R-2600 powered fighter?

[Markus]

And I suppose BMW told the German High command that they could NOT deliver reliable 801 engines in 1941-42

Considering the oh, so reliable R-3350s going into B-29s in 1944 I am less than impressed with Wrights ability to deliver engines I would like to fly behind

The R-1820 and R-2600 worked like the proverbial swiss clockwork, didn´t they? The R-3350´s problems look like the result of wartime rushing-into-service to me.

 

[Shortround6]

The R-1820 and R-2600 worked like the proverbial swiss clockwork, didn´t they? The R-3350´s problems look like the result of wartime rushing-into-service to me.

Actually they didn't, at least the R-1820 didn't. While it seemed to work perfectly well in transports and bombers many people who used in fighters found in had oiling problems in inverted flight in the early war years.

Another consideration is that US engines lagged behind British and German engines in automatic boost and mixture controls. Since both the R-1820 and R-1830 had by far their greatest sales to the airline industry before the war the engines were not built for military requirements. With American airliners having two man cockpits (and the Boeing 214 clipper having a flight engineer) they could afford to use manual leaning of the engines for best cruise and could afford to manually shift or select the supercharger gear to use. Afford in the sense of man hours (man minutes?) available. Time that is not available in a single man fighter cockpit in a dog fight.
These controls were designed, built and fitted to many later later fighters so that one control, the throttle, worked several functions.
Temperature control is another problem. It is going to take a pretty ham fisted airline pilot to thermal shock his engines. As in cut power from a high cruise setting (let alone combat power) and do a too rapid decent that over cools the engine. Most cooling flaps were manually controlled, they may have been power operated but the pilot, co-pilot or flight engineer monitored the gauges and adjusted the flaps and or throttle accordingly. Pilots could screw up P&W R-2800s by making too rapid a decent with not enough throttle to keep the engine temperature in the proper operating range.
Some engines were perfectly happy to cruise along for hundreds of hours with occasional bursts of high power as long as throttle adjustments were made gradually. they weren't so happy (and showed it with much shorter life) with frequent and sudden throttle changes.
I don't know if the R-2600 had this problem but I am pointing out that just because an Engine gives satisfactory service in airline or even bomber use doesn't mean it is a good choice for a fighter.

As far as the R-3350 problems being a wartime rush to service......design work started in Jan 1936. It was basically 2 rows of 9 R-2600 cylinders instead of 2 rows of 7. It is in the details that things went wrong.
Increased work on the R-2600 might have delayed the R-3350 even more.

 

[gjs238]

Increased work on the R-2600 might have delayed the R-3350 even more.

Increased work on the R-2600 might have obviated the need for the R-3350, at least to some extent.

 

[Markus]

Actually they didn't, at least the R-1820 didn't. While it seemed to work perfectly well in transports and bombers many people who used in fighters found in had oiling problems in inverted flight in the early war years.

The last batch of Curtiss Hawks for France had Cyclones, so did the 20+ Hawks the Dutch got. Acc. to "Bloody Shambles No.1" the latter were hangar queens due to engine trouble but the same author does not say a bad word about the Hawks that served over Burma from mid-42 to mid-44. Maybe the Dutch Hawks had reconditioned airliner engines like the British Buffalos?

As far as the R-3350 problems being a wartime rush to service......design work started in Jan 1936. It was basically 2 rows of 9 R-2600 cylinders instead of 2 rows of 7. It is in the details that things went wrong.
Increased work on the R-2600 might have delayed the R-3350 even more.

Sounds like a likely explanantion. Pre-war fighter development was slow too as the demand was rather low.

 

[Shortround6]

I find it hard to understand the difficulty in fielding a R-2600 powered fighter pre or early war, prior to fielding of R-2800 powered fighters.

You can field one, just don't think you are going to have a FW killer on your hands or even a plane that is going to take on 109Fs unless you can get them to come DOWN to your most favorable altitudes.

It might not be all that much fun either in the Pacific over 20,000ft once the A6M3 shows up.

Unless of course you can get Wright to build a 2 stage supercharger which they never did.

Once the P&W R-2800s show up with the two stage supercharger ( or P&W promises the the 2 stage, and remember, there were 2? planes equipped with P&W 2 stage superchargers at the 1939 army fighter trials) The P&W engine not only has a 300hp advantage at sea level, it has a 350hp advantage at 14,000ft and a 500hp advantage at 21,000ft.

This is for a P&W R-2800-8 using Military power, NOT war emergency power, and a 586-C14-BA R-2600 (-13) of 1700hp take off rating

 

[gjs238]

The point (or the question) (or the possibility) is to have a R-2600 powered fighter in service around the time of 12/7/41 (preferably prior to, or at least shortly after.)

The R-2800, superior as it was, just wasn't ready.

2-stage supercharging/high altitude performance isn't the point.

Would/could R-2600 powered fighters have outperformed the R-1830 fighters of the period?
How would they have compared to V-1710 powered fighters?
Would the R-2600 have been superior for ground attack/support, dive bombing, etc. roles?

 

[Shortround6]

The point (or the question) (or the possibility) is to have a R-2600 powered fighter in service around the time of 12/7/41 (preferably prior to, or at least shortly after.)

The R-2800, superior as it was, just wasn't ready.

2-stage supercharging/high altitude performance isn't the point.

Would/could R-2600 powered fighters have outperformed the R-1830 fighters of the period?
How would they have compared to V-1710 powered fighters?
Would the R-2600 have been superior for ground attack/support, dive bombing, etc. roles?

The R-2600 might well have been superior for ground attack/support, dive bombing, etc. Maybe that is why they used in the SB2C, The Vultee Vengence, The Brewster Buccaneer

It was going to have a much harder time showing much superiority in mid to high altitude fighter vs fighter roles.

As has been shown, while it did have more power at 10,000-15,000 ft than the Allison it was not the margin that a comparison of take-off power suggests. The R-2600 is heavier (even including the radiators) and has much more drag unless your alternative history has the US developing the close cowled fan cooled engines well before the FW 190. IF you go that route then the R-2600 only has somewhat more drag.

As far as replacing the R-1830 goes you are replacing an engine that is 6-7 in smaller in diameter. While that may not sound like much (48in to 54-55in) the frontal area is related to the square of the diameter so the change in frontal area goes from 12.6 sq ft for the R-1830 to 16 sq ft for the R-2600. about a 27% increase. Add in the 700-900lb increase in weight over the two stage supercharged R-1830 and once again the power margin at 15000-20,000 ft doesn't look so great. Both the F4F and the P-43 were rather tubby so the difference in frontal area may not be quite as important but the P-43 was viewed ans as an interim fighter built to help Republic expand and train it's work force as much as to get a usable fighter. The first A-20 had a turbo charger but no later ones did including the P-70s which one would think would have benefited. Few, if any other turbo charged installations seem to exist.

With the timing you suggest you are not replacing P-40Cs but rather P-40Es which started coming out of the factory in mid/late 1941 and the P-40F which starts being delivered in Jan, 1942.

 

[gjs238]

Did the Wildcat F4F-4 have 2-stage supercharging?

 

[Shortround6]

Did the Wildcat F4F-4 have 2-stage supercharging?

Yes it did, as did most of the F4F-3 and the FM-1s


a few facts on the early history of the R-2600. As has been noted it was used in the Boeing 314 clipper. It has been said that it was the first engine to designed for 100 octane gas (one source says 115 but that makes no sense because performance numbers over 100 were unknown at the time). later versions were rated for 91 octane however.
The version used in the Boeing 314 was rated at 1500hp at 2300rpm for take-off and 1200hp at 2100rpm at 5400ft for MAX continuous. NOT Military of max for 5 minutes or anything else.
Plane first flew in June of 1938 but first plane was not delivered to the customer until Feb 1939. 6 planes were built in the initial batch. Cruising speed was given as (at 75% power) 175mph at 2,000ft, yes 2,000ft.
A second batch of 6 planes were ordered later under a different or amended type certificate (approval date 5-2-41) that used newer higher powered engines. 1600hp at 2400rpm for take off and 1350hp at 2300rpm at 5000ft max continuous.
The only other civil aircraft to use the R-2600 at this time was the Curtiss CW-20 transport prototypes (later C-46) which first flew on 3-26-1940. The first 26 (?) or so C-46s did use Wright engines after that P&W R-2800s were fitted.

For a good explanation of the development of engines and aircraft of this time see:
http://www.enginehistory.org/References/WWII Eng Production.pdf

 

[gjs238]

Very interesting article!
It seems the R-2600 "issues" were not so much about the engine itself but more of Curtiss-Wright manufacturing constraints.

 

[Shortround6]

In my opinion it is a bit of both, for fighter use anyway.

The R-2600 was in short supply in the early years and it needed modifications (a better supercharger) to make an effective fighter engine, while it was a perfectly good bomber engine as it stood.

A bomber having so much drag to begin with a few extra feet of frontal area doesn't make as much difference as it does on a fighter percentage wise.

If you look at the production numbers be aware that the R-2600 "A" series are the aluminum crankcase 1600hp T.O. rated engines. THE "B" or "BA" engines are the Steel crankcase 1700HP T.O rated engines and the "BB" engines are the 1900HP T.O. versions with the sheet metal cooling fins.

 

[Ivan1GFP]

Sometimes a new engine in an existing plane isn't so straightforward. Consider that a B-25 was tested with R-2800 engines. It was VERY fast and performed well until it lost both its wings on a low level pass. Apparently the difference in weight and power was enough to break a design that wasn't known to be flimsy.

The F4F was a very draggy design and didn't have much stretch left. Even if the clearance problems were easy to fix, with 400 pounds up front, you now have a very different Center of Gravity which might require ballast in the rear which kills yet more performance. Consider that even with the slight increase in power for the FM-2, the fin and rudder needed enlarged.

BTW, what did the P-36 evolve into besides the P-40?

- Ivan.

 

[Markus]

In my opinion it is a bit of both, for fighter use anyway.

The R-2600 was in short supply in the early years ...

Which happens to be the ultimate reason against an R-2600 powered fighter. If there are not even enough engines for the bombers you have to have, you can not spare engines for a fighter you need much less.

 

[Shortround6]

Which happens to be the ultimate reason against an R-2600 powered fighter. If there are not even enough engines for the bombers you have to have, you can not spare engines for a fighter you need much less.

The "Ultimate" reason may be that without more development work for either a better single stage supercharger or a two stage supercharger the R-2600 (assuming the engine could handle it) wasn't going to yield a fighter that would do anything much different than what was in hand.
It wouldn't be enough better than the P-40 at over 15,000ft.
It probably wouldn't be much better than a P-39 down low.

Between fooling around with the Tornado engine and the problems with the R-3350 there may not have been enough engineering capacity to do more than was historically done. Once the R-2800 started to arrive in quantity the writing was on the wall. The R-2600s days were numbered.

 

[Markus]

The "Ultimate" reason may be that without more development work for either a better single stage supercharger or a two stage supercharger the R-2600 (assuming the engine could handle it) wasn't going to yield a fighter that would do anything much different than what was in hand.

On the one hand more development can be done. On the other hand if you consider your current fighters "good enough" -they in fact were- and if you barely have enough R-2600 for the B-25, A-20, TBF...any proposal for an R-2600 powered fighter that is promised to be better than the "good enough"-fighters is DOA.

 

[Shortround6]

Practically anything you could stick an R-2600 into you could also stick an R-2800 into.

While heavier it was a tad smaller in diameter, It' s smaller cylinders promised better cooling and higher rpm. And P&W was further ahead with the supercharger.
So your good enough planes are good enough right now and why devote resources to a second best plane for future production when you have what look like winners already being worked on.

 

[Markus]

Practically anything you could stick an R-2600 into you could also stick an R-2800 into.

While heavier it was a tad smaller in diameter, It' s smaller cylinders promised better cooling and higher rpm. And P&W was further ahead with the supercharger.
So your good enough planes are good enough right now and why devote resources to a second best plane for future production when you have what look like winners already being worked on.

"Good enough right now" as in late-41 was what I intended as later in the war even better planes entered service. But those came too late to be of any help in PTO during the key year 1942. Which brings me to problem #2 of a the proposed R-2600 powered fighter. The modifications to the engine need ... time and the perfectly good R-2800 was just a year behind.

 

[tomo pauk]

Some numbers, with F4F-4 as base airframe.
The 'loaded' weight was some 7950 lbs. The difference between R-1830 (2-stage) and R-2600 of 1941 were 500 lbs, and 250 hp @ 13 kft (1350 vs 1100). The power loading was 0,138 hp/lb, while 'my' pet plane would have had 0,156 hp/lb (with extra 200 lbs added to cover the airframe strengthening) - beating early F4Us (12000 lbs, cca 1850 hp @ 13 kft) and F6F-3, two crucial years earlier atop of that.

 

[gjs238]

Well prior to 12/7/41, if US was looking to evolve fighters past existing R-1830 platforms, perhaps the R-2600 would have been the next step --- the R-2800 would have been the step after that.

If so, then development of R-2600 engines platforms, and production capacity, could have been increased/given higher priority.

But in reality, perhaps, with the R-2800 on the horizon, the attitude was, "Eh, why bother with an intermediate step [the R-2600], let's wait for the R-2800."
There was also a predilection toward inline engines.
But a little problem [war] spoiled those plans...
...So while we waited for R-2800 platforms to develop, we were stuck with R-1830 [and V-1710] platforms during the critical early years.

 

[Shortround6]

Some numbers, with F4F-4 as base airframe.
The 'loaded' weight was some 7950 lbs. The difference between R-1830 (2-stage) and R-2600 of 1941 were 500 lbs, and 250 hp @ 13 kft (1350 vs 1100). The power loading was 0,138 hp/lb, while 'my' pet plane would have had 0,156 hp/lb (with extra 200 lbs added to cover the airframe strengthening) - beating early F4Us (12000 lbs, cca 1850 hp @ 13 kft) and F6F-3, two crucial years earlier atop of that.

Some of your numbers seem a little off, You not only need need a bit of airframe strengthening, you need a bit of "tweaking".

Tweak #1, FM-2 needed more fin and rudder for 1350HP. How much is needed for 1600hp?
Or extended fuselage?

Tweak #2, The 3 bladed props on the F4F-4 and the F6F had about 1 square foot of disc area for every 15 hp.
Working this back for the 1600hp engine means a 11' 8" prop instead of the 9' 9" or10ft prop on Wildcats. Heavier prop and also leads us to.....

Tweak #3, F4F had 8.75 in of ground clearance when plane was level. So you need to make the landing gear about 10 in longer to keep the prop clearance. Now maybe this can be done in the original space but it is sure going to be tricky

Tweak #3A, Ground handling of the Wildcat was called tricky "due mainly to a narrow tread landing gear equipped with rather soft mushy shock struts which on occasion could collapse. Under certain conditions, such as a crosswind, a sudden power application, a sharp taxi turn, a strut collapse, or some combination the aircraft could take quite a roll, and pilots had to be careful not to dig in a wing tip"
quote is from "America's Hundred Thousand" Page 483. Tread of the landing gear was given as 6' 5" (rounding up). while your proposed plane does have it's wing tips 10" higher in the air it also has an extra 500-600lbs up in the nose (which might do wonders for nose overs upon applying brakes) and a LOT MORE torque to go with the higher center of gravity.

Tweak #3B, F4F's used a hand cranked retract mechanism. At what point do you think your larger, heavier, more complicated landing gear would need to go to a power retract system?

Tweak #4, a minor one, Extra fuel to take care of the thirstier engine. The R-2600 is going to suck down roughly 1/3 more fuel unless throttled way back. I am not going to say you need 1/3 more fuel to equal the combat radius (or endurance) of the F4F but 20-25% more might not be out of line. another 35 US gals is 210 lbs plus around another 60lbs for the tankage?

Tweak #5 (optional) With 1600hp on tap and the most powerful fighter available next to the P-38 maybe you can keep the high command from trying to solve the Wildcat's armament dilemma, 4 guns with a fair amount of ammunition or 6 guns with a limited amount of ammunition, 240rpg. Upping the ammo by 60rpg adds about 100lbs while still being well short of the F6Fs 400rpg.


Please note that when Grumman came up with the F6F they not only solved a bunch of the F4F's ground handling problems but a few air handling problems as well.