Old designs with modern engines

[Weaver]

Since there wasn't quite enough space between the A-5's engines for another J-79, I've always thought it a natural for a rocket booster. You could replace the bomb bay tanks with oxidiser tanks and use jet fuel from from the regular tansk. You might even be able to arrange matters so that you could pull the entire rocket and oxidiser pack out and replace it with a full one, meaning you could do the actual refilling in an area wtih better safety than the flight line. You'd have to arrange a thrust structure to mate up the engine with the airframe without putting a compressive load on the oxidiser tanks though.

[Weaver]

What if Gloster decided to run with the Welland engines for a production model or an axial engine rather than the centrifugal family? Certainly the latter would've given it more power in the end, but at what cost?

Credible: they tested axial Metrovick F.2 engines on the Meteor as early as 1943. The main reason for not adopting them was poor reliability:

[jcf]

F404 and F414 are far too new to have been used for an A-5 reengining.
The TF41 is an inch greater in diameter than the J79, 40" vs. 39", which
is really only a .5" increase in terms of fit. A TF41 version that would fit
wouldn't be that great of a challenge. 

[PR19_Kit]

What if Gloster decided to run with the Welland engines for a production model or an axial engine rather than the centrifugal family? Certainly the latter would've given it more power in the end, but at what cost?

They did.

The Meteor F1, the first production version, was powered by Wellands. They only switched to Derwents, a re-designed and up-rated Welland, with the F3.

[Weaver]

F404 and F414 are far too new to have been used for an A-5 reengining.
The TF41 is an inch greater in diameter than the J79, 40" vs. 39", which
is really only a .5" increase in terms of fit. A TF41 version that would fit
wouldn't be that great of a challenge.

However the TF41 needed intakes that could feed it 263lb of air per second, whereas the J79 only needed 169lb/sec.

[Charlie_c67]

What if Gloster decided to run with the Welland engines for a production model or an axial engine rather than the centrifugal family? Certainly the latter would've given it more power in the end, but at what cost?

They did.

The Meteor F1, the first production version, was powered by Wellands. They only switched to Derwents, a re-designed and up-rated Welland, with the F3.

Sorry not the Wellands, I meant the Trents. Got my rivers mixed up 

[PR19_Kit]

Oh yes, the Trents were the first ever turbo-prop. I doubt the Meteor would have had the performance with them.

[Spino]

F404 and F414 are far too new to have been used for an A-5 reengining.
The TF41 is an inch greater in diameter than the J79, 40" vs. 39", which
is really only a .5" increase in terms of fit. A TF41 version that would fit
wouldn't be that great of a challenge.

Exactly what I was thinking.  LTV supposedly mated the afterburner section of an F100 to a TF41 during early testing of the YA-7F, and the resulting engine could deliver something like 26,000lb of thrust in afterburner, similar numbers to a J75 out of an engine not much bigger than a J79.  Would have been perfect for an A-5 provided that the AB section would fit.

[jcf]

F404 and F414 are far too new to have been used for an A-5 reengining.
The TF41 is an inch greater in diameter than the J79, 40" vs. 39", which
is really only a .5" increase in terms of fit. A TF41 version that would fit
wouldn't be that great of a challenge.

However the TF41 needed intakes that could feed it 263lb of air per second, whereas the J79 only needed 169lb/sec.

Yes, but that's something that could be addressed with intake design, and modification of the engine itself.

The Speys used on the Phantom were 43" in diameter with a mass flow requirement of 205lb/sec. The bulging of the F-4 design to accomodate the Spey had as much to do with the design of the airframe as it did with the specs. of the Spey. Get rid of the dopey A-5 tunnel bomb-bay and you have lots of room to work with in terms of enlarging the intake trunking.

I dug out my old Jane's ATWA 1968-1969 and it gives a diameter of 37.5" for the TF41-A-1, rather than the 40" of Wikipedia etc., and it also details the extensive internal changes to the engine that boosted the output to 14,250lb without an afterburner.

All of which suggests that installing a TF41 variant in the A-5 could have been done if there had been any need to do so. But, as there was no reason to do so, it's moot.
However, that does make it Whif fodder.

[Weaver]

F404 and F414 are far too new to have been used for an A-5 reengining.
The TF41 is an inch greater in diameter than the J79, 40" vs. 39", which
is really only a .5" increase in terms of fit. A TF41 version that would fit
wouldn't be that great of a challenge.

However the TF41 needed intakes that could feed it 263lb of air per second, whereas the J79 only needed 169lb/sec.

Yes, but that's something that could be addressed with intake design, and modification of the engine itself.

The Speys used on the Phantom were 43" in diameter with a mass flow requirement of 205lb/sec. The bulging of the F-4 design to accomodate the Spey had as much to do with the design of the airframe as it did with the specs. of the Spey. Get rid of the dopey A-5 tunnel bomb-bay and you have lots of room to work with in terms of enlarging the intake trunking.

I dug out my old Jane's ATWA 1968-1969 and it gives a diameter
of 37.5" for the TF41-A-1, rather than the 40" of Wikipedia etc., and it also details the extensive internal changes to the engine that boosted the output to 14,250lb without an afterburner. the bomb tunnel ends at about the same frame, so it doesn't help with enlarging the intakes, which have a pair of fuel tanks between them.

All of which suggests that installing
a TF41 variant in the A-5 could have been done if there had been any need to do so. But, as there was no reason to do so, it's moot.
However, that does make it Whif
fodder.

The intakes on the A-5 pass through a major fuselage frame at about the wing root leading edge. That would have to either be redesigned with larger holes and thicker material to compensate, or it would have to be made wider and the external shape changed to accomodate it. The bomb tunnel ends at the same frame, so it's not much help in redesigning the intakes, the forward portions of which have a pair of fuel tanks between them.

[Spino]

F404 and F414 are far too new to have been used for an A-5 reengining.
The TF41 is an inch greater in diameter than the J79, 40" vs. 39", which
is really only a .5" increase in terms of fit. A TF41 version that would fit
wouldn't be that great of a challenge.

However the TF41 needed intakes that could feed it 263lb of air per second, whereas the J79 only needed 169lb/sec.

Yes, but that's something that could be addressed with intake design, and modification of the engine itself.

The Speys used on the Phantom were 43" in diameter with a mass flow requirement of 205lb/sec. The bulging of the F-4 design to accomodate the Spey had as much to do with the design of the airframe as it did with the specs. of the Spey. Get rid of the dopey A-5 tunnel bomb-bay and you have lots of room to work with in terms of enlarging the intake trunking.

I dug out my old Jane's ATWA 1968-1969 and it gives a diameter
of 37.5" for the TF41-A-1, rather than the 40" of Wikipedia etc., and it also details the extensive internal changes to the engine that boosted the output to 14,250lb without an afterburner. the bomb tunnel ends at about the same frame, so it doesn't help with enlarging the intakes, which have a pair of fuel tanks between them.

All of which suggests that installing
a TF41 variant in the A-5 could have been done if there had been any need to do so. But, as there was no reason to do so, it's moot.
However, that does make it Whif
fodder.

The intakes on the A-5 pass through a major fuselage frame at about the wing root leading edge. That would have to either be redesigned with larger holes and thicker material to compensate, or it would have to be made wider and the external shape changed to accomodate it. The bomb tunnel ends at the same frame, so it's not much help in redesigning the intakes, the forward portions of which have a pair of fuel tanks between them.

So replace that pair of fuel tanks with a longer, slimmer one (or series of tanks to prevent excessive fuel sloshing during maneuvers) that runs the length of where the bomb tunnel used to be, re-work that fuselage frame, and widen the intakes in the leftover space?  Ehh, maybe a bit more work than anyone would have thought the A-5 was worth, I don't know.  I do love the A-5 but I've never been crazy about its engines or especially its bomb tunnel, that was a huge and frankly dangerous waste of space (the stores train was left on the deck more than once during a catapult shot, resulting in aircraft loss due to rapid CG shift at low speed or something).

[Weaver]

So replace that pair of fuel tanks with a longer, slimmer one (or series of tanks to prevent excessive fuel sloshing during maneuvers) that runs the length of where the bomb tunnel used to be, re-work that fuselage frame, and widen the intakes in the leftover space?  Ehh, maybe a bit more work than anyone would have thought the A-5 was worth, I don't know.  I do love the A-5 but I've never been crazy about its engines or especially its bomb tunnel, that was a huge and frankly dangerous waste of space (the stores train was left on the deck more than once during a catapult shot, resulting in aircraft loss due to rapid CG shift at low speed or something).

Sure, but by the time you've re-worked major elements of the airframe and re-stressed it all, it's effectively a new aeroplane. Most engine swaps are viable because they enable an existing airframe to remain useful and relevant. Replacing J79s with Speys made the UK Phantoms VERY expensive and the unexpected aerodynamic problems also made them the slowest at altitude. Unless you absolutely needed the better deck take-off/landing characteristics (which the RN did) or the range, or the politics, it wasn't worth it. You could say the same about the Avon-Sabre, which involved another expensive near-total airframe rework and played a role in putting the RAAF off the Avon-Mirage (which, ironically, was an easier swap). The Israelis only did the Kfir because the supply of French engines had been cut off while US support was more reliable. Economically, it didn't stack up, but politics favoured it.

[jcf]

F404 and F414 are far too new to have been used for an A-5 reengining.
The TF41 is an inch greater in diameter than the J79, 40" vs. 39", which
is really only a .5" increase in terms of fit. A TF41 version that would fit
wouldn't be that great of a challenge.

However the TF41 needed intakes that could feed it 263lb of air per second, whereas the J79 only needed 169lb/sec.

Yes, but that's something that could be addressed with intake design, and modification of the engine itself.

The Speys used on the Phantom were 43" in diameter with a mass flow requirement of 205lb/sec. The bulging of the F-4 design to accomodate the Spey had as much to do with the design of the airframe as it did with the specs. of the Spey. Get rid of the dopey A-5 tunnel bomb-bay and you have lots of room to work with in terms of enlarging the intake trunking.

I dug out my old Jane's ATWA 1968-1969 and it gives a diameter
of 37.5" for the TF41-A-1, rather than the 40" of Wikipedia etc., and it also details the extensive internal changes to the engine that boosted the output to 14,250lb without an afterburner. the bomb tunnel ends at about the same frame, so it doesn't help with enlarging the intakes, which have a pair of fuel tanks between them.

All of which suggests that installing
a TF41 variant in the A-5 could have been done if there had been any need to do so. But, as there was no reason to do so, it's moot.
However, that does make it Whif
fodder.

The intakes on the A-5 pass through a major fuselage frame at about the wing root leading edge. That would have to either be redesigned with larger holes and thicker material to compensate, or it would have to be made wider and the external shape changed to accomodate it. The bomb tunnel ends at the same frame, so it's not much help in redesigning the intakes, the forward portions of which have a pair of fuel tanks between them.

Look at the A-5 intakes in profile, for a model all you'd really need to do would be to deepen them forward of the frame you're talking about. That's a simple external change. As to a "real world" change take a look at Jumpei Temma's F-4 drawings where he overlays the F-4C and FG.1, the changes in the intake trunk dimensions aren't actually all that dramatic and are mostly in width, there's a slight increase in depth from station 203 to station 359.66 but after that its back to the same outer mould lines of the "side pods" on a regular Phantom.
The changes to the outer mould line driven by installing the Spey in the Phantom were due to the design of the F-4 and would not require the same kind of changes to the A-5 because it has an entirely different layout. There'd be no need to deepen or widen the fuselage because it's a box, not a canoe with side pods like the F-4. They couldn't go inboard on the Phantom so they had to go outboard.

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[Weaver]

Jon:

Agree with you about how to do it model-wise.

Real-world wise, it doesn't matter if you go inboard or outboard when making the A-5's intakes bigger, because they go through a hole in a fuselage frame (two actually, if you count the one at the front of the engine). Whether you make that hole bigger inboard, outboard, upwards or downwards, you're still removing metal from a major structural component, which will require it's redesign and restressing, and all the knock-on consequences for the rest of the airframe. It's not that it can't be done, it's that it involves so much work that it probably wouldn't be economically viable. That doesn't mean it would never be done either: politics and/or military neccessity can sometimes make economically dubious decisions neccessary. If the UK had bought A-5s instead of F-4s, we might well have Spey-ised them too for political reasons, and hang the cost.

It's also worth pointing out that although the changes to the Spey-Phantom might have be slight dimensionally, they were still enough to signifantly screw up the aerodynamics to the detriment of performance. That means that if you expand the A-5's intakes upwards, downwards or outboard, you'll probably also have to put it back in the wind tunnel and make further aerodynamic modifications, at more cost, time etc...

[PR19_Kit]

It's all SO much easier in plastic.........................