Low alt performance of Big Planes in AH

[-lynx-]

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.

------------------
-lynx-
13 Sqn RAF

[juzz]

Who cares, the F4U-4 never even existed anyway. Go find one and mail it to me, then I'll believe it.

[jehu]

According to science, the bumble bee, as well as a Frisbee, should not be able to fly. Mathematically that is.

------------------
jehu

[F4UDOA]

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

[niklas]

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  
(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 ... )

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 (   ), and all i have to say is: the FU4 is too fast.

niklas

[Badboy]

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  

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  

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  

Badboy

[wells]

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.

[F4UDOA]

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

[funked]

*Stupid Comment Deleted*

[This message has been edited by funked (edited 08-09-2000).]

[niklas]

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).]

[F4UDOA]

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  

[PC]

niklas, listen to F4UDOA and please stop with this stupidity, it has gone passed the point of being funny.

PC

[-towd_]

im so confused, blue planes are slower ? right?

shit i need a drink

[PC]

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

[funked]

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?