Hercules Engined Fighters

southjn1982

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Dec 15, 2020
In 1939 Hawker did do tests of a Hurricane using a Bristol Hercules engine (see photo) these eventually led to the Sea Fury and the decision to use the Bristol Centaurus, but how good would a radial-engined fighter based on the Hercules have been? On paper, I think it could have been pretty good, especially for North Africa and the Pacific as well as the FAA the engine was very tough and reliable and was powerful while still being relatively lightweight even by 1939 it was capable of 1300hp and only weighed 100kg more than the Merlin. Does anybody have any good ideas if a Hercules-based fighter would have been useful in secondary theatres and the Fleet Air Arm in the 1939-41 period filling a similar role for the UK as the Wright radials did for the US as the Hercules was 25% more powerful than the engine on the Zero although heavier but was almost as powerful while being 150kg lighter than the BMW801 used on the FW-190.
 

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tomo pauk

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In 1939 Hawker did do tests of a Hurricane using a Bristol Hercules engine (see photo) these eventually led to the Sea Fury and the decision to use the Bristol Centaurus, but how good would a radial-engined fighter based on the Hercules have been? On paper, I think it could have been pretty good, especially for North Africa and the Pacific as well as the FAA the engine was very tough and reliable and was powerful while still being relatively lightweight even by 1939 it was capable of 1300hp and only weighed 100kg more than the Merlin. Does anybody have any good ideas if a Hercules-based fighter would have been useful in secondary theatres and the Fleet Air Arm in the 1939-41 period filling a similar role for the UK as the Wright radials did for the US as the Hercules was 25% more powerful than the engine on the Zero although heavier but was almost as powerful while being 150kg lighter than the BMW801 used on the FW-190.

Are you reading my mind? ;)
(note that the photo is the Centaurus-engined Tornado/Typhoon, not the Hercules-engined Hurricane, but it does illustrate the point)
My take always on the topic: make them in many thousands (even if something with a thinner wing is preferable).
 

southjn1982

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Are you reading my mind? ;)
(note that the photo is the Centaurus-engined Tornado/Typhoon, not the Hercules-engined Hurricane, but it does illustrate the point)
My take always on the topic: make them in many thousands (even if something with a thinner wing is preferable).
I'm sure the Soviets would have liked them as it would be a good rugged fighter but this is the one labeled the Centaurus test bed according to the National archive the one I posted is a Hurricane with a Hercules but might be mislabeled if anyone has the test report I'd love to read it
 

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tomo pauk

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this is the one labeled the the Centaurus test bed according the the National archive
This is Sea Fury (note the angled front decking and the hook) prototype (note the 'P' on fuselage*).

the one I posted is a Hurricane with a Hercules but might be mislabeled
It is not a Hurricane with Hercules.

edit: P in circle meant that 24/7 armed guard is required
 
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southjn1982

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This is Sea Fury (note the angled front decking and the hook) prototype (note the 'P' on fuselage).


It is not a Hurricane with Hercules.
I'm not saying it is I'm just saying that's how it's labeled in the Archive, but in the archive, many things are mislabeled although the P would also be used on a Hurricane being used as a test bed and I'm sure a lot of the lessons learnt from this testbed were used on later designs and i'd love to read the report
 
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tomo pauk

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I'm not saying it is I'm just saying that's how it's labeled in the Archive, but in the archive, many things are mislabeled although the P would also be used on a Hurricane being used as a test bed and I'm sure a lot of the lessons learnt from this testbed were used on later designs and i'd love to read the report
I'd have to correct myself - the P in the circle IIRC meant that aircraft is to be guarded by armed guards 24/7. See here for the captured Fw 190 with the P in circle.
There might be a test-bed with a P in circle, hopefully someone has better information on this.
 

southjn1982

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I'd have to correct myself - the P in the circle IIRC meant that aircraft is to be guarded by armed guards 24/7. See here for the captured Fw 190 with the P in circle.
There might be a test-bed with a P in circle, hopefully someone has better information on this.
I Know that the prototype Mosquito in the De Haviland museum also has a P they claimed it was standard for all prototypes but it makes sense that captured enemy aircraft being evaluated would also get the same treatment as in many ways you treat them the exact same way as you would a prototype.
 

Shortround6

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Let's remember that F.18/37 specification (actually March of 1938?) led to several "designs" some by Bristol and some by others.
This was the replacement for the Hurricane and Spitfire.
bristol_p1837_1.jpg

Bristol and Hawker each schemed fighters using the Sabre, Vulture and Centaurus engines
Gloster schemed a twin boom pusher fighter
gloster_f1837_1.jpg

I am not saying that nobody looked at or sketched a Hercules powered aircraft but it would have been way down on power, It would be competing with the Merlin powered single engine fighters already in production and it offered few, if any advantages over the Merlin powered versions. FW 190 style cowls and radial installations were several years away and the drag of a 1937-38-39 Hercules would have been higher than for the Merlin. You also had to figure for the expected power of the Hercules in those years and not what they got out of it in 1941-42.
 

tomo pauk

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Let's remember that F.18/37 specification (actually March of 1938?) led to several "designs" some by Bristol and some by others.
This was the replacement for the Hurricane and Spitfire.

Bristol tendered with the Type 153 Hercules-powered fighter to the cannon-armed fighter (the F.37/35 specification), that was won by Whirlwind. It is not implausible that Bristol wins, and thus an 1-engined Hercules-powered fighter is made.

I am not saying that nobody looked at or sketched a Hercules powered aircraft but it would have been way down on power, It would be competing with the Merlin powered single engine fighters already in production and it offered few, if any advantages over the Merlin powered versions. FW 190 style cowls and radial installations were several years away and the drag of a 1937-38-39 Hercules would have been higher than for the Merlin. You also had to figure for the expected power of the Hercules in those years and not what they got out of it in 1941-42.

It would've been made instead of Whirly, if the Bristol's A/C wins the bid.
Against the Merlin-powered fighters and on 87 oct fuel, it would've had a 50% greater power at low altitudes, meaning it can climb faster to meet the threat. On 100 oct fuel it still has much more for take off and sustained climb beyond 10000 ft.
Easier to produce and maintain than the Whirlwind (yes, no Merlin there).
Not all Merlin-powered fighters were low-drag aircraft, either. Hurricane didn't took advantage of the small height of Merlin, the radiator was draggy, so was the wing.
 

Snowygrouch

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Hercules is in an awkward situation. Its not really any better than a Merlin power wise, up to Merlin XX, and markedly worse than Merlin 60> and wont fit into any 1938>1942 fighters, it WILL fit into something the size of a Tornado, but, its also much less powerful than the Centaurus, which DOES fit a Tornado. You can say in retrospect that had they never made
a centaurus, and put all the effort into high spec Hercules would it have been good, but that needs hindsight, and, none of the sleeve valve engines got anywhere
near the boost levels used by Merlin/Griffon late war, so you`ve got a performance ceiling there waiting for you too.

Very difficult to see how it could (realistically) have been put into single engine fighter use.
 

Shortround6

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Against the Merlin-powered fighters and on 87 oct fuel, it would've had a 50% greater power at low altitudes, meaning it can climb faster to meet the threat. On 100 oct fuel it still has much more for take off and sustained climb beyond 10000 ft.
Not really.
The FTH of the early Hercules was 4,000ft, yes it has a lot more power than the Merlin III down low. Now lets look at a low altitude Merlin as used in the Fulmar. 1080 hp for take-off. Hercules is better but......................There was unproduced Merlin RM1M engine (Merlin III with a 7.32 supercharger gear that offered 1000hp for take off and 1085hp at 9750ft.
Of course the problem with the Hercules is that while it offers good climb to 10-15,000ft it starts craping out by the time you reached 20,000ft.
You need the Hercules III engine with the two speed supercharger
You also don't get that big a boost from 100 octane fuel in the early Hercules. They allowed 4lbs of boost instead of 3lbs?
You also need the better propellers. For get the wood ones, the two position props are not going to allow the full use of the extra power at low altitudes/climb
You also (unknown in 1938, by late 1939?) have production problems with the early Hercules engines and rather short over haul lives.
Not all Merlin-powered fighters were low-drag aircraft, either. Hurricane didn't took advantage of the small height of Merlin, the radiator was draggy, so was the wing.
If you have 20% more drag in the engine them maybe you can use a low drag airframe. But if your airframe is not among the lowest drag and you stick the radial on it where are you?
And with the Hercules you have about zero hope of getting exhaust thrust in the late 30s or early 40s. They got there but it took a lot of work and took work on cooling the basic engine.
If your early Hercules needs work keeping it cool weaving 28 exhaust pipes though the two row of cylinders just adds to the problem.
 

tomo pauk

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Not really.
The FTH of the early Hercules was 4,000ft, yes it has a lot more power than the Merlin III down low. Now lets look at a low altitude Merlin as used in the Fulmar. 1080 hp for take-off. Hercules is better but......................There was unproduced Merlin RM1M engine (Merlin III with a 7.32 supercharger gear that offered 1000hp for take off and 1085hp at 9750ft.

RAF fighters, to whom Bristol was hoping to sell the Type 153, were never outfitted with either Merlin VIII or the RM1M, so I'm not sure why you are mentioning these engines.

Of course the problem with the Hercules is that while it offers good climb to 10-15,000ft it starts craping out by the time you reached 20,000ft.
You need the Hercules III engine with the two speed supercharger

Yes, Hercules III is needed.
Climb to 15-20k ft is what is needed in BoB, so I'll take it as-is.

You also need the better propellers. For get the wood ones, the two position props are not going to allow the full use of the extra power at low altitudes/climb
You also (unknown in 1938, by late 1939?) have production problems with the early Hercules engines and rather short over haul lives.

One good propeller vs. two good propellers on a Whirly?
Same with Hercules production vs. Peregrine production, including 1939 or 1940. Overhauling one more temperamental engine vs. overhauling two less temperamental engine?
I'll take all of this, too.

If you have 20% more drag in the engine them maybe you can use a low drag airframe. But if your airframe is not among the lowest drag and you stick the radial on it where are you?
And with the Hercules you have about zero hope of getting exhaust thrust in the late 30s or early 40s. They got there but it took a lot of work and took work on cooling the basic engine.
If your early Hercules needs work keeping it cool weaving 28 exhaust pipes though the two row of cylinders just adds to the problem.

I'll agree with a wing of 220-230 sq ft and 15% t-t-c at root. Granted, Spitfire is the most streamlined real thing in the whole Christendom when it was conceived, so this is an even better base.
Some exhaust thrust will be there, the exhaust(s) will be pointing backward after all.
 

Shortround6

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They were all designed for the 2000hp class engines, So you are either low powered in comparison or scaling back/size of the design to a smaller size to suit the Hercules.

AS in how do you scale down a Centaurus (2000hp ) powered fighter to give equal or close to it performance with a 1600hp Hercules (assuming in 1938-39 they can get the Hercules to 1600hp) Yes the engine is lighter so you need a bit less wing and bit lighter construction and bit less fuel but the competing design/s were pretty much pull one engine off and stick the other one on. They had well over 1000 Tornados on order when the Vulture crapped out. Not quite as simple as I just described but changing over to the Sabre didn't seem like that big a deal.
 

tomo pauk

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I think anyone can see why a Hercules wont fit a Spitfire or Hurricane. The modifications would result in effectively a totally different aircraft.

I hoped for a more specific reasoning :)

They were all designed for the 2000hp class engines, So you are either low powered in comparison or scaling back/size of the design to a smaller size to suit the Hercules.

The comment of "and wont fit into any 1938>1942 fighters" describes probably the Hurricane and Spitfire (plus what was suggested by the other companies), not the 2000 HP fighters.
 

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