Post WW II fighters, Ki-84 Hei vs TA-152H vs F8F-2

Ronny

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These fighters are from the end of WW II period,
But they arrive too late to have any impact in the war. However, if they can arrive at the start of WW II
which one is the best as air superiority fighter?
Best here defined as they are most likely to win in air combat when face the others two
Ki-84 Hei
22249C17-2E79-48AC-98FE-03950864C7CD.jpeg

F8F-2 Bear cat
374434DA-8654-4DC3-9593-522EFFEA40AA.jpeg

TA-152H
869FDF2C-355A-4719-900B-9B5443DB48E1.jpeg
 

Foo Fighter

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I think perhaps this topic belongs in alternative history/speculation.
 

riggerrob

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Grumman F8F Bearcat was designed to be a fleet defense interceptor. Try to think of Bearcat as a pre-shrunk Hellcat, built around the same engine, but optimized for rapid climb. The USN hoped that Bearcats could intercept kamakazi well befor ethey got close enough to damage capital ships.
Meanwhile, Kurt Tank designed the Ta 152 as a high-altitude interceptor. Its extended wings and super-charged engine were deigned to still climb well above 30,000 feet where WALLIED heavy bombers cruised on their way to bombarding targets within Germany.
 

Ronny

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Grumman F8F Bearcat was designed to be a fleet defense interceptor. Try to think of Bearcat as a pre-shrunk Hellcat, built around the same engine, but optimized for rapid climb. The USN hoped that Bearcats could intercept kamakazi well befor ethey got close enough to damage capital ships.
Meanwhile, Kurt Tank designed the Ta 152 as a high-altitude interceptor. Its extended wings and super-charged engine were deigned to still climb well above 30,000 feet where WALLIED heavy bombers cruised on their way to bombarding targets within Germany.
I know that, but F8F-2 is introduced much later than Ta-152H so maybe the high altitude capability has been improved
 

Mark Nankivil

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Grumman F8F Bearcat was designed to be a fleet defense interceptor. Try to think of Bearcat as a pre-shrunk Hellcat, built around the same engine, but optimized for rapid climb. The USN hoped that Bearcats could intercept kamakazi well befor ethey got close enough to damage capital ships.
Meanwhile, Kurt Tank designed the Ta 152 as a high-altitude interceptor. Its extended wings and super-charged engine were deigned to still climb well above 30,000 feet where WALLIED heavy bombers cruised on their way to bombarding targets within Germany.
I know that, but F8F-2 is introduced much later than Ta-152H so maybe the high altitude capability has been improved
Two different missions/scenarios. Protection of the fleet/carriers which is a relatively small footprint whereas the Ta152H needed to cover more ground or at least range further to intercept the bomber stream before it got to the Fatherland or the target. Size is always an issue on the carrier as well which drove some of the design requirements. Bearcat was designed to address targets at medium/low altitudes, the Ta-152H at higher altitudes where the bobmers were to be found. If they had flown against each other, the only time they likely would have met was when the Bearcat was intercepting it taking off or landing, much like Mustangs did with Me262s. As for the Ki-84, F6Fs held their own against them over Japan in the final months of the war but that can also be due to the experience of the Hellcat pilots and their superior numbers. The Ki-84 is my favorite of the late war Japanese fighters with the Ki-100 a close second..

Enjoy the Day! Mark
 

Ronny

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Regarding top speed:
At 35,000 ft:

P-51H reached 482.5 mph = 776 km/h
F4U-5 reached 395 knots = 731 km/h
Ta-152H reached 715 km/h
F8F-2 reached 360 knots = 666 km/h
At 25,000 ft:
P-51H reached 487.5 mph = 784 km/h
F4U-5 reached 407 knots = 753 km/h
Ta-152H reached 700 km/h
F8F-2 reached 383 knots = 709 km/h
At 15,000 ft:
P-51H reached 465 mph = 748 km/h
F4U-5 reached 390 knots = 722 km/h
Ta-152H reached 655 km/h
F8F-2 reached 373 knots = 690 km/h
At 5,000 ft:
P-51H reached 445 mph = 716 km/h
F4U-5 reached 364 knots = 674 km/h
Ta-152H reached 607 km/h
F8F-2 reached 353 knots = 653 km/h
Apparently, Ta-152H is nothing specially unless at extremely high altitude, and P-51H is so extremely fast, it even faster than F8F-2 and F4U-5 at low altitude
F8F-2 chart
F8F-2 chart.jpg

P-51H charts
P-51H speed HG.jpg

Ta-152 charts
Ta-152 chart.jpg

F4U-5 chart
F4U-5 chart.jpg
 

HoHun

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Hi Ronny,

Regarding top speed:
At 25,000 ft:
P-51H reached 487.5 mph = 784 km/h
F4U-5 reached 407 knots = 753 km/h
Ta-152H reached 700 km/h
F8F-2 reached 383 knots = 709 km/h

It's worth noting that the P-51H when tested at Wright Field in 1946 only achieved a top speed of (if my conversion is correct) 726 km/h at its high gear full throttle height of 6460 m, using 90" Hg @ 3000 rpm (on a V-1650-9 running full war emergency boost without requiring water injection):


I haven't quite figured out the V-1650-9's history and timeline yet to understand why they would use special high octane fuel for testing when the aircraft was actually supposed to use water injection, though I noticed Calum Douglas' book does have an interesting graph showing the engine's rather complicated family history :)

On a related note, the F8F-2 manuals I have seen indicate that the water injection system was not yet installed at the (fairly late) date the manuals were issued, and I'm not certain they were ever retro-fitted.

Regards,

Henning (HoHun)
 

Ronny

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Hi Ronny,

Regarding top speed:
At 25,000 ft:
P-51H reached 487.5 mph = 784 km/h
F4U-5 reached 407 knots = 753 km/h
Ta-152H reached 700 km/h
F8F-2 reached 383 knots = 709 km/h

It's worth noting that the P-51H when tested at Wright Field in 1946 only achieved a top speed of (if my conversion is correct) 726 km/h at its high gear full throttle height of 6460 m, using 90" Hg @ 3000 rpm (on a V-1650-9 running full war emergency boost without requiring water injection):


I haven't quite figured out the V-1650-9's history and timeline yet to understand why they would use special high octane fuel for testing when the aircraft was actually supposed to use water injection, though I noticed Calum Douglas' book does have an interesting graph showing the engine's rather complicated family history :)

On a related note, the F8F-2 manuals I have seen indicate that the water injection system was not yet installed at the (fairly late) date the manuals were issued, and I'm not certain they were ever retro-fitted.

Regards,

Henning (HoHun)
That because the P-51H in that test carry bomb rack and rockets rack, which slow it down and the aircraft also heavier than other test since it carry full fuel
Capture.JPG

In NA-117 test, gross weight 7302lb, the top speed is 481mph
p-51h-na117.jpg


In NA-126 test, Report No. NA-8284, gross weight 8000lb the top speed is 491mph.
p-51h-altperf-91444.jpg
 

HoHun

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Hi Ronny

That because the P-51H in that test carry bomb rack and rockets rack, which slow it down and the aircraft also heavier than other test since it carry full fuel

From my experience in analysing WW2 aircraft performance, empty bomb racks and rocket launcher stubs don't make enough of a difference in total drag to explain the performance difference. Weight also hasn't much of an influence on top speed at full throttle height since that's a situation dominated by parasite drag.

I don't believe the graph you're showing is actual tested performance, as it's attributed to report NA-8284, which in the revision NA-8284-A clearly states is based on calculations (with some flight test results thrown in, admittedly :):


"Revised performance calculations for the subject airplane have been prepared on the basis of wind tunnel data, estimated engine performance, and correlations with the results of flight tests. These calculations were necessary to provide complete performance data for airplane equipped with an engine incorporating a carburetor for fuel metering instead of the speed density pump originally anticipated in preparing report NA-8284 dates September 25, 1944. This report presents the results of the revised calculations together with a discussion of the data and methods used."

This test ...


... notes that the P-51H achieved 724 km/h at 9370 m (with bomb racks, but no rocket stubs) using only dry war emergency power (67" Hg @ 3000 rpm):

"High speed and climb performance were good and results obtained compare very closely to the manufacturer’s guarantee."

If the full 90" Hg had been available (which due to technical difficulties weren't), the tested P-51H would indeed have been markedly faster, but only at altitudes below the full throttle height for 67" Hg. Above, it was limited by the capability of the supercharger to generate boost pressure, and while that would have been slightly improved by the charge cooling effect of the injected water-alcohol mixture, that effect would have been quite small. (A British report expected a 4% power increase from MW50 on German engines above full throttle height, and that would translated into something like a 1% speed increase.)

Regards,

Henning (HoHun)
 

Ronny

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Hi Ronny
That because the P-51H in that test carry bomb rack and rockets rack, which slow it down and the aircraft also heavier than other test since it carry full fuel
From my experience in analysing WW2 aircraft performance, empty bomb racks and rocket launcher stubs don't make enough of a difference in total drag to explain the performance difference. Weight also hasn't much of an influence on top speed at full throttle height since that's a situation dominated by parasite drag.
The rack will reduce top speed by around 12 mph or around 19 km/h ,as shown on P-51B test. P-51H fly faster and overall a less draggy aircraft, so the effect of the rack on overall speed of the aircraft would be greater compared to P-51B
and even though weight is no longer the dominate influence at high speed, i doubt that it wouldn't make a few percentage different
P-51B.JPG


I don't believe the graph you're showing is actual tested performance, as it's attributed to report NA-8284, which in the revision NA-8284-A clearly states is based on calculations (with some flight test results thrown in, admittedly :):


"Revised performance calculations for the subject airplane have been prepared on the basis of wind tunnel data, estimated engine performance, and correlations with the results of flight tests. These calculations were necessary to provide complete performance data for airplane equipped with an engine incorporating a carburetor for fuel metering instead of the speed density pump originally anticipated in preparing report NA-8284 dates September 25, 1944. This report presents the results of the revised calculations together with a discussion of the data and methods used."
Well, while they certainly didn't fly all point in the envelope to get that chart, they certainly did the flight test to draw the chart, whether the flight test included the top speed test is up to debate


This test ...


... notes that the P-51H achieved 724 km/h at 9370 m (with bomb racks, but no rocket stubs) using only dry war emergency power (67" Hg @ 3000 rpm):

"High speed and climb performance were good and results obtained compare very closely to the manufacturer’s guarantee."

If the full 90" Hg had been available (which due to technical difficulties weren't), the tested P-51H would indeed have been markedly faster, but only at altitudes below the full throttle height for 67" Hg. Above, it was limited by the capability of the supercharger to generate boost pressure, and while that would have been slightly improved by the charge cooling effect of the injected water-alcohol mixture, that effect would have been quite small. (A British report expected a 4% power increase from MW50 on German engines above full throttle height, and that would translated into something like a 1% speed increase.)

Regards,

Henning (HoHun)
In that test,
the flight test crew was unable to obtain preliminary performance at the war emergency rating using water injection (90 “Hg and 3000 RPM) due to the engine surge and general malfunctioning of the water injection system and Simmons manifold pressure regulator
There is quite a big different in speed between 67" Hg and 90" Hg
2222.JPG
 
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HoHun

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Hi Ronny,

The rack will reduce top speed by around 12 mph or around 19 km/h ,as shown on P-51B test. P-51H fly faster and overall a less draggy aircraft, so the effect of the rack on overall speed of the aircraft would be greater compared to P-51B
and even though weight is no longer the dominate influence at high speed, i doubt that it wouldn't make a few percentage different

Thanks for the data points! The P-51B with the razorback actually is cleaner than the P-51D too, so I'm not sure how the P-51H compares, even if it might be cleaner than the P-51D as well.

Well, while they certainly didn't fly all point in the envelope to get that chart, they certainly did the flight test to draw the chart, whether the flight test included the top speed test is up to debate

The top speed test is hard to replace as airframe and engine are subject to some non-linear influences up there. But you're right, they unfortunately were a bit vague on the nature of the tests.

In that test,
the flight test crew was unable to obtain preliminary performance at the war emergency rating using water injection (90 “Hg and 3000 RPM) due to the engine surge and general malfunctioning of the water injection system and Simmons manifold pressure regulator
There is quite a big different in speed between 67" Hg and 90" Hg

Yes, and that makes these graphs a bit suspect. To get from 460 mph to 482 mph (roughly reading the chart) at the same altitude, you need very roughly (482/460)^3 = 15% more power. At the same rpm and the same boost pressure, how is that extra power going to be generated?

One explanation might be that the graph was prepared for an increase in rpm figured in for war emergency power.

You can see the same kind of difference between the 46" Hg and the 67/70" Hg graphs as between the 67/70" Hg and the 80/90" Hg graphs. I'm pretty sure the 46" Hg graph is for a reduced rpm, for example 2700 rpm. By extrapolation, the 80/90" Hg would appear to be based on an engine speed increased beyond the 3000 rpm used with the 67"/70" Hg settings - maybe 3200 rpm, for example.

You can see how at the same rpm, the 67" Hg and the 90" Hg curves could be expected to coincede at altitude, as in this graph:


What do you think of this? It's a fresh thought I haven't cross-checked, so I might well be wrong even if it looks plausible at first sight :)

Regards,

Henning (HoHun)
 

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The Republic P-72 should have been quite the performer. The estimate was for a speed of 504 mph at 25,000 feet with a R-4360-19 engine producing 3,650 hp. Production models were supposed to use the P-47N wing however which had a slightly greater span and would decrease that top speed slightly.

Two USN aircraft worth mentioning are the Grumman F7F and the Boeing XF8B. The F7F might be cheating by using two engines however.
 

HoHun

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Hi again,

To get from 460 mph to 482 mph (roughly reading the chart) at the same altitude, you need very roughly (482/460)^3 = 15% more power. At the same rpm and the same boost pressure, how is that extra power going to be generated?

One explanation might be that the graph was prepared for an increase in rpm figured in for war emergency power.

OK, I just found this graph:


This indicates clearly that my hypothesis regarding War Emergency Power being attained at an engine speed greater than 3000 rpm is not correct.

You can see that the static power (red graph) at 30000 ft is ...

3000 rpm, 90" Hg, water injection: 1450 HP
3000 rpm, 80" Hg, water injection: 1450 HP
3000 rpm, 70" Hg, no water injection: 1220 HP
3000 rpm, 61" Hg, no water injection: 1220 HP

And at 13000 ft ...

3000 rpm, 90" Hg, water injection: 1880 HP
3000 rpm, 80" Hg, water injection: 1880 HP
3000 rpm, 70" Hg, no water injection: 1620 HP

So the assumption apparently is that the addition of water injection at unchanged boost pressure increases horse power by 230 HP in high supercharger gear, and by 260 HP in lower supercharger gear.

As this is a gain in the region of 16 - 19% of brake horse power at the respective altitudes, this seems to be far more than the 4% expected under the same condition by the British estimate I mentioned earlier.

What's more, the power curves in the booklet are not identical to the one used for the revised edition of the NAA report, which due to the substitution of the Bendix speed density pump with a carburetter have a reduced full throttle height.

Original curve with the Bendix speed density pump:


Revised curve with carburettor:


The report (referred to as NA-8284-A, I believe) states:

"These calculations were necessary to provide complete performance data for airplane equipped with an engine incorporating a carburetor for fuel metering instead of the speed density pump originally anticipated in preparing report NA-8284 dates September 25, 1944. "

This leads to the following conclusion:

- The coloured "booklet" figures were prepared on the basis of an estimate of engine power for the expected production configuration, which is shown in p-51h-booklet-pg10.jpg, which is basically identical to that in p-51-powercurve.jpg.
- Engine power had to be revised a bit towards lower altitudes due to the (expected) introduction of a carburettor, and that power curve is depicted in p-51h-na-8284-pg12.jpg.
- The revision of the power curve means that the coloured "booklet" performance figures are purely theoretical as they represent an interim state of planning that was invalidated by the course of engine development.
- The calculated performance resulting from the revision is depicted in this graph: http://www.wwiiaircraftperformance.org/mustang/p-51h-na-8284-pg5.jpg

I hope that helps to sort out the various and partially controdicting charts! :)

Regards,

Henning (HoHun)
 

Ronny

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Hi again,

To get from 460 mph to 482 mph (roughly reading the chart) at the same altitude, you need very roughly (482/460)^3 = 15% more power. At the same rpm and the same boost pressure, how is that extra power going to be generated?

One explanation might be that the graph was prepared for an increase in rpm figured in for war emergency power.

OK, I just found this graph:


This indicates clearly that my hypothesis regarding War Emergency Power being attained at an engine speed greater than 3000 rpm is not correct.

You can see that the static power (red graph) at 30000 ft is ...

3000 rpm, 90" Hg, water injection: 1450 HP
3000 rpm, 80" Hg, water injection: 1450 HP
3000 rpm, 70" Hg, no water injection: 1220 HP
3000 rpm, 61" Hg, no water injection: 1220 HP

And at 13000 ft ...

3000 rpm, 90" Hg, water injection: 1880 HP
3000 rpm, 80" Hg, water injection: 1880 HP
3000 rpm, 70" Hg, no water injection: 1620 HP

So the assumption apparently is that the addition of water injection at unchanged boost pressure increases horse power by 230 HP in high supercharger gear, and by 260 HP in lower supercharger gear.

As this is a gain in the region of 16 - 19% of brake horse power at the respective altitudes, this seems to be far more than the 4% expected under the same condition by the British estimate I mentioned earlier.

What's more, the power curves in the booklet are not identical to the one used for the revised edition of the NAA report, which due to the substitution of the Bendix speed density pump with a carburetter have a reduced full throttle height.

Original curve with the Bendix speed density pump:


Revised curve with carburettor:


The report (referred to as NA-8284-A, I believe) states:

"These calculations were necessary to provide complete performance data for airplane equipped with an engine incorporating a carburetor for fuel metering instead of the speed density pump originally anticipated in preparing report NA-8284 dates September 25, 1944. "

This leads to the following conclusion:

- The coloured "booklet" figures were prepared on the basis of an estimate of engine power for the expected production configuration, which is shown in p-51h-booklet-pg10.jpg, which is basically identical to that in p-51-powercurve.jpg.
- Engine power had to be revised a bit towards lower altitudes due to the (expected) introduction of a carburettor, and that power curve is depicted in p-51h-na-8284-pg12.jpg.
- The revision of the power curve means that the coloured "booklet" performance figures are purely theoretical as they represent an interim state of planning that was invalidated by the course of engine development.
- The calculated performance resulting from the revision is depicted in this graph: http://www.wwiiaircraftperformance.org/mustang/p-51h-na-8284-pg5.jpg

I hope that helps to sort out the various and partially controdicting charts! :)

Regards,

Henning (HoHun)
I think i found where the 495 mph top speed came from
Capture.JPG
 
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HoHun

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Hi Ronny,

I think i found where the 495 mph top speed came from
View attachment 667900

Good find! :)

The second XP-51G was shipped to the United Kingdom in February 1945. This plane was also named Mustang V, and bore the RAF serial number FR410. It is widely reported to have achieved a speed of 495 mph during tests at the A&AEE at Boscombe Down in February 1945, although NAA claimed only 472 mph for the other G at the same altitude.

Boscombe Down tests normally are quite thorough, so that's promising. The test of FR.410 doesn't seem to be on Mike William's site though, and if Joe Bougher writes "widely reported", that probably is a phrase he chose because he wasn't able to verify the claim.

Mike has one test on his site that is relevant to the P-51H, though it's for a Mustang III airframe with a RM 14SM Merlin 100 engine:


Note that the full throttle heights are lower than for the projected data even in the revised report.

This matches this test:

http://www.wwiiaircraftperformance.org/mustang/p-51h-64182.html

C. Critical Altitude.

The critical altitudes for normal rated power climb (46" Hg., MP and 2700 rpm) are 17,400 ft. for low blower and 30,700 ft. for high blower. The critical altitudes for war emergency power climb (90" Hg., H2O and 3000 rpm) are 16,000 ft. for high blower and by extrapolation, approximately 2200 ft. for low blower.

According to my estimate, the static full throttle heights (without ram effect) would be as follows:

- High Gear: 19,500 ft, Low Gear: 4,000 ft ... original draft, Bendix pressure pump
- High Gear: 17,000 ft, Low Gear: 3,500 ft ... revised draft, carburetor
- High Gear: 14,900 ft, Low Gear: 900 ft ... actual testing by USAAF (I calculated these static values from the climb speed values given in the report)

The British test (with ram effect at climb speed) is not directly comparable as the values are for +25 lbs/sqin boost (= 80" Hg) :

- High Gear: 13,000 ft, Low Gear: 1,600 ft

High gear full throttle height is even lower than in the USAAF tests, so maybe that engine was not representative for production status either. Still some things left to be figured out! ;-)

Regards,

Henning (HoHun)
 

HoHun

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Hi agin,


I just found this article explaining the pump and its history:


The article is a bit confusing, as it states, on one hand:
Successfully tested on a Merlin 66, the speed-density fuel metering system then became standard equipment on all following engine models.

But also on the other hand:

A decision was made to use the Speed Density equipped V-1650-11 in the P-51L airplane, and it was necessary to provide Water Injection (ADI) for high power detonation control. The second-generation models incorporating this feature were the SD-400C2 and SD-400D25. A new "Water Regulator" was developed and integrated with the Speed Density Fuel Control.

Engineering and development delayed the production of an initial batch of 70 SD-400C2 units intended for the first batch of 50 P-51L airplanes that was scheduled for completion by September 1945. In June 1945, the decision was made to defer production of this first batch of production aircraft, engines and fuel controls until January 1946.

Development of the SD-400C2 fuel control was not completed prior to the end of hostilities in August 1945, which resulted in the immediate termination of production contracts for the V-1650-11 and the P-51L. Development work did continue on the V-1650-11 until October 1945. Following the third unsuccessful attempt to run a 50-hour preliminary flight-rating test, the program was terminated.

So I suppose this does not imply that the V-1650-9 wasn't planned for, at least, temporarily, a speed density unit. Also "the program was terminated" seems a bit ambiguous as it's not clear if that's the fuel control development program for the V-1650 in general, or the V-1650-11 in particular (or maybe the P-51L in particular).

Regards,

Henning (HoHun)
 
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