drgondog
Major
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P-47N Thunderbolt vs. F4U-4 Corsair - Which was superior?
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Shortround6
Major General
Why would it bleed off any more power than the first blower on the F4U which was also driven by the crankshaft? I believe both engines used the same impeller in the first blower which was geared up 7.29:1 in the P-47 and 7.50:1 in the F4U-4.
Perhaps not as much as is commonly thought. America's Hundred thousand gives a drag co-efficient of .0213 for the P-47B (no number of the P-47N) vs .0267 for the F4U-1D (no number given for the F4U-4) for profile drag flat plate areas of 6.39 sq.ft. for the P-47 vs 8.58 sq.ft. for the F4D-1D. Granted profile drag is not the only drag component acting on a flying airplane but perhaps the P-47 wasn't quite as draggy as most people believe? Or the book is in error?
I would note that the performance figures in "America's Hundred Thousand" give weights. The P-47N's weight is about 2 tons heavier than the F4U-4. This is certainly going to affect things like climb.
I would note that the weights for the P-47N show that while it weighed only 736lbs more than a late model "D" in basic condition ( trapped fuel and oil plus guns) it's performance numbers were taken at a weight 2200lbs heavier than the "D" model performance numbers.
Given that the P-47N will hold 556 US gallons of gas in internal tanks comparing it's performance with full tanks to an F4U-4 holding only 234 US gallons of fuel is going to give the F4U-4 an advantage. dumping 330 gals out of the P-47N should lighten it up by about a ton and show rather different performance figures in some cases.
windswords
Airman
drgondog,
Thanks for posting that document. Do you have the same figures for the 9th AF? The 15th and 12th AF's?
Thanks for posting that document. Do you have the same figures for the 9th AF? The 15th and 12th AF's?
renrich
Chief Master Sergeant
No doubt that the P47N carried a lot of fuel and I think had a bigger wing, to carry that fuel. If the P47N carries only the same internal fuel as the F4U4 then it will weigh less and climb faster. But then it won't have the range which is partly the reason for the bigger wing. Even the P47M which was the limited production buzz bomb chaser and had the same engine as the N model could not better the F4U4's climb performance or low altitude Vmax and was no faster at 25000 feet. I don't have figures for a low weight P47N but must believe that they would not be quite as good as the M model because of higher empty weight and a bigger wing, I think, which contributes to more drag.
I think the drag coefficients given in AHT are correct and that lower DC of the P47 is the result of a smaller wing with a different shape (thinner). Those undoubtedly are the reasons why, along with the high weight, the P47 was such a ground lover.
Vought put together an F4U with trubocharged engine but decided the trade offs were not worth it and opted for a bigger supercharger in the ultimate performing Corsair, the F4U5.
TP, I am only quoting Linnekin and my uncle because they both seemed to have knowledge about the performance of the P47 in mock dogfights against Bearcats and Corsairs. I also seem to recall reading in Tom Blackburn's book, "The Jolly Rogers" that he and other members of his squadron, flying F4U1s, bounced P47s on the east coast in late 1942 and had their way with them. The guys in the P47s, as I recall, kept trying to get the Corsair drivers to get up high with them but the Navy guys sensibly declined.
I think the drag coefficients given in AHT are correct and that lower DC of the P47 is the result of a smaller wing with a different shape (thinner). Those undoubtedly are the reasons why, along with the high weight, the P47 was such a ground lover.
Vought put together an F4U with trubocharged engine but decided the trade offs were not worth it and opted for a bigger supercharger in the ultimate performing Corsair, the F4U5.
TP, I am only quoting Linnekin and my uncle because they both seemed to have knowledge about the performance of the P47 in mock dogfights against Bearcats and Corsairs. I also seem to recall reading in Tom Blackburn's book, "The Jolly Rogers" that he and other members of his squadron, flying F4U1s, bounced P47s on the east coast in late 1942 and had their way with them. The guys in the P47s, as I recall, kept trying to get the Corsair drivers to get up high with them but the Navy guys sensibly declined.
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drgondog
Major
No - all WIP.. I have the 354th in the 9th and all the awards for all 9th AF groups but I don't yet have a good source for losses other than 354FG
davparlr
Senior Master Sergeant
I have seen that data also, but I have a problem with it. When I compare the P-47 to the F4U airspeed at SL and equivalent HP, whether it is the P-47B vs. the F4U-1 or the P-47D-25 vs. F4U-4, both cases having equivalent combat HP at SL, the F4U always comes out on top. In my mind, this is a very good indication of the airframe efficiency. In this case, it a appears that the F4U is a more efficient air vehicle implementation than the P-47. Tis a puzzlement. This, of course, does not negate the performance arguments I have previously presented.
The Cd is never a constant parameter, it depends on your flight regime (power, hight, weight).
The best airframe efficiency with an R-2800 is certainly obtained by a Polikarpov I-185/185, then by Bearcat, not by P-47 or F4U. They were to big and heavy for that.
The P-47 had a very long fuselage, but it was incorporating a turbocharer in it, and it was working well unlike for soviet TK-1 or german turbos, almost because exhaust gazes were previously cooled and smoothed. All that was needing place (size, dimensions) cause the turbo was far away from exhaust holes. Soviet TK-1's were working on very hard conditions (extreme heat, pressure strikes), that explains their failure, despite more advanced steels used.
But even the I-185/187 should have been able to win every simulated fight, aerobatic contest and pylone race, it was a 100% useless fighter for ETO, MTO, PTO due to its short range, and even for America's defense except if the country was invaded*. It was not able to carry roomy extra devices for night and bad weather flights either and moreover locators.
* Some things should have been done, before that, and the I-185 was unable to do them, unlike P-47's and F 4U's...
Back to America in 1940, there were no prouves that stategic and stratospheric "Americabombers" of B-29 class were not to be developped in Germany, Italy, Japan, SU, and worse from all of them altogether...
Imagine USAF nightmares. I can perfectly understand high-altitude fighter request, even at size an weight coast.
That means, a fighter is:
-a weapon
-a tool in the global defence structure.
The best fighter in a "show" is not always the best in the real life.
To resume, i'm not sure that F4U was a "better" plane than the P-47 even if was as fast and could oufight it, both in vertical and horizontal plans, from that point of view.
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drgondog
Major
The flat plate drag for the 51B/D was around 4.65 sq ft at 330mph and 15,000 feet IIRC..
VG-33 was entirely correct that drag figures must be calculated, used and compared at same Reynolds number..
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renrich
Chief Master Sergeant
Dav, it is puzzling to me also about the less than sterling performance of the late P47s, especially those with 2800 HP at lower altitudes. Perhaps that performance issue was the result of the same forces that made the F2G Corsair with 3000 HP very little faster than the F4U4 at low altitudes. I have read that at some point adding HP to an airplane only results in better load carrying ability but no speed gain. Maybe it is propellor efficiency?
For trains and cars it's very simple, the speed increase is proportional to the power cubic root. So for 3% speed increase you need 3 x 3 x3 =27 % power increase. For the plane it's the same, except that for the same wing loading at same AoA your plane is climbing because of the lift increase!
So you reduce your AoA to stay at the same level, and gain some induced drag decrease. Each case being particular, your f=Cl/Cd plays a major rule on your polar point. It means: for the same power X% increase, Mustang gains proportionaly more Y% speed than a Gladiator!
All that does not work about Mach =0,7, since classical prop and wing profiles are quickly loosing properties.
So independently of your power in excess you wouldn' fly much quicker, cause your prop/wing output would be seriously reduced!
Colin1
Senior Master Sergeant
I guess that loosely translates to the closer you are to the edge of the envelope (for a piston-engined fighter) more bhp will have less significance
Regarding the F4U-4 being faster than the P-47N down low, I have always wondered exactly why the maximum speed of the F4U-1, -1A, -1D range from about 390 mph max to 417 mph max. I haven't seen a quote for a P-47 up to P-47D below 400 mph and most are around 430 mph or so. There doesn't seem to be the same variation with the P-47.
BTW, Regarding roll rates, I remember reading in the Motorbooks "Warbird Buyer's Guide" that while the absolute maximum roll rate of the P-47 wasn't extremely high, it wasn't bad and it doesn't lose much under G load while many other fighters lose a large percentage of their roll rate when pulling G as you would in a dogfight. In the same book, the P-47 rated nearly the same as the P-51D in turning ability. The P-51D was slightly better, but the P-47 made up for it by being more controllable.
This is just minorly off topic: Does anyone here have profiles / schematics with dimensions for the P-47D and P-47M or N models? I am curious as to what differences there are because the later models always looked larger to me but I can't quite pin down exactly where.
Thanks.
- Ivan.
BTW, Regarding roll rates, I remember reading in the Motorbooks "Warbird Buyer's Guide" that while the absolute maximum roll rate of the P-47 wasn't extremely high, it wasn't bad and it doesn't lose much under G load while many other fighters lose a large percentage of their roll rate when pulling G as you would in a dogfight. In the same book, the P-47 rated nearly the same as the P-51D in turning ability. The P-51D was slightly better, but the P-47 made up for it by being more controllable.
This is just minorly off topic: Does anyone here have profiles / schematics with dimensions for the P-47D and P-47M or N models? I am curious as to what differences there are because the later models always looked larger to me but I can't quite pin down exactly where.
Thanks.
- Ivan.
Colin1
Senior Master Sergeant
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davparlr
Senior Master Sergeant
I am not sure the increase hp of the late model P-47s were not as productive as the early models. The P-47B, with 2000 hp was capable of 334 mph at SL, while the P-47M, with 2600 hp was capable of 367 mph. I think this is similar to the F4U-1, with 2000 hp is capable of 340 mph at SL and the F4U-4, with 2380 is capable of 380 mph.
The F2G performance always baffled me. However, I think the answer is in its primary design goal and the associated compressor design. I believe the F2G was designed for low level performance, possibly as reported for attacking Kamikazes, and lacked a good high altitude compressor. Its SL speed is quite impressive, nearly 400 mph, about 25 mph faster than the F4U-4. I think this is reasonable since the F2G at 3000 hp had 620 hp more than the F4U-4 at 2380 hp. Its top speed is 431 at only 16,400 ft. compared to the F4U-4's 446 mph at 31,400 ft. The XP-72 with the same, but slightly more powerful, engine was capable of an amazing 490 mph at 25,000 ft. So, I think it had the power to really perform, but it was basically, geared down to fight in the dirt. I would guess that it would be faster than the F4U-4 up to about 10K.
renrich
Chief Master Sergeant
Would not the XP72, if it had gone into production, be more contemporaneous with the F4U5? I believe it was capable, at critical altiude of around 470 mph.
Thanks to Colin for posting the info on the P47s above. To me the significant aspects of those numbers is that they appear, (although I am sure they are not intended to) to show that the maximum performance numbers all occur at the same time. For instance it says that the P47N took 13.5 minutes to climb to 32000 feet, carried 570 gallons of internal fuel, had a maximum range of 920 miles and had either eight or six mgs with either 425 or 267 rounds per gun. Most of us look at those figures and say, "wow." My bet is that when the N climbed to 32000 feet in 13.5 minutes it did not carry 570 gallons of fuel and had only six mgs with only 267 rounds. This is the problem with all our comparisons of performance numbers on all the aircraft we talk about. It is fun to throw around these numbers but they often are misleading.
The F8F was an impressive airplane when it first came out. It could climb like a homesick angel and at low altitudes could outdo almost any other fighter in existence. As the airplane evolved( for instance going from four 50 cals to four 20 mms, getting a taller vertical stabilizer and some engine mods) it's performance deteriorated some but it was deployed on all the Essex type carriers. The Corsair was deployed on the Midway types. The Bearcat must have been the apex of piston engined carrier fighters, on paper. However, in around 1948, the Bearcats were pulled off the carriers and relegated to reserve units and the Corsairs were the fleet fighter. The reason was that the Bearcat could not carry the ordnance the Corsair could and the Corsair was overall just as good as a pure fighter. All those gaudy performance figures that look so good on paper that us "armchair experts" write so knowingly about don't always tell the whole story.
Thanks to Colin for posting the info on the P47s above. To me the significant aspects of those numbers is that they appear, (although I am sure they are not intended to) to show that the maximum performance numbers all occur at the same time. For instance it says that the P47N took 13.5 minutes to climb to 32000 feet, carried 570 gallons of internal fuel, had a maximum range of 920 miles and had either eight or six mgs with either 425 or 267 rounds per gun. Most of us look at those figures and say, "wow." My bet is that when the N climbed to 32000 feet in 13.5 minutes it did not carry 570 gallons of fuel and had only six mgs with only 267 rounds. This is the problem with all our comparisons of performance numbers on all the aircraft we talk about. It is fun to throw around these numbers but they often are misleading.
The F8F was an impressive airplane when it first came out. It could climb like a homesick angel and at low altitudes could outdo almost any other fighter in existence. As the airplane evolved( for instance going from four 50 cals to four 20 mms, getting a taller vertical stabilizer and some engine mods) it's performance deteriorated some but it was deployed on all the Essex type carriers. The Corsair was deployed on the Midway types. The Bearcat must have been the apex of piston engined carrier fighters, on paper. However, in around 1948, the Bearcats were pulled off the carriers and relegated to reserve units and the Corsairs were the fleet fighter. The reason was that the Bearcat could not carry the ordnance the Corsair could and the Corsair was overall just as good as a pure fighter. All those gaudy performance figures that look so good on paper that us "armchair experts" write so knowingly about don't always tell the whole story.
davparlr
Senior Master Sergeant
The XP-72 was actually a contemporary of the F2G. First flight of the XP-72 was in February of 1944, which I believe is before the first flight of the F2G. Testing was impressive, although one was lost, I believe when a turbocharger blew. The AAF ordered 100 to be built but cancelled the order when the need was not established and emphasis was put on jets. U.S. Air Force Museum records the top speed of 490 mph, other sources show 480 mph. I do not know the turbo profile of the XP-72, but if it was the same as the P-47D and M/N, the XP-72 would be generating nearly 3500 hp at 33k ft., around three times the power generated by the highly esteemed Ta-152H. With this power the XP-72 could probably go as fast as a piston powered, propeller driven, fighter could go. The AAF had a powerful fighter on the back burner in 1944 that could have addressed any of the advanced propeller driven aircraft the Axis were developing.
You are right about the data. It probably came from several sources that were not related. Those time to climb numbers seem to be at a lighter weight, probably about the weight of the calculation I did, or around 13,800 lbs or lighter for the N.
Excellent analysis.
Colin1
Senior Master Sergeant
A curious remark
how definitely is probably? I've never considered Roger Freeman to be anything other than a reliable source
Colin1
Senior Master Sergeant
drgondog
Major
Roger was very good - but the scope of his research was unsupported by the readily available resources now available to support his 8th AF histories. His works had errors - which I can relate to Colin (as you may have gathered from some of my annotated remarks in ABD) - I am STILL making corrections to the new book.
For example USAF 85 was not available to him, nor Frank Olynyk's exhaustive research on victory credits which have resulted in the now current updates at USAFHRC's Victory Credits for USAAF/USAF.
I wish I was a lot younger. I was going to do a joint collaboration w/Jeff Ethell to do the 'Opus' of 8th Fighter Command but he screwed it up when he stalled that P-38 on final.. good guy. I had known him from time his father was a squadron CO when dad had the 35th FBW and we were all in Japan together from 1948 to the time he passed on us.
Researching ONE fighter group thoroughly is a major undertaking - doing 15 plus the Scouts would have been a lot of work - actually double because we agreed to 'audit' each other's research.
renrich
Chief Master Sergeant
Don't know where to post this but guess I will here. Played golf today at Antelope Hills muny here in Prescott, AZ. The two courses there are next to the airport. Teed off on number one of the south course about 12:00 noon. Was ready to hit my second shot on the par five when I heard the sound of a big round engine. Looked toward the airport and here came one after the other two F6F Hellcats. They were both in the Navy blue color and after coming off the runway, climbed steeply and made a left turn to the North. I have seen Hellcats in a static display and one flying at an airshow but don't recall ever seeing two together at once. Quite a thrill and I expect I will never see the like again. Wonder how many Hellcats are still flying?
