USAAC/AAF being much improved in 1938-42?

[tomo pauk]

P36 and P40 4 50's with 200 rpg, back armor and self sealing tanks.

That would be roughly standard of P-40D - about 8100 lbs with all 3 tanks full? Or, a P-40C with two outboard LMGs replaced with one HMG - ~8050 lbs with max fuel (819 lbs = 136.5 US gals). Remove V-1710 + cooling system = 1550 lbs less; install 2-speed supercharged R-1830 = 1480 lbs more. Weight reduction = 70 lbs, or less than 1%, with drag increase of 10%? Drag increase = worse mileage (and obviously less speed).

Alternate to P38, that's easy for me, no secret I'm a fan of the Grumman F5F. Build it instead of the Wildcat.
Long nose and long engine nacelles 4 50's 400 rpg with 279 gallons of fuel comes in at 10,900. Add turbo chargers 500 pounds
Add 150 pounds of armor
Add 150 pounds for self sealing tanks. Lowering fuel down to 250 gallons
Weight is now 11,700
Add a 75 gallon tank to each outer wing, weight comes up to 12,000, fuel brings weight up to 12,900.
That's 400 gallons of fuel and it weighs 1,500 pounds less than an early P38 with 300 gallons.
Speed should be same as early P38 but with better climb, better dive and more maneuverable(weighs 1,500 pounds less, has 100 more hp, was dived vertically to 505 mph)
and it's carrier capable.

IMO, a lot of P-38 weight was a result of the choice for a twin-boom aircraft. Booms+pod+engine section (without engine, turbo, plumbng etc.) of P-38J weighted twice of what fuselage+nacelles of DH Hornet weighted. So Id' certainly go with a 'classic twin' layout here.

 

[pinsog]

But it only arrives at the same time as the Corsair and requires twin. Engine training, so no.

The F5F should arrive when the Wildcat did IF it was built instead of the Wildcat. If you look at the early pics it was literally a Wildcat with 2 engines, but then they rebuilt the fuselage without the raised back. If you look at the timeline, it appears to me that they didn't have enough people to work on it, they were probably mostly busy with getting the Wildcat fixed to where it could beat the Buffalo

There was nothing special about the F5F, the engines were available, etc, I think Grumman was simply short handed and they went for a 'sure thing' with the Wildcat instead of taking a chance on a really heavy (compared to current carrier planes) fighter that the Navy might reject because it's too big of a jump in weight etc.

 

[Kevin J]

The F5F should arrive when the Wildcat did IF it was built instead of the Wildcat. If you look at the early pics it was literally a Wildcat with 2 engines, but then they rebuilt the fuselage without the raised back. If you look at the timeline, it appears to me that they didn't have enough people to work on it, they were probably mostly busy with getting the Wildcat fixed to where it could beat the Buffalo

There was nothing special about the F5F, the engines were available, etc, I think Grumman was simply short handed and they went for a 'sure thing' with the Wildcat instead of taking a chance on a really heavy (compared to current carrier planes) fighter that the Navy might reject because it's too big of a jump in weight etc.

I looked it up on Wikipedia, mods for further testing weren't completed until January 1942, so even if you get it into immediate production its not going to be in limited service until July 1942. So the big question is, the Hellcat or the Skyrocket, which is going to be easiest to train pilots to fly? I'd say the Hellcat.

 

[pinsog]

I looked it up on Wikipedia, mods for further testing weren't completed until January 1942, so even if you get it into immediate production its not going to be in limited service until July 1942. So the big question is, the Hellcat or the Skyrocket, which is going to be easiest to train pilots to fly? I'd say the Hellcat.

I know what happened historically. I'm saying if they built the F5F instead of the Wildcat. If you look at the timeline there were long periods where they apparently did nothing

 

[Kevin J]

I know what happened historically. I'm saying if they built the F5F instead of the Wildcat. If you look at the timeline there were long periods where they apparently did nothing

Okay, it's January 1942, the F5F is finally sorted. Production of F4F is in full swing. Production of pilots is in full swing. You don't want novices flying twins. I'm not disputing the F5F is good.

 

[pinsog]

Okay, it's January 1942, the F5F is finally sorted. Production of F4F is in full swing. Production of pilots is in full swing. You don't want novices flying twins. I'm not disputing the F5F is good.

I'm saying the Wildcat is never built at all. A full scale mock-up was completed in October of 1938 and sent to NACA for wind tunnel tests and the first flight was on April 1 1940. I think Grumman and the Navy just dragged their feet on the F5F, with the Navy changing specs etc. this thing should have been in full production and squadron service long before December 1941. Also, I understand and agree it takes longer to train a pilot to fly a twin. But I also believe that if all of the "First Team" high hour pre-war fighter pilots had started the war in turbo charged F5F's then they wouldn't have lost nearly as many of them.

I would also have added dive brakes to the F5F and used it as a dive bomber. Think of a squadron of turbocharged F5F at 25,000 feet with a 1000 pound bomb moving along at 350 mph at Midway, Zeros unable to catch them.

 

[Kevin J]

I'm saying the Wildcat is never built at all. A full scale mock-up was completed in October of 1938 and sent to NACA for wind tunnel tests and the first flight was on April 1 1940. I think Grumman and the Navy just dragged their feet on the F5F, with the Navy changing specs etc. this thing should have been in full production and squadron service long before December 1941. Also, I understand and agree it takes longer to train a pilot to fly a twin. But I also believe that if all of the "First Team" high hour pre-war fighter pilots had started the war in turbo charged F5F's then they wouldn't have lost nearly as many of them.

I would also have added dive brakes to the F5F and used it as a dive bomber. Think of a squadron of turbocharged F5F at 25,000 feet with a 1000 pound bomb moving along at 350 mph at Midway, Zeros unable to catch them.

You keep forgetting that development is an iterative process, you make things up as you go along, you learn from your mistakes. My hunch is that by the time you've sorted the F5F out you've come up with a simpler cheaper solution, the Hellcats. The Italians, Germans and Brits came up with light twins like the F5F and they were all fairly limited in production numbers.

 

[pinsog]

You keep forgetting that development is an iterative process, you make things up as you go along, you learn from your mistakes. My hunch is that by the time you've sorted the F5F out you've come up with a simpler cheaper solution, the Hellcats. The Italians, Germans and Brits came up with light twins like the F5F and they were all fairly limited in production numbers.

From reading the history on it, I don't think there was that much to sort. I think most of it was the typical 1930's confusion on what was needed such as bombs in the wings to bomb bombers in the air, what guns, what engines, it's too heavy so we will buy heavier planes instead. Typical government stuff. They had the full sized model done in October 1938, just build the stupid thing. The F5F was at least large enough to handle reasonable engines such as the 1820 and 1830 and US turbochargers could make those a game changer if properly installed.

 

[Shortround6]

360+ mph max, 330 mph cruise at max weak mixture setting? Not unlike what the bombed-up B.IV D.K.290/G did here on +8.9 psi and +4 psi, respective for max speed and cruise.

Thank you, test of an early A-20
http://www.wwiiaircraftperformance.org/A-20/A-20B_41-2671_PHQ-M-19-1309-A.pdf
349mph at 12,050ft?
And it could do 333mph at 5,000ft.
Test is from Oct 1941.

The Mosquito is better, but it is later and the need (a really big change in performance) isn't really there. To get planes into service in 1942 you had to be designing them in 1940 or before.

An A-20 with turboed V-1710s would've been excellent at least for the tasks in Asia/Pacific - faster than the historical A-20, and with better mileage.
We can recall that DB7 was making 300+ mph at 2x900 HP at 12000 ft, bomb load 2000 lbs, 2x1050 HP for take off. A V-1710 of the era, like the C15 version, will not offer just better streamlinig and better exhaust thrust, but also much better power above 10000 ft.

Unfortunately, although unknown at the time, trying to bomb form high altitudes didn't work very well.

From Joe Baugher's website.
" This was the first aircraft on the A-20 order (39-735). It was fitted with the turbosupercharged R-2600-7 engine which offered a power of 1700 hp at 20,000 feet. Unfortunately, the turbosupercharger installation was large and bulky, and the engines developed serious cooling problems. In the meantime, Air Corps requirements were changing, and there was no longer a perceived need for a high-altitude light bomber. Consequently, a decision was made to convert all the other A-20s on the order to A-20A configuration with 1600 hp Wright R-2600-11 engines without turbosuperchargers. "

The early Pe-2 was good for 2200 lbs of bombs, 320-330 mph on 1050 HP at 13100 ft, 1100 HP for take off.

Not quite, the Pe-2 carried six 220lb inside, four in the fuselage bay and one in each engine nacelle. The 2200lb load required four 550lbs bombs outside. Seed with that load is unreported in western sources?

Bf-110C, Ju-88A1 and Do-215 also offered useful bombload on 1100-1175 HP for take off (even though bomb-bays there were between non-existent and restricted).

True but non-really exceeded the A-20 for internal stowage. And none were faster (in 1941-42) while carrying an internal bomb load. Bf-110 was faster without bombs but with bombs?

The A-20 was not the best possible bomber in 1942 (The XA-26 first flew in July of 1942 and they had started work in the Autumn of 1940) but it was pretty good (good enough?) and the need for a higher performing/speed airplane with V-12 engines has to be balanced against quite possible poorer field performance (Take-off) and engine availability.

 

[tomo pauk]

For a heavy fighter, early on.
As it is said many times, Johnson at Lockheed was looking for a 1500 HP engine to power his proposal for a fighter with heavy firepower; failing that, he will use two engines, but of 1000 HP (= that was future XP-38). Lets have him choose the R-2600 this time. Engine obviously in the front, turbo behind the pilot, the required heavy firepower will be two 37mm cannos in pods under the wings. Wing size of 300 sq ft, has Fowler flaps. The R-2600 is a decent, if unspectacular engine, but fighter can do 400 mph at base power at altitude (1500 HP at 20000 ft) in unarmed prototype form, and 390 mph with 1600 HP engine, new turbo and with guns, self-sealing tanks and pilot protection. To be produced by Lockheed and Republic, while Lockheed works on an up-engined version with R-2800, to be produced in Evansville, Indiana and at Curtiss. Not to be undone easily, Wright strongy suggests 1700 HP R-2600, so a prototype is made for that. Aircraft dives and rolls well, climb is uninspiring.
British and French are eager to buy it, but prefer the weaponry to be changed to combination of 20mm cannons and 0.50 HMGs within the wings. France folds, British take over the whole order. Lockheed makes 300 of the new fighters in 1941, Republic another 150 (no P-43A). In 1942, Locheed does 2000, Republic 800 (half of those 2800 are with R-2800), Evansville factory another 350, Curtiss makes a dozen, all with two wing racks for fuel and bombs, that are retrofitted in early models. The 1700 HP version does 400 mph (service use is mostly West Coast, later Pacific), the 2000 HP version does 420 mph and climbs a bit better.
1st British use notes that aircraft is easily mixed up for Fw 190, so the noses and tails are painted in vivid colors. Above 20000 ft it is better than LW aircraft, under 15000 is inferior. With 300+300 gals of fuel, it can range well into Germany, although British use smaller drop tanks by now.

 

[Kevin J]

From reading the history on it, I don't think there was that much to sort. I think most of it was the typical 1930's confusion on what was needed such as bombs in the wings to bomb bombers in the air, what guns, what engines, it's too heavy so we will buy heavier planes instead. Typical government stuff. They had the full sized model done in October 1938, just build the stupid thing. The F5F was at least large enough to handle reasonable engines such as the 1820 and 1830 and US turbochargers could make those a game changer if properly installed.

Seeing that Grumman first flew the XP-50 in 1941, it looks more like Grumman had too many projects on the go at any one time.

 

[pinsog]

Seeing that Grumman first flew the XP-50 in 1941, it looks more like Grumman had too many projects on the go at any one time.

I agree. Wildcat, XF5F, XP50, Hellcat, Avenger, all at the same time. Only so many people to go around, plus Navy changing equipment and whining about it weighing too much

 

[Shortround6]

From reading the history on it, I don't think there was that much to sort. I think most of it was the typical 1930's confusion on what was needed such as bombs in the wings to bomb bombers in the air, what guns, what engines, it's too heavy so we will buy heavier planes instead. Typical government stuff. They had the full sized model done in October 1938, just build the stupid thing. The F5F was at least large enough to handle reasonable engines such as the 1820 and 1830 and US turbochargers could make those a game changer if properly installed.

Unfortunately actual data on the F5F is a bit short. However it's development was a bit convoluted as it was.
It was designed, for a two stage(?) P & W R-1535 14 cylinder radial that never materialized. P & W quit developing the R-1535 engine in any form and just completed outstanding contracts. The supercharger on this engine was supposed to give 750hp at 17,500ft instead of 750hp at 9,000ft according to one source (which may have made a mistake or two?)
The Wright R-1820 was the closest match in weight so the CG wouldn't be too far off, The Navy F5F never got the turbo charger. The Army P-50 did along with the trike gear.
The Navy F5F got engines with 2 speed superchargers, not two stage. In fact it got the same engine (and one in reverse rotation) that the Buffalo used.
Drag was a lot higher than anticipated and a lot of work was done trying to solve the problems, in some cases the cause was obvious (like the landing gear doors not closing properly) even if the cure wasn't (they made several tries at getting the doors to close properly including new linkage.) in other cases they were trying stabs in the dark, longer engine nacelles, different wing fairings, a more pointed nose, lowering the top of the canopy and others.
Performance figures need to be closely looked at to see if they are real, recorded figures or estimates and what was the configuration of the plane for the performance figures given.

70 flights were supposed to have been made at Bethpage before the plane was delivered to Anacostia on Feb 22nd 1941, by which time the XF4U-1 was demonstrating superior performance.
While the R-1820 and the R-1830 were often interchangeable the F5F may have required a bit more work, the R-1535 went about 1100+ pounds for a single speed/single stage engine. I can't find anything on the two speed or two stage engine. The R-1820s that went into the F5F weighed about 1315-1320lbs, The R-1830 engine that went into the Vultee Vanguard (2 speed) went about 1495lbs, the two stage engine in the F4F went about 1550-1560lbs, the single speed R-183 engine used in the B-24s went about 1500lbs and you need to add the weight of the turbo's (which could be behind the CG?)
The Navy was certainly not happy with size of the R-1820s and the restricted view. The R-1820 was about 13in (330mm) larger in diameter than the R-1535 but accepted the engine in order to reduce the amount of delay before the plane could be delivered. Perhaps the Navy would have insisted on the 6-7in smaller diameter R-1830s for a better view on a production version? and accepted the time needed for the redesign?

Proposed armament varied from four 23mm cannon to four .50 cal machine guns but no guns were ever fitted (neither was armor or self sealing tanks) so listed weights are rather suspect. Either estimates or for a less than fully equipped plane unless test report mentions ballast?

A 10-11,000lb plane may not have been big enough to handle R-1830s with turbos.

 

[pinsog]

Unfortunately actual data on the F5F is a bit short. However it's development was a bit convoluted as it was.
It was designed, for a two stage(?) P & W R-1535 14 cylinder radial that never materialized. P & W quit developing the R-1535 engine in any form and just completed outstanding contracts. The supercharger on this engine was supposed to give 750hp at 17,500ft instead of 750hp at 9,000ft according to one source (which may have made a mistake or two?)
The Wright R-1820 was the closest match in weight so the CG wouldn't be too far off, The Navy F5F never got the turbo charger. The Army P-50 did along with the trike gear.
The Navy F5F got engines with 2 speed superchargers, not two stage. In fact it got the same engine (and one in reverse rotation) that the Buffalo used.
Drag was a lot higher than anticipated and a lot of work was done trying to solve the problems, in some cases the cause was obvious (like the landing gear doors not closing properly) even if the cure wasn't (they made several tries at getting the doors to close properly including new linkage.) in other cases they were trying stabs in the dark, longer engine nacelles, different wing fairings, a more pointed nose, lowering the top of the canopy and others.
Performance figures need to be closely looked at to see if they are real, recorded figures or estimates and what was the configuration of the plane for the performance figures given.

70 flights were supposed to have been made at Bethpage before the plane was delivered to Anacostia on Feb 22nd 1941, by which time the XF4U-1 was demonstrating superior performance.
While the R-1820 and the R-1830 were often interchangeable the F5F may have required a bit more work, the R-1535 went about 1100+ pounds for a single speed/single stage engine. I can't find anything on the two speed or two stage engine. The R-1820s that went into the F5F weighed about 1315-1320lbs, The R-1830 engine that went into the Vultee Vanguard (2 speed) went about 1495lbs, the two stage engine in the F4F went about 1550-1560lbs, the single speed R-183 engine used in the B-24s went about 1500lbs and you need to add the weight of the turbo's (which could be behind the CG?)
The Navy was certainly not happy with size of the R-1820s and the restricted view. The R-1820 was about 13in (330mm) larger in diameter than the R-1535 but accepted the engine in order to reduce the amount of delay before the plane could be delivered. Perhaps the Navy would have insisted on the 6-7in smaller diameter R-1830s for a better view on a production version? and accepted the time needed for the redesign?

Proposed armament varied from four 23mm cannon to four .50 cal machine guns but no guns were ever fitted (neither was armor or self sealing tanks) so listed weights are rather suspect. Either estimates or for a less than fully equipped plane unless test report mentions ballast?

A 10-11,000lb plane may not have been big enough to handle R-1830s with turbos.

Empty weight at 8100 pounds, loaded weight was 10,100 normal 178 gallons of fuel, overload was 10,900 with 277 gallons of fuel. Radio was already installed. Add pilot, oil, etc and it works out to have been ballasted for 4 50's and ammo. I have it broke down exactly in another thread somewhere

Why would a 10-11,000 pound plane not be able to handle turbocharged 1820's?

 

[pinsog]

XF5F Skyrocket

Empty weight 7990
Normal Loaded weight 10,021 leaves 2,031 pounds for load.
178 gallons of fuel is 1,068 pounds
150 pounds of oil (P36 oil times 2)
200 pound pilot

Leaves 613 pounds for weapons
4 50's is 300 pounds
300 rounds per gun is 300 more pounds

Empty weight 7990
Overload weight 10,892 leaving 2902 for load
277 gas is 1662
150 pounds of oil
200 pound pilot
Leaves 890 pounds for weapons
4 50's is 300 pounds
500 rounds per gun is 500 pounds

 

[Shortround6]

For a heavy fighter, early on.
As it is said many times, Johnson at Lockheed was looking for a 1500 HP engine to power his proposal for a fighter with heavy firepower; failing that, he will use two engines, but of 1000 HP (= that was future XP-38). Lets have him choose the R-2600 this time. Engine obviously in the front, turbo behind the pilot, the required heavy firepower will be two 37mm cannos in pods under the wings. Wing size of 300 sq ft, has Fowler flaps. The R-2600 is a decent, if unspectacular engine, but fighter can do 400 mph at base power at altitude (1500 HP at 20000 ft) in unarmed prototype form, and 390 mph with 1600 HP engine, new turbo and with guns, self-sealing tanks and pilot protection. To be produced by Lockheed and Republic, while Lockheed works on an up-engined version with R-2800, to be produced in Evansville, Indiana and at Curtiss. Not to be undone easily, Wright strongy suggests 1700 HP R-2600, so a prototype is made for that. Aircraft dives and rolls well, climb is uninspiring.
British and French are eager to buy it, but prefer the weaponry to be changed to combination of 20mm cannons and 0.50 HMGs within the wings. France folds, British take over the whole order. Lockheed makes 300 of the new fighters in 1941, Republic another 150 (no P-43A). In 1942, Locheed does 2000, Republic 800 (half of those 2800 are with R-2800), Evansville factory another 350, Curtiss makes a dozen, all with two wing racks for fuel and bombs, that are retrofitted in early models. The 1700 HP version does 400 mph (service use is mostly West Coast, later Pacific), the 2000 HP version does 420 mph and climbs a bit better.
1st British use notes that aircraft is easily mixed up for Fw 190, so the noses and tails are painted in vivid colors. Above 20000 ft it is better than LW aircraft, under 15000 is inferior. With 300+300 gals of fuel, it can range well into Germany, although British use smaller drop tanks by now.

Uh, Tomo, the 1600hp R-2600 had a lot of cooling troubles when equipped with a turbo charger. At least in the A-20, For some reason (known to Wright?) turbo R-2600s are very few in number. Not sure if the performance numbers will hold up. P-38Ds and Es were in the 380-390mph range at 20,000ft with 2300hp. P-47B needed 1625hp at 25,000ft to do 392mph.

Wright delivers 443 of the 1700hp version in 1941, 206 of them in Dec. This is the engine used in the B-25, about 500 built (needing 1000 engines) by late spring of 1942. This is also the engine used the Avenger.

Not sure when the 37mm cannon got the horseshoe feed, the older ones (Airacuda) used a 5 round box magazine, a 15 round belt is listed, not sure how many planes used it.

 

[Shortround6]

XF5F Skyrocket

Empty weight 7990
Normal Loaded weight 10,021 leaves 2,031 pounds for load.
178 gallons of fuel is 1,068 pounds
150 pounds of oil (P36 oil times 2)
200 pound pilot

Leaves 613 pounds for weapons
4 50's is 300 pounds
300 rounds per gun is 300 more pounds

Empty weight 7990
Overload weight 10,892 leaving 2902 for load
277 gas is 1662
150 pounds of oil
200 pound pilot
Leaves 890 pounds for weapons
4 50's is 300 pounds
500 rounds per gun is 500 pounds

1200 rounds of .50 cal ammo is 360lbs, 2000 rounds is 600lbs.

The turbos need about 12 cubic feet of space (minium) for the installation and plumbing for the intercooler.
The turbos are not heavy on their own, about 120-130lbs each if I remember right.
but.

Closest air intake in the wing is the carb air, the one closest to the engine is the intercooler air, the inlets between the engines are the oil coolers.

P-38s devoted around 400-600lbs for the turbos, high number is for a P-38J, low number is an estimate for the YP-38 as the supercharging weight was lumped in the accessories, However the YP-38 used the wing leading edge as the intercooler and so saved weight that way. P-38s also used 11ft 6in props instead of the 10ft 3in used on the Buffalo or the 10ft or under props used on the F4F. trying to use small props on a turbocharged engine at high altitude is probably a mistake. YP-38 props were about 346lbs apiece. P-38J props were a lot heavier.
XF5F didn't have armor or self sealing fuel tanks?

One source claims the XP-50 went 8,307lbs empty, 10,558lbs loaded and 13,060lbs max but these may be estimates. "Normal" range was estimated at 585miles but conditions not given.

 

[pinsog]

1200 rounds of .50 cal ammo is 360lbs, 2000 rounds is 600lbs.

The turbos need about 12 cubic feet of space (minium) for the installation and plumbing for the intercooler.
The turbos are not heavy on their own, about 120-130lbs each if I remember right.
but.
View attachment 568882

Closest air intake in the wing is the carb air, the one closest to the engine is the intercooler air, the inlets between the engines are the oil coolers.

P-38s devoted around 400-600lbs for the turbos, high number is for a P-38J, low number is an estimate for the YP-38 as the supercharging weight was lumped in the accessories, However the YP-38 used the wing leading edge as the intercooler and so saved weight that way. P-38s also used 11ft 6in props instead of the 10ft 3in used on the Buffalo or the 10ft or under props used on the F4F. trying to use small props on a turbocharged engine at high altitude is probably a mistake. YP-38 props were about 346lbs apiece. P-38J props were a lot heavier.
XF5F didn't have armor or self sealing fuel tanks?

One source claims the XP-50 went 8,307lbs empty, 10,558lbs loaded and 13,060lbs max but these may be estimates. "Normal" range was estimated at 585miles but conditions not given.

I used the wwiiaircraftperformance P36 that lists 200 rounds of 50 weighing 50 pounds, but I realize that even different bullets and loads of 50 could weigh much different over 2000 rounds. I used 500 pounds but 100 extra pounds on a 2400 hp fighter isn't much of a concern.

They specifically moved the engines forward on the F5F so 2 stage engines could be used later, I believe they intended the intercooler to go directly behind the engine like in an F4F. I guessed 500 pounds for the added weight. It would certainly fit, they fit in the XP50.

The B2 turbocharger weighed 135 pounds.

Quick question for you Shortround, best guess on how much a 75 gallon wing tank would weigh installed in the outer wing like a Corsair, SBD or Whirlwind?

 

[Shortround6]

They specifically moved the engines forward on the F5F so 2 stage engines could be used later, I believe they intended the intercooler to go directly behind the engine like in an F4F. I guessed 500 pounds for the added weight. It would certainly fit, they fit in the XP50.

There were no two stage Wright R-1820s that were mechanically driven (at least not that made it to production). I have not seen anything about a planned two stage engine at this point in the war although one might have been planned.
I have no idea why they would move the heavier R-1820 engines further forward than the R-1535 engines.

I would also note that you need bigger intercoolers for 1200hp at 25,000ft than you do for 1200hp at 20,000ft let alone 1000hp at 19,000ft like the F4F. The air is thinner so you need more volume for the same mass/weight and you have to compress the air more making it hotter to get the same manifold pressure.

As for the fuel tanks, a lot depends on the actual shape of the tank, flat tanks weigh more than deep tanks, self sealing material was heavy, SPD needed 218lbs to change from unprotected out tanks to protected tanks. It took 232lbs to protect the main tanks. I don't know what the unprotected tanks weigh.

 

[pinsog]

There were no two stage Wright R-1820s that were mechanically driven (at least not that made it to production). I have not seen anything about a planned two stage engine at this point in the war although one might have been planned.
I have no idea why they would move the heavier R-1820 engines further forward than the R-1535 engines.

I would also note that you need bigger intercoolers for 1200hp at 25,000ft than you do for 1200hp at 20,000ft let alone 1000hp at 19,000ft like the F4F. The air is thinner so you need more volume for the same mass/weight and you have to compress the air more making it hotter to get the same manifold pressure.

As for the fuel tanks, a lot depends on the actual shape of the tank, flat tanks weigh more than deep tanks, self sealing material was heavy, SPD needed 218lbs to change from unprotected out tanks to protected tanks. It took 232lbs to protect the main tanks. I don't know what the unprotected tanks weigh.[/

Apparently Grumman wanted to do it and not the Navy. I assume however they arranged it inside the XP50 is how they would arrange it inside the nacelles of the XF5F. I imagine the intercooler directly behind the engine and the turbo near the back of the wing. I know turbocharger controls weren't perfected until early to mid 1942 and I also seriously doubt the Navy would have gone for a turbocharged fighter, but I still believe it could have easily been done and nothing could have touched it in overall performance until the late war Corsair and Bearcat.

By the time the Corsair came out the F5F could had the 1350 hp 1820's that had 1480 hp with water injection and almost no increase in weight.

Any idea what props the XP50 was using?