Radial engine in a Spitfire
Discussion
Would it have been possible and did the designers ever consider it?
Might have saved weight and vulnerability of cooling system, and possibly made more power. Was a suitable engine available that could fit the Spit’s slim fuselage?
Obviously the Tempest went through this conversion, albeit in a chunkier airframe.
The things one ponders when should be doing something else. …
Might have saved weight and vulnerability of cooling system, and possibly made more power. Was a suitable engine available that could fit the Spit’s slim fuselage?
Obviously the Tempest went through this conversion, albeit in a chunkier airframe.
The things one ponders when should be doing something else. …
Some interesting information here comparing the Merlin to (radial) Hercules installation in the Lancaster.
https://rec.aviation.military.narkive.com/u5WbXDhU...
What other aircraft used both formats? Top of head I can think of the Halifax, Beaufighter and maybe Whitley. I'm sure there are others. Radial made a big improvement to the Halifax.
https://rec.aviation.military.narkive.com/u5WbXDhU...
What other aircraft used both formats? Top of head I can think of the Halifax, Beaufighter and maybe Whitley. I'm sure there are others. Radial made a big improvement to the Halifax.
Bristol Mercury (Gloster gladiator, Blenhiem) was putting out over 800hp in the mid thirties. But Merlin had much more development potential.
The Curtiss Hawk 75 went the other way, P+W radial to Allison v12 in the P-40. FW190 had version with both BMW radial and DB603 / Jumo 213 water cooled V12 engines.
So it probably could have been done, but a big draggy radial on the front would have had an impact on the speed of the aircraft I would have thought.
The Curtiss Hawk 75 went the other way, P+W radial to Allison v12 in the P-40. FW190 had version with both BMW radial and DB603 / Jumo 213 water cooled V12 engines.
So it probably could have been done, but a big draggy radial on the front would have had an impact on the speed of the aircraft I would have thought.
Edited by lufbramatt on Wednesday 19th April 14:58
It would certainly have been possible in a structural and engineering sense. But it would have been largely pointless because the Spitfire's airframe was designed around the Merlin (or, at least, certainly a liquid-cooled V12), with the width and depth of the fuselage and cockpit being essentially determined by those dimensions of the powerplant. It was the same philosophy as the Bf109 and the P-51 - the slimmest, sleekest possible airframe for the engine while being able to accommodate all the other necessary equipment. Notice how both the Spitfire and the 109 have various bulges and protrusions on their cowlings so they fit around ancillary parts as tightly as possible - and both tended to sprout more of such things as development progressed and more stuff was needed.
So any radial powerplant would have been far wider than the fuselage behind it, especially if it was going to be of the same power output as the V12. It would create far more drag and performance across the board would be inferior.
The balance flipped back and forth between air-cooled and water-cooled engines in the inter-war period and through the war years. Coming out of WW1 it was generally considered that water-cooled inline engines produced less drag and radials. But water-cooled engines had a limit imposed by their cooling system, and above a certain power point the size of the cooling surfaces needed started imposing more drag. Meanwhile the development of NACA cowlings and the Townend ring greatly reduced the drag of air-cooled radials, so the pendulum swung back in that direction. Then the development of pressurised and glycol-based cooling systems, and greater understanding of things like the Meredith effect, began to greatly reduce the size and drag imposed by a radiator, so the mid-1930s sees a switch back to the liquid-cooled V12. That generally holds right through the war for non-naval fighters, but then as power demands keep rising and aerodynamic advances keep being made the point is reached where it becomes more aerodynamically efficient to cool a radial engine directly with air through an optimised cowling than to take the heat away from the engine in liquid and then cool that liquid with air via a radiator. Fighters were now routinely operating at altitudes above 25,000 or 30,000 feet where the air temperatures are so low that air cooling becomes much more efficient, and in general there had been a shift away - especially on the Allied side - from the 'minimalist' dogfighter typified by the Spitfire and Bf109 towards bigger, bulkier, better-armed, better-armoured aircraft that achieved high performance through sheer power.
It's significant to consider the aircraft that were converted the other way - from air-cooled radial to liquid-cooled V12. The Curtiss P-36 (radial) became the P-40 (V12), but because the fuselage was unchanged, and was sized and shaped to accommodate a radial engine in a blended cowling with adjustable flaps, it was much deeper than the Allison V12, so the radiators and oil coolers could be tucked under the engine in the nose, giving the aircraft its distinctive 'shark mouth' appearance. The Hawker Tempest started off with a fully streamlined V12 (with a Spitfire-like 'bullet' nose and the radiators in the wings), then went to an air-cooled radial, then went back to a liquid-cooled V12 with the coolers in the chin, but with the whole powerplant sheathed in a cowling similar to that for the radial, to the production model with a more P-40 style arrangement. The Fw190 started off with a radial and ended up with an inverted V12, but with an annual radiator that gave the nose essentially the same shape.
So any radial powerplant would have been far wider than the fuselage behind it, especially if it was going to be of the same power output as the V12. It would create far more drag and performance across the board would be inferior.
The balance flipped back and forth between air-cooled and water-cooled engines in the inter-war period and through the war years. Coming out of WW1 it was generally considered that water-cooled inline engines produced less drag and radials. But water-cooled engines had a limit imposed by their cooling system, and above a certain power point the size of the cooling surfaces needed started imposing more drag. Meanwhile the development of NACA cowlings and the Townend ring greatly reduced the drag of air-cooled radials, so the pendulum swung back in that direction. Then the development of pressurised and glycol-based cooling systems, and greater understanding of things like the Meredith effect, began to greatly reduce the size and drag imposed by a radiator, so the mid-1930s sees a switch back to the liquid-cooled V12. That generally holds right through the war for non-naval fighters, but then as power demands keep rising and aerodynamic advances keep being made the point is reached where it becomes more aerodynamically efficient to cool a radial engine directly with air through an optimised cowling than to take the heat away from the engine in liquid and then cool that liquid with air via a radiator. Fighters were now routinely operating at altitudes above 25,000 or 30,000 feet where the air temperatures are so low that air cooling becomes much more efficient, and in general there had been a shift away - especially on the Allied side - from the 'minimalist' dogfighter typified by the Spitfire and Bf109 towards bigger, bulkier, better-armed, better-armoured aircraft that achieved high performance through sheer power.
It's significant to consider the aircraft that were converted the other way - from air-cooled radial to liquid-cooled V12. The Curtiss P-36 (radial) became the P-40 (V12), but because the fuselage was unchanged, and was sized and shaped to accommodate a radial engine in a blended cowling with adjustable flaps, it was much deeper than the Allison V12, so the radiators and oil coolers could be tucked under the engine in the nose, giving the aircraft its distinctive 'shark mouth' appearance. The Hawker Tempest started off with a fully streamlined V12 (with a Spitfire-like 'bullet' nose and the radiators in the wings), then went to an air-cooled radial, then went back to a liquid-cooled V12 with the coolers in the chin, but with the whole powerplant sheathed in a cowling similar to that for the radial, to the production model with a more P-40 style arrangement. The Fw190 started off with a radial and ended up with an inverted V12, but with an annual radiator that gave the nose essentially the same shape.
Kawasaki Ki-100
https://en.wikipedia.org/wiki/Kawasaki_Ki-100
Originally powered by a license built version of the DB601 V12, which never worked properly, re-engined with a Mitsubishi radial after the engine factory was bombed. Comparable performance but top speed was lower with the radial.
https://en.wikipedia.org/wiki/Kawasaki_Ki-100
Originally powered by a license built version of the DB601 V12, which never worked properly, re-engined with a Mitsubishi radial after the engine factory was bombed. Comparable performance but top speed was lower with the radial.
2xChevrons said:
The Hawker Tempest started off with a fully streamlined V12 (with a Spitfire-like 'bullet' nose and the radiators in the wings), then went to an air-cooled radial, then went back to a liquid-cooled V12 with the coolers in the chin, but with the whole powerplant sheathed in a cowling similar to that for the radial, to the production model with a more P-40 style arrangement.
A common-ish fuselage aft of the firewall developed from the Hurricane and fitted for the disastrous RR Vulture, the Sabre and the Centaurus; the only ones with V12s were prototypes.Simpo Two said:
Another factor is that liquid-cooled engines are more vulnerable to combat damage. But I think I'd take the greater speed.
For it’s initial role as an interceptor speed was probably an advantage, later in the war when it was employed to attack ground targets maybe survivability was more important than speed. Just interesting to see what it would have looked like with a big radial up front.
hidetheelephants said:
A common-ish fuselage aft of the firewall developed from the Hurricane and fitted for the disastrous RR Vulture, the Sabre and the Centaurus; the only ones with V12s were prototypes.
I find the Vulture story a sad one - as there was nothing really wrong with the engine fundamentally. Rolls Royce were directed to spend their engineering effort developing the Merlin therefore the R&D the Merlin received which resulted in its transformation from an unreliable, self-grenading engine to the well-loved and reliable engine was denied to the Vulture. The Vulture everyone considers a disaster was the straight-off-the-drawing-board engine. RR's engineering team knew what was wrong with it and had clear thoughts on what steps had to be taken to make it reliable (and powerful) but it wasn't allowed to happen.It's worth noting that the engine was only unreliable running at high RPM and high power. In the absence of the development programme to focus on Merlins, the Vulture was made reliable by limiting its maximum operating RPM which strangled its power output.
There are far too many words there for 95% of consumers though, so the Vulture is summarised as "unreliable and under powered" which is rather misleading.
The Sabre on the other hand was an absolute liability and Napier simply didn't know how to make it work properly. Almost strangely given how Rolls Royce were instructed to dump with Vulture (and Peregrine) and concentrate on making better Merlins, the Air Ministry wanted the Sabre to work and forced Bristol to share their hard-earned technological know-how on sleeve valves with Napier. It was only then that the Sabre was any use at all.
Engine choices in World War 2 were not just about the performance of the engine. With such massive build programmes spread across dozens of different types, the Air Ministry was very concerned about the industrial capabilities of the country to turn out multiple types of engines for multiple projects.
This problem was ampified because of the need to keep developing these engines so that they did not fall behind what the enemy was doing.
In the end, a limited number of engines were selected for development with other engines receiving lower priority or even being cancelled altogether.
This problem was ampified because of the need to keep developing these engines so that they did not fall behind what the enemy was doing.
In the end, a limited number of engines were selected for development with other engines receiving lower priority or even being cancelled altogether.
Ayahuasca said:
Simpo Two said:
Another factor is that liquid-cooled engines are more vulnerable to combat damage. But I think I'd take the greater speed.
For it’s initial role as an interceptor speed was probably an advantage, later in the war when it was employed to attack ground targets maybe survivability was more important than speed. Just interesting to see what it would have looked like with a big radial up front.
Evidence seems to suggest that the design of the liquid-cooled system played a much bigger part in survivability than whether an engine was air- or liquid-cooled. The Typhoon and the P-40 both spent the last years of the war being used predominantly in the ground attack role and suffered no higher casualty rates than the P-47 in the same duty. A constant factor was that troops on the ground, whether firing rifles or AA cannons, commonly neglected to put enough lead on when targeting, so many rounds passed behind the aircraft and hits tended to be in the rear and centre. The same went for aerial combat, where most hits came from behind (or behind/above) and also tended to be towards the rear. The Typhoon, Tempest and P-40 all had their coolers in the nose, away from the most commonly hit areas and in a compact arrangement that minimised the runs of the coolant pipes between engine and radiator. The Spitfire, Hurricane and P-51 all had their radiators in more aerodynamically optimal position - under the centre section or under the wing(s), which put them in the line of return fire - the P-51/A-36 with its radiator behind the cockpit was especially vulnerable - and required longer runs of pipes.
2xChevrons said:
The Typhoon and the P-40 both spent the last years of the war being used predominantly in the ground attack role and suffered no higher casualty rates than the P-47 in the same duty.
From memory the P47 had a huge amount of plumbing snaking up and down the fuselage, for intercoolers and so on, which might have bought its survivability down.Yertis said:
2xChevrons said:
The Typhoon and the P-40 both spent the last years of the war being used predominantly in the ground attack role and suffered no higher casualty rates than the P-47 in the same duty.
From memory the P47 had a huge amount of plumbing snaking up and down the fuselage, for intercoolers and so on, which might have bought its survivability down.Yertis said:
From memory the P47 had a huge amount of plumbing snaking up and down the fuselage, for intercoolers and so on, which might have bought its survivability down.
IIRC the Jug could actually soak up a good deal of punishment. Those tubes carried air and exhaust not coolant.From Wiki: 'Nicknamed the "Jug" owing to its appearance if stood on its nose, the P-47 was noted for its firepower as well as its ability to resist battle damage and remain airworthy.'
The P-47 has always amused me. Much has been made of it's large turbocharger and all the advantages of power and altitude performance that brought. It's power was no better than the supercharged versions of the R2800 powering numerous other aircraft and its ceiling about the same as supercharged aircraft like the Spitfire IX, Bf109F and G, the P-51B through D and the F4U Corsair.
Objectively, the P-47 was a very complicated, large and heavy solution to not that complicated a problem. There's probably a good reason its overall powerplant layout was unique - there was simply a better way to do it!
Objectively, the P-47 was a very complicated, large and heavy solution to not that complicated a problem. There's probably a good reason its overall powerplant layout was unique - there was simply a better way to do it!
jamieduff1981 said:
The P-47 has always amused me. Much has been made of it's large turbocharger and all the advantages of power and altitude performance that brought. It's power was no better than the supercharged versions of the R2800 powering numerous other aircraft and its ceiling about the same as supercharged aircraft like the Spitfire IX, Bf109F and G, the P-51B through D and the F4U Corsair.
Objectively, the P-47 was a very complicated, large and heavy solution to not that complicated a problem. There's probably a good reason its overall powerplant layout was unique - there was simply a better way to do it!
Materials technology was barely up to making turbos work properly, the same thing that retarded turbojets.Objectively, the P-47 was a very complicated, large and heavy solution to not that complicated a problem. There's probably a good reason its overall powerplant layout was unique - there was simply a better way to do it!
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