam.

 

[Pioneer]

Possibly more interesting to me than the fighters and bombers are the helicopters. The RAAF was commanded by bomber pilots in the early Cold War and were closely integrated into the RAFs FEAF so had little to no interest in Army cooperation and therefore little to no interest in acquiring helicopters.

The big buys were 27 Wessex by the RAN, 47 H-13 for the joint Army-RAAF 16 AOP Flight (became Army 1st Avn Regt in 1966) and 42(?) UH1 for the RAN (7) and RAAF.

However, the RAN also received 2 Westland Scout (1963) for Hydro Survey and the RAAF 3 Alouette III (1964) for Womera rocket range work. It'd be cool to see more of either of these types instead of the later batches H-13s, they could do good work in Vietnam.

Well, if we're talking helicopters, then one would hope the eleven AH-1G Huey Cobra was selected in December 1970, at a program cost of $12.4m would go ahead, regardless of the end of the VietNam War.

Given Australia's actual real-world threat analysis, these AH-1G's could have served the RAAF and later Australian Army Aviation well into the 2000's......

ADF Serials - Bell AH-1 Cobra

Regards
Pioneer

 

[Rule of cool]

Well, if we're talking helicopters, then one would hope the eleven AH-1G Huey Cobra was selected in December 1970, at a program cost of $12.4m would go ahead, regardless of the end of the VietNam War.

ADF Serials - Bell AH-1 Cobra

Regards
Pioneer

IIRC that order was to include 84 OH56s, 42 UH1s, 12 CH47s as well as the 11 AH1Gs. In the end it was cut down to 56 OH56s and 12 UH1s with 12 CH47s following a few years later.

Personally I'd like to see the Scout adopted instead of the later batches of H-13s, after all 16 AOP was RAAF dominated, so the Scout is bought in decent numbers during the Vietnam era and is more suitable than the Sioux for arming-up. The Scout would also have a grearter service life and not need replacing in 1971, so the 1971 helicopter order might get those AH1Gs in service.

 

[Rule of cool]

Wiki has a good precis on Air Marshal Murdoch, Chief of Air Staff 1965-69, which were the Vietnam War leadup and peak years. In particular very poor handling of the Army cooperation/helicopters, although he did like Harriers over AH1Gs for the close support role. Sadly his 3-year tenure was extended by a year, it would have been better if he was replaced after 3 years and indeed shuffled out earlier using some administrative excuse. The RAAF might have kept the helicopters if Murdoch wasn't in such a key position.

Individuals in key positions and lines on org charts are so important, especially in smaller air arms whose fleet decisions are not regular like the US' for example.

 

[Elan Vital]

What the RAAF was interested in was the Atar 9K(-10) which was to be fitted to the Mirage IV bomber, which had the performance offered by the Avon without the risk. However this engine wasn't available in time for the RAAF decision so Mirage IIIO were fitted with Atar 9C.

So an early, slightly worse Mirage 50?

 

[Pioneer]

The Australian government, wanting to keep the Australian aviation manufacturing sector vibrant and up to date in modern aviation technology, takes up Dassault offer to licence-build the Mirage F1E in Australia in the 1970's to replace the RAAF's Avon Mirage IIIO(F). But, the Australian government and RAAF specify a Spey-powered Mirage F1E, so as to bring Australian aviation engine industry into the modern turbofan era.
At the same time the Australian government pursues the proposal by CAC/GAF to license-build a derivative of Douglas' proposed Spey-powered CA-4E Skyhawk for both the RAAF and RAN to replace their earlier Avon-powered Skyhawk's. The Spey-powered derivative of the Skyhawk offering superior performance, range and payload capabilities, while also incorporating the ability to employ modern precision guided weapons......

Regards
Pioneer

I should have clarified in more detail that when I state the Dassault Mirage F1E, I meant the F1E [E for Export] derivative, powered by the SNECMA M53 turbofan - also known as the Mirage F1 M53, developed for the European Fighter Competition.
In a sense, the Australian order for a modified derivative of the F1E/F1 M53 powered by a Rolls-Royce Spey turbofan saves the program and much personal investment by Dassault. For the significant redesign of the rear fuselage and air intakes need for the larger diameter and higher mass airflow for the SNECMA M53, is utilised for the Spey.
The additional advantages offered by the utilisation of the revised F1E/F1 M53 design is it's multi-role avionics, increased internal fuel capacity, strengthened landing gear and a rectractable flight refuelling probe...........offering the RAAF an exceptional multi-role fighter of significant capability and performance at a substantial cost lower than the McDonnell Douglas F-4 Phantom II.....

Regards
Pioneer

 

[Rule of cool]

Sounds risky and expensive, especially since by the 70s the Communist threat in the region had pretty much stabilised. What do you want the ADF to do by going out on such an independent limb?

 

[GTX]

I should have clarified in more detail that when I state the Dassault Mirage F1E, I meant the F1E [E for Export] derivative, powered by the SNECMA M53 turbofan - also known as the Mirage F1 M53, developed for the European Fighter Competition.
In a sense, the Australian order for a modified derivative of the F1E/F1 M53 powered by a Rolls-Royce Spey turbofan saves the program and much personal investment by Dassault. For the significant redesign of the rear fuselage and air intakes need for the larger diameter and higher mass airflow for the SNECMA M53, is utilised for the Spey.
The additional advantages offered by the utilisation of the revised F1E/F1 M53 design is it's multi-role avionics, increased internal fuel capacity, strengthened landing gear and a rectractable flight refuelling probe...........offering the RAAF an exceptional multi-role fighter of significant capability and performance at a substantial cost lower than the McDonnell Douglas F-4 Phantom II.....

Regards
Pioneer

Not sure if a Spey version would have been beneficial. Doing a quick comparison:



Generally the Spey is a bigger, heavier engine thus necessitating heavier airframe structure. It also has lower thrust. airflow would be much the same so intakes for F1-M53 should be fine. Spey only really wins in terms of SFC though given the need for heavier airframe, I suspect that advantage would have been voided.

 

[Rule of cool]

Any version of the Mirage F1E isn't a patch on the superlative F/A18A.

 

[H_K]

The additional advantages offered by the utilisation of the revised F1E/F1 M53 design is it's multi-role avionics, increased internal fuel capacity, strengthened landing gear and a rectractable flight refuelling probe...........offering the RAAF an exceptional multi-role fighter of significant capability and performance at a substantial cost lower than the McDonnell Douglas F-4 Phantom II...

If you can find a way to incorporate a modern track-while-scan, look-down shoot-down radar on the Mirage F1 then you have a real winner IMHO. As the dated avionics were as much of an issue as the engine, if not more so.

Any version of the Mirage F1E isn't a patch on the superlative F/A18A.

There’s almost a 10 year difference between the 2, so not surprising.

The F/A-18A should be compared to its contemporary the Mirage 2000C RDI… I imagine things would be even, and kinematics much in the Mirage 2000´s favor.

 

[Rule of cool]

There’s almost a 10 year difference between the 2, so not surprising.

The F/A-18A should be compared to its contemporary the Mirage 2000C RDI… I imagine things would be even, and kinematics much in the Mirage 2000´s favor.

That pretty much encapsulates the RAAF goal of maintaining a capability edge in the region. We become one of the first export customers for a state of the art aircraft, we've tended not to get combat aircraft well into their production cycle.

 

[Pioneer]

That pretty much encapsulates the RAAF goal of maintaining a capability edge in the region. We become one of the first export customers for a state of the art aircraft, we've tended not to get combat aircraft well into their production cycle.

Yes, and unfortunately, we've paid for that notion of obtaining state-of-the-art/cutting edge ideology more than once - the F-111C and F-35 being the most obvious acquisition which has come back and bitten factual capability vs sales catalogue.

Regards
Pioneer

 

[Pioneer]

Sounds risky and expensive, especially since by the 70s the Communist threat in the region had pretty much stabilised. What do you want the ADF to do by going out on such an independent limb?

Being much more independent, due to the demise of the trumped-up Communist threat/Domino Theory and all that idelogical shit, which should have been explicitly apparent after our blind faithful experience in VietNam.

Regards
Pioneer

 

[Pioneer]

Not sure if a Spey version would have been beneficial. Doing a quick comparison:

View attachment 759723

Generally the Spey is a bigger, heavier engine thus necessitating heavier airframe structure. It also has lower thrust. airflow would be much the same so intakes for F1-M53 should be fine. Spey only really wins in terms of SFC though given the need for heavier airframe, I suspect that advantage would have been voided.

Thanks for the technical data for comparing the M53 and Spey, and thanks for your view.
I'm opting for the Spey for a few reasons and as you'd appreciate, that SFC you so kindly allude to, is one of the principle reason, given the necessity of range/endurance in and around the likes and size of Australia.
I'm also conscious, that at the time of the Mirage F1E/F1 M53, the M53 turbfan had only started flight testing started in July 1973 (using a Caravelle flying test-bed) and the engine first went supersonic in a Mirage F.1 test bed at the end of 1974. This means, if the RAAF went with the M53 engine, it's reliability wouldn't necessarily be truely reliable, unlike the tested and proven Spey Mk.202, which by ~1974 had been flying in RAF and RN F-4M/K Phantom II's for what, close to six years?

Again, as I've alluded in my earlier post, the notion is importantly the economics of commonality, with the RAAF and RAN operating respected derivatives of the Spey-powered McDonnell Douglas CA-4E/F Skyhawk.

Regards
Pioneer

 

[Pioneer]

In the case of replacing my GAF/Dassault Mirage F1E (Spey-powered) in the 1980's, I would opt for liaising strongly with Canada, to become launch customer for the Northrop F-18L/TF-18L Cobra.
Now, I appreciate what everyone says about the hesitation/reluctance to be the launch customer, it being too risky......
But in truth, with the communality of 71- percent with that of the McDonnell Douglas F/A-18 Hornet, it's not as risky as many might allude.....
The F-18L retains 99-percent commonality in terms of the F/A-18A/B's systems, including avionics, radar and ECM....
Then there's the F-18L's 3,493kg (7,700 Ib) lighter weight than the carrier-centric F/A-18A/B Hornet. Many state that the inherent carrier strengths of the F/A-18A/B are advantages to the RAAF, allowing it to operate from astute airfields. But the truth is, I'm not aware of the RAAF putting this to practice, let alone it part of its operational doctrine (although, I think it should be).
So, in the 1990's, when the region becomes more prosperous, putting greater emphasises on education and real-world trade and finance, an as such begins to upgrade their militaries to modern standards, including the purchase of state-of-the-art fighters and strike aircraft like the F-16, F/A-18D, MiG-29's and Su-27's, the F-18L, unlike the RAAF's legacy F/A-18A/B Hornet's, stays relevant in air-to-air combat (helped by it's midlife upgrade, which includes more powerful F404-GE-402's).

Regards
Pioneer

 

[zen]

Spey has potential for higher thrust.
205 was projected to 25,000lb reheated and UK funded this, but cut the F4 fleet post Cold War.

 

[Archibald]

So an early, slightly worse Mirage 50?

From 1968 the Atar 9K50 was specifically designed for the operational Mirage F1, IOC in spring 1973. Yet it took until 1979 until it found its way into the Mirage V airframe. The prototypes Mirage F1 (02 / 03 / 04, spring 1969, after the 01 killed René Bigand two years before, May 1967) flew with Atar 9K-31.
A case can be made that the 9K50 is available from 1970 if somebody wants more power for its Mirage IIIE (lots of avionics) or Mirage V (much less avionics, cheaper bomb truck).
...
brain fart
...
https://en.wikipedia.org/wiki/Dassault_Mirage_III#Milan
D'oh, stupid me. Milan actually put a 9K50 into a Mirage IIIR... in 1970.
...
(another brain fart)
...
Mirage IIIC2

 

[Rule of cool]

Yes, and unfortunately, we've paid for that notion of obtaining state-of-the-art/cutting edge ideology more than once - the F-111C and F-35 being the most obvious acquisition which has come back and bitten factual capability vs sales catalogue.

Regards
Pioneer

The F111 and F35 were bought during their development phase, not when they were just entering service in their home country. The Mirage and Hornet were both just entering service when selected.

Being much more independent, due to the demise of the trumped-up Communist threat/Domino Theory and all that idelogical shit, which should have been explicitly apparent after our blind faithful experience in VietNam.

Regards
Pioneer

I do like a more independent defence and foreign policy, but that doesn't require non standard fighters, just a good spread of suppliers, good spares and ordnance stocks and a robust industry.

One reason I'm so interested in British gear in the Cold War is because it gives Australian foreign policy choice.

 

[Pioneer]

The F111 and F35 were bought during their development phase

That was specifically the point I was trying to make mate. Sorry I didn't articulate it well.

Regards
Pioneer

 

[Scott Kenny]

Again, as I've alluded in my earlier post, the notion is importantly the economics of commonality, with the RAAF and RAN operating respected derivatives of the Spey-powered McDonnell Douglas CA-4E/F Skyhawk.

That would likely be worth pursuing.

It's certainly why the USMC wants only F-35s as their fighter, and why their H-1s use exactly the same dynamic components and tail boom. It gives you "deeper" spare parts bins when your Skyhawk engines can get an afterburner bolted on and stuck into the Mirages, or a Mirage engine gets the AB unbolted and stuffed into the Skyhawk.

 

[H_K]

Not sure if a Spey version would have been beneficial. Doing a quick comparison:

Generally the Spey is a bigger, heavier engine thus necessitating heavier airframe structure. It also has lower thrust.

The M53-P2 didn’t exist until 1985 and was a later development that couldn’t be retrofitted on earlier aircraft.

We should be comparing the M53-2 (1976) which had 54.4kN dry (12,200lbf) / 83kN AB (18,700lbf) thrust, or the slightly improved M53-5 (1979) which had an improved reheat with 88.2kN (19,800lbf) thrust.

 

[NOMISYRRUC]

At the same time the Australian government pursues the proposal by CAC/GAF to license-build a derivative of Douglas' proposed Spey-powered CA-4E Skyhawk for both the RAAF and RAN to replace their earlier Avon-powered Skyhawk's. The Spey-powered derivative of the Skyhawk offering superior performance, range and payload capabilities, while also incorporating the ability to employ modern precision guided weapons...

Was the Spey-Skyhawk a proper proposal or have you made it up?

 

[Archibald]

We have a Spey - projects thread somewhere. https://www.secretprojects.co.uk/threads/rolls-royce-spey-based-projects.471/

First post: Spey - Skyhawk. So it was kinda real.

 

[Rule of cool]

On helicopters.
The RAAF-Army bought ~14 H-13 by 1961 (Army pilots crashed 5 in a few years) then bought another 53 from 1965-68, that is to say after the RAN bought 2 Scouts and the RAAF bought 3 Alouette IIIs. The Alouette IIIs were used for 3 years until 1967 then disposed of.

Personally I'd prefer the RAAF-Army to buy Scouts instead of 53 H-13s, and either Scouts or UH-1B for Woomera instead of Alouete IIIs, so that they will be transferred to the ADF from 1967.

 

[Pioneer]

Was the Spey-Skyhawk a proper proposal or have you made it up?

Yes it was a proper project NOMISYRRUC. It was originally marketed to both RCAF as thr CA-4E/F and if I remember correctly, it later become known and marketed as the International Skyhawk. Apart from the Spey engine, it incorporated a dorsal hump fuel tank, in place of the avionics dorsal hump - a conformal tank if you like.

I'll attempt to find more details for you, I know its on this forum.....

Regards
Pioneer

 

[NOMISYRRUC]

Yes it was a proper project NOMISYRRUC. It was originally marketed to both RCAF as the CA-4E/F and if I remember correctly, it later become known and marketed as the International Skyhawk. Apart from the Spey engine, it incorporated a dorsal hump fuel tank, in place of the avionics dorsal hump - a conformal tank if you like.

I'll attempt to find more details for you, I know its on this forum.....

Regards
Pioneer

Thank you.

I'd had another case of false memory syndrome because before I thought you'd suggested an Avon powered Skyhawk before I checked the thread. I'm glad that you did because it stopped me from asking why have an Avon powered Skyhawk when the (IIRC) A-4A-to-C Skyhawks had Wright J65 engines which were licence built A.S. Sapphires.

Unfortunately, fitting Rolls-Royce engines to existing aircraft has been a hit and miss affair. For every unqualified success like the Spey-Buccaneer and Spey-Corsair II there's been a qualified success like the Nene-Vampire (for the RAAF), Avon-Sabre (for the RAAF) and Spey-Phantom. The Spey-Skyhawk may turn out to be the next Spey-Phantom rather than the next Spey-Buccaneer.

 

[Rule of cool]

A bigger question is did the RAAF want any version of the A4 in the 60s?