P-40 Warhawk/Kittyhawk

[Shortround6]

Elvis
I'm not sure how you'd get that to work, there is an awful lot of aeroplane behind the main landing gear on the P-37 and even if you did somehow persuade it to keep its nose gear on the ground, where would the nose gear fold into?

Have a look at the P-37 in profile in Aviation Pictures/Curtiss P-40 Pictorial History, it really is a non-starter.

The pilot's lack of view while taxying was something that prop job drivers just learned to live with, sure, there were tails chewed off the guy in front and worse but by and large, they coped with it.

Another problem with long noses is deflection shooting. If both planes are turning and the pursuer has to "lead" the target there is only so much lead that can be applied before the target disappears below the nose.

Bell had also schemed a "model 3" a little earlier than the Aircobra (the model 4). imagine an Aircobra with the engine move forward but still leaving room for a 25mm cannon in front with the pilot sitting not only behind the engine but behind the trailing edge of the wing.

The state of the art in turbo installations in 1939-40-41 was actually pretty dismal. Lots of potential when things worked right but too often they didn't and minor problems, like way higher than estimated drag, caused the potential not to be realised for a while longer.

 

[Clay_Allison]

Why was the P-40 so much heavier than the P-36 anyway? The P-36 had a loaded weight of 5,600 lb, the P-40 wound up being 8,200. There had to be some way to just put upgraded R-1830 engines (or even R-2000) in the P-36 and add guns and resealing fuel tanks for less than 2,800 pounds. The P-36 was very well liked by the Finns and the French pilots who flew them. You'd think that they could have continued to be developed as an all-altitude dogfighter to supplement their heavy ground-pounding counterpart.

 

[Elvis]

Clay,

Maybe the P-40 was heavier due to balancing out the heavier V-12 engine?
...just a guess.
FWIW, I think most of the importP-36's were actually powered by R-1820's.
This is actually a lighter weight engine than either the R-1830 or R-2000.
Notice the nose of an FM-2 compared to an F4F sometime. Notice the FM's nose looks longer?
That's because there's about 187 lbs. difference between the P&W engine and the Wright, so the Wright engine was placed a little farther away from the firewall in order to help balance the plane out.
----------------------------------------------------------------------

Shortround,

I'd have to to research the bore and stroke of the R-2800 and R-2600, but I seem to remember the Wright engine having an unusually long stroke....possibly longer than that of the P&W.
This would probably account for the increased surface area of the R-2600, compared to the R-2800.

...and feel do that research for me, if you like.


Elvis

 

[Shortround6]

Clay,

Maybe the P-40 was heavier due to balancing out the heavier V-12 engine?
...just a guess.
FWIW, I think most of the importP-36's were actually powered by R-1820's.
This is actually a lighter weight engine than either the R-1830 or R-2000.
Notice the nose of an FM-2 compared to an F4F sometime. Notice the FM's nose looks longer?
That's because there's about 187 lbs. difference between the P&W engine and the Wright, so the Wright engine was placed a little farther away from the firewall in order to help balance the plane out.
----------------------------------------------------------------------

Shortround,

I'd have to to research the bore and stroke of the R-2800 and R-2600, but I seem to remember the Wright engine having an unusually long stroke....possibly longer than that of the P&W.
This would probably account for the increased surface area of the R-2600, compared to the R-2800.

...and feel do that research for me, if you like.


Elvis

THe Wright engine was a 9 Cyllinder single row radial while the P&W R-1830 was a 14cylinder 2 row radial. Depending on model the P&W engine could be a foot longer. Of course this is measured from the front of the propellor shaft to the end of the last accessory ( generator, fuel pump, vacumm pump,etc) bolted to the back of the engine.

I should hope the R-2600 used a longer stroke, it was a 14 cylinder engine after all But it was only .3125in (8mm) longer. It used the same sized cyliinders as the Wright R-3350 and strangly enough, depending on model and source, the two Wright engines had the same diameter.
It's problem as a fighter engine from a design standpoint ( I have no idea if there were service issues) was that for slightly less frontal area the P&W R-2800 offered more power. The 150-400hp advantage of the P&W (depending on year, model, etc) was probably enough to offset it's greater weight.

 

[Shortround6]

Why was the P-40 so much heavier than the P-36 anyway? The P-36 had a loaded weight of 5,600 lb, the P-40 wound up being 8,200. There had to be some way to just put upgraded R-1830 engines (or even R-2000) in the P-36 and add guns and resealing fuel tanks for less than 2,800 pounds. The P-36 was very well liked by the Finns and the French pilots who flew them. You'd think that they could have continued to be developed as an all-altitude dogfighter to supplement their heavy ground-pounding counterpart.

Again the"all-altitude" problem is a supercharger problem. Even early models of the Merlin 61 were compressing the ambiant air at 23,500 ft by a factor of 5.1 to 1. No singlestage supercharger can match that no matter how many gears are put on it. And that is for a power output of 1,390HP.

While there is some weight growth on the P-40 that is hard to account for you do have to make sure you are comparing apples to apples. For instance the P-36A at 5,600lbs had only one .50 cal gun and one .30 cal gun. It might also have had only 105 US gallons of fuel on board. There was an internal auxilary tank of 57 gallons and the P-36A is also listed as having a MAX gross weight of 6,010 pounds.

To try to equilize things the P-36A in one source says 4,567lb empty compared to the XP-40s 5,417lb empty and 6,260lbs with 100gallons of fuel. Production P-40s ( two .50 cal guns only) are given as 6,787lbs "normal " gross weight which I interperate as with 100-105 gallons of fuel ( XP-40 weighed 83lbs more than that with overload fuel). By the time we get to the P-40C the empty equiped weight (with some armour and self sealing tanks) is 5,812lbs and normal loaded is 7,549lbs. Now you have added 85-90lbs worth of .30 cal guns in the wings and about 100lbs of .30cal ammo. but not including gun mounts, heaters, ammo boxes etc.

How much of the 850 pound difference between a P-36A and the XP-40 is due to other things than the engine swap I don't know.

One spec for a P&W R-2000 that I have found gives a weight of 1595lbs a take off rating of 1450HP but a military rating (NOT WER) of 1100hp at 16,000ft in high gear. Not sure of the year of the engine.

 

[Clay_Allison]

Again the"all-altitude" problem is a supercharger problem. Even early models of the Merlin 61 were compressing the ambiant air at 23,500 ft by a factor of 5.1 to 1. No singlestage supercharger can match that no matter how many gears are put on it. And that is for a power output of 1,390HP.

While there is some weight growth on the P-40 that is hard to account for you do have to make sure you are comparing apples to apples. For instance the P-36A at 5,600lbs had only one .50 cal gun and one .30 cal gun. It might also have had only 105 US gallons of fuel on board. There was an internal auxilary tank of 57 gallons and the P-36A is also listed as having a MAX gross weight of 6,010 pounds.

To try to equilize things the P-36A in one source says 4,567lb empty compared to the XP-40s 5,417lb empty and 6,260lbs with 100gallons of fuel. Production P-40s ( two .50 cal guns only) are given as 6,787lbs "normal " gross weight which I interperate as with 100-105 gallons of fuel ( XP-40 weighed 83lbs more than that with overload fuel). By the time we get to the P-40C the empty equiped weight (with some armour and self sealing tanks) is 5,812lbs and normal loaded is 7,549lbs. Now you have added 85-90lbs worth of .30 cal guns in the wings and about 100lbs of .30cal ammo. but not including gun mounts, heaters, ammo boxes etc.

How much of the 850 pound difference between a P-36A and the XP-40 is due to other things than the engine swap I don't know.

One spec for a P&W R-2000 that I have found gives a weight of 1595lbs a take off rating of 1450HP but a military rating (NOT WER) of 1100hp at 16,000ft in high gear. Not sure of the year of the engine.

The F4F-3 had a two-stage supercharger with the same engine though with the R-1830-76 engine, P&W alone (apparently) among American engine makers saw the need to develop a two-stage supercharger and one was available for the R-1830 before pearl harbor! It seems pretty clear that the engine switch was a mistake and that the successor to the P-36 in whatever form should have had the R-1830.

 

[Shortround6]

The F4F-3 had a two-stage supercharger with the same engine though with the R-1830-76 engine, P&W alone (apparently) among American engine makers saw the need to develop a two-stage supercharger and one was available for the R-1830 before pearl harbor! It seems pretty clear that the engine switch was a mistake and that the successor to the P-36 in whatever form should have had the R-1830.

I have been able out find out very little about the R-1830-76 engine except that is was supposed to have "surging problems" and that later versions of the Wildcat (like the F4F-4) went back to a 2 speed single stage supercharger. A 2 stage R-1830 was also used in the XP-41 according to some sources.
This engine was rated at 1200hp at 2700rpm for take-off and had max continous ratings of 1050Hp at sea level, 1080hp at 4000ft, 1080hp at 11,000ft and 1050hp at 17,500ft all at 2550rpm. it aslo weighed 200lbs more than a single stage R-1830.
Army went with Turbo-ed R-1830s in the P-43s, I don't know if the Army was still favoring the Turbos in therory but the record of the P-43s shows that Turbos weren't quite ready for prime time at that time.
By the way, an experimental P-36 (actually the company owned demonstrator hawk 75R) with a turbo was reported to have made 330mph at 15,000ft and compeated in the same trails that saw the P-40 adopted.

 

[Clay_Allison]

I have been able out find out very little about the R-1830-76 engine except that is was supposed to have "surging problems" and that later versions of the Wildcat (like the F4F-4) went back to a 2 speed single stage supercharger. A 2 stage R-1830 was also used in the XP-41 according to some sources.
This engine was rated at 1200hp at 2700rpm for take-off and had max continous ratings of 1050Hp at sea level, 1080hp at 4000ft, 1080hp at 11,000ft and 1050hp at 17,500ft all at 2550rpm. it aslo weighed 200lbs more than a single stage R-1830.
Army went with Turbo-ed R-1830s in the P-43s, I don't know if the Army was still favoring the Turbos in therory but the record of the P-43s shows that Turbos weren't quite ready for prime time at that time.
By the way, an experimental P-36 (actually the company owned demonstrator hawk 75R) with a turbo was reported to have made 330mph at 15,000ft and compeated in the same trails that saw the P-40 adopted.

The army's obsession with Turbos (along with their general dismissal of high altitude performance) was the single most unfortunate idea that existed in prewar aerial doctrine with the possible exception of the self-defending bomber. The two problems were, of course, related since the lack of a recognized need for escort fighters led to an obsession with low-altitude performance at the cost of air superiority.

Still, the -76 existed and the two-stage supercharger was worth 200 pounds. A little development and we could have had an all altitude fighter with 4 guns, self-sealing tanks, and a little pilot armor at 6250 pounds loaded.

 

[Elvis]

THe Wright engine was a 9 Cyllinder single row radial while the P&W R-1830 was a 14cylinder 2 row radial. Depending on model the P&W engine could be a foot longer. Of course this is measured from the front of the propellor shaft to the end of the last accessory ( generator, fuel pump, vacumm pump,etc) bolted to the back of the engine.

I should hope the R-2600 used a longer stroke, it was a 14 cylinder engine after all But it was only .3125in (8mm) longer. It used the same sized cyliinders as the Wright R-3350 and strangly enough, depending on model and source, the two Wright engines had the same diameter.
It's problem as a fighter engine from a design standpoint ( I have no idea if there were service issues) was that for slightly less frontal area the P&W R-2800 offered more power. The 150-400hp advantage of the P&W (depending on year, model, etc) was probably enough to offset it's greater weight.

It appears the R-2600 is a de-stroked, 14-cylinder version of the R-1820 (6.125 x 6.3125 vs. 6.125 x 6.875) so I must've been thinking of a different engine, when I made my "unusually long stroke" comment in an earlier post.
Still, the R-2800 had a slightly shorter stroke (6") than R-2600, which should translate to a shoter cylinder, thus the lessened frontal area, in comparison to the Wright engine.
The R-2800's main attributes were lots of power (pretty much more than anything else we had) along with lots of reliability.
There's many stories of R-2800 powered aircraft still running well enough to bring the pilot home, despite severe battle damage.
That kind of reputation will get you work, and lots of it!
------------------------------------------------------------------------------------

Shortround,

I don't know what you're getting at with the comments about the length of afforementioned engines. We were discussing the different in frontal area of those engines, but I'm sure it'll be pertinent information somewhere down the line, so thanks for conveying that anyway.



Elvis

 

[Elvis]

Clay,

Maybe the P-40 was heavier due to balancing out the heavier V-12 engine?
...just a guess.
FWIW, I think most of the importP-36's were actually powered by R-1820's.
This is actually a lighter weight engine than either the R-1830 or R-2000.
Notice the nose of an FM-2 compared to an F4F sometime. Notice the FM's nose looks longer?
That's because there's about 187 lbs. difference between the P&W engine and the Wright, so the Wright engine was placed a little farther away from the firewall in order to help balance the plane out.


Elvis

The information I relayed in this post, that I've highlighted in the quote, is incorrect.
Sorry about that guys, I was thinking of a different comparison when I wrote that.
According to the Aviation-History page on both the R-1830 and the R-1820, the difference in the listed weights of those engines (geared version) is only 102 lbs.




Elvis

 

[Elvis]

I have been able out find out very little about the R-1830-76 engine except that is was supposed to have "surging problems" and that later versions of the Wildcat (like the F4F-4) went back to a 2 speed single stage supercharger. A 2 stage R-1830 was also used in the XP-41 according to some sources.
This engine was rated at 1200hp at 2700rpm for take-off and had max continous ratings of 1050Hp at sea level, 1080hp at 4000ft, 1080hp at 11,000ft and 1050hp at 17,500ft all at 2550rpm. it aslo weighed 200lbs more than a single stage R-1830.
Army went with Turbo-ed R-1830s in the P-43s, I don't know if the Army was still favoring the Turbos in therory but the record of the P-43s shows that Turbos weren't quite ready for prime time at that time.
By the way, an experimental P-36 (actually the company owned demonstrator hawk 75R) with a turbo was reported to have made 330mph at 15,000ft and compeated in the same trails that saw the P-40 adopted.

From what info I've picked up on the web, concerning the R-1830 (mainly when used in the Wildcat), the "-76" version of that engine used an older cylinder head design and suffered from (lack of) cooling problems.
The replacement "-86" and "-90" engines addressed this issue and made the engine more reliable with a longer TBO period.
This was augmented by mods to the prop and cowling, to further improve cooling of the engine.


Elvis

 

[Clay_Allison]

I always heard that the F4F operated fine at altitude if you could get it there. The problem was the climb rate from having an overly heavy plane.

 

[Elvis]

Clay,

That metality is derived mainly from the "-4" / FM-1 version of the Wildcat.
Much like the later versions of the Brewster Buffalo before it, the plane was modified with more armour, fuel capacity and guns, gaining quite a bit of weight, while the powerplant was never addressed.
This degraded certain performance aspects that made it even less of an adversary for the Zero and other axis aircraft.
As for climb rate in particular, the "-3" actually wasn't too bad, for a pre-war aircraft. 2350 ft./min. is the figure I often see for that one.
However, the above mods slowed the ascent rate to 1950 for the "-4" / FM-1.
The problem seemed to be corrected fairly quickly, though and the next version, the FM-2, was re-engined and re-designed to make it (probably) the best version that existed.
The FM-2 had a climb rate of 3650 ft./min. and had a top speed in the 320-330 mph range.
Those two performance aspects, alone, made it a much better adversary to the Zero than the "-4" could've ever hoped to have been.
FWIW, there were more FM-2's built than any other version of the Wildcat. In fact, I believe FM-2 production alone exceeds the total number of Wildcats that were built before it.
According to the History of War website, "In all 7,885 Wildcats were produced by Grumman and General Motors. Over 60% were General Motors produced FM-2s. 1,100 were supplied to the Royal Navy.'
Again, according to their production figures, there were 4,777 FM-2's built during the war. This leaves only 3,108 Wildcats that weren't FM-2's.



Elvis

 

[Shortround6]

You are quite right about the performance of the FM-2 but since the first one wasn't delievered from the factory until sept of 1943 or 9 months after the Hellcat stared to be delivered or just 2 months before the P-51B arrives in England the FM-2 and it's engine don't realy solve the early 1942 problem.

 

[Elvis]

....yeah, and?


Elvis