DarrenW
Staff Sergeant
The P-47's turbo system was far more efficient because unlike the supercharged F4U and F6F it continuously maintained the higher boost pressures from sea level up to critical altitude.
F4U vs F6F & Top-Speed: Let's Settle This
- Thread starter Zipper730
- Start date
The P-47's turbo system was far more efficient because unlike the supercharged F4U and F6F it continuously maintained the higher boost pressures from sea level up to critical altitude.
- Thread starter
- #82
According to this report, there was a cover over the redesigned tail-wheel. As for the effects on performance, it does seem that there is a substantial performance effect by removing the tail-hook and fairing it over, removing the catapult hooks, and things of that sort. The airplane's paint finish was about normal for a combat aircraft, and the radio, if I recall correctly, remained installed. The report that you have for the drag improvement for A/C #02334 seemed to indicate the removal of the radio antenna, though the shell-ejector openings were not faired over.
That said, looking at your numbers, I see an increase of speed of 13-15.7 mph. I'm not sure how many of these mods were actually implemented on combat aircraft for land-based ops. That said, you'd get around 408-411 mph top speed. That seems to jibe with your figures of 407 mph @ 24800'.
BTW: What is a "free air therm. and additional channel"?
Yeah, I'd imagine! If my calculations are right...
... the blades are supersonic at the tips at peak altitude. I could imagine a diameter reduction would be of benefit as you're basically beating the air into bloody submission.
Wait, I thought lean mixture meant a low fuel/air ratio? Is that air/fuel?
I think you're mixing up horsepower with boost pressure. Manifold pressure stays the same, but a throttling loss is incurred at lower altitudes with superchargers.
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You thought right. Your understanding appears a little confused. Theoretical peak power occurs at the ideal, or stoichiometric fuel/air ratio, which is at or near lean mixture peak cylinder temperature. So best power occurs at lean mixture settings. The problem is that most engines can't sustain those temperatures for long without overheating and detonating.
Rich mixtures don't GIVE you more power, they help you SUSTAIN more power by cooling the cylinder temps and holding off detonation. Now in a speed test run, you're getting the optimum engine cooling airflow so you've got a little "thermal cushion" in case you want to venture a little on the lean side for a little more power. It's a risky business, however, only to be engaged in with thorough knowledge and good instrumentation.
Some highly efficient modern GA aircraft routinely operate on the lean side of peak cylinder temp when in max range cruise, but they have much lower "power density" and more efficient cooling than a WWII R2800.
Cheers,
Wes
- Thread starter
- #84
I thought the rich mix was basically right up on the ideal mix for peak power.
I'd have figured excess fuel would just smother things if you didn't have enough air...
FLYBOYJ
"THE GREAT GAZOO"
DarrenW
Staff Sergeant
Yeah I could have worded that better. I should have said that the turbocharger allowed for a constant realization of boost pressures which resulted in constant horsepower, as there were no shift points along the way to detract from maximum horsepower being attained from S/L to critical altitude.
Oh no, he just might do that.
FLYBOYJ
"THE GREAT GAZOO"
- Thread starter
- #89
It was a misunderstanding. Early on, I thought rich meant too much, lean meant too little for optimal and stoichiometric was right on the middle; then I remember seeing a number cited for rich a long time ago (and that's probably the problem), and I think it was 1/6 (fuel/air) which seems very little (might sound stupid but I figured the numbers would be like 1/3 based on the fact that 65% of the air in the combustion chamber was unused), so I guessed the rich mixture was the ideal for power, and lean was best for fuel economy: I'm not sure where I got these ideas from.
Regardless, I stand corrected.
BTW: The ratio for gasoline is 1/14.7 fuel/air. No idea what jet-fuel would be, but if I were to make a guess, I would figure diesel would be closest.
When will you stop guessing? If you think it is important read up on it and remember it?
- Thread starter
- #91
According to this site, the ratio is about 15.06%
THINK about this for a second. Would it make sense to have a cockpit mixture control that in its normal range of operation was capable of flooding the engine or leaning it to failure in flight? Would you want to fly that beast? So does it make sense to worry that selecting rich mixture might "smother" the engine?
Now in modern simple airplanes at high altitude, full rich mixture can make an engine run rough and mighty thirsty, but that's because the mixture isn't altitude compensated, and most simple GA airplanes don't cover such a wide range of altitudes. When you see a mixture control with "AUTO" settings for "RICH" and "LEAN", that implies it's altitude compensated, and will adjust the RICH -> LEAN range for the ambient pressure altitude.
Cheers,
Wes
- Thread starter
- #93
In old teacher voice: And we now get to the subject of improper wording j/k
I kind of get what you're saying, the ability to get the most horsepower for MAP across the entirety of the performance envelope.
I should have used a different word than smother, that does sound similar to flooding the carburetor. I meant something more like it'd reduces combustion to a degree.
It's not so much an issue of flooding the carburetor as it is of making the mixture to the cylinders too rich to support combustion. ("Yes, Virginia, it is actually possible to do that"). Clearly you've never adjusted the mixture screw on a lawn mower engine.
And yes, it does reduce combustion efficiency to a degree from optimum stoichiometric mixture. That's the "insurance premium" you pay to keep detonation from destroying your engine. The extra fuel cools things down a bit and some of it gets exhausted unburned, contributing to the light show at the exhaust stacks.
Cheers,
Wes
Shortround6
Lieutenant General
Corsair engine flight chart.
copied from Zeno's Warbird Videos - World War II Pilot Training videos & air combat documentaries playing for free over the Internet
A lot of these military engines don't seem to act like regular car, motorcycle or lawn mower engines.
Please note the fuel flow figures (3rd column from the right) and the war emergency row.
They had a de-enrichment circuit in the carb that cut the fuel flow when the water injection was operating. It would quickly restore full fuel flow automatically when the water ran ran out. when running in auto rich these engines were far into the richer than stoichiometric ratio would call for area. The extra fuel was being used as a coolant to some extent and not only can you find videos/pictures of some of these planes trailing black smoke on take-off (or the famous puff of black smoke when opening the throttle that sometimes fooled opponents into thinking they had scored hits?) but there are stories of unburned fuel coming out the exhaust pipes.
But then regular car, motorcycle or lawn mower engines are NOT taking in air/fuel mixture than is several hundred degrees F. and under pressure.
Look again, the Corsair was using about 1/2 gallon a minute of gas as a coolant at military power.
copied from Zeno's Warbird Videos - World War II Pilot Training videos & air combat documentaries playing for free over the Internet
A lot of these military engines don't seem to act like regular car, motorcycle or lawn mower engines.
Please note the fuel flow figures (3rd column from the right) and the war emergency row.
They had a de-enrichment circuit in the carb that cut the fuel flow when the water injection was operating. It would quickly restore full fuel flow automatically when the water ran ran out. when running in auto rich these engines were far into the richer than stoichiometric ratio would call for area. The extra fuel was being used as a coolant to some extent and not only can you find videos/pictures of some of these planes trailing black smoke on take-off (or the famous puff of black smoke when opening the throttle that sometimes fooled opponents into thinking they had scored hits?) but there are stories of unburned fuel coming out the exhaust pipes.
But then regular car, motorcycle or lawn mower engines are NOT taking in air/fuel mixture than is several hundred degrees F. and under pressure.
Look again, the Corsair was using about 1/2 gallon a minute of gas as a coolant at military power.
Dawncaster
Airman 1st Class
- 110
- Dec 23, 2013
I'm Sorry, Please understand that there are many omissions to meet the 20k character limit and the lower the content, the worse the condition is. It was especially painful when the cited post was changed and the content had to be rewritten. In fact, it's dropped. Mayday! 
re-upload with red circle for wooden block, and new another shot.
This is early F4U-1's tail wheel section, the tail wheel of the dash-1 Corsair was exposed even after tail wheel door closed. early F4U-1's low tail wheel was not exposed much, but high tail wheel was exposed more.
The report pointed out that the position was farther with switching from low tail wheel to high tail wheel, because it was taller.
As a result, because the previous low tail wheel had been removed and the position of the new high tail wheel was farther, so the slot in that place became gap. of course, it creates drag or other problems. However, the report continues. Wrote 'But' and describe how solved it - with the wooden block, gap was closed and faired. so there is no need to worry about additional drag from gap.
In conclusion, the report describes its role, It seems to prevent the loss of the performance caused by installing a new tail wheel, instead of special extra performance. this is what I understand.
In fact, few early Birdcage F4U-1s had a fully retractable tail wheel unit. look at the slotless tailwheel door and the tiny size tail wheel.
and among the changes that have been made since F4U-1 BuNo.17930, there was a format that complements the rear of the exposed tail wheel to turn into a streamlined teardrop(I don't have the exact expression for it) shape
'The airplane was a late model production type incorporating all the latest changes, including the raised cabin installation.'
This is the first mentioned in changes list. If you read normally, you can see that the F4U-1 BuNo.17930 was being compared to Birdcage(low cabin) F4U-1.
Conversely, I want to ask a question. Why did you judge that it was comparing to the production model for that time? don't forget, the raised cabin F4U-1(F4U-1A) was already put into combat even in 1943.
Removing the folding mechanism and tail hook, after halves of the doors were bolted closed and the cove for the tail hook was skinned over. the aircraft was to average an increased top speed of 4 mph, saved weight was 80 lbs.
As above, Land-based configuration gives additional 4 mph actually for Corsair, there was no additional 6(or 8) mph.
And seems need some explanation for others also.
F4U-1 BuNo.17930's drag condition was corrected for standard but F4U-1 BuNo.02390 was not.
F4U-1 BuNo.02390 was one of the first batch(2153~2736) birdcage Corsair, It showed problem I mentioned in the previos post.
Let's see what that resulted.
Despite F4U-1 BuNo.02390's higher manifold pressure caused by the 25 drill waterjet, there was a loss of altitude performance, so it produces less horsepower than the F4U-1 BuNo.17930 at many altitudes. However, F4U-1 BuNo.02390 was faster than F4U-1 BuNo.17930 at all tested altitude, This seems shows that the drag condition of the F4U-1 BuNo.02390 was superior than navy standard F4U-1 BuNo.17930, The report noted that the F4U-1 BuNo.17930's drag condition was corrected to standard, but no similar content was found for F4U-1 BuNo.02390 in the report. It was expected to be similar to the land-based F4U-4's drag condition.
So, the report distinguished between F4U-1 BuNo.17930 and F4U-1 BuNo.02390 for speed comparison, but not for climb or other comparisons, It's presumed that the performance difference between the two F4U-1s was not meaningful except Vmax.
And there seems a difference between F4U-1 BuNo.02390's +8 mph drag reduction content and your uploaded photos and content.
These were not actually done with F4U-1 BuNo.02390, only taped wing fold joint was actually done in the flight test for it.
This is actually done in flight test for F4U-1 BuNo.02390's wing section.
This was also not actually done with F4U-1s, unlike the F6F-3/5, the tail wheel of the F4U-1s were exposed when flying except for the few F4U-1s I mentioned above, and the F4U-1s had to be actually tested for flight, making it impossible to achieve such drag reduction. since the F4U-1 BuNo.02390 was of the first batch Corsair, may be able to achieve a complete seal for wind tunnel test, If it had tiny tail wheel unit and slotless tail wheel door. However, flight testing requires taxiing and takeoff, so also impossible for F4U-1 BuNo.02390
Perfect sealing was seems possible because it was a Hellcat and also because it was a wind tunnel test. Well, at least, the Corsair model used in the wind tunnel test was seems the one of the first batch Birdcage F4U-1, considering the cabin's shape, it can be seen that it was early model even within Birdcage F4U-1s. so the tailwheel could be retracted completely in wind tunnel test. of course, as mentioned above, applying to the current topic is unpractical.
And It has already been revealed in the drag-speed chart in the last post that the removal of the tail hook and fair cut-out was only provides an additional performance of 0.6 mph. It's more clear from the drag coefficient and the additional performance obtained.
for example, remove catapult hook, it gives 2.4 mph with reduce 0.0030 drag cofficient. the drag coefficient of the arresting hook is 0.0005, which is one-sixth, so if remove it, can assume that can get an extra performance of 0.4 mph. However, the F4U-1 BuNo.02334 obtained 0.6 mph by just fair arresting hook cut-out. that may be the difference in drag, but the 0.0005 drag coefficient might not included creating a cutout on the smooth fuselage, In that case, 0.4 for hook removed and 0.2 mph for cut-out filled.
In my view, for estimated +8 mph, smooth and faired cowling would have had a substantial impact. because impact of the other drag reduction seems not so great.
To install the six guns, need to dig the leading edge of the smooth wing, drill six holes for muzzles, and make six slots for the shell ejector on the under surface. and It's drag cofficient was equivalent to catapult hook - 0.0030. so, can expect to lose 2.4 mph due to the additional drag gained by installing six guns(0.4 mph per gun). then, let's calculate the drag corresponding to 6 of the 12 slots for the shell ejector.
Thankfully, the report you linked to contains information about the extra drag caused by installing x 4 cannon barrels on leading edge. It showed that the F4U-1 with four cannons had a 1 mph speed loss compared to a smooth wing. and the based lift cofficient is unknown, but it also showed 1 mph per 0.0002 for F4U-1.
Referring to other report, it appears to be the drag coefficient obtained at close about 0.2 lift coefficient(just close, difference of 0.0001 occurred on the P-51). and the drag coefficients in the above report were averaged. then now let's look at the drag coefficient that the six gunports impose on the F4U-1. surprisingly, it's zero on average and increase the maximum lift cofficient. It's probably because of the guns that are installed completely inside the wing and gunports design with less gap unlike such as P-51B's. the difference in drag coefficient between 6 gunports and 4 cannon barrels was only about average 1 mph imposed for F4U-1 as above.
http://www.wwiiaircraftperformance.org/f4u/f4u-1d-acp.pdf
and it seems proved with actual performances at F4U-1C/D's ACP. because the Vmax of the F4U-1D and F4U-1C, which have the same drag coefficient except for the armament, differed by only 1 mph at Vmax.
Then now, 2.4 mph penalty entirely could be given to the F4U-1's shell ejector tapping.
Lastly, the Mustang was aerodynamically a much cleaner aircraft than the F4U-1 and It's wings were especially. but laminar flow airfoils are very susceptible to aerodynamic contamination, It seems possible to produce more sensitive results for equivalent drag sources that interfere with the flow of air, and the number of taped under surface slots was equal on both model - three per wing so there were no more taped slots for F4U-1.
Then let's compare it with the actually obtained values. comparing the performance reduction when installing the x4 cannon barrels uploaded above, can see that the Mustang was about 20% more affected than the F4U-1. and for six taped under surface slots, 3 mph for Mustang and up to about 2.4 mph for F4U-1, so the Mustang was 25% more affected. It seems reasonable.
As a result, 4 mph for F4U-1's land-based configuration and up to about 2.4 mph for shell ejector taping, If the shell ejector tapings were Navy standard for the F4U-1, can expect a loss of 2.4 mph for combat service for F4U-1 BuNo.17930 and ACP's official performances, which considered as standard drag condition by the Navy. Also, even though it was considered standard by the Navy, if you think its performance benefits Land-based configuration, can subtract an additional 4 mph. So with the adverse assumption for Navy's standard drag condition, can expect a performance loss is total 4(land-based configuration) + 2.4(shell ejector tapings) = 6.4 mph. this is at least the result obtained by combining the results actually obtained in flight test or calculated in report.
In my view, Navy standard not include land-based configuration of course. otherwise, the speed curves contained in F4U-1 Buno.17930's report and F4U-1's ACP cannot match up to about 16.5k ft(until the old propeller blades begin to lose efficiency), as actually obtained. however, assuming the worst is the least guaranteed performance, I considered both.
(I think Zipper 730's calculation is a good indication of why the early F4U-1's old 13'4" prop was losing efficiency at high altitude high speed range)
In conclusion, the F4U-1 BuNo.17930's 431 mph seems the best performance actually achievable with standard drag condition for standard production F4U-1 with 13'1" prop as Navy stated, even assuming the worst, can subtract up to 6.4 mph.
It was official performance cleard with operation restrictions for standard configuration, from actual flight test. If it was not the actual performance, it was specified in the ACP and It also specifies whether it was a production model or prototype.
Military documents used the ACP to cite the performance of the F4U-1 during the period of validity of the ACP. If the ACP is revised, the old version becomes invalid and the new ACP indicates what the old version was.
ACP, SAC or british aircraft cards, the advantage of 'official' performance is that seems more reliable than individual reports. their performances were corrected to military standards for service use and also cleared for operation restrictions. for example, the water injected F4U-1s in early 1944 use a neutral blower stage to use combat power at sea level in the multiple reports. however, lack of test data with raised cabin F4U-1 or does not meet required performance for operation restrictions, whichever, It seems insufficient to be cleared so could't included in ACP. In fact, unlike the F4U-1s mentioned above, the critical altitude of the cleared water injected neutal blower stage was sea level. I think it's because of the difference in operation restrictions. and estimated that more accurate and practical operation restrictions were applied over time as operating hours increased and more data obtained.
Also, in some cases, it's corrected to the condition that the fuel tank is permanently full. If the performance increase due to the consumption of fuel was included in the official performance, an aircraft that would rise with full tank and jettison it in the operating area would not have been able to achieve it. I am not sure if this applies to how many official performances. However, these examples make the official performance appear to be slight more certain.
Lastly, I don't understand about denying official performance just because didn't find a refered flight test report on the website, even more so if it's not certain that the website contains ALL the Corsair's flight test reports during World War II.
'Look at this F6F-5 BuNo.58310 graph, the auto-lean curve showed faster than the auto rich at altitude, the vmax was about 8 mph faster, and the critical altitude increased about 400 ft. The report noted a loss in output from auto-rich due to caburation problems. Due to the similarity of the engine, the Corsair may also consider the possibility of experiencing the similar problem.'
'Compare the power curves of the F4U-1 BuNo.17930 and F4U-1 BuNo.50030, can see that a similar result is happening, despite the slightly higher manifold pressure caused by the 25 drill water jet, it shows lower altitude performance. on the other hand, it seems that the F4U-1s in early 1944 basically used lean mixture, It was a time when F4U-1's water injection had just begun to be used for battle. In the comparison report with the Fw 190 mentioned above, the F4U-1 also used a lean mixture, but experienced overheating. I guess that more detailed and practical operation restrictions have been applied over combat time increasing, for official performance, it must run for 5 minutes and the cylinder temperature should not exceed 260, as a result, it seems showed the lowered official performance. The F4U-1 BuNo.50030's report contained effort for meet the operation restrictions, However, that is not found in the report of F4U-1 BuNo.17930, perhaps this made the difference.'
I was also not convinced that it was AUTO LEAN or AUTO RICH. But I assumed so. even if a higher manifold pressure was achieved, it was because the data were actually obtained that the use of AUTO RICH mixture for cooling lowered the altitude performance. another example is the F4U-1 BuNo.02390 I mentioned at the above of this post. and I think my explanation of the bold part in above paragraph was lacking in the previous post.
This is part of the report for F4U-1 BuNo.50030, the report states that performance has been reduced to standard conditions in accordance with standard flight test methods. In the report of F4U-1 BuNo.17930, no similar content can be found and I speculated that it was the main factor that made a difference in performance. also, since the F4U-1s in the report included over-boosting to the extent that they did not meet the requirements, I expected that the AUTO RICH mixture was likely used for cooling.
It's not just faulty pressurization, It would lead to a fatal malfunction, spark to jump the gab and burn out the distributor points, there were complete engine failure on some flights above 29,000 feet.
for Hellcat, If the F4U-1's improvements were properly feed back and applied to the F6F-3, the F6F-3 would be free in this problem, because the first air combat was in the fall of the 1943 for Hellcat.
Seems to be misunderstood or misread, if not, I don't know why are you trying to treat official performance for cleared with operation restrionction at standard configuration as a special modified configuration... Read above, I think your calculation missed the starting point. there was no substantial performance effect.
http://www.wwiiaircraftperformance.org/f4u/f4u-1-02334.pdf
In the F4U-1 BuNo.02334's report, standard F4U-1 expected 404 mph @ 25300' for military power and ACP showed 407 mph @ 24800' actually obtained for military power. this is a fairly close result and seems resonable for Navy's estimate.
Considering this, it's even more so.
I think there seems no 'special tail wheel faring' for F4U-1 BuNo.17930, In my view, It was steamlined wooden block and of course included in photo I uploaded. to be exact, I don't know what 'fairing' you mentioned.
re-upload with red circle for wooden block, and new another shot.
This is early F4U-1's tail wheel section, the tail wheel of the dash-1 Corsair was exposed even after tail wheel door closed. early F4U-1's low tail wheel was not exposed much, but high tail wheel was exposed more.
The report pointed out that the position was farther with switching from low tail wheel to high tail wheel, because it was taller.
As a result, because the previous low tail wheel had been removed and the position of the new high tail wheel was farther, so the slot in that place became gap. of course, it creates drag or other problems. However, the report continues. Wrote 'But' and describe how solved it - with the wooden block, gap was closed and faired. so there is no need to worry about additional drag from gap.
In conclusion, the report describes its role, It seems to prevent the loss of the performance caused by installing a new tail wheel, instead of special extra performance. this is what I understand.
In fact, few early Birdcage F4U-1s had a fully retractable tail wheel unit. look at the slotless tailwheel door and the tiny size tail wheel.
and among the changes that have been made since F4U-1 BuNo.17930, there was a format that complements the rear of the exposed tail wheel to turn into a streamlined teardrop(I don't have the exact expression for it) shape
Same as above. see what the report says exactly.
'The airplane was a late model production type incorporating all the latest changes, including the raised cabin installation.'
This is the first mentioned in changes list. If you read normally, you can see that the F4U-1 BuNo.17930 was being compared to Birdcage(low cabin) F4U-1.
Conversely, I want to ask a question. Why did you judge that it was comparing to the production model for that time? don't forget, the raised cabin F4U-1(F4U-1A) was already put into combat even in 1943.
According to Dana Bell, 965 FG-1s were delivered with land-based configuration, It's one of the factory built version.
Removing the folding mechanism and tail hook, after halves of the doors were bolted closed and the cove for the tail hook was skinned over. the aircraft was to average an increased top speed of 4 mph, saved weight was 80 lbs.
As above, Land-based configuration gives additional 4 mph actually for Corsair, there was no additional 6(or 8) mph.
And seems need some explanation for others also.
F4U-1 BuNo.17930's drag condition was corrected for standard but F4U-1 BuNo.02390 was not.
F4U-1 BuNo.02390 was one of the first batch(2153~2736) birdcage Corsair, It showed problem I mentioned in the previos post.
Let's see what that resulted.
Despite F4U-1 BuNo.02390's higher manifold pressure caused by the 25 drill waterjet, there was a loss of altitude performance, so it produces less horsepower than the F4U-1 BuNo.17930 at many altitudes. However, F4U-1 BuNo.02390 was faster than F4U-1 BuNo.17930 at all tested altitude, This seems shows that the drag condition of the F4U-1 BuNo.02390 was superior than navy standard F4U-1 BuNo.17930, The report noted that the F4U-1 BuNo.17930's drag condition was corrected to standard, but no similar content was found for F4U-1 BuNo.02390 in the report. It was expected to be similar to the land-based F4U-4's drag condition.
So, the report distinguished between F4U-1 BuNo.17930 and F4U-1 BuNo.02390 for speed comparison, but not for climb or other comparisons, It's presumed that the performance difference between the two F4U-1s was not meaningful except Vmax.
And there seems a difference between F4U-1 BuNo.02390's +8 mph drag reduction content and your uploaded photos and content.
These were not actually done with F4U-1 BuNo.02390, only taped wing fold joint was actually done in the flight test for it.
This is actually done in flight test for F4U-1 BuNo.02390's wing section.
This was also not actually done with F4U-1s, unlike the F6F-3/5, the tail wheel of the F4U-1s were exposed when flying except for the few F4U-1s I mentioned above, and the F4U-1s had to be actually tested for flight, making it impossible to achieve such drag reduction. since the F4U-1 BuNo.02390 was of the first batch Corsair, may be able to achieve a complete seal for wind tunnel test, If it had tiny tail wheel unit and slotless tail wheel door. However, flight testing requires taxiing and takeoff, so also impossible for F4U-1 BuNo.02390
Perfect sealing was seems possible because it was a Hellcat and also because it was a wind tunnel test. Well, at least, the Corsair model used in the wind tunnel test was seems the one of the first batch Birdcage F4U-1, considering the cabin's shape, it can be seen that it was early model even within Birdcage F4U-1s. so the tailwheel could be retracted completely in wind tunnel test. of course, as mentioned above, applying to the current topic is unpractical.
And It has already been revealed in the drag-speed chart in the last post that the removal of the tail hook and fair cut-out was only provides an additional performance of 0.6 mph. It's more clear from the drag coefficient and the additional performance obtained.
for example, remove catapult hook, it gives 2.4 mph with reduce 0.0030 drag cofficient. the drag coefficient of the arresting hook is 0.0005, which is one-sixth, so if remove it, can assume that can get an extra performance of 0.4 mph. However, the F4U-1 BuNo.02334 obtained 0.6 mph by just fair arresting hook cut-out. that may be the difference in drag, but the 0.0005 drag coefficient might not included creating a cutout on the smooth fuselage, In that case, 0.4 for hook removed and 0.2 mph for cut-out filled.
In my view, for estimated +8 mph, smooth and faired cowling would have had a substantial impact. because impact of the other drag reduction seems not so great.
Firstly, remember the end of my paragraph you quoted. I wrote 'for example, Corsair's drag cofficient for install all six guns was just equivalent to catapult hook, so even at the worst, the effect is only slight as below chart.'
To install the six guns, need to dig the leading edge of the smooth wing, drill six holes for muzzles, and make six slots for the shell ejector on the under surface. and It's drag cofficient was equivalent to catapult hook - 0.0030. so, can expect to lose 2.4 mph due to the additional drag gained by installing six guns(0.4 mph per gun). then, let's calculate the drag corresponding to 6 of the 12 slots for the shell ejector.
Thankfully, the report you linked to contains information about the extra drag caused by installing x 4 cannon barrels on leading edge. It showed that the F4U-1 with four cannons had a 1 mph speed loss compared to a smooth wing. and the based lift cofficient is unknown, but it also showed 1 mph per 0.0002 for F4U-1.
Referring to other report, it appears to be the drag coefficient obtained at close about 0.2 lift coefficient(just close, difference of 0.0001 occurred on the P-51). and the drag coefficients in the above report were averaged. then now let's look at the drag coefficient that the six gunports impose on the F4U-1. surprisingly, it's zero on average and increase the maximum lift cofficient. It's probably because of the guns that are installed completely inside the wing and gunports design with less gap unlike such as P-51B's. the difference in drag coefficient between 6 gunports and 4 cannon barrels was only about average 1 mph imposed for F4U-1 as above.
http://www.wwiiaircraftperformance.org/f4u/f4u-1d-acp.pdf
and it seems proved with actual performances at F4U-1C/D's ACP. because the Vmax of the F4U-1D and F4U-1C, which have the same drag coefficient except for the armament, differed by only 1 mph at Vmax.
Then now, 2.4 mph penalty entirely could be given to the F4U-1's shell ejector tapping.
Lastly, the Mustang was aerodynamically a much cleaner aircraft than the F4U-1 and It's wings were especially. but laminar flow airfoils are very susceptible to aerodynamic contamination, It seems possible to produce more sensitive results for equivalent drag sources that interfere with the flow of air, and the number of taped under surface slots was equal on both model - three per wing so there were no more taped slots for F4U-1.
Then let's compare it with the actually obtained values. comparing the performance reduction when installing the x4 cannon barrels uploaded above, can see that the Mustang was about 20% more affected than the F4U-1. and for six taped under surface slots, 3 mph for Mustang and up to about 2.4 mph for F4U-1, so the Mustang was 25% more affected. It seems reasonable.
As a result, 4 mph for F4U-1's land-based configuration and up to about 2.4 mph for shell ejector taping, If the shell ejector tapings were Navy standard for the F4U-1, can expect a loss of 2.4 mph for combat service for F4U-1 BuNo.17930 and ACP's official performances, which considered as standard drag condition by the Navy. Also, even though it was considered standard by the Navy, if you think its performance benefits Land-based configuration, can subtract an additional 4 mph. So with the adverse assumption for Navy's standard drag condition, can expect a performance loss is total 4(land-based configuration) + 2.4(shell ejector tapings) = 6.4 mph. this is at least the result obtained by combining the results actually obtained in flight test or calculated in report.
In my view, Navy standard not include land-based configuration of course. otherwise, the speed curves contained in F4U-1 Buno.17930's report and F4U-1's ACP cannot match up to about 16.5k ft(until the old propeller blades begin to lose efficiency), as actually obtained. however, assuming the worst is the least guaranteed performance, I considered both.
(I think Zipper 730's calculation is a good indication of why the early F4U-1's old 13'4" prop was losing efficiency at high altitude high speed range)
In conclusion, the F4U-1 BuNo.17930's 431 mph seems the best performance actually achievable with standard drag condition for standard production F4U-1 with 13'1" prop as Navy stated, even assuming the worst, can subtract up to 6.4 mph.
It was official performance cleard with operation restrictions for standard configuration, from actual flight test. If it was not the actual performance, it was specified in the ACP and It also specifies whether it was a production model or prototype.
Military documents used the ACP to cite the performance of the F4U-1 during the period of validity of the ACP. If the ACP is revised, the old version becomes invalid and the new ACP indicates what the old version was.
ACP, SAC or british aircraft cards, the advantage of 'official' performance is that seems more reliable than individual reports. their performances were corrected to military standards for service use and also cleared for operation restrictions. for example, the water injected F4U-1s in early 1944 use a neutral blower stage to use combat power at sea level in the multiple reports. however, lack of test data with raised cabin F4U-1 or does not meet required performance for operation restrictions, whichever, It seems insufficient to be cleared so could't included in ACP. In fact, unlike the F4U-1s mentioned above, the critical altitude of the cleared water injected neutal blower stage was sea level. I think it's because of the difference in operation restrictions. and estimated that more accurate and practical operation restrictions were applied over time as operating hours increased and more data obtained.
Also, in some cases, it's corrected to the condition that the fuel tank is permanently full. If the performance increase due to the consumption of fuel was included in the official performance, an aircraft that would rise with full tank and jettison it in the operating area would not have been able to achieve it. I am not sure if this applies to how many official performances. However, these examples make the official performance appear to be slight more certain.
Lastly, I don't understand about denying official performance just because didn't find a refered flight test report on the website, even more so if it's not certain that the website contains ALL the Corsair's flight test reports during World War II.
Page 51 of the ACP specifies that it's a 6443A-21 propeller with a diameter of 13'4". as described above, multiple ACPs for the same a/c do not exist until a new revision is issued.
Remember what I wrote in the previous post. what I just expected based on the data actually obtained.
'Look at this F6F-5 BuNo.58310 graph, the auto-lean curve showed faster than the auto rich at altitude, the vmax was about 8 mph faster, and the critical altitude increased about 400 ft. The report noted a loss in output from auto-rich due to caburation problems. Due to the similarity of the engine, the Corsair may also consider the possibility of experiencing the similar problem.'
'Compare the power curves of the F4U-1 BuNo.17930 and F4U-1 BuNo.50030, can see that a similar result is happening, despite the slightly higher manifold pressure caused by the 25 drill water jet, it shows lower altitude performance. on the other hand, it seems that the F4U-1s in early 1944 basically used lean mixture, It was a time when F4U-1's water injection had just begun to be used for battle. In the comparison report with the Fw 190 mentioned above, the F4U-1 also used a lean mixture, but experienced overheating. I guess that more detailed and practical operation restrictions have been applied over combat time increasing, for official performance, it must run for 5 minutes and the cylinder temperature should not exceed 260, as a result, it seems showed the lowered official performance. The F4U-1 BuNo.50030's report contained effort for meet the operation restrictions, However, that is not found in the report of F4U-1 BuNo.17930, perhaps this made the difference.'
I was also not convinced that it was AUTO LEAN or AUTO RICH. But I assumed so. even if a higher manifold pressure was achieved, it was because the data were actually obtained that the use of AUTO RICH mixture for cooling lowered the altitude performance. another example is the F4U-1 BuNo.02390 I mentioned at the above of this post. and I think my explanation of the bold part in above paragraph was lacking in the previous post.
This is part of the report for F4U-1 BuNo.50030, the report states that performance has been reduced to standard conditions in accordance with standard flight test methods. In the report of F4U-1 BuNo.17930, no similar content can be found and I speculated that it was the main factor that made a difference in performance. also, since the F4U-1s in the report included over-boosting to the extent that they did not meet the requirements, I expected that the AUTO RICH mixture was likely used for cooling.
It's not just faulty pressurization, It would lead to a fatal malfunction, spark to jump the gab and burn out the distributor points, there were complete engine failure on some flights above 29,000 feet.
for Hellcat, If the F4U-1's improvements were properly feed back and applied to the F6F-3, the F6F-3 would be free in this problem, because the first air combat was in the fall of the 1943 for Hellcat.
Seems to be misunderstood or misread, if not, I don't know why are you trying to treat official performance for cleared with operation restrionction at standard configuration as a special modified configuration... Read above, I think your calculation missed the starting point. there was no substantial performance effect.
http://www.wwiiaircraftperformance.org/f4u/f4u-1-02334.pdf
In the F4U-1 BuNo.02334's report, standard F4U-1 expected 404 mph @ 25300' for military power and ACP showed 407 mph @ 24800' actually obtained for military power. this is a fairly close result and seems resonable for Navy's estimate.
Considering this, it's even more so.
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DarrenW
Staff Sergeant
Hi Dawncaster,
Very nice parade of data, I appreciate all the hard work you went through to provide it. I gave you some more bacon...
I'm sorry that you feel that I'm discounting "official performance" as this couldn't be farther from the truth. Like most investigations, it's always best to have as many different sources of data to draw conclusions from. You definitely seem very well-schooled concerning the F4U so I was just casually asking if you could produce more than what we normally find on the Williams/Stirling website. It was never meant to dismiss what has already been discussed in this rather lively thread.
I understand this. The only difference is that inspection trial test reports tell us so much more concerning the aircraft under test. The ACP was a handy performance document to be used operationally, so they lack a lot of the detailed testing parameters which one can find in the inspection trials.
So basically your theory is that the performance figures for the F4U-1D's were taken while utilizing auto-rich settings, as this is a way to explain why the two ACPs in question show the same Vmax for a 'clean' F4U-1 while using the two different propeller types. Sorry, but I don't agree with this line of logic because by the time the latter ACP was printed (1 August 1945) auto-lean was the accepted mixture setting (pilot manuals confirm this) and one would expect testing to be performed in order to show operational considerations.
I was only suggesting that maybe the performance data shown in ACP dated 1 March 1944 was for an airplane which was fitted with the 13' 1" propeller, even though the document listed the production propeller instead. You insisted earlier that it was extremely common for this propeller to be fitted to Corsairs by this time so that's why I put forth my own theory but you roundly dismissed it and that's ok. We'll most likely not solve this question in the immediate future without new data coming to light. Until then, I will accept that the "official" maximum speed of the F4U-1D is 417 mph, because both Chance-Vought and the US Navy say it is so.
We both can agree however that a dedicated land-based F4U-1D would be faster than the carrier version but by how much is still in debate. Could it be the 8 mph difference seen when comparing official and non-official figures (417 mph vs 425 mph)? I don't know but it could be one possibility for the disparity.
About the spent cartridge ejector slots. Your deductions seem plausible when doing the math but in reality we wouldn't know for sure how much tapping them up would improve the speed of the Corsair without actual wind tunnel testing. I still believe that the increase will be more than that experienced by the Mustang.
Also, the during testing the US Navy concluded that the drag difference between the birdcage and blown canopies was negligible at best. NACA was most likely describing a different type canopy than the one adopted during production. Perhaps the NACA version wasn't blown and thus more streamlined than what ended up on production machines. This seems plausible according to the description found in rhe NACA document.
So even with these questions we can still say with a fair degree of certainty that the F4U was faster than the F6F at all altitudes, as long as power settings and configurations were similar. The amount of the speed differential however has yet to be fully determined.
Very nice parade of data, I appreciate all the hard work you went through to provide it. I gave you some more bacon...
I'm sorry that you feel that I'm discounting "official performance" as this couldn't be farther from the truth. Like most investigations, it's always best to have as many different sources of data to draw conclusions from. You definitely seem very well-schooled concerning the F4U so I was just casually asking if you could produce more than what we normally find on the Williams/Stirling website. It was never meant to dismiss what has already been discussed in this rather lively thread.
I understand this. The only difference is that inspection trial test reports tell us so much more concerning the aircraft under test. The ACP was a handy performance document to be used operationally, so they lack a lot of the detailed testing parameters which one can find in the inspection trials.
So basically your theory is that the performance figures for the F4U-1D's were taken while utilizing auto-rich settings, as this is a way to explain why the two ACPs in question show the same Vmax for a 'clean' F4U-1 while using the two different propeller types. Sorry, but I don't agree with this line of logic because by the time the latter ACP was printed (1 August 1945) auto-lean was the accepted mixture setting (pilot manuals confirm this) and one would expect testing to be performed in order to show operational considerations.
I was only suggesting that maybe the performance data shown in ACP dated 1 March 1944 was for an airplane which was fitted with the 13' 1" propeller, even though the document listed the production propeller instead. You insisted earlier that it was extremely common for this propeller to be fitted to Corsairs by this time so that's why I put forth my own theory but you roundly dismissed it and that's ok. We'll most likely not solve this question in the immediate future without new data coming to light. Until then, I will accept that the "official" maximum speed of the F4U-1D is 417 mph, because both Chance-Vought and the US Navy say it is so.
We both can agree however that a dedicated land-based F4U-1D would be faster than the carrier version but by how much is still in debate. Could it be the 8 mph difference seen when comparing official and non-official figures (417 mph vs 425 mph)? I don't know but it could be one possibility for the disparity.
About the spent cartridge ejector slots. Your deductions seem plausible when doing the math but in reality we wouldn't know for sure how much tapping them up would improve the speed of the Corsair without actual wind tunnel testing. I still believe that the increase will be more than that experienced by the Mustang.
Also, the during testing the US Navy concluded that the drag difference between the birdcage and blown canopies was negligible at best. NACA was most likely describing a different type canopy than the one adopted during production. Perhaps the NACA version wasn't blown and thus more streamlined than what ended up on production machines. This seems plausible according to the description found in rhe NACA document.
So even with these questions we can still say with a fair degree of certainty that the F4U was faster than the F6F at all altitudes, as long as power settings and configurations were similar. The amount of the speed differential however has yet to be fully determined.
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Dawncaster
Airman 1st Class
- 110
- Dec 23, 2013
Hi Dawncaster,
Very nice parade of data, I appreciate all the hard work you went through to provide it. I gave you some more bacon...
So basically your theory is that the performance figures for the F4U-1D's were taken while utilizing auto-rich settings, as this a way to explain why the two ACPs in question show the same Vmax for a 'clean' F4U-1 while using the two different propeller types. Sorry, but I don't agree with this line of logic because by the time the latter ACP was printed (1 August 1945) auto-lean was the accepted mixture setting (pilot manuals confirm this) and one would expect testing to be performed in order to show operational considerations.
I was only suggesting that maybe the performance data shown in ACP dated 1 March 1944 was for an airplane which was fitted with the 13' 1" propeller, even though the document listed the production propeller instead. You insisted earlier that it was extremely common for this propeller to be fitted to Corsairs by this time so that's why I put forth my own theory but you roundly dismissed it and that's ok. We'll most likely not solve this question in the immediate future without new data coming to light. Until then, I will accept that the "official" maximum speed of the F4U-1D is 417 mph, because both Chance-Vought and the US Navy says it is so.
We both can agree however that a dedicated land-based F4U-1D would be faster than the carrier version but by how much is still in debate. Could it be the 8 mph difference seen when comparing official and non-official figures (417 mph vs 425 mph)? I don't know but it could be one possibility for the disparity.
So even with these questions we can still say with a fair degree of certainty that the F4U was faster than the F6F at all altitudes, as long as power settings and configurations were similar. The amount of the speed differential however has yet to be fully determined.
Well, the previous post was 'dropped' as I said. I cut the quote to the limit, but couldn't include more contents, you'll find out it if you try to write a new article quoting the whole my post. and I tried to write a new article with the remainder, but canceled due to I have no power for it. A post that only has the word "deleted" is a trace for it. due to the lack of energy, this post has a lot of recycled parts....
Firstly, I really don't seem to be good at explaining, as you said, Mixture was a hypothesis to explain the actual power losses, but the important thing about it is that there has actually been a loss in power. I think it's because of the difference in operation restrictions.
This is part of the report for F4U-1 BuNo.50030, the report states that performance has been reduced to standard conditions in accordance with standard flight test methods. In the report of F4U-1 BuNo.17930, no similar content can be found and I speculated that 'standard' Flight Test Methods was the main factor that made a difference in performance. I think it is the same as operation restriction.
Perhaps the operation restrictions in early 1944, when the F4U-1 ACP and F4U-1 BuNo.17930 were tested, was lax compared to 1945 when F4U-1 BuNo.50030 or F4U-1D were tested. and seems that It's more accurate and practical operation restrictions were founded over time as operating hours increased and more data obtained.
For propeller blade design and suggestion about it, my lack of explanation seems to have caused the problem again. I wrote 'new 6501A-0 propeller blade start service with VF-17 in solomon campaign and many F4U-1s have replaced propellers with this new type', but I didn't mean it was extremely common. for example, If the limited to F4U-1 of VF-17, it could be said to be common. but if expand the target to the entire F4U-1s in operation, there were far more old 13'4" propeller than the new 13'1" propeller. to be exact, many F4U-1s have been replaced with new propellers, but not much compared to the whole. I just wanted to say it started service early and was not unique. well.. I doubt that I expressed it correctly this time. In conclusion, considering the characteristics of the ACP mentioned in the last post, It's highly unlikely to be the performance of the 13'1" propeller for me.
Also, it should not be overlooked that there is actually another 'standard' sample with a 13'1" propeller, F4U-1 BuNo.17930. cross-validation with ACP and F4U-1 BuNo.17930 well shows both the matching and difference of performance that should be between the 13'1" propeller and the 13'4" propeller under the same 'standard' drag condition(showed the characteristic of a 13'4" propeller losing efficiency in a high-altitude, high-speed range above 16.5k ft, while at the same time the two F4U-1s show matching performance at same drag conditions below 16.5k ft.). It seems allows to infer that the performance of the ACP was that of a 13'4 "propeller.
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DarrenW
Staff Sergeant
Don't you just love talking Corsairs and Hellcats? It's probably one of my favorite past times, and I thank Zipper very much for creating this very interesting thread....
DarrenW
Staff Sergeant
That's ok because it's very hard sometime to convey exactly what you mean in such a way that all will understand exactly as it was intended. I have done that a few times here as well.
So maybe the extra performance achieved when using the more efficient propeller wasn't that spectacular after all? If the increase was only a few miles per hour at best it might still be beneficial to some extent but not a true game changer. That could be another explanation for the similar speeds with different propellers.
And I do trust quite a bit about what you had to say here and I learned a lot, because you are a "Corsair guy" while my area of study is the Hellcat.
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