R-1830 in a fighter plane: any ways to concieve a performer?

[msxyz]

Adding a turbocharger as second stage will increase performance at high altitudes almost for free (the engine is not robbed of any power to compress the air) but it adds weight and complexity. Let's be realistic. If all you have is 1200-1300HP you want your plane to be as light as possible. A two speed, single stage supercharger would be a better option, the only added weight being the additional gearbox and extra clutch needed.

Here's come another dilemma. Should you sacrifice armor protection and a certain tolerance to damage or design the lightest possible frame?

Early Mitsubishi A6Ms were incredibly light for a plane of that size (around 1600Kg empty) but also very vulnerable. Its main antagonist in the PTO, the F4F-3, was praised for its robustness but it weighted (empty) nearly 1 ton more. A sweet spot would be somewhere between these two extremes, around 1900-2000Kg (4400lbs).

My "What IF" fighter built around a P&W R-1830 would be something like this: it uses a Pratt&Whitney R-1830 with single stage, two speed supercharger; it has the fuselage of a Nakajima Ki-44 Tojo, mated to the wings of a Me-109G. Empty equipped weight would be around 2000Kg, take-off weight around 2600-2700Kg.
It would reach around 580Km/h at about 4500m (15000ft). A decent fighter by 41-42 standards but hopelessly underpowered later in the war.

 

[Shortround6]

Oh, one of my favorite could-have-beens, the Whirlwind with the R-1830s
The range would be easily increased by installing the additional fuel tanks in space previously used by radiators (twice as much fuel possible?), while at 20000 ft it would be something like 2 x 950 HP vs. 2 x 700 HP for historical Whirly. 3 cannons, or 5 HMGs? The weight would be increased, though, and so will be the drag.

The R-1830s are about 400lbs heavier each (heavier than a Merlin XX) than the Peregrine engines. Some of the radiator space might be used by the inter-coolers (only way your getting 900hp at 20,000ft is with the two stage engine.

Thanks for the data. I'll just comment about the bolded part: the airframe used did have shortcoming, to forestall an even greater speed increase - draggy wings. It would be interesting to see what the 2 stager would be making with thinner wings, or laminar flow ones? Or, sticking it onto a smaller lighter airframe, like that of the VG-33, or CW-21, or Yak-1/3?

The airframe was a Hawk 81A and might not have had self sealing tanks or armor. From the picture available it doesn't seem to have wing guns. Check out the Swedish fighter, that is about as small as you are going to get. The two stage R-1830 was about 400lbs heavier than a Hispano V-12. It was about 300lbs heavier than the CYclone and was maybe 200lbs heavier than the M-105 in the Yaks. And for all three you need to find space for the intercooler/s and ducting.

The single stage engine was about 100lbs lighter (unless you try for the 1350hp version) but didn't need the space for the intercooler/s.

 

[gjs238]

Could the Vultee P-66 Vanguard be a contender?

 

[tomo pauk]

IMO it could. It was faster then the F4F, on less HP/altitude. The wing are was modest, and the wings look really thin, hence allowing for the low drag. Say, remove the fuselage guns ammo, so the space can be vacated for the intercooler(s). Wings receive HMGs (4 total), 300-350 rpg.

The R-1830s are about 400lbs heavier each (heavier than a Merlin XX) than the Peregrine engines. Some of the radiator space might be used by the inter-coolers (only way your getting 900hp at 20,000ft is with the two stage engine.

The intercoolers being mounted akin to the F4F, so the inter-spar space can be used for the additional fuel? The weight would be really going up.

The airframe was a Hawk 81A and might not have had self sealing tanks or armor. From the picture available it doesn't seem to have wing guns. Check out the Swedish fighter, that is about as small as you are going to get.

Agreed about the Swedish fighter as being the smallest, but still able to 'support' the 2 stager.

The two stage R-1830 was about 400lbs heavier than a Hispano V-12. It was about 300lbs heavier than the CYclone and was maybe 200lbs heavier than the M-105 in the Yaks. And for all three you need to find space for the intercooler/s and ducting.

The Hispano V-12 has some 1000 HP, at best, at cca 10500 ft (the rarely used 12 Y 51) - even the the V-1710C-15 beats it easily above 12000 ft - maybe 600-650 HP at 20000 ft? An 1/3rd power deficit. The Cyclone-powered Wildcat was never a contender vs. the R-1830-powered one, at least until the ADI was introduced for the Cyclone. And then only at lower altitudes, for the FM.
At 6000m, (cca 19000 ft), the P&W has 1000 HP vs 830 of the M-105.
The intercoolers indeed need the space, so the guns ammo need to go to the wings. Easier to do with US fighters, than with European ones.

The single stage engine was about 100lbs lighter (unless you try for the 1350hp version) but didn't need the space for the intercooler/s.

Agreed.

 

[davebender]

What's wrong with that? Most WWII aerial combat took place below 19,000 feet and the R1830 engine was relatively light in weight.

Fw-187A0 achieved 329 mph @ 13,780 feet with 1,400 total hp (Jumo 210G engines). Performance should increase quite a bit with 2,000 total hp.

 

[Shortround6]

It depends on which front you were on. While a lot of combat DID take place under 19,000ft, an awful lot of it Started at over 19,000ft and ended below 19,000ft, in some cases well below 19,000ft.

BUT allowing your enemies to dive on you from above the majority of the time because your plane/s lack altitude ability is not a good idea no matter what theaverage height was.

The R-1830 was adequate (but no more than that) in 1940-41, it began slipping after that.

The R-1830 and R-1820 were distinctly low attitude engines, They may have worked on the Russian front but that is about it. They often had critical altitudes of 1000-2000 meters in low gear (if they had two gears) and 3500-4500meters or so in high gear. Many French and Italian single speed radials were rated at 3500-4200 meters and their take-off rating suffered because of it.

The R-1830 was good for 1050 hp at take off at 2700rpm at 42in MAP on 87 octane fuel. It was good for 900hp/2550rpm/12,000ft/34in max continuous on 87 octane. A few models were rated on 91 octane and a few on 91/96.

By the summer 1942 wasn't the Japanese Sakae radial available in a two speed version that offered around 1000hp at 20,000ft or so?

If you want to beat the A6M3 Zero you had better not be much heavier.

 

[davebender]

F5F powered by R1830 engines would hold it's own vs the A6M3.

 

[Aaron Brooks Wolters]

Again, you guys know a lot more about this stuff than I do so I won't claim to know anything about this but here is a T-6 Texan with a R-1830 with a supercharger on it. It gave the P-51s a run for the money at the Winston Salem, NC airshow this year. I don't know the gentleman that owns it but I do know it is based at Morganton, NC. It, in my opinion performed very well and was joy to watch.

 

[Shortround6]

delete

 

[tomo pauk]

Again, you guys know a lot more about this stuff than I do so I won't claim to know anything about this but here is a T-6 Texan with a R-1830 with a supercharger on it. It gave the P-51s a run for the money at the Winston Salem, NC airshow this year. I don't know the gentleman that owns it but I do know it is based at Morganton, NC. It, in my opinion performed very well and was joy to watch.

Many thanks for posting the pictures, Aaron. Did you bothered to check out whether the engine is/was fan cooled (fan being between cylinders and the prop)?

 

[Aaron Brooks Wolters]

No sir I did not, but I will make a point to check that out the next time I am around the aircraft. Seeing as how the cowling is closed down around the opening I would tend to think it was. I do know that the aircraft can make it from Morganton,NC to Airventures and back with out refueling and if I am not mistaken that is impressive. I am trying to get in touch with a friend of mine who knows the aircraft but have not heard back from him yet. If I do I will ask more questions and see what I can come up with. I think this would have made a great little fighter. And I think it would make decent answer to the question of the this thread. But that is just my opinion and we know what there like. Didn't mean to butt in on the discussion going on here.

 

[Shortround6]

Don't worry about butting in. Such an aircraft does show what is possible although with more details it may also show what was not possible.

fans usually cannot be added to an existing engine, that is one that has already been manufactured. They need a drive system capable of handling 50-100hp. They may also need an extended propeller shaft.

This plane appears to use some sort of ejector exhaust and the placement of the exhaust pipes may help suck air through the cowling. Ground running and climbing are usually the problem areas for air cooled engines. While not making a lot of power (heat) on the ground there is also very little airflow through the cowling. Climbing may require full power or close to it (max continuous?) with 1/2 or less of the airflow that a full speed run gives the engine.
This plane appears to my eye ( which is getting increasingly squinty and needing help as I get older) to be flown from the rear seat area of what the plane was as a two seater. CG reasons?
Perhaps there is still a rear seat but entire cockpit area is moved back?
Fuel tank in fuselage for extra fuel capacity?
In any case it is not carrying the 500-1000lbs of armament that a fighter would need.


I have found some figures for the P-40 airframe with the R-1830-SSC7-G engine (one built?), according to this source in Sept of 1942 it showed a speed of 389mph at 22,700ft and climbed to 15,000ft in 5.5 minutes and to 20,000ft in 7,7 minutes using military power for the entire climb and not just the first 5 minutes. Again, the "equipment" fit is unknown. P&W engine sheet says it was a Hawk 81A. Photo seems to show NO guns in the wings and there certainly weren't any in the fuselage. Status of armor and self-sealing tanks is unknown but the first few hundred Hawk 81s didn't have them.

Part of the problem with an R-1830 powered fighter is the 6 years of WW II and advancements made. The state of the "ART" in cowling design for radial engines made tremendous advances from 1938 to 1942 let alone to 1945 meaning a considerable difference in performance potential for a 1944-45 R-1830 powered aircraft compared to a 1939-1940 aircraft even if BOTH had the same 1200hp engine.
Spending design time on an R-1830 powered fighter in 1942-43 is a waste of resources unless for some reason ( like Sweden or Australia) it was the ONLY engine available.

 

[msxyz]

(...)
Part of the problem with an R-1830 powered fighter is the 6 years of WW II and advancements made. The state of the "ART" in cowling design for radial engines made tremendous advances from 1938 to 1942 let alone to 1945 meaning a considerable difference in performance potential for a 1944-45 R-1830 powered aircraft compared to a 1939-1940 aircraft even if BOTH had the same 1200hp engine.
Spending design time on an R-1830 powered fighter in 1942-43 is a waste of resources unless for some reason ( like Sweden or Australia) it was the ONLY engine available.

Indeed, cowling design in an airplane with a radial engine is possibly THE single most important aspect of its design.

Gains of 10-20 Km/h in top speed have been attained in many aircrafts just by redesigning the cowling shape or the gills.

Speaking of the devil, after WW2 ended for the Italians, they installed the R-1830 in several of their three engines transport/bombers, some of which remained in active duty (mainly as low cost, low tech transports) till the early '60s. Despite switching from a 800-900HP design of 1,4 meters (the Alfa Romeo version of the Pegasus) to a smaller one of 1100-1200 HP, top speed usually never went up more than 10-15 Km/h.. They probably didn't spend time to redesign the nose or the nacelles to the new engines.

 

[gjs238]

Spending design time on an R-1830 powered fighter in 1942-43 is a waste of resources unless for some reason ( like Sweden or Australia) it was the ONLY engine available.

Designing one in 42-43 may well be a waste of resources, but fielding one in the "early war" years prior to the arrival of the R-2800 powered fighters may have been wonderful. With the benefit of hindsight, was an early war R-1830 powered non-navalized fighter superior to the F4F, P-35, P-36 and at least the equivalent of the P-40 possible?

 

[Shortround6]

For the US Navy the F4F had been designed in 1937/38, Vought was working on the F4U in 1939.

Working with the P-36/P-40 family P&W did get the above mentioned aircraft to exceed P-40 performance but too late.

It depends on what you mean by "possible" as it has been done but not with knowledge that was available at the time.

The R-1830 offered no more power at 12,000-15,000 in it's 2 speed single stage versions than the -39 Allison used in the P-40E. Unless you can get the drag down to the level of the Allison there isn't much hope.
If you are willing to accept less structural strength than US fighters, and a lighter armament (the J-22 was stressed for 6Gs/10 ultimate unlike the US 8G/12G requirement and initially carried two big Brownings and two small ones) there isn't much hope.