Does anyone have a best guess on how fast the Grumman XF5F Skyrocket was at sea level

GregP said:

A P-40Q with the then-available engines would have been head and shoulders better than the stock P-40 for the theaters where the P-40 was deployed. I am having a very hard time understanding why that is so hard to see. It had a bubble canopy, turned better, climbed better, rolled better, and was and faster. All seem like pluses to me.
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Problem with your scenario might be that USAF was not keen to wait in 1944, let alone in 1943, for yet another short ranged fighter. Not for MTO, let alone for Asia/Pacific.

Obviously the XF5F should have been designed from the start with the P&W 1830, 4 inches less diameter and better power at high altitude. Could it have been ready for the war if it had been made a priority? The F6F, F4U and P47 were being developed alongside the R2800. The XF5F would have used, we hope, the P&W 1830 which was already being used in the Buffalo and the Wildcat, so all they had to do was design the plane and not wait on the engines to be developed also.

What rating did the P&W 1830 have in early 1942 at a couple of given altitudes…say sea level 12,000 and 20,000 feet?

pinsog said:

Obviously the XF5F should have been designed from the start with the P&W 1830, 4 inches less diameter and better power at high altitude. Could it have been ready for the war if it had been made a priority?

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It would require a substantial effort for the F5F to be ready for early 1942, but the R-1830 was as ready as possible already in late 1941. In 1941, though, P&W have had problems delivering the 2-stage engines in quantity needed, hence the use of 1-stage engines in the Wildcat, plus the Cyclones.

The F6F, F4U and P47 were being developed alongside the R2800. The XF5F would have used, we hope, the P&W 1830 which was already being used in the Buffalo and the Wildcat, so all they had to do was design the plane and not wait on the engines to be developed also.

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The Buffalo used only Cyclones (R-1820).

What rating did the P&W 1830 have in early 1942 at a couple of given altitudes…say sea level 12,000 and 20,000 feet?

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At 12000 ft, the 2-stage R-1830 will give around 1200 HP, at 20000 ft a bit less than 1000. The 1-stage, 2 speed will give a bit more than 1000 at 12000 ft, and around 800 at 20000 ft.

The P-40 was in service when the war ended and even after in the PTO and CBI at LEAST. If it was good enough to serve, it was good enough to improve. And the P-40Q with the existing engine would have been lighter, would have rolled better, and would have had a bubble canopy, all of which were good improvements on the basic P-40 that remained in service throughout the war.

No amount of "but ifs" will change the fact that we were flying them in combat throughout the war, or that improvment of the airframe was not possible. We did fly 'em and improvements are always welcome in the field.

The P-38K to me seems to fit in the the same category as the P-40Q, maybe even more so. It must have been one of those same budgeting / war decisions where they go what we have now is good enough...

Cheers,
Biff

GregP said:

The P-40 was in service when the war ended and even after in the PTO and CBI at LEAST. If it was good enough to serve, it was good enough to improve. And the P-40Q with the existing engine would have been lighter, would have rolled better, and would have had a bubble canopy, all of which were good improvements on the basic P-40 that remained in service throughout the war.

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Define 'the existing engine' 1st. If it is a 1-stage V-1710 - basically, you are trying to sell the bubble top clipped winged P-40N with 4 guns in 1944-45, same thing that USAF rejected (bar clipped wings) - yep, there was a bubble top XP-40N. If the engine is the 1st available 2-stage V-1710, so we can have it abroad in early 1944, then it is a 400 mph P-40Q. Sounds good, except maybe to the pilots that might favor something from a considerably faster trio of available fighters, as well as generals that are trying to find a role for a short ranged fighter above vast Asian expanses, and no drop tanks can mask the fact that less than 150 gals are carried internally.

No amount of "but ifs" will change the fact that we were flying them in combat throughout the war, or that improvment of the airframe was not possible. We did fly 'em and improvements are always welcome in the field.

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Nobody is trying to undermine P-40s war record.

BiffF15 said:

The P-38K to me seems to fit in the the same category as the P-40Q, maybe even more so. It must have been one of those same budgeting / war decisions where they go what we have now is good enough...

Cheers,
Biff

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Wasn't budgeting with the P38K, they didn't want to shut down production for the 2 or 3 weeks it would take to change the line up to P38K

Pinsong,
Concur! That's what I was insinuating by "war decisions". You said it better!
Cheers,
Biff

You could get 3 P-40Q's for the price on one P-38 ... that just doesn't fit logically with using more P-38s.

GregP said:

You could get 3 P-40Q's for the price on one P-38 ... that just doesn't fit logically with using more P-38s.

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Not sure about that "three for one" thing...

The flyaway cost of the P-38 in 1944, was just over $97,000 and the P-40's 1944 flyaway cost was nearly $45,000.

Yeah, probably 2 for 1. I'd stick with the P-40Q, had it been available. Also, if the P-40Q were being deployed to theaters flying P-40s, then the mechanics would not have had to be retrained completely. All in all, the P-40Q still looks to me like it should have been built ... but should have been built a year earlier.

Yes, I know it didn't happen, and the P-40Q is also in good company as being a good one that was not adopted. And I'm talking about possible deliveries in mid 1943, not in 1944, so the P-38's price would be higher. A P-38 cost $120,407 in 1942 and $105,567 in 1943 while the P-40 was $59,444 in 1942 (1/2 a P-38 ) and $49,449 (1/2 a P-38 ) in 1943.

That assumes, of course, that you could get Curtiss to expend the effort a year earlier. There was no technology change, just an overall cleanup.

Part of the problem with the F5F was that it was designed for some version of the P&W R-1535 twin row radial. I am not sure of the exact details, like what kind of supercharger (how many speeds or stages), but P&W canceled any and all development of the R-1535 engine although continuing production of existing types/models to fulfill existing contracts and provide spares.
This left Grumman and the Navy scrambling for a replacement engine for the partially completed design ( I don't know how much metal was actually cut at this point.) The Wright R-1820 is obviously much larger in diameter but it is also closer in weight to the R-1535 than the R-1830 was. Especially if advanced superchargers where used on the R-1830 (R-1820s used in the F5F were about 175lbs lighter each than an R-1830 with a 2 speed supercharger, 230-240lbs lighter than a two stage R-1830). Given the engine placement/location on the F5F major changes in engine weight might call for rather extensive redesign (or large amounts of ballast)
The F5F was also sort of a proof of concept design. More to explore possible advantages and disadvantages rather than be a real production aircraft as built.
Actual speeds obtained by the prototype were limited by landing gear doors that refused to close properly despite several attempts to fix them. Engine over-heating was also a chronic problem in the early stages of the aircraft's life. Better cooling is generally equal to higher drag for air cooled engines in 1940 and 1941 (things got better later).

A true service version would have many modifications making performance comparisons to this "semi-finished" prototype even more risky to make.

BiffF15 said:

The P-38K to me seems to fit in the the same category as the P-40Q, maybe even more so. It must have been one of those same budgeting / war decisions where they go what we have now is good enough...

Cheers,
Biff

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Biff - I never have bought that explanation. Bodie claimed it in his book but introducing the changes from P-38J/L to K would have been about the same as going from P-51B to P-51D and that production line did not 'stop' at all.

The primary changes from B to D were a.) new canopy b.) modified cockpit enclosure c.) new windscreen/top cowl d.) new aft side panels both sides e.) new root chord/wing leading edge design (and analysis) which changed the washout from 0 wing station to WS 61, f.) new main wheel door, g.) change ammo storage and feed system, h.) add one more gun each wing. Not to mention a significant incorporation of Temporary Change EO's to include reverse rudder boost tab, electrical and hydraulic changes, etc.

Yet, the production line didn't skip a beat.
It seems like two components - namely cowl and the GFE prop were the design and cost factors and also seems plausible to fund a special project to construct the stamping dies and modify support structure for the cowling - and divert P-38J/L into a separate open air line as the changes are made, then integrate the remainder of the J/L line with the new dash number mods.

The flight tests published on Mike Williams site show a slightly improved performance over the P-38L until you dig a little deeper and note that it is being tested under combat load out gross weight. 600 pounds is really important on relative climb and some value for top speed due to induced drag considerations. My personal view based on that limited sample is that AAF didn't see any real value in the change.

I have been wrong before.

Too bad the prop with wide blades, whether 3- or 4-bladed, was not installed on the 'regular' P-38J/L. With or without the ADI system, that eventually got installed in all US fighters that mattered from early 1944 on, should've boosted the RoC considerably,