British escort fighter--what might it have been like?

[Shortround6]

Why should not the Merredith effect be applicable to the leading-edge radiators, wing radiators, or annular radiators for example?

The "effect" can be applied to just about any duct that has a heat source in it. However the effectiveness of the entire duct/heat source is rather variable.

You are trying to do 2 things at once.
Cool the engine with a minimum of drag.
Actually create positive thrust.

You might be able to create positive thrust (speed/mass of exiting air is greater than the speed/mass of the incoming air) but if the size of the installation needed to do it increases the overall drag of the aircraft (large duct with large skin surface/skin drag) you not get the results you want.

 

[tomo pauk]

<snip>

Thank you.
There is a reason why I've asked the fellow member the specific question
I'll wait for the answer.

 

[Deleted member 68059]

Yes but you have to decide what you are going to do while still on paper. The fuel needs to be at a certain location in the wing in regards to the center of gravity and for most planes the CG is around 30% of the cord, While still on paper you can slide the wing backwards and forwards to get the engine and all the other bits to balance the where the fuel goes.

It is often overstated, But people were fumbling around trying to get things to work
View attachment 700484
Like the caption says, different radiator installations between water and ethylene-glycol using the same engines and same airframe.
Now try to figure out the differences in a Meredith "duct" considering the different amount of air flow and the different temperature difference between the air and the radiator surfaces.
Also note that somehow the difference in the weight of the radiator/coolant needs to be adjusted for.

Not really, The D. 520 carried about 396 liters of fuel in the fuselage tank, just about the same as a 109 (lets not argue about 4 liters) and not much different than a Spitfire.
It's range came from two things, it was a small and lower in drag than some other fighters and it carried about 240 liters in the wing tanks. However handling was not all it could have been with the wing tanks full. VG-33 numbers may have been a bit exaggerated? yes it was small and streamline.

This is all true, but omits the "final objection" that Glycol has considerably inferior heat transfer properties to water. Meaning you need bigger radiators, somewhat
obliviating the reasons for using it in the first place (in pure form).

 

[NevadaK]

I've seen a few of these escort fighter threads on the forum and the solution always seems to be put more fuel in the Spitfire, but I don't think that actually responds to the role of an escort fighter and the qualities that made the P-51 as successful as it was. First, almost nobody in the late thirties early forties was thinking of designing a long range escort fighter because first, they didn't think there was need and second, they didn't think it was possible. Strategic air strategy centered on the operation of bomber fleets under the presumption that they were invincible, consequently strategies didn't exist for fighter supported operations or even the destruction of enemy air power through aerial engagement at a great distance. Whether through lack of imagination or the lack of available technology, the escort fighter wasn't a cornerstone of air forces planning in the late 30's. The only truly long range fighter early in the war, the Zero, was developed for carrier operations in the Pacific not for long range strategic escort. The compromises for that long range have been covered extensively in this forum.

A couple years back, I was reading an essay about escort fighters in WW2 and what constituted the most important qualities. (My apologies for not having that source handy) Range, the ability to engage the enemy on equal terms, endurance in combat, and a fuel efficient high speed cruise were the four that were considered the most essential qualities. The importance of high speed cruise was surprising to me as it related to how the escort fighter relied on the ability to dictate the terms of engagement with the enemy forces. The Mustang's great differential in cruising speed allowed it to spot enemy forces, move into position for engagement that put the German forces at a disadvantage. Early long range fighters such as the Zero, do not possess the ability to cruise at speed without significant reduction in range and endurance. I think in the late thirties, the Zero offers the road map most aviation designers would have taken for a long range fighter: make it as light as possible with a low cruise speed. I also think it's worth remembering that the Mustang was bit of an accident. It was designed to be fast, which it was, but it wasn't until it was re-engined until it possessed all the qualities that made it as successful as it was. In that sense, I think it could be said that nobody actually set out to design a long range escort fighter in WW2. It just kind of happened.

 

[Shortround6]

This is all true, but omits the "final objection" that Glycol has considerably inferior heat transfer properties to water. Meaning you need bigger radiators, somewhat
obliviating the reasons for using it in the first place (in pure form).

True, the US had tried to use a 300 degree coolant temperature at some point but also found that operating at anywhere near that just transferred some of the heat load to the oil requiring s different oil flow and larger oil supply and oil cooler/s. Which also negated the savings in radiator size.

The Photo is from a 1936 book that was a 3rd edition (1928 and 1932) and the copy I have is an ex library book from the US Military Academy at West Point.

I don't know how old the photo was but the section on cooling (all types) is about 11 pages. There may have been alone slight updating from the 1932 edition?
The engineers/designers were still trying to figure out how all this stuff worked. They were estimating that the Glycol system would save about 50% over a pure water system and this is after accepting 250 Degrees as the operating temperature. What they found out in 1937 may be different.
Several problems were noted in the text including the Glycol's "much greater ability to leak".

This book was published the year after Meredith's paper was read/published and no mention is made of it. Other later pre WW II text books do mention it. In my view it took a while to even figure out the different cooling systems (water, Glycol, pressurized water, steam, water/Glycol mix) each of which might require a bit different tweaking of the system in order to get the Meredith effect to actually work.

It does make it hard to view the 1930s with a crystal ball and say they should have known "XYZ" and designed accordingly and had 440mph aircraft in 1941.

 

[Shortround6]

I've seen a few of these escort fighter threads on the forum and the solution always seems to be put more fuel in the Spitfire, but I don't think that actually responds to the role of an escort fighter and the qualities that made the P-51 as successful as it was. First, almost nobody in the late thirties early forties was thinking of designing a long range escort fighter because first, they didn't think there was need and second, they didn't think it was possible. Strategic air strategy centered on the operation of bomber fleets under the presumption that they were invincible, consequently strategies didn't exist for fighter supported operations or even the destruction of enemy air power through aerial engagement at a great distance. Whether through lack of imagination or the lack of available technology, the escort fighter wasn't a cornerstone of air forces planning in the late 30's. The only truly long range fighter early in the war, the Zero, was developed for carrier operations in the Pacific not for long range strategic escort. The compromises for that long range have been covered extensively in this forum.

A couple years back, I was reading an essay about escort fighters in WW2 and what constituted the most important qualities. (My apologies for not having that source handy) Range, the ability to engage the enemy on equal terms, endurance in combat, and a fuel efficient high speed cruise were the four that were considered the most essential qualities. The importance of high speed cruise was surprising to me as it related to how the escort fighter relied on the ability to dictate the terms of engagement with the enemy forces. The Mustang's great differential in cruising speed allowed it to spot enemy forces, move into position for engagement that put the German forces at a disadvantage. Early long range fighters such as the Zero, do not possess the ability to cruise at speed without significant reduction in range and endurance. I think in the late thirties, the Zero offers the road map most aviation designers would have taken for a long range fighter: make it as light as possible with a low cruise speed. I also think it's worth remembering that the Mustang was bit of an accident. It was designed to be fast, which it was, but it wasn't until it was re-engined until it possessed all the qualities that made it as successful as it was. In that sense, I think it could be said that nobody actually set out to design a long range escort fighter in WW2. It just kind of happened.

The US was specifying a range of 2,000 miles for it's medium bombers in 1939 (B-25 and B-26) , they didn't get it but the idea of trying to design a single engine fighter (or even a twin) that could fly 2000 miles using the engines of 1939 (or promised in 1939) let alone the heavy bombers.
On February 1, (1939) the USAAC went through the formality of issuing Type Specification C-212 which called for a heavy bomber that was to have a maximum speed greater than 300 mph, a range of 2000 miles, and a ceiling of 35,000 feet. This lead to the B-24.
Now design a fighter to match it. And try to justify buying fighters that will only be able to escort it 50% of the way.

 

[tomo pauk]

First, almost nobody in the late thirties early forties was thinking of designing a long range escort fighter because first, they didn't think there was need and second, they didn't think it was possible.

The only truly long range fighter early in the war, the Zero, was developed for carrier operations in the Pacific not for long range strategic escort. The compromises for that long range have been covered extensively in this forum.

Luftwaffe was specifying ling-range fighters as early as 1934:
In 1934 the concept of the "armament aircraft III" was developed. The associated Luftwaffe High Command study introduced the term "Zerstorer" for a twin-engined escort fighter with articulated cannon armament designed to have a forward and upward arc of fire. The destroyer's task was to escort bombers by fighting enemy interceptors.

Bf 110 was, at least for European theater, a true long-range fighter already in 1939.

 

[Acheron]

Bf 110 was, at least for European theater, a true long-range fighter already in 1939.

And (somewhat) recently, people have started to argue that it could have been at least a decent fighter during the BoB, if it had been allowed to fight on its terms (high-speed) instead of being shackled to the bombers. No idea how much merit the idea has.

 

[BarnOwlLover]

Why should not the Merredith effect be applicable to the leading-edge radiators, wing radiators, or annular radiators for example?



Fuselage was an excellet location for the fuel tanks, eg. Spitfire was able to carry there ~160 imp gals (192 US gals).



Got some link?

You yourself have referred to this report a time or two on how the Spitfire could've been improved. Even if all of these weren't entirely practical to use, plenty could've been used to boost the Spitfire's speeds.

Improvements to the Spitfire

1939-early 1940 (not forgetting that the Spitfire didn't see intensive combat, particularly against fighters, until May 1940): Constant-speed propellers (priority for C/S props was given to bombers). Better protection for fuel tanks; in the interim, this would have to be the linatex that was...

ww2aircraft.net

As to the Meredith effect, it's been stated on this forum that to make best use of it, you need a long enough duct to slow the air down before it reaches the radiator core, and a suitable exit duct to gently/properly accelerate the air out of the duct. It's been said that the Hornet's and Mosquito's radiators did use the Meredith effect, but how well compared to say the Mustang (especially the XP-51F/G, P-51H and the F-82), I can't say, but I'd suspect as far as exploiting the effect, the Mosquito and Hornet probably weren't as successful. And the radiator entry and exit tracts on the Tempest I and Fury I are even shorter than on the Hornet or Mosquito, even if using the same concept.

That being said, those solutions don't need a duct to be mounted under the fuselage or under the wings for the radiators, and the leading edge radiators add hardly any frontal area. Any other effects regards to the airflow over/under the wings are perhaps debatable, as well as vulnerability to combat damage (ie, I don't see how they'd be more vulnable than the chin radiators on the Typhoon or Tempest V/VI or the Griffon Fury).

 

[tomo pauk]

You yourself have referred to this report a time or two on how the Spitfire could've been improved. Even if all of these weren't entirely practical to use, plenty could've been used to boost the Spitfire's speeds.

Not the same Spitfire - RAE doc dealt with the Mk.V.
The Mk IX already have had a host of improvements vs. the Mk.V, such are:
- less draggy exhausts (worth 7 mph if installed on the Mk,V per the RAE report)
- better carburetor (adds 10 mph on the Mk.V)
- improved fit & finish (Mk.V was bad here, Mk.IX improved on this)
- integral BP glass.

I'm not sure that extra nip & tuck can help the Mk.IX to mimic the speed figures of the Merlin Mustangs. Possibly the wheel wells covers and retractable tailwheel as on the Mk.VII/VIII? Extra 10 mph?

 

[BarnOwlLover]

Same document said that the absolute ideal Spitfire IX had a top speed of 445 mph. Even the more realistic 436-438 mph figures would've been extremely respectable. This also makes me wonder (though not 100% related to topic) what made the Spiteful faster than the Griffon-powered Spitfires, and what improvements could've been made.

 

[BarnOwlLover]

I've seen a few of these escort fighter threads on the forum and the solution always seems to be put more fuel in the Spitfire, but I don't think that actually responds to the role of an escort fighter and the qualities that made the P-51 as successful as it was. First, almost nobody in the late thirties early forties was thinking of designing a long range escort fighter because first, they didn't think there was need and second, they didn't think it was possible. Strategic air strategy centered on the operation of bomber fleets under the presumption that they were invincible, consequently strategies didn't exist for fighter supported operations or even the destruction of enemy air power through aerial engagement at a great distance. Whether through lack of imagination or the lack of available technology, the escort fighter wasn't a cornerstone of air forces planning in the late 30's. The only truly long range fighter early in the war, the Zero, was developed for carrier operations in the Pacific not for long range strategic escort. The compromises for that long range have been covered extensively in this forum.

A couple years back, I was reading an essay about escort fighters in WW2 and what constituted the most important qualities. (My apologies for not having that source handy) Range, the ability to engage the enemy on equal terms, endurance in combat, and a fuel efficient high speed cruise were the four that were considered the most essential qualities. The importance of high speed cruise was surprising to me as it related to how the escort fighter relied on the ability to dictate the terms of engagement with the enemy forces. The Mustang's great differential in cruising speed allowed it to spot enemy forces, move into position for engagement that put the German forces at a disadvantage. Early long range fighters such as the Zero, do not possess the ability to cruise at speed without significant reduction in range and endurance. I think in the late thirties, the Zero offers the road map most aviation designers would have taken for a long range fighter: make it as light as possible with a low cruise speed. I also think it's worth remembering that the Mustang was bit of an accident. It was designed to be fast, which it was, but it wasn't until it was re-engined until it possessed all the qualities that made it as successful as it was. In that sense, I think it could be said that nobody actually set out to design a long range escort fighter in WW2. It just kind of happened.

I think the reason for this is, one, the Spitfire was in British service back then and already had the Merlin in it, two, the Mustang was Allison powered and wasn't good enough at altitude, and three, the Spitfire was the most capable dogfigher in Allied service at the time.

What I'm advocating for is a British-built alternative to the Mustang that had the best aspects of both it and the Spitfire. I'd even argue that the Hawker Tempest (be it V, II, VI or even the stillborn Tempest I) or the Sabre or Centaurus Fury might have been good candidates for escort fighters, though the Sabre and Centaurus engines would suffer from having single stage superchargers (limiting high altitude performance), and maybe those planes would be a bit short-legged on internal fuel (Tempest I had a range of 770 miles on internal fuel, and the Tempest II had a range of I think 800 or so miles). Hence why I think it would make sense for this plane to maybe be Merlin powered. Though that might lead to the fighter being a bit on the small side to house all the fuel (or maybe not, given that even the Allison Mustang was a bit larger than the Spitfire).

Maybe I should say that this fighter should be like a circa 1942 piston powered (Merlin powered) equivalant to the de Havilland Vampire, or maybe even a single seat, single engine "half a DH Hornet".

 

[tomo pauk]

Same document said that the absolute ideal Spitfire IX had a top speed of 445 mph. Even the more realistic 436-438 mph figures would've been extremely respectable. This also makes me wonder (though not 100% related to topic) what made the Spiteful faster than the Griffon-powered Spitfires, and what improvements could've been made.

Have you read the page 4 and 5 of the RAE report?


The highlighted passages note that ideal Mk.IX will not be a combat aircraft. We can also recall that PR Spitfires powered by same engines were still slower than the Merlin Mustangs, despite all the care to be of impeccable surface, retractable U/C and lack of weapons - Morgan ans Shacklady give 417 mph top speed for the PR Mk.XI.
We also don't know whether the people at RAE took the effects of compressibility in their calculations - improvements that can gain 10 mph on the 360 mph base speed might not give the same amount of speed gain with the 400 mph base speed.

 

[wuzak]

As to the Meredith effect, it's been stated on this forum that to make best use of it, you need a long enough duct to slow the air down before it reaches the radiator core, and a suitable exit duct to gently/properly accelerate the air out of the duct. It's been said that the Hornet's and Mosquito's radiators did use the Meredith effect, but how well compared to say the Mustang (especially the XP-51F/G, P-51H and the F-82), I can't say, but I'd suspect as far as exploiting the effect, the Mosquito and Hornet probably weren't as successful. And the radiator entry and exit tracts on the Tempest I and Fury I are even shorter than on the Hornet or Mosquito, even if using the same concept.

There has to be a balance between the length of the duct, the space required for the duct and the losses associated with a longer duct.

The Mustang's radiator was tall and needed a lot of vertical expansion from the inlet. The wing mounted radiators were not very tall and quite wide, meaning the vertical expansion required was not a lot, so the wing radiators did not need as long an inlet duct.

 

[Shortround6]

The Mustang's radiator was tall and needed a lot of vertical expansion from the inlet. The wing mounted radiators were not very tall and quite wide, meaning the vertical expansion required was not a lot, so the wing radiators did not need as long an inlet duct.

yes and no.

If you could expand the air (either vertically or horizontally ) you could reduce the velocity as it went through the radiator matrix, reducing the velocity also reduces the drag of the air going through the matrix.
Now you have to accelerate the air back up to the speed of the plane before it exits the plane in the converging duct.

The real problem was in expanding the air in such a way so that eddies are not created before matrix and compressing/directing the air after the matrix without eddies or without to big a difference in the airflows between the top and bottom of the duct.

The Meredith effect itself may not depend on the slowing down of the cooling air before it hits the radiator. It does depend on heat of the radiator adding to the energy of the air flowing through the duct. It is a balancing act. Unlike a jet engine you have a very small amount of heat (or heat difference ) to cause the air to expand and flow faster.

 

[NevadaK]

The US was specifying a range of 2,000 miles for it's medium bombers in 1939 (B-25 and B-26) , they didn't get it but the idea of trying to design a single engine fighter (or even a twin) that could fly 2000 miles using the engines of 1939 (or promised in 1939) let alone the heavy bombers.
On February 1, (1939) the USAAC went through the formality of issuing Type Specification C-212 which called for a heavy bomber that was to have a maximum speed greater than 300 mph, a range of 2000 miles, and a ceiling of 35,000 feet. This lead to the B-24.
Now design a fighter to match it. And try to justify buying fighters that will only be able to escort it 50% of the way.

Thank you, Shortround6.

You bring appreciated depth to my post.

Kk

 

[NevadaK]

I think the reason for this is, one, the Spitfire was in British service back then and already had the Merlin in it, two, the Mustang was Allison powered and wasn't good enough at altitude, and three, the Spitfire was the most capable dogfigher in Allied service at the time.

What I'm advocating for is a British-built alternative to the Mustang that had the best aspects of both it and the Spitfire. I'd even argue that the Hawker Tempest (be it V, II, VI or even the stillborn Tempest I) or the Sabre or Centaurus Fury might have been good candidates for escort fighters, though the Sabre and Centaurus engines would suffer from having single stage superchargers (limiting high altitude performance), and maybe those planes would be a bit short-legged on internal fuel (Tempest I had a range of 770 miles on internal fuel, and the Tempest II had a range of I think 800 or so miles). Hence why I think it would make sense for this plane to maybe be Merlin powered. Though that might lead to the fighter being a bit on the small side to house all the fuel (or maybe not, given that even the Allison Mustang was a bit larger than the Spitfire).

Maybe I should say that this fighter should be like a circa 1942 piston powered (Merlin powered) equivalant to the de Havilland Vampire, or maybe even a single seat, single engine "half a DH Hornet".

Greetings BarnOwlLover,

I think your statement "the Spitfire was the most capable dogfighter in Allied service at the time" illustrates what I believe is a bit of a misunderstanding of what made a great escort fighter during WW2. The Spitfire v Mustang debate has been more than exhaustively covered in this forum. The Spitfire's excellence as a dogfighter comes at the cost of three of the escort fighter's essential qualities: speed, endurance, and efficient high speed cruise. The Tempest/Fury airframe might be possible, but I think it would require better high altitude capability as well as new wing similar to the development from the P-47D to the P-47N to be able to occupy the same role as the Mustang. If you are really pushing for a purely UK development of a Mustang like long range escort fighter, then I think it is going to come from a manufacturer who is willing to think outside the norms, similar to how NAA approached the design of the Mustang. Martin Baker has been brought up already, but it might also come from someone like Folland who proposed this fighter in 1943 (Folland Fo.117) or Miles who proposed this in 1941 (Miles M.23). None of these have exceptional range, but at least show where some other design talent could be found.

 

[BarnOwlLover]

Hence my proposal of and aircraft that was essentially "half a Hornet", since it would be single seat, single engine, have sufficient range, and for sure (even with a Merlin 60 series engine instead of the 130 designed for the Hornet) would have the speed and agility required, and might be as good as, if not better, than the mass produced Merlin Mustangs (not counting the P-51H). Also, de Havilland and their design team did show that "thinking outside the box" concept with the Mosquito, Vampire and Hornet.

However, if they were to design such a fighter, there would've been basically only a brief period of time for them to have done so from late 1941-early 1942. Since this is a hypothetical thread, lets take the DH example. In that period stated, they were being under utilized by the RAF, meaning they did have design, R&D and maybe some production to spare. That, however, if we look at the realities, rapidly changed in early 1942. The Mosquito would quickly come into huge demand once it entered service in it's recon, bomber, heavy fighter and night fighter roles. The RAF and the Air Ministry took the project for a jet fighter that would yield the Vampire a lot more seriously. And even though de Havilland would drop the DH.102 project (for a medium bomber that was basically a slightly enlarged Mosquito), it would be resurrected as the DH.103 (Hornet) long range fighter project. And even though that didn't gather a ton of interest from the Air Ministry at first, the expansion of British action outside of the CBI theater in the Pacific Theater would make the Hornet very appealing.

Hence, you can maybe say that if the Hornet was prioritized earlier, the British would've had their own equivalent to the P-38 in both Europe and the the Pacific. But though the Hornet is a single seater, it's twin engine so doesn't really fit in here as such.

And the problem with Miles and Folland is that though they did produce good designs if they were given a chance, it seems that the Air Ministry didn't take those designs seriously, or looked at the size of those companies and judged them as too small to make the numbers required if adopted. Not to mention that those companies did also fill niches that others couldn't due to being back-logged. Martin-Baker, for example, made seats, cannon feed systems, and ultimately developed the modern incarnations of the ejection seat. And Miles still made trainers and light aircraft for the RAF and Royal Navy. Of course, these are interesting "what could've been" items themselves.

 

[NevadaK]

Hence my proposal of and aircraft that was essentially "half a Hornet", since it would be single seat, single engine, have sufficient range, and for sure (even with a Merlin 60 series engine instead of the 130 designed for the Hornet) would have the speed and agility required, and might be as good as, if not better, than the mass produced Merlin Mustangs (not counting the P-51H). Also, de Havilland and their design team did show that "thinking outside the box" concept with the Mosquito, Vampire and Hornet.

However, if they were to design such a fighter, there would've been basically only a brief period of time for them to have done so from late 1941-early 1942. Since this is a hypothetical thread, lets take the DH example. In that period stated, they were being under utilized by the RAF, meaning they did have design, R&D and maybe some production to spare. That, however, if we look at the realities, rapidly changed in early 1942. The Mosquito would quickly come into huge demand once it entered service in it's recon, bomber, heavy fighter and night fighter roles. The RAF and the Air Ministry took the project for a jet fighter that would yield the Vampire a lot more seriously. And even though de Havilland would drop the DH.102 project (for a medium bomber that was basically a slightly enlarged Mosquito), it would be resurrected as the DH.103 (Hornet) long range fighter project. And even though that didn't gather a ton of interest from the Air Ministry at first, the expansion of British action outside of the CBI theater in the Pacific Theater would make the Hornet very appealing.

Hence, you can maybe say that if the Hornet was prioritized earlier, the British would've had their own equivalent to the P-38 in both Europe and the the Pacific. But though the Hornet is a single seater, it's twin engine so doesn't really fit in here as such.

And the problem with Miles and Folland is that though they did produce good designs if they were given a chance, it seems that the Air Ministry didn't take those designs seriously, or looked at the size of those companies and judged them as too small to make the numbers required if adopted. Not to mention that those companies did also fill niches that others couldn't due to being back-logged. Martin-Baker, for example, made seats, cannon feed systems, and ultimately developed the modern incarnations of the ejection seat. And Miles still made trainers and light aircraft for the RAF and Royal Navy. Of course, these are interesting "what could've been" items themselves.

Hmm, let us not forget that in 1940, North American Aviation only had a trainer in production and a medium bomber in development when it was contracted to design the Mustang.

 

[GrauGeist]

NAA had quite a few projects going before 1940.
NA-16 (trainer BT series)
NA-19 (trainer BT series)
GA-15 (observation O-47)
NA-26 (trainer SNJ/AT-6)
NA-50/68 (fighter P-64)
NA-64 (trainer "yale")
NA-69 (attack A-27)

And of course, the B-25 was under development, soon to be introduced.

The aircraft listed do not include a few prototypes developed but never produced (XB-21, NA-35, etc.)