F-4 Phantom engine upgrade

[_Del_]

^if successful that has a huge market internationallly, as well. Not just Phantoms, but everything with a J79 or new builds looking in the F404 range.

Also, depending on the timeline, the J79 eventually got to 18,900 lb thrust, which would be a great help on the short decks. I think it really depends as someone noted above on when the "alt"-history begins in this story.

 

[Archibald]

We are, somewhat, missing the author main objective.

I think what he wants, at core, is just to
- extend existing USN Phantoms lives
- to provide Essex with a viable interceptor until the end of Cold War
(that is, 15 years + of Essex carriers, 1975-1990)

This is a "secondary & opportunistic" program compared to Hornet / Nimitz / Tomcat / whatever else

The "engine trick" is just a "bonus" to help the old Phantoms operating out the old Essex.

In such context, there is no massive upgrade possible.
The move is essentially, opportunistic
"hey we need to extend these Essex past 1975 and up to 1990 at least"
and then
"drat, the Crusaders won't last that long
"and there is not enough money for a brand new aircraft
"only solution: Phantoms, second-hand ones survivors of Vietnam.
"Not even new ones, even if the production line keep running until 1979
"Problem is that old Phantoms on old Essexes while proven in 1961 - is really a little tricky...
"F401 re-engining should help a little, less fuel, more thrust..."
"Yeah but only if we can swap them straight for the old J-79s.
"No way to remake a Spey-F-4K nightmare.. we can't afford massive airframe surgery or new airframes"

 

[Archibald]

^if successful that has a huge market internationallly, as well. Not just Phantoms, but everything with a J79 or new builds looking in the F404 range.

Also, depending on the timeline, the J79 eventually got to 18,900 lb thrust, which would be a great help on the short decks. I think it really depends as someone noted above on when the "alt"-history begins in this story.

And by this metric (opportunistic, off-the-shelf) there are only three possible engines
- F401, because F-14B
- something derived of the J101 (as suggested by Overscan and my little self) because F-18 is coming
- uprated J79 as suggested above

How about the boosted variant from the F-16/79 (the castrated F-16 offered to Taiwan to not upset the PRC) ?
Bad for a F-16 of course, but perhaps good enough for a revamped Phantom

So at the end of the day there are three main options
- F401 > makes the updated Phantom related to the F-14B
- J101 > makes the updated Phantom related to the coming Hornet
- boosted J79 (well, the Phantom itself plus F-16/79 later)

 

[SSgtC]

All good options. But yes, I'm aiming primarily for a, "we need to keep this fleet viable until 1990. But it can't cost a lot of money. And it can't jeopardize the F-14 or the VFAX program." And to get the funds in during the post Vietnam draw down, it'll have to be pitched as being as close to "off the shelf" as possible. Given that the Navy originally suggested that the F401 could be used as a sort of "common" engine for several different aircraft (including the F-4), it just makes sense to me that they would co-develop a version of the F401 for both the Tomcat and the Phantom.

 

[Archibald]

Fact is Hornet and F-16/79 won't happen until 1979... F401 win. Makes sense.

 

[SSgtC]

Fact is Hornet and F-16/79 won't happen until 1979... F401 win. Makes sense.

Plus it can be pitched as a joint DOD program with the F-4, F-14, F-15 and F-16 all using a common engine core.

 

[Archibald]

Lol the Hornet will feel quite alone...

 

[SSgtC]

Lol the Hornet will feel quite alone...

Nah. GE won't give up that easy. When the F100/F401 start running into problems, they'll be very quick to offer a replacement option.

 

[Archibald]

How about GE, about 1970, smarting from the loss of both F100 and F401 contracts with their GE1/10, don't invest in J101 for Northrop P-530, but instead design a GE1/10 derivative with smaller fan, compatible with J-79 installation. This wins a contract for Phantom reengining, and is very successful with the Navy and even sells abroad, leading to GE proposing and winning a development of this engine for the F-14B to replace the troubled F401.

Just as Overscan said...

 

[Trident]

WI some second-world F-4 user (Australia, Greece, Iran, Israel, Japan, South Korea, Spain, Turkey, West Germany, UK, etc.) runs a fowl of USA politics, so has to search elsewhere for replacement engines?

Well, this basically *has* happened to Iran, right? The idea of a Phantom upgrade with Russian avionics/engines along the lines of the proposed South African Mirage F.1 or Indian MiG-21 upgrades has occurred to me before. RD-33 engines, Zhuk-derivative radar, L150 RWR, R-73 & R-77 AAMs...

 

[overscan (PaulMM)]

Slimming down the F401 to fit J-79 form factor isn't much easier than GE scaling the GE1/10. GE1 family was a huge modular engine program from tiny to giant with a number of prototype engines constructed and several actually built engines emerging from it. Also the F100 / F401 were pretty troublesome.

 

[SSgtC]

Slimming down the F401 to fit J-79 form factor isn't much easier than GE scaling the GE1/10. GE1 family was a huge modular engine program from tiny to giant with a number of prototype engines constructed and several actually built engines emerging from it. Also the F100 / F401 were pretty troublesome.

No, it's not. And I don't plan on making the development of the F401 all roses and sunshine. There will still be plenty of issues during the development and GE will certainly be offering an alternative, likely based on the GE1/10

 

[orlovsky]

The problem is the cats on the Essex class. The C11 cat struggled to get a Phantom into the air when it was hot and the aircraft was heavy. Adding a few thousand pounds of thrust (and deleting a couple thousand pounds of weight) helps that problem immeasurably. The USN had a possible fix for it (essentially an F-4K with the J79 and without the blown flaps) that would allow the C11 to launch a fully loaded Phantom at 90° temperature. But I don't see the Navy wanting a special model of Phantom just for the Essex. New engines are useful for every model.

Edit: In the TL, the Navy will also have zero interest in upgrading the Phantom too much and endangering the F-14 program. New engines (that are very close to "off the shelf") can be sold as a limited, though still useful, upgrade to keep the fleet viable until they are phased out of service.

Hello. Longtime lurker, got lots of information from here; on this, I can chip in a few bits of random information I've collected over the years, maybe something is helpful for your scenario:

- Coral Sea and FDR operated F-4s (B, N, J and S) with their C-11-1 catapults. They had the problem with hot/heavy, but it seems that was not a big deal.
- Due to the already mentionned size/fuel demands, you'd probably have to compromise on the nr of F-4s, 24 would be very demanding on an Essex.
- The "F-4K with the J79" - the extended 40 inch nose wheel strut would probably suffice to solve the takeoff problem. The RN report on the F-4K has data on the (probable?) testing of the F-4B with the extension, and it is worth 10-12 kts or about 5000 lbs takeoff weight.
- Does anybody know why the USN did not use the extension? Heat problems should be less than with the Spey, and even that was soluble with the JBDs as on Ark Royal. I can only guess, two aspects seem plausible:
-- The C-11 catapult would be phased out with the retirement of the Essexes and the SCB-101.66 refits of the Midways. That FDR and Coral Sea soldiered on with the old cats was not planned; also, both would be decommissioned in the late 70s anyway, the reprieve for Coral Sea was another unplanned development.
-- Caygill, Phantom from the Cockpit, quotes from the F-4K testing that weight would be limited to about 10x540 lb bombs, giving all up about 50k lbs due to "aircraft weight, centre of gravity and balance problems". The catapult limit of USN F-4s was usually 56k lbs; this may be a downside of the high AoA?
- There was a plan to reopen the production line of the F-4J about 1973 for the Marine Corps, somehow related to the F-14 contract problems. The idea went nowhere as the upfront costs were too high. (Here, starting p 395: https://books.google.at/books?id=s5...4sKHd7fDPgQ6AEwAHoECAMQAg#v=onepage&q&f=false ). But you could depart with the project going through, or more money for the CILOP phantoms (like new engines) as a compromise to fill a few extra decks, with a certain delay for the F-14.
- Most turbofans would require a higher air intake than the J79; that was the case with they Spey, and would also be so for example with the M53. Even the PW1120 required about 4 % more ( https://asmedigitalcollection.asme....V002T02A008/2395305/v002t02a008-84-gt-230.pdf ), so probably some change to the air inlets necessary, too.

 

[SSgtC]

The problem is the cats on the Essex class. The C11 cat struggled to get a Phantom into the air when it was hot and the aircraft was heavy. Adding a few thousand pounds of thrust (and deleting a couple thousand pounds of weight) helps that problem immeasurably. The USN had a possible fix for it (essentially an F-4K with the J79 and without the blown flaps) that would allow the C11 to launch a fully loaded Phantom at 90° temperature. But I don't see the Navy wanting a special model of Phantom just for the Essex. New engines are useful for every model.

Edit: In the TL, the Navy will also have zero interest in upgrading the Phantom too much and endangering the F-14 program. New engines (that are very close to "off the shelf") can be sold as a limited, though still useful, upgrade to keep the fleet viable until they are phased out of service.

Hello. Longtime lurker, got lots of information from here; on this, I can chip in a few bits of random information I've collected over the years, maybe something is helpful for your scenario:

- Coral Sea and FDR operated F-4s (B, N, J and S) with their C-11-1 catapults. They had the problem with hot/heavy, but it seems that was not a big deal.
- Due to the already mentionned size/fuel demands, you'd probably have to compromise on the nr of F-4s, 24 would be very demanding on an Essex.
- The "F-4K with the J79" - the extended 40 inch nose wheel strut would probably suffice to solve the takeoff problem. The RN report on the F-4K has data on the (probable?) testing of the F-4B with the extension, and it is worth 10-12 kts or about 5000 lbs takeoff weight.
- Does anybody know why the USN did not use the extension? Heat problems should be less than with the Spey, and even that was soluble with the JBDs as on Ark Royal. I can only guess, two aspects seem plausible:
-- The C-11 catapult would be phased out with the retirement of the Essexes and the SCB-101.66 refits of the Midways. That FDR and Coral Sea soldiered on with the old cats was not planned; also, both would be decommissioned in the late 70s anyway, the reprieve for Coral Sea was another unplanned development.
-- Caygill, Phantom from the Cockpit, quotes from the F-4K testing that weight would be limited to about 10x540 lb bombs, giving all up about 50k lbs due to "aircraft weight, centre of gravity and balance problems". The catapult limit of USN F-4s was usually 56k lbs; this may be a downside of the high AoA?
- There was a plan to reopen the production line of the F-4J about 1973 for the Marine Corps, somehow related to the F-14 contract problems. The idea went nowhere as the upfront costs were too high. (Here, starting p 395: https://books.google.at/books?id=s522AAAAIAAJ&pg=RA2-PA397&dq="f-4j"+"appropriations"+1974&hl=de&sa=X&ved=2ahUKEwjRwYjcseDqAhUox4sKHd7fDPgQ6AEwAHoECAMQAg#v=onepage&q&f=false ). But you could depart with the project going through, or more money for the CILOP phantoms (like new engines) as a compromise to fill a few extra decks, with a certain delay for the F-14.
- Most turbofans would require a higher air intake than the J79; that was the case with they Spey, and would also be so for example with the M53. Even the PW1120 required about 4 % more ( https://asmedigitalcollection.asme....V002T02A008/2395305/v002t02a008-84-gt-230.pdf ), so probably some change to the air inlets necessary, too.

Good info. I knew about the proposed mods to the F-4B from a proposal sent to Australia for an Essex class.

For some reason, I had thought that the SCB-110 refit that the Midway class received installed C7 cats on the bow instead of the C11-1 that Oriskany received. Apparently though, the Midways flew Phantoms with the C11s.

My guess on why the USN didn't use the nose wheel extension was simply that they didn't need to. In general, more powerful catapults and faster ships made it so they didn't need the 10-12kt wind over deck reduction.

I was not aware that there had been a proposal to reopen the F-4 line for the USMC. I can see where the Corps may have been interested, but damn, that would have been expensive.

Yes, the PW1120 did require some modifications to the engine inlets, but it was apparently a pretty straightforward and simple change.

 

[orlovsky]

My guess on why the USN didn't use the nose wheel extension was simply that they didn't need to. In general, more powerful catapults and faster ships made it so they didn't need the 10-12kt wind over deck reduction.

That is certainly part of the explanation. The SACs for the F-4J and F-4S show that already with the C-7, things get much easier. But difficult to get the extra 50ft needed into an Essex; the nosewheel extension might be the simplest solution for your scenario - unless there is some other drawback.

 

[SSgtC]

My guess on why the USN didn't use the nose wheel extension was simply that they didn't need to. In general, more powerful catapults and faster ships made it so they didn't need the 10-12kt wind over deck reduction.

That is certainly part of the explanation. The SACs for the F-4J and F-4S show that already with the C-7, things get much easier. But difficult to get the extra 50ft needed into an Essex; the nosewheel extension might be the simplest solution for your scenario - unless there is some other drawback.

The only drawback I can think of is the afterburner scorching the deck. Apparently when the F-4K crossdecked to some of the US supercarriers, the afterburners left long scorch marks on the decks

 

[GTX]

I knew about the proposed mods to the F-4B from a proposal sent to Australia for an Essex class.

Are you able to share the details of that proposal please?

 

[SSgtC]

I knew about the proposed mods to the F-4B from a proposal sent to Australia for an Essex class.

Are you able to share the details of that proposal please?

I'll have to find it again, but sure. It was from a 1962 proposal to replace Melbourne

 

[GTX]

Thank you - keen to see the specifics of the proposal.

 

[orlovsky]

It is discussed here https://www.secretprojects.co.uk/threads/ran-essex-class.12645/ , with excerpts linked. The report is in the National Archive of Australia ( https://recordsearch.naa.gov.au/SearchNRetrieve/Interface/SearchScreens/BasicSearch.aspx ), but the URL keeps moving.

 

[orlovsky]

The only drawback I can think of is the afterburner scorching the deck. Apparently when the F-4K crossdecked to some of the US supercarriers, the afterburners left long scorch marks on the decks

I was not able to find anything on the trials, only that an F-4B with the extended nose strut had been tested on a US carrier. The Report for the RN F-4K has data for the modified F-4B's launch speeds from 1962. There and in the F-4B for Australia file, no deck cooling problems are mentioned.

Maybe they didn't want to raise the issue, or it was only due to the Spey's larger afterburner flame (more air from a turbofan and more fuel burnt, and sitting closer to the deck than the J79). I am wondering whether somebody has information on this?

 

[SSgtC]

The only drawback I can think of is the afterburner scorching the deck. Apparently when the F-4K crossdecked to some of the US supercarriers, the afterburners left long scorch marks on the decks

I was not able to find anything on the trials, only that an F-4B with the extended nose strut had been tested on a US carrier. The Report for the RN F-4K has data for the modified F-4B's launch speeds from 1962. There and in the F-4B for Australia file, no deck cooling problems are mentioned.

Maybe they didn't want to raise the issue, or it was only due to the Spey's larger afterburner flame (more air from a turbofan and more fuel burnt, and sitting closer to the deck than the J79). I am wondering whether somebody has information on this?

I'm personally thinking it may have been a Spey specific problem combined with the rear of the aircraft being angled more at the deck

 

[orlovsky]

Very plausible, as it seems people were genuinely surprised when the deck of USS Saratoga started to "melt".

I do not know whether this has been linked here already, Phantoms flying from USS Oriskany (probably at light carqual weights, esp starting at 3:06):

View: https://www.youtube.com/watch?v=e92t7kgV_Ws

 

[SSgtC]

Very plausible, as it seems people were genuinely surprised when the deck of USS Saratoga started to "melt".

I do not know whether this has been linked here already, Phantoms flying from USS Oriskany (probably at light carqual weights, esp starting at 3:06):

View: https://www.youtube.com/watch?v=e92t7kgV_Ws

Very cool video. I did not know that the E-1 could launch from a carrier without the cat. And it was very interesting to see the crew strike down a chopper into the hanger with the rotors still turning.

As for the Phantom, they could fly from an Essex at, I think, anything up to 50,000 pounds give or take without issue. In they video, judging from the sheer number of types on board in going to guess they were doing carrier qualifications

 

[Archibald]

I checked just to get an idea...

McDonnell F-4K Phantom FG.Mk.1

The last Phantom FG.Mk 1 (XV592) was delivered on November 21, 1969.

The production F-4M differed only in detail from the YF-4M. A total of 116 production Phantom FGR.Mk 2s were delivered to the RAF. The first F-4M to reach Britain was XT891, which arrived at Yeovilton on July 18, 1968. Two days later, it was transferred to No. 23 Maintenance Unit at Aldergrove in Northern Ireland. 115 more F-4Ms were delivered to the same unit.

The last example (XV501) was delivered on October 29, 1969.

However, repairs to XV434 (which had been damaged during an earlier accident) delayed its delivery until June 16, 1970.

Just asking for the sake of curiosity, could the USN had procured some batches of British Phantoms ? putting some A-7 / TF41 components into the British Spey for the sake of commonality.

Ling Temco Vought A-7D Corsair II

The first Spey-powered A-7E flew for the first time on March 9, 1969.

 

[SSgtC]

Theoretically, sure. But there were so many different systems in the British Phantoms that they were practically a different aircraft from the F-4J. The Navy would need different training pipelines for both aircrew and maintainers. For just a few squadrons worth, it just isn't worth the added cost. I think a late top-up order for F-4Js is more likely. Though even that's iffy. The Tomcat was only a year from first flight then and the Navy is not going to want to jeopardize it's hot new fighter. Not after the fight they just went through to get it.

 

[_Del_]

I tried that, he didn't like it. Would have helped the RN afford more, too, if they bought in some bulk. Better range and endurance, which is probably more useful than the top end speed. TF-41 is already in the fleet inventory. Seems ideal to me to grab a few, if you need short -deck capability. UK already kindly paid for development.

 

[SSgtC]

I tried that, he didn't like it. Would have helped the RN afford more, too, if they bought in some bulk. Better range and endurance, which is probably more useful than the top end speed. TF-41 is already in the fleet inventory. Seems ideal to me to grab a few, if you need short -deck capability. UK already kindly paid for development.

Except you can't fit the TF-41 into existing airframes. That requires new build aircraft. And no way in hell will the Navy do anything that jeopardizes the F-14. And telling Congress that they want new build Spey Phantoms will do that. That's why I didn't like it. Not because it wasn't a good idea.

 

[zen]

Of course on occasion I've mused over an earlier alternative UK engine for British F4s, namely RR's RB.106 Thames or Bristols BE.30 Zeus. Two of the more interesting what if engines from the UK.
Which dimensionally was supposed to fit in were an Avon can. Though the reheat chamber was roughly Spey sized.
The RR engine expected to reach 15,000lb dry......

 

[SSgtC]

Of course on occasion I've mused over an earlier alternative UK engine for British F4s, namely RR's RB.106 Thames or Bristols BE.30 Zeus. Two of the more interesting what if engines from the UK.
Which dimensionally was supposed to fit in were an Avon can. Though the reheat chamber was roughly Spey sized.
The RR engine expected to reach 15,000lb dry......

Damn. That's practically what the J79 put out in burner. Why did they end up going with the Spey instead? Engine commonality with the Buccaneer S.2?

 

[zen]

Of course on occasion I've mused over an earlier alternative UK engine for British F4s, namely RR's RB.106 Thames or Bristols BE.30 Zeus. Two of the more interesting what if engines from the UK.
Which dimensionally was supposed to fit in were an Avon can. Though the reheat chamber was roughly Spey sized.
The RR engine expected to reach 15,000lb dry......

Damn. That's practically what the J79 put out in burner. Why did they end up going with the Spey instead? Engine commonality with the Buccaneer S.2?

It was a two spool twin shaft turbojet, mid 50's effort but cancelled along with various scaled versions.
Closest approximately engine built was Canada's Orenda Iriquois.
More thirsty than a Spey and not so good for low level, but up high and fast was its designed regime.

 

[Archibald]

Well Avro Canada actually designed early sketches of the Arrow with RB.106. No surprise the final Iroquois looks like a RB.106 or, more exactly, the scaled-up RB.122 planned for... F155T hence FD.3. The irony !

 

[Archibald]

Yeah the crux of the story is "second hand Phantoms" not "new Phantoms" (even with the ploy of British ones). The refurbished Phantoms are an opportunistic move which shall cost the least possible money - not to jeopardize the Tomcat and later, the Hornet.

Still fact is there is an interesting "alternate history inside another alt history" where the USN gets slightly more ambitious and buy "new" British Phantoms at an earlier date (1965 ? 1967 ?) as a "stopgap" for Essex that are losing their Crusaders and will soon need a new interceptor.

British Phantoms in USN livery in Vietnam, out of Essex... alternatively, the RN gets those Franklin and Bunker Hill rebuild, plus Eagle, and gets more Phantoms, and in turn this impact the USN to keep some Essex a little longer... with off-the-shelf British Phantoms.

 

[isayyo2]

While the "Advanced Phantom Projects" thread was linked, I don't think its contents were shared to the fullest. Looking at Post #136 there are some interesting options for SSgtC's ongoing and excellent TL Cold Warriors.

The first variation is (referred to as the F-4J+) which was a minimum change of the upcoming F-4J. Improvements were made to the wing, and high lift devices, the catapult performance, and it was to be equipped with a modified AWG-10 with multi-shot capability for the AIM-7F Sparrow III missile.

The final design study was the F-4(FV)S with an advanced engine. This design would incorporate the increase area intakes of the F-4K along with the General Electric GE-1 engine. This design would have improved approach speeds, service ceiling, and acceleration time.

F-4X Navy Proposal

A copy of the McDonnell Aircraft F-4X proposal for the US Navy. Report No F333, dated Jan 1967. From Kim Simmelink’s sources":"The Navy c...

aviationarchives.blogspot.com

A good start would be introducing the F-4J+ into the active F-4J production line which ran from Dec. 66 to Jan. 72; since extending the service lives of the Essex's would now be expected, then perhaps the F-4J/J+ would incorporate the extending nose gear as well?

Come mid 70s and the Essex's are here to stay, the F-4S program would start up and would be a thorough modernization, life extension, and incorporate lessons learned from Vietnam: i.e. solid state electronics, maneuvering slats, cockpit ergonomics/VTAS, TISEO/TCS?, and the big one: new engines - Either from GE or P&W, take your pick. Funding is the biggest issue of course, mostly with developing a new engine but I think we might just be able to persuade the Shah to fund some of its development, much like how he provided funds for the F-14 program.

Upgraded F-4E's with the new electronics and engines for His Majesty's Imperial Air Force, perhaps a near common engine for his new F-14s, and a greatly reduced bill for the Navy and USMC; too much of a stretch? Whatever F-4E upgrades get developed with Iran could also be applied to Greece/Turkey, South Korea, Japan, and maybe Taiwan too in this alternative timeline.

 

[Archibald]

This design would incorporate the increase area intakes of the F-4K along with the General Electric GE-1 engine.

Now that's interesting. The Phantom needed turbofans, but Spey (or TF30 for that matter) was too large. Now, the next generation would be much more compact - for a thrust not unlike the old J79, more or less 8 metric tons. GE1 or J101 or F404 would be pretty fine. So would (the irony !) RB199 - Tortom anybody ? Or Hortom ?

Somewhat ironically, a Phantom with the GE medium-size turbofan would be instant death knell for the P530 Cobra... and its many developments leading to the Hornet...

And before the RB199 was that AFVG engine called RB172. Around which was designed Britain's own atempt at a modern Phantom: the Blackburn P.141.
Now that's an idea: a Phantom with two RB172s, post AFVG debacle. Note that the RB172 rebranded M45 on the other side of the channel was shrunk into the Adour, and thus that peculiar Phantom would be related somewhat to the Jaguar.

How about that... a RB172 Phantom could fill the role of (altogether) F-4K, Tornado and Jaguar...

 

[isayyo2]

This design would incorporate the increase area intakes of the F-4K along with the General Electric GE-1 engine.

Now that's interesting. The Phantom needed turbofans, but Spey (or TF30 for that matter) was too large. Now, the next generation would be much more compact - for a thrust not unlike the old J79, more or less 8 metric tons. GE1 or J101 or F404 would be pretty fine. So would (the irony !) RB199 - Tortom anybody ? Or Hortom ?

Somewhat ironically, a Phantom with the GE medium-size turbofan would be instant death knell for the P530 Cobra... and its many developments leading to the Hornet...

And before the RB199 was that AFVG engine called RB172. Around which was designed Britain's own atempt at a modern Phantom: the Blackburn P.141.
Now that's an idea: a Phantom with two RB172s, post AFVG debacle. Note that the RB172 rebranded M45 on the other side of the channel was shrunk into the Adour, and thus that peculiar Phantom would be related somewhat to the Jaguar.

How about that... a RB172 Phantom could fill the role of (altogether) F-4K, Tornado and Jaguar...

Hmmmm an RB199-X derivative sized up to replace the J79, now there's a market for that!

There's 260 German F-4s that could be upgraded in the 80s, the Italian F-104S-ASA upgrades, and just maybe the fledgling Gripen could take on a non-American engine as backup Eurofighter?

 

[Apophenia]

.. before the RB199 was that AFVG engine called RB172.

Sorry to go off topic but I wanted to ask about the Snecma/Bristol Siddeley M45G becoming the RB.172 in the later Rolls-Royce designation system. Was that designation number then re-assigned?

I have RB.172 as R-R's internal designation for the T172 Adour.

For the M45 series, I have Rolls-Royce designations: RB.407 (M45M low-bypass turbofan); RB.410 (M45S geared turbofan); RB.411 (M57HA, M45H turboshaft derivative); RB.415 (M45SF low-bypass); RB.423 (M45R gas-generator); RB.424 (M45T geared turbofan); RB.427 (M45SE turboshaft?); and RB.433 (M45/M45SD-02 hybrid). Anyone have more?

 

[sferrin]

Would a pair of J75s have been too big? I seem to recall an F-101 configuration looked at with that configuration.

 

[zen]

RB.172 started life as a RR alternative to the RR-MTU RB.153.
In essence removing the German elements and adding further modularity.

This was later scaled down such that two would power the Anglo-French Supersonic Trainer. This because of an insistence on twin engines for that.

M45 however was a BSEL-SNECMA engine of similar size and power to the RB.153 and RB.172.

 

[SSgtC]

Would a pair of J75s have been too big? I seem to recall an F-101 configuration looked at with that configuration.

For the F-4? Yeah, way too big. The J75 had a 50.4" diameter and was 252" long. The J79 was over a foot narrower at 38.3" diameter and nearly four feet shorter at 207.3". But that's too be expected when the J75 developed damn near as much thrust at Military Power (16,500 pounds) as the J79 did in afterburner (17,000 pounds).