Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: juzz on November 30, 2000, 10:36:00 AM
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F4U-4
I look at this (http://www.history.navy.mil/branches/hist-ac/f4u-4.pdf) .pdf document and really wonder about the climb and speed curves in it(Short story: they show 452mph at 20500ft and 4770fpm initial climbrate).
My problem is that the engine power at "maximum" isn't given. (http://bbs.hitechcreations.com/smf/Smileys/default/frown.gif)
In one book I have seen the top speed of the F4U-4 listed as 445mph at 26,269ft, and WEP output for the R-2800-18W engine as 2485HP.
The Chance Vought website (http://www.vought.com/y40-50/prod_40/ww2_f4u/f4u-4/spec_f4u-4/spec_f4u-4.html) shows the F4U-4 top speed as 446mph(at sea level oops!), and initial climbrate as 3870fpm. This site claims 2450HP for the R-2800-18W with WEP.
I have also read here (http://www.csd.uwo.ca/~pettypi/elevon/baugher_other/f4u.html) that later production F4U-4 had the R-2800-42W engine with 2760HP at WEP. Hmmmm.
My questions are:
1. What's up with the "maximum" engine power performance of the F4U-4 in the .pdf?! I've heard before it was with special fuel - did it have like 3000HP or something?!
2. What was different about the -18W and -42W engines? Anyone know why the latter is more powerful?
Ki-84-I
I read that an "early production" Ki-84-I reaches 392mph at 6100m. According to the article, early production Hayates had the Homare 11 and 12 engines, and late production had the model 21(same as N1K2-J) and 23 engines.
Their output is as follows:
Homare 11: 1820HP at takeoff, 1650HP at 2000m and 1440HP at 5700m.
Homare 12: 1825HP at takeoff, 1670HP at 2400m and 1500HP at 6600m.
Homare 21: 1990HP at takeoff, 1850HP at 1750m and 1625HP at 6100m.
Homare 23: 2000HP at takeoff, 1670HP at 1440m and 1570HP at 6850m.
A postwar US test of a restored, "late production" Ki-84-I revealed a top speed of 427mph at 20,000ft.
My questions are:
1. How fast should a late production wartime Hayate with the Homare 21 go - anyone got numbers?
2. Anyone got any climb data? I think 5.9 minutes to 5000m is a bit slow for the Ki-84-I. (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
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Juzz, the reason that the pdf flight test data from the Navy site being too high is easy (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
Look under the Fuel & Oil section on page 5.
Fuel Grade......115/145
Sooooped up fuel (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
But thats also the answer to your Ki-84 question.
The 392mph number is with Wartime Japanese 87 octane fuel (probably with pine oil additives), and the 427mph is standard US 100 octane fuel.
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Vermillion
**MOL**, Men of Leisure
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Juzz,
I can't resist answering F4U questions so bare with me rambling on. The hardest thing about any of this warbird stuff is finding the source information. Navy and Marine aviation is not nearly as well documented as Air Force(Army Air Force) was in WW2.
1. The first PDF you have listed is accurate however misleading. All of the test are valid except the test was done with 115/145 fuel. In other words 115 octane fuel as compared to standard 100 octane aviation gas.
2. The PDF is very specific about the PW-R2800-18W engine. I believe the HP stated in the PDF doc. is accurate for military power at 2100HP. The Combat power rating for the F4U-4 is 2380HP from "America's Hundred Thousand". Most of the increase in performance in the F4U-4 was from the addition of a 4 blade prop, a cleaner drag condition and higher manifold pressure. The actual increase in HP was only from 2250HP in the -1A/D to 2380HP in the -4.
3. The change in engines from -18W to -42W did have a performance increase but what that is we will never know because of lack of documentation. This is from "Warbird History F4U Corsair". "F4U-4B's BuNo 97486 and later constructed after August 16,1946, were built with the R-2800-42W engine. Although similar to the R-280018W, the -42W developed higher performance ratings with 115/145 octane fuel". Which tells me 2 things.
A. The test in the PDF was an early model -4 with 6 50cals and a -18W engine, and is not an overestimation of the A/C performance.
B. The 115 octane fuel was not uncommon for fighters in 1944/45 if P&W was designing engines to run with it.
In any case all listed performance figures I have seen list the top speed at approx. 450MPH. With an initial climb of 4770fpm bring on the FW-190D9
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The F2G didnt even climb at 4770fpm, if those numbers are for an F4U4 then they are very very innacurate.
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OK, so what is the "maximum" output of the -18W using 115/145 octane fuel? There is NO WAY the -4 could achieve such performance with even 2485HP. let alone 2380HP. C'mon, you really think that with not even 300HP more, climbrate could go up over 1500fpm?!
The speed and climb curves show that the first supercharger gear isn't even engaged, indicating they were running VERY high boost during those tests.
I'm very much inclined to believe the Vought figure of 445mph/3870fpm for a WW2 service -4 with about 2400HP at WEP. But I wanted to know exactly how they got 452mph/4770fpm.
Vermillion, you missed the point. Early model Hayate does 392mph with either 1440HP or 1500HP. Late model does ???mph with 1625HP.
We know a well-maintained example did 427mph post-war, with ????HP.
So a wartime late model Hayate with the Homare 21 is somewhere between 392mph and 427mph. Does anyone have any idea of exactly where though?
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Juzz,
Use the cube root of the power ratios
(1625/1440)^1/3 * 392 = 408 mph
(1625/1500)^1/3 * 392 = 403 mph
The higher grade fuel in the F4u-4 test would allow for higher manifold pressures to be used in combat power. With 100 grade fuel, combat manifold pressure was very near 59" Hg. With 115 grade fuel, that could be increased by 15% to about 68". From P-47 data, 64" produced 2600 hp and 72" produced 2800 hp.
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hmm in this PDF document they mention:
1700HP >> 2910ft/min (normal)
??HP >> 4770ft/min (maximum)
the difference is 1860ft/min = 9.5m/s
To lift 5500kg with 9.5m/s your propeller must produce:
5500*9.81*9.5=511.5KW or ~700HP
With an prop efficiency of 0.85 (very good) your engine must do: 820HP
1700+820=2520HP
So Maximum engine power must have been at least 2520HP.
btw, an Interavia message reported for an F4U -4 with 2330hp takeoff power and 12500lb 17m/s or 3340 ft/min initial climbrate (maybe without wep)
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Hi
Niklas, I have the same inital climb rate for the F4U4 of 3340 fpm, And F2G initial climb of 4400fpm, this data from "F4U Corsair In Detail and Scale" by Bert Kinzey
thanks GRUNHERZ
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Gents,
That PDF doc as well as others is a source document from the department of the Navy and it is specific enough to tell you the fuel grade used in the test. Which BTW is much more specific than some Luftwaffe docs I have seen in another post which has some of you dancing in the streets. As for the HP available it used brake HP instead of rated HP. The difference being that break HP is what is avaialbe at the end of the drive shaft/Prop, adjusting for lost power. 2100HP is the figure given.
As far as 4770fpm or 3870fpm being out of line with F4U performance. Well as a matter of fact it falls quite nicely in with the heavier P-47M or N and later F4U-5. Even the rated initial climb on the 21,500lb F7F-3 Tigercat is 4,500FPM.
Also the performance gain in the F4U-4 was only partially due to an increase in power. It was mostly due to a cleaner drag condition and blade prop. The HP was only a piece if the performance gain as seen in this test of a F4U-1A(pure fighter not modeled in AH) F4U-1 modified to F4U-4 drag condition with higher manifold pressure and a P-51B. http://members.home.net/markw4/index2.html (http://members.home.net/markw4/index2.html)
Notice the increase in performance without a change in HP.
BTW where does Bert Kinsey quote his source from??
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Niklas,
Your probably right about the 2,500Hp for the 4,770fpm. 2,380HP is the listed Combat Hp for the R2800-18W.
At 2380HP climb is
Combat=3870FPM
Military=3400FPM
Normal=Not listed
Does anyone have a F4U-4 pilots manual?
Pilots manuals typically list normal power and military power climb as well as stall speeds for various conditions.
Niklas do you have a copy of the FW190D9 pilots manual? What is the level stall speed?
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As a result of this discussion, I would expect a WW2 era F4U-4 as might be added to AH to fly at 445mph/3870fpm and not at the souped-up 115 octane level.
Btw F4UDOA; those LW docs clearly indicate C3 or B4 fuels and MW 50 additive where used.
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Juzz,
Your the first person to mention that.
What is the octane rating on these fuels?
Also how common was MW50? I thought the Germans had major fuel problems 1944/45.
BTW, I have no problem with the 3870fpm numbers being used for the F4U-4. It is still a beast and will be the fastest bird in the bunch below 25K even with the FW190D9 and P-47M. The conservative speed chart in AHT shows the F4U-4 hitting close to 440mph at around 18K. Also the test was done at 12,500lbs climb to 25K in under 8min. Consider the climb of this bird at 50% fuel or approx 11,000lbs. Probably back up to around 4400fpm.
Although I don't think you will see any perk plane below 25K. They are all alt monkey's and far to valuable to be furballing at 10K. You will probably have "perk" wars at 25k and up and the rest of the plane set below 20k.
[This message has been edited by F4UDOA (edited 12-01-2000).]
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C-3 was 96 octane, sometimes stated as rated at 100 octane.
B-4 was 87 octane.
A-3 was 80 octane, sometimes stated as rated at 85 octane.
Sources:
Luftwaffe Fuel types (http://www.warbirdsresourcegroup.org/LRG/fuels.html)
Squadron Signal Pub. Bf-109 in action, Pt 2.
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Flakbait
Delta 6's Flight School (http://www.worldaccessnet.com/~delta6)
Whattaya mean I can't kill em? Why the hell not?!
(http://www.worldaccessnet.com/~delta6/htbin/behappy.jpg)
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Would the Ki-84-I be a perk plane? It's top speed is relatively slow, but how does it go at lower altitudes?
Perk planes at 25k+ only? I'll be laughing when the first Fw 190D-9 gets run down by a Spitfire F.IX at 30k. (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
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I can't remember a stall speed number for a 190D9, and i have no pilot manual.
But usually you'll find in german pilot manuals only landing and takeoff speeds.
mw50 was standard in 190D. A 190D9 pilot confirmed this to me.
When you look at the rated altitude of a 190D9 then it should be obvious that a 190D9 with a jumo213A is not the best high altitude fighter.
When you increase manifold pressure, you gain ususually also more engine power. And 65' compared to 60' is a big difference. Though they write for both engines 2250hp, i'm convinced that the engine of the F4u with 65' produced more power.
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Swipe!
(http://members.home.net/markw4/P51vsF4U9.jpg)
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btw, there exists a specific engine chart for the R-2800-8 engine which says:
takeoff: 54´ >> 2000 hp
wep: 57.5´ >> 2250 hp
now, when 2.5´ difference in manifold pressure gives you 250hp more power, then it´s not difficult to estimate where you are with another 2.5´ (60´) or even another 7.5´ (65´) manifold pressure.
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Niklas,
Actually it depends. I have that chart in the F4U-1 pilots manual. Notice the power varies with alt. and manifold pressure.
Notice when the F4U hits 60" of manifold pressure it is at 20,000ft. So that is also the alt where the modified F4U hit 65". But the changes in horsepower at that alt are much less because the lower air density reduces power output.
Take off 54" 2000HP Sea level
War emergency 57.5" 2250HP SL
" " 59.0" 2135HP 15,000FT
" " 59.5" 1975HP 20,000FT
These numbers are from the pilots manual. It is possible that the numbers are more conservative that was actual use of the A/C. But it still shows the higher the alt. the manifold pressure is checked the less effect it has on actual power output.
Also at the bottom of the page in which this data is printed, these numbers are not from flight test. The P-51B vrs F4U chart is from an actual flight test.
Later
F4UDOA