Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: fire_ant on August 07, 2000, 05:22:00 PM
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I wanted to ask, if not actually gripe, about the low altitude performance, especially in speed and acceleration, of the really big BnZ fighters such as the P-47 and the Corsair. I notice these things are very very fast at low altitude in AH and out run practically anything. My question is, is this historically accurate? Do big high drag fighters go fast at sea level? Or is the entire AH arena situated on a 10,000' high plateau? Because this doesn't jibe with what I'd understood from historical accounts.
Has anyone on this board read Ira Kepfords famous anecdote of barely escaping from 3 zero's in his corsair by using the new water injection WEP system and a lot of luck? If I understand what he had written there, a zero could easily out-run a corsair on military power at sea level if the F4U wasn't in some high E state from diving. I dont think a zero would be able to get anywhere near a fleeing corsaair in this game, WEP or not.
I have read similar accounts by many other pilots, inlcuding Saburo Sakai's account of a zeros performance, and various accounts regarding the P-47 in the ETO and MTO, in which low altitude performance was considered a problem.
But if the AH developers are going by the numbers, and I don't have those in front of me, I guess this is just how reality looked. It seems things are stacked heavily in favor of the BnZ fighters over the TNB.
DB
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The problem with being low is that anyone can dive on you. It's easy to gain 100 mph in a dive that could give a speed advantage to even a zero.
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if you have enough alt to dive to get 350mph when you have a real fast zero comin at ya all you have to do is a 90 degree break turn to get away. they cant follow cuz their ailerons are locked up past that speed
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Maybe you misunderstood Kepford. Every flight test I have seen shows the F4U to be faster than the Zeke at all altitudes. Maybe Kepford was in a situation where he was accelerating from low speed. In that case the Zeke had the capability to stay near the Corsair until 200-250 mph or so.
Also size has nothing to do with top speed. An F-105 is a lot bigger than an F-84, but it's a lot faster too. All that matters is thrust and drag.
[This message has been edited by funked (edited 08-08-2000).]
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Fire_ant the speeds are correct. And yes in AH the maximum level speed of your aircraft changes with altitude.
If you look in the Help section, you will find charts for almost all the planes with speed vs. altitude, and climbrate vs. altitude.
What you are describing is the the age old engineering problem of design tradeoffs. In other words, to get an increase in one performance characteristic you must usually give up performance in another area.
Like Funked said, maximum speed is a function of thrust (engine power) and drag. To get the most engine power, you usually had to go to bigger and heavier engines (US type planes). And when you make the aircraft heavier (and keep the wings the same size), it makes the aircraft perform worse in turnrate.
Now there are alot of other factors, including increasing engine performance without increasing size or weight, so this isn't always true. But its a good generalization.
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Vermillion
**MOL**, Men of Leisure
"Real Men fly Radials, Nancy Boys fly Spitfires"
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Fire-ant,
Real quick and dirty. The F4U was one of the fastest birds at sea level. It put out 2250HP at sea level and had a very low power to weight ratio at low alt. Weight devided by power that is(The Me109G10 is king in that regard). At 10K the HP dropped off to 2000HP, and 20k it was at just over 1900HP. These three Alts are the three engine stages or "Blower shift points".
So don't be deceived by size. Even a P-51D only has the slimest of margins at low alt vrs the F4U or Vrs the P-47D30 at any alt.
Bye the way. The A/C chasing Kepford in his daring escape were not Zero's. They were
Ki-44 Shoki's. A much faster bird than the Zero. Especially at sea level but still not as fast as the F4U.
Later
F4UDOA
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the F4u is indeed way too fast. Iīll never believe that 2250HP can push a 12000lb fighter with a wingarea of ~315ft^2 to 359Mph at sealevel. Unpossible!
All AH planes with the exception of the pony have a Cd0 of ~0,23-0,25, the F4U has a Cd0 of ~0,17, though it had a bad wing design, poor surface quality and due to the huge engine a big frontal area and a lot of surface area for the fuselage...
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niklas, thats a good one! Do you have any idea what you talking about? (http://bbs.hitechcreations.com/smf/Smileys/default/rolleyes.gif)
PC
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Often I've read about P-47 being good at altitudes above 22-25k, but in AH that plane is good at any altitude almost. (perhaps mostly because of supercharger and poor performance of LW planes at those altitudes?)
P-47 was amazing, but in AH it has even more amazing performance at low altitude if talking about maneuvering.
From my understanding low flying P-47 were in fight sort of brick vs. mosquito, which I don't think it is in AH (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
Though, it has seem to lost part of that unbelievable E retaining during latest patch or second latest?
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Fishu - WATER INJECTION!!!
Niklas - There is some variation in flight test data for the F4U-1D but the lowest numbers I have seen are still in the 350 mph range at sea level.
[This message has been edited by funked (edited 08-08-2000).]
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Niklas,
I'am surprised that you feel a larger WW2 fighter would be slower for some reason.
Not only is the F4U listed sea level max speed at 360MPH with combat power but in flight test vrs the FW190, P-51B and A6M-5 it exceeded that number in side by side speed runs at sea level.
I will give you 4 reasons the F4U-1 was so fast at sea level compared two it's contemporaries.
1. The front cowl area is much smaller than either the F6F or P-47 due to the oil coolers being moved to the wing roots. Reducing the area most responsable for drag in a radial engine.
2. The wings attach to the fuselauge at a 90 degree angle. This is the most efficient means of attaching a wing to the body and further reduces drag.
3. Air intake into the engine at nuetral and low blower stages is taken in more directly into the engine and creates a RAM air effect.
Even though the manifold pressure is rated the same in an F6F and F4U the Grumman engineers swore that this was the reason for the Corsairs superior performance at low alt.
4. The reason I think is most responsable.
The Prop blade on the F4U is a more efficient prop. Even on the F4U-1 somewhere in 1943, the Vought people switched the blade type on the F4U-1's from a three blade 6443A-21 also used on the F6F to the three blade 6501A-0. The F4U-4 used the same blade only a 4 blade prop. Grumman did not change to this blade type through out production.
I am reading this directly from the F4U-1 Flight manual.
Quote "Production airplanes are normally equiped with Hamilton Standard Hydromatic three blade 6443A-21 or 6525A-21 propellers with a diameter of 13'4". Hamilton standard blades designated 6501A-0 and 6541A-0 having a diameter of 13'1" may also be used on these airplanes. These latter propellers should be used whenever available since they improve performance".
Combine those 4 reasons in combination with one another and the fact that it's speed was measured independantly in 4 different flight test and it becomes even more believable.
Then consider the F4U-4 had only 200hp more and had a top speed of 380MPH at sea level and a 4.9 minute climb time to 20,000ft.and was a heavier airplane. I believe Boone Guyton the cheif test pilot of the F4U descibed it best "The F6F was an airplane of evolution and the F4U was an airplane of revolution"
Later
F4UDOA
For F4U-4 flight data
http://www.history.navy.mil/branches/hist-ac/f4u-4.pdf (http://www.history.navy.mil/branches/hist-ac/f4u-4.pdf)
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funked, test data or calculated data??
You find for example 316MPH for the 2000HP type, that would mean maximum ~330mph for 2250HP
(from 214th.com)
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Niklas,
214th.com is a gaming website. Do you have any more reliable historic data??
F4UDOA
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f4udoa
214th.com/ww2/usa/f4u is a gaming website?
I donīt think so. BTW they have your PDF document there.
or check www.odyssey.dircon.co.uk/f4u.htm (http://www.odyssey.dircon.co.uk/f4u.htm)
they list f4u-1a with maxspeed 395MPH (compared to 417MPH from 214th)
1. The front cowl area is much smaller than either the F6F or P-47 due to the oil coolers being moved to the wing roots. Reducing
the area most responsable for drag in a radial engine.
ahh the oil coolers are in the wing roots? That means air that passes through the wing canīt flow over the wing and produce lift right? And the 30° angel of the wingroots to have a low gear means that you lose another 15% lift in the wingroot section...
2. The wings attach to the fuselauge at a 90 degree angle. This is the most efficient means of attaching a wing to the body and
further reduces drag.
Youīre right, planes like the cessna which are optimized for high speed and low drag have the wings 90° attached to the fuselage, while planes like modern jet airliner where low drag isnīt very important are build with wings swept back.
And of course 90° for the F4U makes a big difference to 80-85° designs of the other WW2 fighters.
The only reason why the F4U has wings with 90° angel attached to the fuselage is because they needed so much wingarea (the heavy engine...)! Thatīs why it has an almost rectangular wingdesign, to realize an acceptable wingloading without loosing to much rollrate. Because big wingspan means low rollrate. The result is the lowest aspect ratio of all ww2-fighters that i know, and withit a lot of induced drag in a slow flight!
3. Air intake into the engine at nuetral and low blower stages is taken in more directly into the engine and creates a RAM air
effect.
Even though the manifold pressure is rated the same in an F6F and F4U the Grumman engineers swore that this was the reason for
the Corsairs superior performance at low alt.
Ahh something like the mystically engine heat factor/radiator energy recovery of the P51 eh? Maybe AH should be named Secrets weapons of the USAAF...
The propeller...Do you really think it can give you 30-40MPH more topspeed??
BTW i donīt compare the F4u to the P47, and not to the F6F. I compare it to all other planes included in AH. And you canīt tell me that the F4U has a 30% better Cd0 than all other AC of AH except the P51!
Now to your F4u chart. According to the chart the F4u-4 can go with ~2500HP up to 10k feet- it even has in 10k more power than at sealevel with WEP, while nominal engine power gets less (compare climbrate, climbrate @10k with wep is higher than @0k)
Can you pls explain me how the F4u-4 can go with 2500HP up to 10k and a F4U-1D with 2250HP only up to 3K AND why power increases with altiute and wep while power decreases with altitud and nominal power?
And compare the critical altitudes of climb and speed: the difference is even 4k... thatīs a lot!
I have the P51-F4u chart btw. The P51B is listed with 360MPH @ sealevel with only 1440HP....
This chart is not based on flight tests, itīs a calculation. And i think for a simple comparison they neglected for both AC something, interference between wing and fuselage for example.
Like i said i donīt believe it!
niklas
[This message has been edited by niklas (edited 08-09-2000).]
[This message has been edited by niklas (edited 08-09-2000).]
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Niklas, I'm talking about tests.
You sure that 316 wasn't knots?
If you're gonna start a "Secret Weapons of the US" campaign, why don't you look into the climb rate of the Fw 190A-5, or the top speed of the Me 109G-10. Neither one of those makes much sense if you look at power, weight, and drag.
Or what about the Typhoon? Similar size and power to the F4U, but 20 mph faster.
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Niklas: What's lift got to do with drag? Radiators in the wingroots produce less drag and the wing area behind them is still generating lift. Less drag with the same thrust equals more airspeed. It's that simple whether you believe it or not.
As for your obvious scepticism on Pony's radiator scoop/exhaust performance ("...Ahh something like the mystically engine heat factor/radiator energy recovery of the P51 eh? Maybe AH should be named Secrets weapons of the USAAF...") I can point out the infamous V1. It used the same principle for propelling itself through the air - the ramjet, albeit with more efficient way to heat the air passing through it. Once again, it worked regardless of your beliefs...
funked - I think you nailed it, 316 kts = 355 mph.
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-lynx-
13 Sqn RAF
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Who cares, the F4U-4 never even existed anyway. Go find one and mail it to me, then I'll believe it.
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According to science, the bumble bee, as well as a Frisbee, should not be able to fly. Mathematically that is.
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jehu
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Niklas,
Still a non believer huh.
Well 1st off the first production F4U-1's did have a top speed of 395MPH. Then they changed the surface drag condition of the airplane by fairing and sealing the wings and cowl. You can check that on the NACA server server report #829 on the lift coefficients of WW2 fighters. Then they changed the canopy, prop blade design and added water injection and that was the -1A.
And thats were you get 417MPH.
The four reasons I gave you for the A/C's performance being better than it's two closest contemporaries are all real and valid. Your analogy to a cessna(what cessna I have know idea) having gull wings and airliners having swept wings is rediculous).
The only reason the F4U had gull wings is to give it prop clearance. Unless you have some documant to prove otherwise. And swept wings are more efficient in flight close to mach 1.
Other that the Me262 and Me163 I don't remember any swept wing designs on fighters.
Big wingspan equals low roll rate??? You must have another agenda with this post because the F4U had either best or the second best roll rate out of all american designs. It could roll circles around a Spitfire over 300MPH and the spit had an elliptical wing.
Also you said it had to have a large wing to give it acceptable wing loading? It had the second best wingloading of all modern Amercian designs next to the F6F. In fact compared to the P-38, P47 and P-51 it is the only one with wingloading under 40lbs per sq foot.
And the result of this wing is a low aspect ratio. Tell me Niklas what is the aspect ratio of a F-15? It(the F4U) also had high lift, which causes high induced drag. So at low speed it may be draggy but it has a ton of lift which means it's fly's well at low speed. A requirement of any carrier fighter. But at high speed induced drag Cdi doesn't mean anything(as much). It goes to almost nothing and the zero lift drag means everything. And thats where the F4U does very well. Isn't that the ideal for a fighter plane? Low drag at high speed and high lift at low speed.
And now as you say to my chart. My chart?
That chart is from the DOD(department of defense). I really don't understand what you ranting about? At combat power the best climb is almost 4800fpm and normal power it is just under 3000FPM. The HP drops from combat of 2450HP to normal which is 1700HP.
3K is 60% of 4800, and 1700 is 70% of 2450.
It sounds pretty linear to me. But more importantly it can be verified with other flight test comparisons with other A/C. IE. the F4U/F6F vs FW190 as well as comparson flights at the joint fighter conferances.
Niklas your chart is gone now so either you found your own mistake or you are trying to make your numbers come out the way you want them too. In any case there is a mountain of data on this subject.
Later
F4UDOA
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Funked, i donīt know, but they say there 509KmH @ sealevel.
And we talk here about the F4U ok? (But a little thought from me: EVERY Plane that has a good climbrate for itīs power/weight ratio >> P38, P47, Macci and yes 190A5 has also a good E-Retention. Is it possible that E-Retention is a result of the adjustment of climbrate? That would mean Pyro needed to lower for some planes the induced drag to get the desired climbrate...? Just a thought, but worth another thread)
Can we exclude the Typhoon? I donīt know anything about it, and sorry: itīs maybe fast in AH but elseway you can forget it. Iīm convinced that a real plane with such a performance never would have been build!
And the G10 doesnīt make sense, funked?? 2000HP for a 7400lb fighter, with a wingarea of ~175ft^2 ??? In 4000ft even ~2150 HP ??? Damn, a real G10 will accelerate in a turn where other planes will slow down! The Cd0 of the 109 is one of the WORST in AH with ~0,026!!!
OK letīs compare the G10 to the F4U (i think everyone knows that drag is a linear function of surface area)
The F4U
-has 76% (!!!) more wingarea
-at least 50% more fuselage area and frontal area
-60% more weight!!
-A worse Aspect Ratio of 5,3 compared to 6,0 for the G10 (the engineers of the Thunderbolt tried at least to do make the best of the low AR with a kind of elliptical shape)
-only 12,5% more power
-and ist ONLY 6% SLOWER AT SEALEVEL!!!!!
ANY QUESTIONS???
Lynx it is not so easy. You get lift because you force air to accelerate over your wingsurface. The air that goes into the wing canīt go over the wing, right? Why do you think Messerschmitt placed the oil cooler in the rear part of the wing, where the boundary layer is close to get turbulent??
So Lynx you want to say that the P51 used a smiliar princip like a V1? So the P51 is half a JET???? And those P51 Jet driver want to deny the LW the ME262???? HYPOCRYTES (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
(btw Atkinns said that the laminar wing had no advantage in a level flight, only in a dive. But i canīt believe that this effect gives the P51 so much impulse - or... the speed data of the P51 is a little bit too good ... (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif) )
OK F4U: When will you finally understand and accept: They used the faired and sealed F4U in the NACA829 Report just for a comparison to see how much lift can be improved!! The faired and sealed F4U is NOT the production type!!! This is called Service wing, and the difference is avaible at page 20: Under best cicumstences maye Clmax of 1,3 without propwash effects! NOT YOUR 1,48!!! (Btw i canīt see cannons/guns in the picture, which will reduce Clmax again. For example for the P51 Clmax guns reduce Clmax from ~1,4 down to 1,28... see page 26)
Roll rate: pls take a book flight mechanics part I or II and look for the formula of max. Roll speed. Is is proportional to V/wingspan. Over 300Mph the F4u has maybe an advantage due to the mechanical boost. This is btw a weakness of the spit that is not included in AH, it suffered like the 109 from high stick forces in a fast flight for a roll.
Ok you said the best or second best of all AMERICAN designs. I agree, no problem. Which plane should roll faster? The Pony? it has itsself a big wingspan.
The Jug? Try to bring 15000lb in a roll motion...
A fact that is btw not included in AH and leads to a disadvantage of the lighter axis fighter: AH doenīt know roll accerleration! You have immediatly full rollspeed, and you will stop rolling immediatly when you release your stick. I think 15000lb in a roll motion wonīt stop so fast, youīll have a lot more problems to control a quick roll compared to a 7000lb fighter.
Ok, the P38 has a bit roll accerleration. BUT definitly not enough! Damn two heavy engines each 8ft out of the center of rotation, a wingspan of almost 50ft.... Who really believes that the P38 was able to roll even with servo aillerons so fast (and roll accelerate so fast) like the AH P38??
What rests? P40 at low altitudes maybe. Other fighters at slow speeds.
I bet the famous roll rate of the Fu4 was at high speed and maybe in high altitudes right?
Wingloading: It was designed for carrier operations, right! Do you want to land with 100MPH on a carrier? A higher wingloading was definitly not acceptable for carrier operations like you said. Unfortunality the huge engine and the poor visibility cost the life of some american boys... (BTW if the forward sight was so bad, why has the AH F4U the best view for deflection/tracking shots???)
but it has a ton of lift which means it's fly's well at low speed.
A requirement of any carrier fighter. But at high speed induced drag Cdi doesn't mean anything(as much). It goes to almost
nothing and the zero lift drag means everything. And thats where the F4U does very well.
You see, that is the point. You think you can have a huge wingarea, and at the same time extraordinary low total drag. THAT is the point where i say this is NOT possible, i donīt believe this! Too much surface area, drag, for 359MPH with 2250HP. A Cd0 of ~0,017 compared to 0,024 for the SPIT - sorry something is wrong, and you know that, though youīll never admit it!
oh and pls donīt start telling me from this flight comparison with that poorly maintained 190 that parked somewhere and was flown by a pilot who had almost no experience with the 190....
many words, poor english ( (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif) ), and all i have to say is: the FU4 is too fast.
niklas
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Hi jehu,
Originally posted by jehu:
According to science, the bumble bee, as well as a Frisbee, should not be able to fly. Mathematically that is.
Actually that one was solved some time ago (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
Not so long ago aerodynamic theory was unable to explain how something
as un-aerodynamic as a Bee was able to fly. The currently accepted theory was inadiquate. But the Bee did fly rather well, so something was missing. The
answer has recently (relatively speaking) been attributed to something
called vortex lift.
Vortex lift is a feature of highly swept leading edges, like those on
delta wings. The F-16, F/A-18 and Su27 for example, take advantage of this type of lift with highly swept forebody strakes or leading edge root extensions. The
vortices from them become vissible as water vapour condenses from the low pressure regions inside them when the aircraft is generating lift.
The vortex lift from the root extensions is additional to the lift generated by the aerofoils. But there is more to it than that... Even vortex lift along with the aerodynamic lift won't provide enough lift to get our friend the Bee airborne.
It turns out that the lift is even further enhanced by interaction of the vortices from the Bee's wings. This effect is also used on aircraft with Delta wing and Canards like the Eurofighter. The Canards bring even further enhancement and an additional source of lift due to the interaction of the vortices of the canards and main wing.
The hard part to grasp here is that the canards on the Eurofighter, just like the wings of a Bee, greatly contribute to the lift because the vortex interaction with the main wing flow increases total lift to more than the sum of both individual lifting surfaces! Sounds like magic? Well the Bee does fly doesn't it (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
Also the same effect is fully exploited
in the Eurofighter configuration where the leading edge vortices from both
canard and wing can interact to produce very high lift values. The Eurofighter canard has been placed in such a position so that mutual stabilization of the vortex through interference effects can be achieved. That is with the canard wing slightly above the main wing and close coupled with it. The point in all this is that not only can the forces that keep the Bee airborne be fully explained, aircraft designers have been taking advantage of the theory for some time...
I for one am very happy that Bees can fly because I do like Honey!!
I guess the real question here is can a Bee fly inverted (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
Badboy
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Niklas,
Keep in mind that the Cd0 you are quoting are based on wing area. You should convert it to an f value for comparison with other planes. It may turn out that a plane with higher Cd0 has much less wing area and thus a lower f value.
f = equivalent flat plate area
= Cd0 * Wing Area
Also, cross reference the speeds for sea level and at altitude and see if they check out/make sense.
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Niklas,
You should number your issues so I can address them 1 at a time.
First lets look at a G10. It was desinged to fly at a loaded weight of around 5500lbs and then it was forced to fly at 7500lbs because they did not change the airframe and put a 2000hp engine in it. evryone knows about the torque of the F4U with a 2000hp engine. With a wing area of 177sq ft the Me109 must have been almost unflyable with barely enough control surface to overcome the gyroscopic forces. Plus the 109 had one of the worst surface finishes of any WW2 fighter with many external protrutions causing heavy drag.
With a rudder that small that airplane must have been almost unflyable.
What is the flat plate drag area of the 109?? The F4U was 5.93 sq ft. The FW190 was 5.18sq. Ft. Which means that the 190 had 87% of the Flat plate drag area of the F4U.
However it only had 73% of the Horsepower of the F4U. Which means the F4U had 14% more thrust to drag than the FW190A5 and should be 14% faster right? The FW190A5 had a max speed at sea level of 335MPH at sea level then the F4U should be 14% faster assuming that they weight the same. That is 50MPH faster at sea level. Then reduce that by the percentage of additional weight which is 30% of 50MPH and it should be 35MPH faster which bring the F4U sea level speed to 370mph at sea level. So by your standards the F4U is now 10mph to slow at sea level.
And yes the drag condition was changed on the F4U due to leaky cowl flaps leaking oil on the wind shield. Those flaps were then sealed to prevent leaking on the windscreen.
If you read the P-51B vs The F4U report you can read about the surface condition of the wing being smoothed adding an additional 8mph to the top speed.
Also the Max Cl of the wing is 1.48 with the prop on with prop wash and 1.88 with full flap. The F4U had a clean stall of 96MPH no flap right from the pilots manual. Solve for the Max cl and see what you get. It's senseless to use the no propeller number because they don't fly without them.
As far as roll goes your forgetting the human factor. With a small airplane you have small control surfaces and high stick forces. The F4U at the 1944 fighter conferance was said to have the second best Ailerons at 350MPH to the P-51 and the second best ailerons at 100mph to the F6F. Mechanical or not they were the best through out the speed range. It seems to me that it is common knowedge that the smaller fighters like the Spitfire and Me109 had a harder time at high speed.
(BTW if the forward sight was so bad, why has the AH F4U the best view for deflection/tracking shots???)
Because it was in real life. It had the smallest front cowl area of either the Hellcat or Thunderbolt. On carrier landing the AOA is just too high. But the view forward was said to be the best for tracking delection. The gun site is also a factor in view from the cockpit and is much less of a blindspot in the F4U.
As far as the 190 that was tested against the F4U/F6F. It flew exactly to spec as far as top speed attained and rated boost and manifold pressure. And I will garauntee you that the pilot flying that plane had more experiance than what was left of the Luftwaffe by then. Also it was probably in better flying condition than most Luftwabbles of the time as well.
Oh and the Spits Cdo being higher than the F4U. I think you are over looking a couple of things.
1.The Spit's wing area was not that small.
242sq FT. Larger than a P-51 at 233.19.
2. The Spit for all it glory was an under achiever. It had the same Merlin as the P-51 and was much lighter but yet it was some 30MPH slower at critical alt.
3. The Spit had a 1400HP engine and was almost the same size as the Me109 but was outclimbed significantly by a comprable 109 model.
4. A recent issue of Air Classics magazine highlights the Spit XIV with a 5 blade prop and 2035Hp engine. In the Thompson trophy races of 1947 this airplane running 150octane fuel finished third behind a P-51K and the winner the F2G Corsair. It lap speeds were 359MPH and the F2G Corsair ran an average of 386Mph. As many of these airplanes as there are left none have seriously competed in air racing IE the
P-51, F8F, Sea Fury or F4U Corsair.
To quote the pilot of the Racing Spitfire
"For all the power available in that big Griffon 65 type Aircraft is not that good a particularly unlimited air racer. It's surprisingly slower than a stock Mustang and as you add more power, the coolant doors on the radiators open up and it feels like you accidentially put the flaps down"
Whoow
Later
F4UDOA
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*Stupid Comment Deleted*
[This message has been edited by funked (edited 08-09-2000).]
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F4udoa, the 109 was continuously improved! The Gustav Airframe is based on the Franz, and even the earliest F1 Airframe is designed for 6710lb! Please donīt compare a Emil to a Gustav!!
They did not change the Airframe? Hey why the K-Series?? To include all those changes which were made in the different G-models in one plane!
I donīt have the picture here, but iīll send it to you when i get it- it shows how the surface area of drag components were continously decreased! A G10 has no "Beulen" anymore. It does not have guns in the wings, nor like the F4U (and now from Naca829 report page 20) "an exceptionally large number of cover plates, access doors, and construction irregularities"
The G10 unflyable? Look at the V-wing from the front, this will stable the plane a lot but reduces roll rate. And it had from the beginning an asymmetric vertical stabilizer which compensates a lot. Donīt forget that all engines are usually not mounted straight on, but with a certain angel in the airframe to compensate torque effects too.
And afaik the G10 had already the bigger tail ("aufgestocktes Leitwerk")
pls donīt only post numbers but give me the source too. If all calculations and charts are based on that flate plate drag number for the F4u than i donīt wonder myself anymore that official charts look excellent. The question is.. is the number correct? I assume that you have the plate area for the 190 from the drag coefficient list that i sent wells and vermillion a time ago (if not where do you have it from? ).
Ok maybe you donīt understand the footnotes there. They say: "surface quality INCLUDES accounts on manufacturing workmanship, cooling system, cockpit and interference"
That means additional drag effects are included.
And THIS is what i think is not included for the F4U, especially interference effects between wing and fuselage!
However it only had 73% of the Horsepower of the F4U. Which means the F4U had 14% more thrust to drag than the FW190A5
and should be 14% faster right?
NOT right.
A. Drag increases with v^2 that means 14% more thrust to drag means root(1.14)=6,7% more speed. And donīt forget that with more speed propeller force gets less and less, so youīre maybe 5% faster with 14% more thrust to drag. Right?
Again, your calculations are nice, but what if the basic number is wrong?
With a small airplane you have small control surfaces and high stick forces.
Absolutly wrong. Unlogical. When i have small surface areas for a small and light plane the stick force (assumung the same stick) is of course lighter, because i have for example only to pull half the ailleron area into the air compared to an aircraft which is double as big!
If you still think a big wingspan is good for a quick roll rate, then - following your logic- a Boing 747 (assuming no roll rate limitations etc.) would be the king of roll rate. It has hmmmmm ~5 times bigger wingspan than a 190 so i think - again, following your logic- a roll rate of 2 full circles/ second should be possible (note: weight is not important!).
The problem of the small fighter were the limitated place in the cockpit and thus small stick lenght. F=M/l . And in a fast flight things get different.
It doesnīt surprise me that the F4U shines at very high speeds (what i said already) and at extremly low speeds. 100MPH is for land-based fighter close to landing/stall speed. That means a P47 canīt use full aillerons at 100MpH anymore, it would stall. With the lower landing speed, the F4U (and Hellcat, both carrier planes), have more reserves for ailleron use at 100Mph.
A comparison between 150 - 200Mph would be interesting...
and btw, iīm not too much interested in SPITS. But when it has such a huge wingarea than the Cd0 for the spit should be even lower than for the F4u right?
niklas
[This message has been edited by niklas (edited 08-09-2000).]
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Niklas,
Yes the flat plate drag area comes from Wells as does the Flat plate area for the F4U. I understand that you are trying to account for all surface flaws but I think you are missing the larger point. In order to say that ANY A/C data that is so widely accepted you have to have a comparison with a A/C that you believe has accurate data. But you are saying that you don't accept the F4U, F6F or P-47 data for being accurate. These A/C were flight tested against all major European types at one time or another and the results are well documented as are the results of direct combat. If you are to say that the F4U can't fly 360MPH at sea level then you better have more data than "I don't think it can.
The Me109 did have several changes to the surface area of the aircraft but the basic structure remains the same. I don't believe an A/C with a wing area that small or a tail surface that small could handle a 2000hp engine and remain stable enough for combat missions. The Rudder on the F4U is HUGE compared the 109 rudder and it still had Torque effect. It is a wonder that it doesn't just spin around like a top. And the Drag even on the K-4 is still evident. Itwas also known to have weak landing gear through out the production history. There is no reason to beleive that other structural defects did not exist. The Germans were more than willing to send their pilots up in less than safe A/C during the war witness the ME163.
NOT right.
A. Drag increases with v^2 that means 14% more thrust to drag means root(1.14)=6,7% more speed. And donīt forget that with more speed propeller force gets less and less, so youīre maybe 5% faster with 14% more thrust to drag. Right?
Again, your calculations are nice, but what if the basic number is wrong?
Ok 5% faster. That puts the F4U at 352MPH. Sounds pretty close to me. And the "basic number" may be wrong? It may be, but I've got multiple flight test that say it's right.
Even you have to say that it is allot of data that points in that direction.
quote:
With a small airplane you have small control surfaces and high stick forces
You paraphrased my quote. What I said was
It seems to me that it is common knowedge that the smaller fighters like the Spitfire and Me109 had a harder time at high speed.
Really I was just stating the obvious. The 109, spit and Zero all had poor ailron response at high speed. Why I'm not sure. It may have to due with a high aspect ratio. Todays modern fighters have extreme low aspect ratio wings as do acobatic A/C and they are the best rolling A/C in the world. Any A/C with high aspect ratio IE TA-152 or P-38 tend to get stuck in the mud intiating a roll. In anycase the F4U's roll curve from "America's Hundred Thousand" looks like a virtical spike from low speed up to 300MPH.
You mentioned the Cdo for the Spit being lower than the F4U again but you may not be seeing everything. The Spit was much slower than it should have been for such a clean looking airplane. Why was it so much slower than the P-51 with less weight and equal HP? Why was it's climb so much less than Me109? I think your looking at the Spit vs F4U comparison in the wrong way. Don't ask why the F4U was so fast. Ask why the Spit was so slow. The Spit V was no faster than a Me109F4 with greater horsepower and climbed at a much slower rate.
Later
F4UDOA
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niklas, listen to F4UDOA and please stop with this stupidity, it has gone passed the point of being funny.
PC
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im so confused, blue planes are slower ? right?
shit i need a drink
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TOWD, I'll try to clear this up:
Blue planes are BAD, mkay.
LW planes are GOOD, mkay.
Facts should be left out of the BBS, mkay.
I hope this clears it up, mkay.
PC
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F4UDOA don't waste your breath.
Niklas do you really think Pyro doesn't have a lot of flight test data for the F4U-1D? Or do you not trust US flight test data?
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The Spitfire is slower because of all the crap hanging out under the wings - "cooling drag". (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
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Niclas - that's how the ramjet works: air is entering one end of the tube, heated and expelled from the other at a greater velocity generating thrust. You can use fuel, radiator heat, even nuclear reactor (there was a prototype built in the States) to heat the air but the principal remains the same...
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-lynx-
13 Sqn RAF
[This message has been edited by -lynx- (edited 08-10-2000).]
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Originally posted by -lynx-:
Niclas - that's how the ramjet works: air is entering one end of the tube, heated and expelled from the other at a greater velocity generating thrust. You can use fuel, radiator heat, even nuclear reactor (there was a prototype built in the States) to heat the air but the principal remains the same...
So is it safe to say that "Roger Ramjet" got his name by farting?
Now how about d'em dummy scram-jets? (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
(The engine or the bozos from NY; your pick)
- Jig who is in no way being serious.
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Originally posted by niklas:
f4udoa
Youīre right, planes like the cessna which are optimized for high speed and low drag have the wings 90° attached to the fuselage, while planes like modern jet airliner where low drag isnīt very important are build with wings swept back.
HAHAHAHAHAHAHAHAHAHAHAHHAHAH hihihihihihi huhuhuhuhu hehehehe MUAHHAHAHAhahaha
I've got tears in my eyes now really Niklas if that was a troll then a good one
DW6
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RGR That Funked, I'm out.
Jigster, stop that. You made me hurt myself.
Roger Ramjet, geez I can't stop crying.
Someone call the parmedics, I think I sprained my splean. Ouch it hurts.
Later
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Originally posted by F4UDOA:
Niklas,
214th.com is a gaming website. Do you have any more reliable historic data??
F4UDOA
yup, 214th.com as a whole is a gaming website. I was the XO of VMFA214 BlackSheep that flew in the EIDOS CK beta, and that's our base of operations. If you go through the sims section you can still see it.
HOWEVER
The WWII museum was put together with the best information we could compile on the aircraft. I know, because I helped Widowmaker dig up all the information/pics/mpgs-avis. The museum has been a work in progress for a long time, and I believe now officialy classifies as a hobby (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
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Originally posted by funked:
Fishu - WATER INJECTION!!!
Okey... so this means german planes flies with steam engine.
A Sticker saying: "Reply to Funked"
[This message has been edited by Fishu (edited 08-10-2000).]
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Duckwing, i didnīt thought it was necessary to add smilies to this sentencet ot show how i meant it (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
wells, where do you have the drag area for the F4U from? Pls mail me the document.
I mean what if wells calculated this value? That would mean wells calculated from the 355mph value the drag area, and F4UDoa recalculated from the drag area back the topspeed and WHAT A SURPRISE itīs 355mph (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
So when the F4U is so fast we get 2 basic conclusions for a high performance fighter design:
Heavy is better than light
Big is better than small
Indeed, the F4u IS a revolution hihi (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
niklas
[This message has been edited by niklas (edited 08-10-2000).]
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Come on....
Everyone knows that "Old Man Vought" was actually an Alien.
And with that kind of technology, even pigs can fly.... errr ummm.... a Hog can fly (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
------------------
Vermillion
**MOL**, Men of Leisure
"Real Men fly Radials, Nancy Boys fly Spitfires"
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Originally posted by Fishu:
Okey... so this means german planes flies with steam engine.
I dare ya to make me explain water injection beyond the point of increasing manifold injection. Go on punk do you feel lucky? do ya?
The effect is actually somewhat simular to a steam engine.
- Jig
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Originally posted by Jigster:
I dare ya to make me explain water injection beyond the point of increasing manifold injection. Go on punk do you feel lucky? do ya?
The effect is actually somewhat simular to a steam engine.
Sorry.. forgot one thing...
*attachs "reply to Funked" sticker into the post*
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Niklas,
I have the stake for your heart.
I have the early war performance doc. exactly what is posted for various A/C on the 214th web site for the F4U-4 for the birdcage F4U-1 without water injection at a max 2000HP.
Here it is power loading listed at 6.8 so the HP must be at around 1700HP
military power
Vmax=395MPH at 23000FT.
Vmax at sea level=341MPH
Normal power about 1573HP power loading=8.9
Vmax at sea level with an external drop tank at 14000lbs=310MPH
Next the F4U-1D with water injection
12,039LBS power loading listed at 6.1 so we are talking 1973HP
Vmax=417MPH at 19900FT
Vmax at sea level=359MPH<===HELLO
At normal power
Vmax at 14000LBS with external drop tank=384MPH at 24600FT
Vmax at sea level with external drop tank 14000LBS=315MPH
Niklas even at normal power with an external drop tank at 14000lbs power loading at =>8.9<= the F4U is faster than you think it should be. How much more documantation would you like??
Later
F4UDOA
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Hi juzz
Originally posted by juzz:
The Spitfire is slower because of all the crap hanging out under the wings - "cooling drag". (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
Actually the Spitfire is slower by design. Nope, they didn't want it to be slow, but it was the price they had to pay for its superfluous manoeuvrability. It turns out that the design criteria that produce high-speed aircraft conflict with those that produce highly manoeuvrable aircraft. So for example, aircraft that are manoeuvrable generally have a low wing loading, while aircraft that are faster have a higher wing loading. There are very good aerodynamic reasons for that and it was simply the case that when the Spitfire was designed, high manoeuvrability was thought to be more important. That's why the Spitfire has elliptical wings for low induced drag and high sustained turn rates, and a low wing loading for high instantaneous turn rates. The penalty resulting from the low wing loading is paid for in the lower top speed. However, having said that, the Spitfire did have the highest dive speed, and got closer to Mach 1 in a dive than any other W.W.II aircraft.
Badboy
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Originally posted by F4UDOA:
Niklas,
Here it is power loading listed at 6.8 so the HP must be at around 1700HP
military power
Vmax=395MPH at 23000FT.
Vmax at sea level=341MPH
F4UDOA
Ok guys, I see folk quoting drag coefficients, engine power and equivalent flat plate areas and making predictions about top speeds, but we can put this on a scientific basis, we can use those values to calculate the top speed.
I've done the math and the equation can be used to calculate the top speed given the data you guys have been quoting.
I've just tested it on the F6F-5 for example and given a peak prop efficiency of 83% from an engine delivering 2000HP and wings with an area of 334ft^2 and a Cd0 of 0.0223 the top speed at sea level clocks out at 320mph. I have a published value of 318, so the calculation has less than a 1% error.
Now don't lynch me because of my data
If anyone would like to post some data sets, I'll do the calculations and post the top speeds?
Data required is:
Prop Efficiency (e)
Altitude (h)
Engine Horsepower (hp)
Wing Area (s)
Zero Lift Drag Coefficient (Cd0)
The aircraft weight and induced drag are neglected, which result in a very small error, often less than 1%.
Badboy
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Badboy,
How's the research going, do you have anything to share?? When will you be publishing or disclosing your research?
What do you think about this topic? Is it impossible for a 12000lb A/C to fly 360MPH at sea level?
I just looked up the F7F stats on the 214th.com. It had a speed of 380MPH at 20,000lbs. at sea level. It must be full of helium I guess. Right Niklas?
Later
F4UDOA
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Fishu, water injection on the P-47D was the same as MW 50 on German planes. Except Republic actually installed it instead of just fooling around with prototypes for 2 years. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
P-47D30 had 2600 hp with water injection, and that power was sustained from sea level up to 25,000 feet.
[This message has been edited by funked (edited 08-10-2000).]
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Originally posted by funked:
Fishu, water injection on the P-47D was the same as MW 50 on German planes. Except Republic actually installed it instead of just fooling around with prototypes for 2 years. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
P-47D30 had 2600 hp with water injection, and that power was sustained from sea level up to 25,000 feet.
[This message has been edited by funked (edited 08-10-2000).]
..and german planes are on their best in low, while P47 gains that higher where germans lack the supercharger...
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Badboy,
I was just looking at your last post and I was hoping you could do the same calculation and show the math for the F4U-1D. Top speed at sea level for this A/C should be 359MPH.
The engine delivers the same rated horsepower as the F6F-5 at 2250HP from the manual. I noticed you used 2000HP for your calculation but I'm not sure if you were using BHP or HP. In any case here are the stats for the F4U-1D.
Prop efficiency I don't know but the blade design is different than that used in the F6F-5. The F4U-1D used the 6541A-0 or 6501A-0 which is different from early model F4U's and is said to increase performance as stated in the pilots manual.
Altitude=Sea level
HP=2250HP
Wing Area=314^2ft
Cdo=This is the question to be answered. How low was the F4U Cdo. I unfortunately do not know how to calc. this number as a static value. I know it varies with speed but I don't know how to determine what the "baseline" Cdo of any A/C is. Obviouly it is very low at higher speed to allow the F4U to reach a high speed at low alt. I believe this is mostly because of high wing loading and a low aspect ratio of 5.35.
Thanks
F4UDOA
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Ok, here's some f values calculated from the Cd0, wing area and data for max speed at sea level, using my spreadsheet that I made available on this board a little while back.
P-51D - 0.0169 * 235.75 = 3.98 sq ft
P-47D - 0.02064 * 300 = 6.19 sq ft
F4u - 0.018 * 314 = 5.65 sq ft
P-38J - 0.02264 * 327.5 = 7.41 sq ft
109G - 0.0258 * 173 = 4.46
190A - 0.02328 * 197 = 4.59
Looks reasonable to me
[This message has been edited by wells (edited 08-10-2000).]
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You got it Fishu.
So P-47D-30 has about the same speed as a Fw 190A-5 at sea level, but at 25,000 feet the 190 has lost a lot of power, while the Jug still has full power and is much faster.
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Originally posted by funked:
You got it Fishu.
So P-47D-30 has about the same speed as a Fw 190A-5 at sea level, but at 25,000 feet the 190 has lost a lot of power, while the Jug still has full power and is much faster.
I think I've known and said that long time ago.. but thing is that P47 low altitude seems to be a beast, which I didn't really mind it to be in WB or real life stories, until above 20k...
Could think that 5k P47 would be dead meat for advantageous 190 or 109, but it performs *very* good against them in AH that low. (at least did?)
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Fw 190A-5 and all Me 109 variants in AH will out climb and out accelerate the P-47D at 5k. In my experience they can out turn the Jug too. Of the Luftwaffe fighters, only the Bf 109F-4 is slower than the Jug at 5k, and only the Fw 190A-8 is outclimbed/accelerated by the Jug at 5k. The only way the Jug is not dead meat is if he starts higher or uses his superior armament and armor. Above 5k his diving ability becomes a factor if he needs to escape.
Real life Luftwaffe results were not good against the P-47 at any altitude, so I wouldn't complain. If anything, the D-30 is conservatively modeled - its performance is close to some data I have seen for D-25 (2300 hp).
[This message has been edited by funked (edited 08-11-2000).]
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no one realizes that the p47 is just as slow as the p38 on the deck in AH (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
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Niklas,
I don't know if you've already been corrected. You said way back:
"The Jug? Try to bring 15000 pounds into a roll motion"
Ahem. It has been said often enough to you that weight matters very little in aerodynamics. The T-Bolt had the best roll rate of any USAAF fighter, bar none, and the second best roll rate in the ETO. Only the FW-190 out rolled it. How could weight possibly effect?
The weight of the fuselage is lifted at all, and the weight of the wings doesn't matter because rolling is function of increasing the lift on one wing and decreasing it on another. Pure aerodymanics. Weight effected the dive of an airplane. Period. Bye.
------------------
"If I told you that there were a squadron of fighters waiting to pounce the moment you fired at me, would you believe me?"
"No."
"Er... how about just one then?"
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I think he was talking about roll acceleration, where weight is a factor. The wings, landing gear, guns and ammo only weigh about 3500 lbs in the P-47.
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ispar, youīre absolutly right if you only compare sustained max. roll rate. I said myself later with the "example"of the 747 that weight is not important for a max. roll rate. But like for the topspeed you must first accelerate to the max. roll rate, and here DOES weight play a roll, in the acceleration progress (not only weight but where the mass is or how far it is outside of the center of gravity). In a scissor manoevre for example, roll acceleration is important too- scissors in a slow fight against a P38 work fine usually (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif) . And now it depends on the test method.
Btw, if youīre convinced that the P47 outrolled the F4U than adress your posting pls to F4Udoa - now, after F4Udoa admitted that the F4U is only superior compared to other american aircrafts at ultra low speeds and very very high speeds you can be right for the usual combat speed range. But you have to clarify that with him, not with me
niklas
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actually, the P-47's roll rate kinda sucked
http://naca.larc.nasa.gov/reports/1952/naca-tn-2675/ (http://naca.larc.nasa.gov/reports/1952/naca-tn-2675/)
but it could definitely outroll a 109 at high speeds
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Niklas,
I have data on the rolling ability of the F4U, P-47 and all other American types. In comparison testing the F4U was said to be equal to the FW190A5. These test were not documented by NACA so I will not debate the fine rolling qualities of the FW190.
However the P-47 was less than a steller rolling A/C. I have however seen some mention of the P-47 being an exceptional rolling A/C. However I do not now where this information durives. The factors that affect roll positively are some of the that affect range negatively. They are
1.Aspect ratio. It seems that A/C with a high apsect ratio have a purpose build for range. IE P-38, A6M-5 Zero and your 747 Niklas. But these long narrow wings take a long time to get moving. I believe the Spit also suffered from this but It's range also seemd to lack from small internal fuel stores. The Spit is an airplane that baffles me completely.
2. Area of Aileron. This seems to be the down fall of the P-47. Either the ailerons are not far enough out on the wing on the are displaced is just to small. If you cannot deflect enough air you will not have positive aileron response.
3. Stall speed. If the P-47 had the best ailerons in the world it would make a difference at low speed. With a stall speed as high as the Tbolts you don't have to deflect your ailerons very far before your on your inverted heading for terra firma.
In anycase they would appear ineffective.
4. Weight. Not total weight but distribution of weight. The F4U after the very early model carried no fuel in the wings so it had very little to slow down the start of a roll. By contrast the P-38 would have a hard time entering a roll especially at low speed where the airflow is much less.
It seems like there is a inverse relationship between range and roll. It is hard to have both. The Mustang is the exeption to that rule as there are exceptions to all rules of aerodymamics. The Laminer wing of the Mustang made for great range while the relatively low aspect ratio allowed for a high rate of roll although it suffered at low speed. By contrast the Grumman F6F had a low aspect ratio large ailerons and rolled well at low speeds but was only in the range of a P-47 at high speed, go figure.
Later
F4UDOA
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All other things being equal, roll rate is only dependant upon wingspan. You can have a wing of any area or aspect ratio, but the higher span will roll slower. The thing with the Spitfire and P-47 with their elliptical planforms, is that the ailerons have to be 'inboard' a tad and the hinge line is at an angle, both of which reduce the rolling authority. The elliptical planform is good though, for lower roll inertia.
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Wells,
Why was the F4U's rolling ability so exceptional? It had quite the wing span.
Do you have any NACA docs on it??
Thanks
F4UDOA
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There are so many aerodynamic factors that aren't taken into account in this thread, it makes my head hurt. I'm surprised that no-one mentions airfoil data anywhere. The top speed speed algorythm posted by badboy is pretty decent. But as far as roll rates and acceleration and such I haven't seen much usefull input. Roll is affected not so much by wingspan or aspect ratio, but by how the weight is dispersed around the c/g. Also the size, location and aerodynamics of the control surfaces themselves play a huge part in how quickly you can roll(pitch and yaw as well). I think the biggest problem I see here is a lack of accepted real data, both actual flight test data and design data(C/L, horsepower, weight, airfoil, prop efficiency, etc...) I believe if we could see the actual data AH uses for the aircraft we could pinpoint problems in the FM much easier. Untill then it's all pointless isn't it (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
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Originally posted by F4UDOA:
Badboy,
I was just looking at your last post and I was hoping you could do the same calculation and show the math for the F4U-1D.
Thanks
F4UDOA
Hi F4UDOA,
Hope you don't mind if I try and answer several posts in one go.
Firstly I'd like to clear up the confusion about the aircraft weight. It is true that weight is an important factor when you consider sustained and instantaneous turning ability and climb rate for example, but it is not so important when considering top speed. Weight will of course have an influence on the top speed, just a very small one. Weight has a much greater impact on acceleration, which influences how long it takes for an aircraft to reach its top speed, but if other things remain equal the weight has an almost negligible influence on the top speed itself. So for example, the difference in top speed for an aircraft with a full load of fuel, and one nearly empty, is often less than a couple of knots and almost always results in less than 1% error. However, that is providing the difference in weight is internal, because external stores change the drag, and that does have a significant influence on speed.
So, regardless of the weight, can an aircraft travel at 360mph at sea level?
I will answer that, but perhaps not in the way you might have hoped. What I will do is explain what that would require. Exactly how much power is required to push an aircraft through the dense sea level air at a specific speed?
I've placed a graphical surface at the end of this message which shows the relationship between the brake horse power, the speed and the equivalent flat plate area for any aircraft at sea level with a prop efficiency of 85%. There is nothing contentious about that surface, it is simple aerodynamics and a little math and could apply equally well to any aircraft. The only compromise being the assumption about the prop efficiency.
So, suppose you want to know if an aircraft can reach 380mph at sea level with an engine delivering 2000hp? Follow the red line up from 380mph until it reaches 2000hp and then follow it down to see that it would require an equivalent flat plate area of 5 ft^2 or less to travel that fast. Basically, any aircraft with an f value less than 5 should be able to do it. For a speed of 360mph with the same power, any aircraft with an f value less than 6 ft^2 would be ok. So for the F4U providing it had a Cdo less than 6/314 = 0.19 it should be able go that fast. The chart should allow you to check other combinations.
The big question of course is did any of the aircraft you have been discussing really have f values that low? Almost every version of the F7F is claimed to be faster than 360mph at sea level, with the claims for the fastest reaching as high as 394mph. The F4U-4 is quoted at 381mph at sea level and the F2G2 (Goodyear) an amazing 399mph. Of course I can't defend those claims, because like everyone else, I'm at the mercy of my sources (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
Hope that is helpful, here is the graph
(http://www.netcomuk.co.uk/~badboy/PDF/power2.gif)
Badboy
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Originally posted by Badboy:
So, suppose you want to know if an aircraft can reach 380mph at sea level with an engine delivering 2000hp? Follow the red line up from 380mph until it reaches 2000hp and then follow it down to see that it would require an equivalent flat plate area of 5 ft^2 or less to travel that fast. Basically, any aircraft with an f value less than 5 should be able to do it. For a speed of 360mph with the same power, any aircraft with an f value less than 6 ft^2 would be ok. So for the F4U providing it had a Cdo less than 6/314 = 0.19 it should be able go that fast. The chart should allow you to check other combinations.
[/B]
Oops, sorry guys, I can't read my own chart (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
I've misread the f values, 5 should be 4.5 and the 6 should be 5.5 giving 5.5/314 = 0.0175... fumbled but not dropped (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
Badboy
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Originally posted by wells:
All other things being equal, roll rate is only dependant upon wingspan. You can have a wing of any area or aspect ratio, but the higher span will roll slower. The thing with the Spitfire and P-47 with their elliptical planforms, is that the ailerons have to be 'inboard' a tad and the hinge line is at an angle, both of which reduce the rolling authority. The elliptical planform is good though, for lower roll inertia.
If memory serves, it is inversly proportional to the fourth power of the span, which is why they clipped the wings of the Spitfire, the small reduction in the span had almost no effect on the lift but resulted in a dramatic increase in roll rate.
Badboy
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DOA,
The F4u's ailerons deflected 19 up, 14 down. It's roll rate at 300 mph was 90 deg/sec, right? Compare that to the P-51, where the ailerons deflected only 10 up and 10 down for a very close to equal roll rate. The P-47, while having similar span to an F4u, the ailerons only deflected 16 up, 12 down. That's why I said, everything else being equal.
Badboy, the relationship is direct (inversely)...no powers. The wingtip on a wing that has twice the span has to travel twice the distance for the same helix angle.
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Originally posted by funked:
Fw 190A-5 and all Me 109 variants in AH will out climb and out accelerate the P-47D at 5k. In my experience they can out turn the Jug too. (edited 08-11-2000).]
I was outrun by P-47's in AH while flying various Me 109 types, including once the G-10 but I was out of WEP... it also blows the macchi c205 away in speed and accel which seems absurd to me too....
DB
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fire_ant, if that happened at 5k then they must have started faster or higher than you.
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WROOOOOOOOM
<sound of G10 engine>
Awww <in love>
And how's this for a *real* 109 engine start: http://www.geocities.com/stsantasatan/engstart.wav (http://www.geocities.com/stsantasatan/engstart.wav)
Listen to it, in awe (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
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StSanta
JG54 "Grünherz"
"If you died a stones throw from your wingie; you did no wrong". - Hangtime
[This message has been edited by StSanta (edited 08-12-2000).]
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Niklas said: The 109 was constantly improved.
Perhaps you're from Venice and feel that adding gondolas to an airframe constitutes an improvement? (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
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SnakeEyes
o-o-o-
=4th Fighter Group=
[This message has been edited by SnakeEyes (edited 08-12-2000).]
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Originally posted by fire_ant:
I was outrun by P-47's in AH while flying various Me 109 types, including once the G-10 but I was out of WEP... it also blows the macchi c205 away in speed and accel which seems absurd to me too....
At least P47 seems to accerlate alot faster than Typhoon and also maintain speed better.
in Typhoon you turn just a tiny bit and speed is gone, while in P47 you can turn without much fear of getting too slow on tiny turn.. (if you get, you will anyway accerlate enough quick)
Though, I must admit this is the best P47 I've ever flown in any game.
P-47 is sooo fun plane.
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It's got to be that *nasty* Tiffie wing design Fishu bleeding all of the E in turns... it's not terribly efficient.
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SnakeEyes
o-o-o-
=4th Fighter Group=
[This message has been edited by SnakeEyes (edited 08-12-2000).]
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Originally posted by wells:
DOA,
Badboy, the relationship is direct (inversely)...no powers. The wingtip on a wing that has twice the span has to travel twice the distance for the same helix angle.
Sorry, I was a bit vague in my last post, it was late. When you compare the rolling performance of aircraft it makes sense to relate it to the stick force because your average pilot could only reasonably be expected to apply about 50lbs laterally, in any case it is common to assume equal pilot physiology, so equal stick force is a valid assumption in that respect. The calculations for the time to bank through a given angle, for a given stick force varies with the fourth power of the wing span. Also there is a damping effect that depends on the aspect ratio and the rate of roll. For any given aspect ratio the difficulty of providing light ailerons also varies as the fourth power of the span so that during WWII the problem of aileron ballance was very delicate. Aileron hinge moments are very sensitive to small proturberances on the control surface as well as to the curvature of the profile. Since (in the UK and Germany any way) the standard of worksmanship deteriorated as time went on, there was often a large variation in aileron heaviness between aircraft of a given type.
So for example, the clipped wings of the Spitfire that reduced the span by a little more than 11%, increased the roll rate from 105dps at 170kts to 150dps.
As a further example, the Me109E had very good aileron control upto about 170kts, above that speed the ailerons became rapidly heavier so that by about 260kts, they were almost solid. Specifically, the Me109E took 4 seconds to bank 45 degrees at 350kts (11dps) which for a fighter is excessive. The later Spitfires rate of roll at 350kts was 60dps, and the Fw190 was even higher.
I think many pilots would agree that these issues are very important from the perspective of air combat. In many ways, a good roll rate, or more importantly, good acceleration into the roll, was considered more important than turn rate and second only to the ability to hold a high speed dive with precision. The ability to break rapidly, is not only a life saver, but has very strong tactical implications in air combat. A good roll rate, properly applied can be converted directly to angular gains in a turning engagement. I think Andy has an explanation of the OODA cycle on the web? I have one somewhere if anyone is interested in the details.
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Fishu, if we are still talking about 5k, the P-47D-30 should accelerate a little better than a Typhoon in level flight at low speeds. It's got a better power:weight ratio as evidenced by the climb rates at 5k on the HTC charts.
At high speeds (above 250 mph or so) I would expect the Typhoon to accelerate better though. Typhoon AFAIK is the fastest accelerating plane above 250 mph and below 7,000 feet. P-51 and G-10 are pretty fast in that regime too.
I already did a lot of Typhoon acceleration tests, so I'll do a P-47D-30 test to compare.
[This message has been edited by funked (edited 08-12-2000).]
[This message has been edited by funked (edited 08-12-2000).]
[This message has been edited by funked (edited 08-12-2000).]
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Originally posted by Badboy:
When you compare the rolling performance of aircraft it makes sense to relate it to the stick force because your average pilot could only reasonably be expected to apply about 50lbs laterally, in any case it is common to assume equal pilot physiology, so equal stick force is a valid assumption in that respect.
As an afterthought, one of the most impressive applications of that principle occurred during the Korean conflict when the F86, with its hydraulically powered ailerons, was able to use that advantage to defeat the superior turn rate of the MiG15. It turns out that the main proponent of the theory, (Colonel Boyd USAF) was instrumental in having the F86's ailerons so equipped. I feel confident that it was the roll rate advantage (without wishing to play down the skill and courage of the pilots involved) that was largely responsible for the high kill ratio achieved during that conflict. I'm not sure offhand what US aircraft had powered ailerons during WWII, I think the P-38 did, even though its roll rate was not particularly impressive. I'll have to check. But it is easy to see a strong correlation between the W.W.II aircraft that had light ailerons at high speeds and those that were most successful.
Badboy
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Great thread to read. Thanks guys!
-Westy
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Originally posted by funked:
Fishu, if we are still talking about 5k, the P-47D-30 should accelerate a little better than a Typhoon in level flight at low speeds. It's got a better power:weight ratio as evidenced by the climb rates at 5k on the HTC charts.
At high speeds (above 250 mph or so) I would expect the Typhoon to accelerate better though. Typhoon AFAIK is the fastest accelerating plane above 250 mph and below 7,000 feet. P-51 and G-10 are pretty fast in that regime too.
I already did a lot of Typhoon acceleration tests, so I'll do a P-47D-30 test to compare.
Begining of acceleration is slow in Typhoon, but that thing flies very fast at low..
Outruns Bf109G10 on the deck (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
But that plane sure does lose its speed VERY easy compared to other planes..
I had a *long* run with BF109G10 chasing my Typhoon as I were looking for tanks and told him not to, but he still kept chasing...
There I noticed how easily Typhoon looses speed in small turns, because I had before that flown P47 many times and felt Typhoon like fast rocket that you don't really wan't to turn after you set its course..
Where P47 did not loose speed as easy and did also maneuver far better. (not to talk about that E retention in any case..)
Typhoon is not as maneuverable in real life either as P-47, but I don't think that P-47 either is any stunt machine..
Do I have to mention those several times when I kept zooming multiple targets alone in P-47 with droptank in it? it hold E *pretty* well...
I have seen this happen in Yak also, when P-47 with lower E pulls up after me after I have dive & pull up.. and keep E better than P-51 which had faster speed before pull.
(not to mention that P-47 hitting me from 1.3k away two seconds before we both stalled (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif))
(and yes.. .50 caliber in AH can hit up to 1.5k in any plane)
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Originally posted by Badboy:
I'm not sure offhand what US aircraft had powered ailerons during WWII, I think the P-38 did, even though its roll rate was not particularly impressive. I'll have to check. But it is easy to see a strong correlation between the W.W.II aircraft that had light ailerons at high speeds and those that were most successful.
P-38 L model had hydraulical ailerons at least..
I don't think that J or any previous one had.
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Originally posted by Badboy:
As an afterthought, one of the most impressive applications of that principle occurred during the Korean conflict when the F86, with its hydraulically powered ailerons, was able to use that advantage to defeat the superior turn rate of the MiG15. It turns out that the main proponent of the theory, (Colonel Boyd USAF) was instrumental in having the F86's ailerons so equipped. I feel confident that it was the roll rate advantage (without wishing to play down the skill and courage of the pilots involved) that was largely responsible for the high kill ratio achieved during that conflict. I'm not sure offhand what US aircraft had powered ailerons during WWII, I think the P-38 did, even though its roll rate was not particularly impressive. I'll have to check. But it is easy to see a strong correlation between the W.W.II aircraft that had light ailerons at high speeds and those that were most successful.
Badboy
Col. Boyd was quite a man...
BadBoy, ever read anything about the problem
with the F-86F's aileron's locking up during a roll at low altitude?
Boyd, Ascani, and Yeager happened upon it when Emmet Hatch augered one time...took 'em forever but they went to one of the assembly lines that installed them. Turns out a guy was putting a bolt in backwards. (http://bbs.hitechcreations.com/smf/Smileys/default/eek.gif)
I would guess the reason the P-38 got boosted ailerons due to the difficulty of turning the yoke at high speeds
- Jig
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Badboy, P-38L had powered ailerons. Roll rate was exceptional at high speeds because full aileron deflection could be achieved.
The Corsair used balance tabs on the ailerons, giving a similar effect.
Late model Hellcats had balance tabs as well, but they don't appear to have been as effective.
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Hmmm. That assertion wasn't based on hard factual data, so... I stand corrected (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif). Interesting discussion chaps, glad it's cooled down a bit.
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"If I told you that there were a squadron of fighters waiting to pounce the moment you fired at me, would you believe me?"
"No."
"Er... how about just one then?"