Best R-4360-powered Fighter?

[SpicyJuan11]

Which R-4360 based design had the best potential as a true fighter to take on the next wave of piston-engined Axis designs in mid-late 1945? By that I mean Fw 190A-10 (BMW 801F), Fw 190D-13/D-15, Ta 152C/Ta 152H, Bv 155C. Do 335, A7M, J6K, Ki-100, N1K5.

The point here isn't asking "what if XF8B vs Ki-100", I am asking which American design, the F2G, XF8B, or XP-72 had the best potential to be fully developed into a fighter.

The F2G didn't have the water injection of the XF8B, but if it had, would it have been faster? Was the XF8B a "jack of all trades, master of none" as a "5 in 1" fighter with its own internal bomb-bay?

Was there any advantage in having a massive R-4360 powered fighter when compared to the other alternatives coming online in 1945 (P-51H, XP-47H, F8F, etc).

Obviously jets were coming into service anyways, but for the sake of discussion (that is, the discussion of the future course of piston-engined fighters), let's assume they aren't a factor in any way.

I don't have any references at hand, so here is a quick summary of the different aircraft's performance based on wikipedia (which I'm sure will be corrected)

Empty Weight
XF8B - 13,500 lbs
XP-72 - 11,500 '
F2G - 10,250 '

Max takeoff weight
XF8B - 21,700 lbs
XP-72 - 17,500 '
F2G - 15,400 '

Powerplant
XF8B - 3,600 hp XR-4360-10
XP-72 - 3,500 hp R-4360-13
F2G - 3,000 HP R-4360-4
Max Speed
XF8B - 450 mph
XP-72 - 490 '
F2G - 430 '
Rate of Climb
XF8B - 2,000 ft/min
XP-72 - 5,280 ft/min '
F2G - 4,400 ft/min
Service Ceiling
XF8B - 37,500 ft
XP-72 - 42,000 '
F2G - 38,800 '
Wing Loading
XF8B - 41.9 lb/sq
XP-72 - 48.1 '
F2G - 42.5 '

A very interesting note by wiki:

Test pilot Tom Bellinger stated flatly that his no flights ever exceeded 500 mph with the dash 13 engine. With the planned but never installed dash 19 engine rated at 3,650 HP at 25,000 ft (3,000 HP at military power) a top speed of 504 mph at approximately 25,000 feet was expected. Planned further development of the dash 19 engine was expected to yield approximately 4,000 hp and a speed of 540 mph at 25,000 ft.

How would the F2G have performed with such an engine? Would it have blown the F4U-5 out of the water?

 

[Skyediamonds]

I Googled the Super Corsair; both the "stock" & the clipped winged air racer.

The fastest stock Super Corsair was 431+ mph
The fastest air racer version was 438 mph.

I find this surprising as the air racing version had its wings clipped & all excess naval equipment removed & yet there's only an 8 mph gainedzz

 

[Shortround6]

I find this surprising as the air racing version had its wings clipped & all excess naval equipment removed & yet there's only an 8 mph gainedzz

altitudes and perhaps the difference between straight line speed and lap times?
Corsairs picked up around 40+ mph going from sea level to 16,000ft.
The Air Races in the 1940s were at under 1000ft.
Times from the 2006-2008 races in Reno are at around 5000ft and summer desert temperatures.

 

[GregP]

I'm thinking the XP-72 and F2G were both very capable fighters and could have been developed into thoroughbreds. The issue with "developed into" is usually weight gain. Either one would be fine if the weight wasn't increased much.

The XF8B, to me at least, much more of a Super Skyraider than a fighter. The speed and rate of climb are not competitive with the other two, but it could haul some ordnance, was likely quite maneuverable, and was well-armed. A slight redesign with some serious weight-cutting attention might have moved it out of the attack category into the fighter category but, as they stand, I'm leaning heavily toward the other two airplanes.

Looking at them. the XP-72 seems to offer a better view forward than the F2G, but that may well be wishful thinking. Neither exactly gets away from the "hose nose" monicker. The P-47 usually gets less than its share of praise, except from pilots. If you talk with the ones who prefer other fighters over the P-47, they rarely have any P-47 time under their belts. If you talk with the ones who flew P-47 and love them, they generally HAVE time in other fighters and prefer the P-47 after becoming familiar with it.

I'm leaning toward the XP-72 for serious development of an R-4360 fighter, but there would be no argument if the F2G were selected, unless top speed was a major factor. I think it should be since all of the late-war adversaries were getting faster. If so, the XP-72 has it hands down with a 59 mph speed advantage. The XP-72, then, is 13.8% faster, has a 20% better climb rate, and an 8% better ceiling. The F2G has 40% more range, but the XP-72 still has a 1200-mile range. Not too sure the 1900+ miles of the F2G versus the 1200 miles of the XP-72 are relevant, but they might be depending on mission. The F2G has about a 13% lower wing loading but, again, I'm not too sure that matters for these airplanes at the times when they would have been flying missions since everything else that was going to be competing against them was also getting heavier and faster than earlier fighters.

 

[Skyediamonds]

altitudes and perhaps the difference between straight line speed and lap times?
Corsairs picked up around 40+ mph going from sea level to 16,000ft.
The Air Races in the 1940s were at under 1000ft.
Times from the 2006-2008 races in Reno are at around 5000ft and summer desert temperatures.

I agree that the Corsair did indeed, pick up over 40 mph but as you noted, that's at Fl 160. The altitude at Stead is 5,029, which made this airfield ideal for air racing. I was comparing the two Super Corsairs under similar conditions.

 

[Supercharged]

I have another question regarding the XP-72, how is it possible that she was much faster than the P-47D at altitude?

If you compare the numbers you will see what i'm talking about....

XP-72
speed: 490 mph TAS @ 25.000ft
normal weight: 14.760 lbs
power available @ 25.000ft: 2400 BHP @ 2700 RPM @ 52"in/hg (military 5 min.)

P-47D
speed: 438 mph TAS @ 25.000ft
normal weight: 13.230 lbs
power available @ 25.000ft: 2300-2600 BHP* @ 2700 RPM @ 56"in/hg + water WEP (5 min.)

* quite hard to figure out the exact numbers....

I got my data from here:

P-47 Performance Tests

https://enginehistory.org/Piston/P&W/R-4360/WaspMajorIndex.pdf

Republic XP-72 Super Thunderbolt / Ultrabolt Fighter

The Republic XP-72 could have been one of the greatest piston-engine fighters ever built. However, because of jet aircraft and the end of World War II, the P-72 never entered production.

oldmachinepress.com

The XP-72 with her "early" b-series R-4360 reaches full throttle height and maximum speed at approximately 25.000ft. But the P-47D with WEP rating reaches the same power at same altitude. Where is XP-72 speed advantage of almost 50 mph coming from??

 

[tomo pauk]

The XP-72 with her "early" b-series R-4360 reaches full throttle height and maximum speed at approximately 25.000ft. But the P-47D with WEP rating reaches the same power at same height. Where is XP-72 speed advantage of almost 50 mph coming from??

Result of the combination of rose-tinted glasses carried by the people itching to represent the XP-72 as a non plus ultra fighter, and the actual, additional 400+- HP worth of exhaust thrust?

 

[tomo pauk]

The F2G didn't have the water injection of the XF8B, but if it had, would it have been faster? Was the XF8B a "jack of all trades, master of none" as a "5 in 1" fighter with its own internal bomb-bay?

Boeing's aircraft was indeed looking like 'look what we can do now with obscene amount of power', rather than 'we've made an A/C to rule them all' - just IMO.
F2G's main disadvantage was that it was with an 1-stage S/C (vs. the XP-72 and F8B with 2-stage S/Cs, as well as when compared with other late war fighters with modern S/Cs), thus being way behind the curve above 20000 ft. Water-alc injection was easy to retrofit.

Was there any advantage in having a massive R-4360 powered fighter when compared to the other alternatives coming online in 1945 (P-51H, XP-47H, F8F, etc).

XP-47H was probably never going to became online, due to it's engine being of undefined quality, so to speak
IMO, the R-4360 powered fighters were in the "why bother?" zone. Americans were starting to produce the superlative P-47N and F4U-4, as well as, indeed, the latest Mustangs, that were far more 'realistic' aircraft, and the 1st two actually saw combat. The Big War just ended, the jets were the future, despite the clumsy starts by the many companies.

 

[Supercharged]

Powerplant
XF8B - 3,600 hp XR-4360-10
XP-72 - 3,500 hp R-4360-13

Where do you got this numbers from?

 

[MIflyer]

The P-72A probably would have been built on the superior P-47N airframe, giving it more range. Word is, the real reason the F2G was built was to ensure that the USMC won the postwar National Air Races. Of course, jets spoiled that plan. I plan to use a Hawk P-47 kit with a AMT F7F cowling to build my P-72.

 

[MIflyer]

Well, what about the Vultee XA-41? It has a 4360 and showed superb maneuverability as well as reportably the ability to outrun a P-51B at low altitude.

 

[33k in the air]

First flight dates:

XP-72, Feb. 2, 1944
XA-41, Feb. 11, 1944
XF8B, Nov. 27, 1944
XF2G, July 15, 1945

Assuming a timely and mostly trouble-free development time of 14 months, only the XP-72 and XA-41 might have seen wartime service, with the former having a combat debut in early April 1945 and the latter in mid-April 1945.

(The fastest time from a new aircraft prototype first flight to combat service debut, of the aircraft I've looked at, was 14 months, achieved by the Lancaster and F6F Hellcat. The only aircraft to do it faster was the TBF Avenger, whose prototype first took flight on Aug. 7, 1941, while its combat debut was June 4, 1942, during the Battle of Midway. That's a time span of just 10 months.)

 

[NevadaK]

There was a brief, but informative thread about the F2G a little while ago. Here is the link:

Why was the F2G so "slow"

Same as the thread title. Why was the F2G, despite the increase in power by almost 600HP (3,000HP vs 2,380HP of the F4U-4) and carrying two less machine guns, although still weighing 1,000 pounds heavier (10,249 lbs vs 9,205), the F2G was, according to Wikipedia, 15 mph slower (431 vs 446)...

ww2aircraft.net

The second tab has charts showing that the F2G excelled at low altitude.

 

[33k in the air]

The second tab has charts showing that the F2G excelled at low altitude.

My understanding is that the F2G was intended as a lower altitude kamikaze interceptor, and thus was optimized for low altitude speed.

 

[Admiral Beez]

Stick the R-4360 onto a Hawker Fury (or Tempest) like the post-war Reno racers did. Here's the Sea Fury named Dreadnought with its R-4360 showing.

View: https://www.youtube.com/watch?time_continue=3&v=SkYx4Cti6Z4&embeds_referring_euri=https%3A%2F%2Foldmachinepress.com%2F&source_ve_path=Mjg2NjY&feature=emb_logo

Mind you, the MiG-15 killing Centaurus Fury is more than sufficient to keep up with anything the Luftwaffe can throw up.