Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: BigCrate on April 06, 2002, 12:12:13 AM
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Ok my F4U climb rae ? is
Why does the F4U and P-47 climb so poorly???
I thought the F4U was a good climber. most version of the F4 in AH have the same paddle props as the P-38k was fitted with.
And all had well over 2000HP P&W 2800 engines. Plus those big gull wings.
So why does the F4 climb so poorly??
Cw
=Twin Engined Devils=
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If I were going to guess I would say that the F4U doesnt climb well due to the shape of its wing. Its probably a semi-semetric shape. This is the reason a P51 pilot on the history channel gave for the P51 not being as good of a climber as the Spitfire.
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climb performance is just power to weight ratio.
more power, less weight = better climb.
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the prop efficiency and aircraft drag etc also affect climb but not nearly as much as power to weight ratio
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Going by the data, the f4u-1 ought to have just about the best climb rate of any pacific war plane. Only the 109f or Spit9 should be clearly superior, and even then only at low altitude. The trick is usually finding the best speed at which to climb... If that is not the case in AH, something is modeled wrong, or you've got a whole lot of gas on board...
-Blogs
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because its a hog. It belongs down low snotting around the muck. :D :D
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Originally posted by Tac
because its a hog. It belongs down low snotting around the muck. :D :D
Shut your trap, thats my baby your talking about :D
Booky
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A p51 can climb away from a spitfire at 200mph.
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If I recall right HT once said something about F4u's performance and how its poor prop efficiency at low speeds made it accelerate poorly. Maybe that has also something to do with climb?
This was in beta or shortly there after so I don't even pretend to remember 100% correctly.
// fats
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Heya's
,
This question has been at the top of my list for years.
First things first. The power loading of the F4U-1 and 1D is amoung the best of all American fighters and better than any production model P38. The F4U-4 is far and away the best American fighter in this regard. Here is a quick breakdown of 1944 fighters except the F4U-1A from 1943 best to worst.
1. F4U-1D
Weight = 12,175LBS
HP= 2250
Power to weight ratio=5.411
2. P-38L
Weight = 17,500LBS
HP= 3200
Power to weight ratio= 5.468
3.F6F-5
Weight= 12,485LBS
HP=2250
Power to weight ratio= 5.54
4. P-51D
Weight 9611lbs (AH listed Normal Weight. 100% internal fuel is 10,100)
HP=1720
Power to weight= 5.58
5.P-47D-30
Weight= 14500
HP=2600
Power to weight =5.576.
6. F4U-1A (Empty wing tanks)
Weight=12,037
HP=2135 (later -1A's had 2250HP)
Power to weight ratio= 5.63 (5.34 with later 1944 HP)
Here are the drag Cdo of these A/C best to worst
1. P-51D = .017
2. F4U-1/1D= .020
3. P-47D= .022
4. F6F-5= .023
5. P-38L= .028
Based on this alone the F4U-1D should be the best climber/Accelerator amoung these A/C. However there is the question of prop efficiency. Well I know that there was a prop change right around 1944 that change the F4U prop from a 3 blade toothpic to a three blade paddle and it increased climb significantly. So why isn't it as good or better than the other A/C in AH?
All I can tell you is that anecdotally the F4U outclimbed most other fighters. I cannot however provide hard data to that effect. However this is what I do have.
1. In the test performed between the F4U-1A(2250HP 1944) and P-51B the F4U outclimbed the P-51 and reached a top speed of 365MPH at sea level and 430MPH at 20K.
2. In the test performed in late 1942 with a very early model F4U-1 against the captured A6M2 (Koga's Zero) the F4U was equal to if not slightly less in rate of climb up to 20K where the F4U was far superior.
3. In the 1944 test between the F4U-1D and A6M5 the F4U-1D was equal in climb up to 12k where it was 750FPM better and 500FPM superior at 17k and above. In the same test the F6F-5 was inferior up to 12k equal to 17K and superior above that alt.
4. In the test between the F4U-1D, F6F-3 and FW190A5 the F4U was SUPERIOR in climb at it's best climbing speeds of 160MPH and lower to both other A/C. It was slower in climb than the 190 at speeds above 160MPH(140Knots).
5. In a modern test in 1989 by a group of modern test pilots the F4U finished second to the F6F-5 in climb to 10K. It was superior to the P-51D and P-47D-30. The F6F however was 500lbs lighter than the F4U during this test. It would normally be 500Lbs heavier.
6. In Butch O'Hare's memoirs "Fatefull Rendevous" he comments on his squadron of F6F-3 taking a climb to 20,000ft challenge by the members of a F4U-1 Squadron in 1943. He says that it was widely recognized that the F4U climbed approx. 750fpm better than the F6F-3 but they took the challenge anyway. His squadron lost the bet but "not by much" so he was satisfied.
I don't think Butch O'Hare was saying this for my benifit.
In any case I have power to weight and drag numbers that point towards this as well as annecdotal evidence and flight test data. However I do not have NAVAIR docs to prove otherwise. So I guess I will keep on searching.
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DOA lots of good info!!! But I think your wrong on thinking that any f4 could out climb or stay with a spit or 109 in a climb.. I also think your wrong on thinking the f4s could out climb a P-38 any P-38. The 38s had a big damn aspect ratio mixed with a good power loading. And you got a P-38 climb rate :). I do think the hogs should be between the 51s climb and the 38s climb rate. Based on the info you gave.
Cw
=Twin Engined Devils=
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You've got a lot of apples and oranges going on in your comparisons. Different propellers matter. Different super chargers matter. Different variants of the same engines matter. An F4u1 with a 2250 HP engine was not a production model. It was more likely an F4u-3 or -4.
Good data on the climb rates for various F4u types
can be found in the book US Navy Aircraft Since 1911 (Swanborough and Bowers?).
A climb rate chart for the f4u-1 can be found in the pilot's manual.
Standard aircraft Characteristics Charts for the F4u-4 can be found at http://www.history.navy.mil/branches/hist-ac/fighter.htm
All the numbers are quite impressive. Not only does that f4u outclimb the F6f, but its forward rate of speed is also faster. It's also a great spiral climber, which many planes cannot do well.
The only wrinkle is that the best speed of climb for an F4u is closer to its stall speed than it is in an F6.
-Blogs
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Heya Bigcrate,
I don't mean to say that the F4U should outclimb those Euro rockets like the 109 and Spit. I'm not crazy and their power loading is much better than the F4U. That's why I listed the American A/C for referance. The P-38 climb is a function of more area of wing being hit with prop wash creating greater lift. However the F4U's acceleration should be better or at least equal to the P-38 based on power to weight and drag coefficient.
JoeBlogs,
The F4U is on area that I have more information on than anyone I have ever spoken too, including Pyro. I have many Vought original Docs, Flight Manuals and countless others.
The F4U HP.
F4U-1 early 2,000HP
F4U-1A early 2135HP
F4U-1D and late -1A 2250HP
F4U-3 with supercharger 2800HP
F4U-4 2450HP
F4U-5 2800HP
AU-1 I need to look at my books. The rest is from memory. I am not in my library right now.
Anyway I am sure I will post the docs shortly.
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F4udoa, lift from prop wash does not effect climb rate.
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Hitech
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I have read that the addition wing area covered by prop wash increases the lift, as well as the the high aspect ratio adding to lift coefficient. Both A/C have the same Airfoil so why the increased climb rate when the F4U has power loading, Wing loading and drag on it's side. Also based on power loading and drag the F4U should accelerate better as well.
If I'm wrong great. But why??
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DOA,
Think drag, not lift. The drag coefficients you gave are only good at high speeds, where you can't climb too good. I bet the drag coefficient on the F4u at climb speed is about 0.04. A high aspect ratio reduces the induced drag, which is greatest at slow speeds.
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F4udoa:
After sending my last note, I thought, Blogs the F4u-1D has the R2800-20W and that means 2250 HP.
Are you sure the F4u and F6f have the same airfoil? Seems to me a different aspect ratio should almost certainly imply a different cross section. Even so, the two wings are set at a different angle of attack..
Other advantages of the F4u -- the gull wing lets the wings meet the fusalage at right angles, which some engineers argue is more aerodynamic. The wings are smoother too - spot welded in front and fabric covered in back.
I hope you tell us when your site is back up. I am very much a collector of aviation materials and I am always looking for more. What do you regard as your best finds?
-Blogs
JoeBlogs,
The F4U is on area that I have more information on than anyone I have ever spoken too, including Pyro. I have many Vought original Docs, Flight Manuals and countless others.
The F4U HP.
F4U-1 early 2,000HP
F4U-1A early 2135HP
F4U-1D and late -1A 2250HP
F4U-3 with supercharger 2800HP
F4U-4 2450HP
F4U-5 2800HP
AU-1 I need to look at my books. The rest is from memory. I am not in my library right now.
Anyway I am sure I will post the docs shortly. [/B][/QUOTE]
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Wells,
I thought Cd was constant? I know Cdi changes with speed but shouldn't the A/C with the lowest Cd climb better than one with higher drag such as the P-38? If the drag of the F4U is .04 at high AoA what is the P-38? They both have the same airfoil and the 38 has two engines nacelles to deal with. Does aspect ratio account for that much climb? What about acceleration? Does it work the same.
JoeBlogs,
My best find would be the Fw190 vrs F4U F6F and the P-51B vrs the F4U.
I got them from the author of "America's Hundred Thousand". He has the original copies and I scanned and posted them. You may see them on the web in various places now but I assure you they came from me first. I know because Frances Dean made notes in pencil on the reports. Every time I see them posted I see the notes on them so I know the copies came from me since Mr.Dean never published them. Hehe, my contribution to society.
Also the Docs I got from Vought have alot of good info I have never seen anywhere else on the F2G, F4U-3(a monster), F4U-4 and F4U-5. The F4U-3 was superior to the F2G in almost every way except sea level performance. It had a top speed of 490MPH at 27K.
I will do my web page soon I promise.
FYI, Barret Tillmans Corsair book has some very good annecdotal info but not much documentation. I would luv to speak to him an pic through his collection.
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DOA,
Calculate induced drag at 150 mph for both planes.
F4u with 314 sq ft of wing, aspect ratio = 5.35
Cl = 0.664
Cdi ~ 0.026
Induced drag ~ 470 lbs
P-38 with 327.5 sq ft and 8.25 aspect ratio
Cl = 0.929
Cdi ~ 0.033
Induced drag ~ 622 lbs
If the P-38 had the same aspect ratio as the F4u, induced drag would go up 54% to 959 lbs. So, the P-38 gains 337 lbs of *excess thrust* by having a higher aspect ratio. Since it weighs 17500 lbs, the climb rate benefits by 250 ft/min or so.
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F4UDOA
The materials "Fw190 vrs F4U F6F, and the P-51B vrs the F4U," are those gov docs or articles in Flight Journal?
On CD, my aerodynamics are rusty but I thought that while you can nail two of the three drag parameters using dimensional information, the third can only be gotten from wind tunnel/flight tests (at least with the math available at the time, todays computers are getting us closer to full simulation of these effects).
Also doesn't CD vary with angle of incidence, a function of the planes design and the angle of attack in the optimal climb attitude?
-Blogs
Originally posted by F4UDOA
Wells,
I thought Cd was constant? I know Cdi changes with speed but shouldn't the A/C with the lowest Cd climb better than one with higher drag such as the P-38? If the drag of the F4U is .04 at high AoA what is the P-38? They both have the same airfoil and the 38 has two engines nacelles to deal with. Does aspect ratio account for that much climb? What about acceleration? Does it work the same.
JoeBlogs,
My best find would be the Fw190 vrs F4U F6F and the P-51B vrs the F4U.
I got them from the author of "America's Hundred Thousand". He has the original copies and I scanned and posted them. You may see them on the web in various places now but I assure you they came from me first. I know because Frances Dean made notes in pencil on the reports. Every time I see them posted I see the notes on them so I know the copies came from me since Mr.Dean never published them. Hehe, my contribution to society.
Also the Docs I got from Vought have alot of good info I have never seen anywhere else on the F2G, F4U-3(a monster), F4U-4 and F4U-5. The F4U-3 was superior to the F2G in almost every way except sea level performance. It had a top speed of 490MPH at 27K.
I will do my web page soon I promise.
FYI, Barret Tillmans Corsair book has some very good annecdotal info but not much documentation. I would luv to speak to him an pic through his collection.
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Hi F4UDOA,
do you happen to have the climb rates for the F4U versions you posted the weight/power data for? I'd check if the data scales well - if it doesn't, probably a propeller change or something similar is to blame.
It's of course a simple "all else being equal" analysis, but that might be just what we need to confirm that all else wasn't equal ;-)
Regards,
Henning (HoHun)
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HoHun,
I absolutely do.
You can find them here.
F4U-1 and -1D performance and climb. (http://www.geocities.com/slakergmb/id63.htm)
The -1 and -1D have differant prop designs. The latter being a paddle blade. In the F4U flight manual for the -1 it says to use the 6501A-0 design as it increases performance.
JoeBlogs,
Flight Journal did a lousy job with the report. I don't know were they got there copy. For the full report go here.
FW190 vrs F6F, F4U-1D (http://www.geocities.com/slakergmb/id88.htm)
Notice the hand written scibble on the report. This was in pencil on the original copy I scanned.
BTW. I now AoA affects drag. But the F4U still has less total drag and better thrust to weight.
Wells,
The F4U still has less drag than the 38 and better thrust to weight. What Gives?? Also how about acceleration??
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Uber links dude. - blogs
Originally posted by F4UDOA
HoHun,
I absolutely do.
You can find them here.
F4U-1 and -1D performance and climb. (http://www.geocities.com/slakergmb/id63.htm)
The -1 and -1D have differant prop designs. The latter being a paddle blade. In the F4U flight manual for the -1 it says to use the 6501A-0 design as it increases performance.
JoeBlogs,
Flight Journal did a lousy job with the report. I don't know were they got there copy. For the full report go here.
FW190 vrs F6F, F4U-1D (http://www.geocities.com/slakergmb/id88.htm)
Notice the hand written scibble on the report. This was in pencil on the original copy I scanned.
BTW. I now AoA affects drag. But the F4U still has less total drag and better thrust to weight.
Wells,
The F4U still has less drag than the 38 and better thrust to weight. What Gives?? Also how about acceleration??
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One minor (perhaps) thing I noticed. I've no idea how to translate knots into MPH (that isnt my point though). The (very nice) page you linked to has 3 climb speeds on there.
At 140 knots- the U.S. planes were better.
At 160 knots- (i cant remember)
At 180 knots- The 190 was better.
What speed is auto-climb set to in Aces High? I believe it is around 165-170 mph, so how many knots is that?
This could play a large role in why the plane doesnt climb as well as you think it should... the A6M5s best climb speed was around 122 miles per hour at sea level.. in Aces High if you hit auto-climb, you start climbing at about 160-170 mph or so. So the Zeke doesnt climb as well as it 'should'- because it is going to fast.
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Hi F4UDOA,
>The -1 and -1D have differant prop designs. The latter being a paddle blade. In the F4U flight manual for the -1 it says to use the 6501A-0 design as it increases performance.
Thanks! According to my estimate, the paddle blade brought an increase of about 7% in the propeller efficiency in the climb. A paddle-blade equipped F4U-1 would have climbed at 3170 fpm instead of the 2880 fpm at WEP. The F4U-1D still was better at 3370 fpm, but that was due to the increase in power from 2135 to 2250 HP.
On the other hand, the paddle blade apparently was not as good in high-speed flight - I'd say it cost the F4U about 7 mph top speed at sea level. (Drag differences between the F4U-1 and -1D may account for some of that, though.)
By the way, that F4U-4 is quite a monster - though no WEP power rating is given, the climb rates indicate that it used no less than 3000 HP :-)
Regards,
Henning (HoHun)
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Urchin: Animal did post this link in another topic. There's a very nice converter for speeds, temperatures, areas etc...
http://www.joshmadison.com/software/convert/download.asp
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It should be noted that 2250hp is only available at sealevel. In 2k or so, power dropped already down to 2000hp.
Looking at the propeller in the drawings iīd say every F4U in the comparison has a kind of paddle blade propeller. Or is the Hamilton 6443 equal to the Curtiss714?
F4UDOA, i always wanted you ask something: You published once a huge PDF document with many good aircraft data (climb, speed, drag, takeoff...). I only have hardcopies, but the scan qualitiy was poor so the prints are very hard to read.
I know that it must have been a lot of work to scan them, but is it *maybe* possible to scan them again in higher resolution, say 200dpi? Iīm not sure, but it is possible that it was scanned in Colourmode or greyscale? 200dpi and black&white scan mode (not greyscale!) should keep size small and it maybe becomes much better readable.
About the aircraft comparison test: I think it says a lot what the title says of the doc i was speaking about:
CVA airplanes (?)
F4U-1
F4U-4
F4U-3
RIVAL AIRPLANES <<<<< P51, P38, F6F(?)
So when the P51 and P38 are in official documents labeled rivals, then you shouldnīt be surprised about the result of the F4U-P51 comparison, nor the other aircraft comparison. I smell a huge interest from someone to have at least on the paper a clearly superior aircraft. I heard that the USAAF and Navy didnīt liked them very much?
The part "The fw190 and the corsair were ABOUT equal in rate of roll" tells you a lot. Itīs funny to read how those vague expressions are choosen in a situation of clear disadvantage, comparing REAL performances!
Oh yes, those comparison reports tell you a lot, and i donīt mean only flight performances ;)
niklas
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Urchin,
I use a this web page for my metric as well as nautical mile conversions.
Conversion charts (http://convert.french-property.co.uk/index.htm)
140 Knots = 161MPH. The best climb speed for an F4U is 155MPH.
I haven't really experamented with sustained climb at different speeds. I tend to use zoom climb alot in AH. I build my speed to 300MPH and use a very low G pull and sustain a 4K a minute climb for some time. Flying the F4U in AH takes patience. I will test for best climb speed and post soon.
HoHun,
7% sounds about right. The late model F4U-1's would have climbed the best considering they were lighter and had less drag depending on condition(also they had the full 2250HP). The F4U-1D is the only A/C in AH that is modeled with external stores pylons regardless of loadout. Thes pylons took about 10MPH speed through out the speed range. In the "clean" condition the F4U-1D is as fast if not faster than the -1. The P-51,P-47 and F6F all carried similiar pylons but do not have them when not carrying bombs or DT's. And they are not penalized in speed when they drop there ordinance either.
Niklas,
I imagine you as an evil proffessor in a Labratory somewhere trying to build Frankenstein. Probably because your post are always so fiendish ;)
Anyway I will will scan those docs in high res and post them.
They do say "Rival" on the charts but remeber it was a business to sell airplanes in this country. It was not a government run project. Based on that the test that were conducted such as the P-51B vrs F4U/F6F. A6M2/5 vrs F4U and others and FW190 vrs F4U and F6F were all conducted by the Government. NAVAIR specifically, and there interest was providing the best chance for the Naval Aviators to win not to sell Airplanes or propaganda.
Reasons this is true
1. All of the enemy A/C tested either performed exactly to performance specs or exceeded them. Ala the Ki-84 flying at 422MPH. I doubt any Japanese pilot ever flew a KI-84 that fast. The FW190 A5 flew exactly to spec. and the A6M2 flew according to the intelligance report many sorties with no operation failures even when the allied A/C such as the P-51A and P-40 were unable to because of mechanical problems.
2. The test performed by the Navy on the P-51B and later the P-51D were not just comparisons but suitabilty trials. It was to be designated the Seahorse had it had better low speed handling. They also tried the P-39 which would have been a tail dragger with a tail hook and designated the Aerobonita. The Airforce never tried to adopt the F6F or F4U for it's own use. However the one Army Air Corps pilot did score a kill in an borrowed F4U-1 on Gaudacanal in 1943. The Only AF victory in a Marine A/C of the war.
3. In the Vought archives docs you refer to the "Rival" A/C are also all performing up to spec if not better. Take a look at the P-47D stats. It's listed as being faster than anywhere I have ever seen listed by Republic. Also the test against the P-51B ,it was clearly superior over 25K and described as such.
So you see not everyone is as fiendish as you Niklas :p
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Wells,
The F4U still has less drag than the 38 and better thrust to weight. What Gives?? Also how about acceleration??
Power loading doesn't tell you squat about T/W if you don't know the prop efficiency at the climb speed. I wouldn't call a 1% difference in power loadings 'better', equal is more like it. Sure the F4u has less drag, but it's got less power too. There's a couple of other things I thought of that might benefit the P-38. It's got a lower power loading on the prop disc (power per unit area), which makes prop efficiency a tad better, it varies with speed. It has a faster best climb speed (180 vs 155?). There's an advantage there too, since climb rate depends on the speed that you climb at.
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Hi F4UDOA,
another thing to consider when comparing the P-38 and the F4U is that the P-38 uses a turbo-supercharger while the F4U benefits from exhaust thrust.
I have no idea whether the power rating for the F4U's R-2800 takes the exhaust thrust into account. I've seen exhaust thrust handled by adding a constant amount of horsepower for a specific (high) speed, so if it was done like that for the F4U, the F4U doesn't actually have the quoted power available in a low speed climb. (The ram effect is probably calculated for a fixed speed, too.)
The P-38 doesn't enjoy the advantage of exhaust thrust, but as the turbo-supercharger operates (mostly) independend of the aircraft's speed, it did have its rated power available at low speeds, too, which might be a difference to the F4U's rating.
Regards,
Henning (HoHun)
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Wells,
I would not even question what you are saying except for this.
The climb differance between the F4U-1D and P-38L is very large even at the F4U's best rated alt at sea level. The power loading as you say is 1%. If not better for the F4U then equal. Ok then the variables.
1.Prop efficiency at climb speed. => If the differance between the prop efficiency of a paddle blade and a standard prop is only 7% then how much of a gap in efficiency could there be? Surely less than 7%? 7% of 4000FPM is 280. So the climb differance couldn't be more than that could it?
2. Two prop nacelles providing independant thrust.=> I can't even imagine what this means in terms of climb rate or if any engineer would even calculate this into his climb rate prediction. I have never seen anything to lead me to believe that twin engines would be more efficient in climb than a single. Surely the added drag penalty would be greater than the benifit of two engines.
3. Higher climb speed providing higher climb rate. => I was always under the impression that wing loading was the deciding factor in climb speed? Even late model F4U's have higher climb speeds because of higher weights than the early models. The climb speeds of Zero's, Spits and 109's are lower than the F4U's and yet their climb rates are higher than the P-38's. Certainly there is no rule dictating this.
4. High aspect ratio and induced drag=> I know the benifit of high aspect ratio is low induced drag however. Lift is also tied to induced drag. So if the F4U has higher induced drag then it also has high lift correct? So doesn't that mean it takes less power to fly?? Also since the Cl of the F4U-1D was reduced to 1.49(no flap) shouldn't that reduce the induced drag as well? I thought those two things are directly proportionate. The Spitfire had an extremely low Clmax as well giving it low induced drag and better E retention I believe.
I know all of these points are my limited understanding of aeodynamics but none of these things seem to account for the dramatic differance in rated climb.
HoHun,
What do you mean by the F4U not having rated power at climb speed? I don't understand what that means?
Thanks
F4UDOA
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Hi F4UDOA,
>What do you mean by the F4U not having rated power at climb speed? I don't understand what that means?
The exhaust thrust of its engine contributes to propelling the F4U. By how much is speed-dependend - the faster it goes, the more power from the thrust.
If the power rating is for high speed, it might be that it includes a number of horse powers for thrust ("shaft-equivalent power") though it doesn't benefit from them at a lower speed.
The P-38's turbo-supercharged Allison engines don't provide any exhaust thrust, so their rating hardly varies with speed.
Regards,
Henning (HoHun)
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F4UDOA In answer to your questions
1. If you increase EFF by 7% say from 63 to 70 plus look at the fact that lets say 20% of the 63 % is used up by drag you are increasing available climb HP from 43 to 50 or aprox 14% change in climb rate.
2. Props can be more effecint for the same resones a padle blade raises eff,basicly you don't need to make each prop as big. So weather 2 props or 1 prop is better is not a simple question.
3. Best climb speed is a function of 2 items for a prop plane.
A. is prop eff (varies with speed),and B is total drag on the plane.
The CL you are quoting is a MAX Cl, the Induced drag is the Id CO * Current CL ^2
i.e. Induced drag =(Id * CL^2 * ro/2 *V^2 * (wing area))
max CL only comes into play at MAX AOA.
This question
So if the F4U has higher induced drag then it also has high lift correct? the answere is no. Gliders are a great example, very high lift but low induced drag.
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If only I had 20 more points on my IQ instead of having enormous genitals;)
Anyway back to reality.
1. If you increase EFF by 7% say from 63 to 70 plus look at the fact that lets say 20% of the 63 % is used up by drag you are increasing available climb HP from 43 to 50 or aprox 14% change in climb rate.
OK, then shouldn't the same apply from F4U-1 to F4U-1D? If the F4U-1D benifited 20% by the addition of a paddle prop should have raised the climb from 2900FPM to 3500FPM not including the increase in HP from 2135hp to 2250HP?
The question about multi engine or single engine is really a product of the P-38 which I am using for comparison. Not because I have a problem with the 38 but because it is a comparison between one of the best climbing and one of the worst.
These two A/C are opposites in every way. And in my eyes the F4U holds many of the cards. Thrust to weight and profile drag. While the 38 has aspect ratio and total thrust.
This question
So if the F4U has higher induced drag then it also has high lift correct? the answere is no. Gliders are a great example, very high lift but low induced drag.
I know that high aspect ratio (a glider) reduces induced drag. However this is my question. If the F4U has high induced drag should it not also have high lift.
My understanding is that induced drag is a by product of lift (minus either a high aspect ratio or elliptical wing) . So if there is high induced drag then where is the lift? And the benift of the lift?
Conversely the F4U-1D had a spoiler strip lowering MaxCl. Did this not also reduce induced drag. Note: Your equation may have explained that but I can't figure that out (see the genital reference above).
HoHun,
Thanks, I understand what that means fianlly. That information is posted in the F4U pilots manual as well as the P-38 manual. It does not list HP with or without RAM but it does increase critical Alt. However it does the same in both the F4U and P-38??
Hitech,
I have a theory on why the F4U's climb is not higher based on your information that would correspond to the Flight test comparisons I have with the A6M5, FW190, and P-51
The F4U-1D in AH is the only bird modeled with twin external stores pylons regardless of loadout and the drag penalty that comes with it. The P-47, P-51 and F6F all have similar pylons but do not have them modeled with the a/c at all times.
This chart shows the increase in speed without the pylons of 10MPH through out the speed range. Obviously the drag penalty would also reduce climb. Using the 20% prop efficiency gain would put the climb at approx. 3500FPM over the 2900FPM of the -1. The extra HP from 2135 to 2250 would increase it even further. This would be more in line with the comparisons of other fighter types.
F4U perf chart (http://www.geocities.com/slakergmb/id74.htm)
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Wells,
I would not even question what you are saying except for this.
The climb differance between the F4U-1D and P-38L is very large even at the F4U's best rated alt at sea level.
I was not aware that the difference was that large. What are the climb rates you refer to? From the sim, flight tests, pilot manuals, what?
2. Two prop nacelles providing independant thrust.=> I can't even imagine what this means in terms of climb rate or if any engineer would even calculate this into his climb rate prediction. I have never seen anything to lead me to believe that twin engines would be more efficient in climb than a single. Surely the added drag penalty would be greater than the benifit of two engines.
If the P-38 could have a single 3200 hp engine turning same RPM, it would require a prop diameter of 13.2 ft, since prop diameter varies with power^(1/5). It would produce 13% *less* thrust than having two 1600 hp engines, each turning a 11.5 ft prop.
3. Higher climb speed providing higher climb rate. => I was always under the impression that wing loading was the deciding factor in climb speed? Even late model F4U's have higher climb speeds because of higher weights than the early models. The climb speeds of Zero's, Spits and 109's are lower than the F4U's and yet their climb rates are higher than the P-38's. Certainly there is no rule dictating this.
Here's the climb rate equation again.
climb rate = (T - D) * V / W
There are two things that go into climb rate, angle and speed. (T - D)/W is the sine of the angle. The best speed depends on slope of the drag curve. It's possible that one plane could have a faster climb speed at a shallower angle and still outclimb another plane with a slower climb speed and a steeper angle.
4. High aspect ratio and induced drag=> I know the benifit of high aspect ratio is low induced drag however. Lift is also tied to induced drag. So if the F4U has higher induced drag then it also has high lift correct?
Relative to itself, yes.
So doesn't that mean it takes less power to fly??
No, it means it takes less speed to fly. Power required depends on drag.
Also since the Cl of the F4U-1D was reduced to 1.49(no flap) shouldn't that reduce the induced drag as well? I thought those two things are directly proportionate. The Spitfire had an extremely low Clmax as well giving it low induced drag and better E retention I believe.
This is true, but the Cl is not 1.49 in a climb. If it were, you'd be looping.
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Just curious about your pylon theory f4udoa, what makes you think it has extra drag in ah from the pylons?
f4udoa in my glider example i was showing you that a higher induced drag does not imply more lift, hence my glider example which has less induced drag and more lift. Max CLs are mostly do to the airfoil shape.
On induced drag it's easyer to think of it varing with the AOA ^ 2 for a given air speed. The spoiler strip on the f4u just lowered it's MAX aoa and hence lowered it's Max cl, the induced drag stayed the same for any given AOA, and lift changes propotently to AOA.
Ill have to double check with pyro, but I do not belive our 1d has a padle blade.
And on the % we were using, I was just picking numbers to show you how to do the math, what it realy changed between padle and not and the % of HP used for drag I would have to go work out.
But what it realy comes down to is the climb rates we use are listed for the 1d in a number of places.
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"Ill have to double check with pyro, but I do not belive our 1d has a padle blade. "
That would explain everything :)
J_A_B
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There's also the possibility of cowl flaps being partially opened during the climb with the F4u. I believe the manual says 2/3 open for takeoff or something like that. With them being right in the propwash, the drag they create is amplified.
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Hi FAUDOA,
>If the F4U-1D benifited 20% by the addition of a paddle prop should have raised the climb from 2900FPM to 3500FPM not including the increase in HP from 2135hp to 2250HP?
I just noticed I made a slight mistake - the increase in absolute propeller effectiveness seems to be about 5%, not 7%.
Either way, this increase only suffices to explain the increase in climb rate from the real F4U-1 to the real F4U-1D. Just as I posted above, the F4U-1 with the F4U-1D's propeller would have achieved 3170 fpm instead of 2880 - that's a 10% increase.
If I consider the effect of the pylons 10 mph at sea level top speed and "remove" them from my simple model, the difference in propeller effectiveness is 6%, and the pylon-less paddle-blade power-boosted F4U-1 climbs with 3480 fpm now, a 21% increase over the basic pylon-less F4U-1 but only a 3% increase over the heavier, pylon-equipped F4U-1D.
(If it seems strange that the pylons have a much larger effect on the F4U-1 than on the -1D, that's just the normal bullwhip effect of reverse engineering ;-)
Regards,
Henning (HoHun)
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Hitech,
On the other issues on Physics I have to depend on others to tell me if I am right or wrong, however when it comes to F4U details I know the answer more often than not.
Your F4U FM's(F4U-1, F4U-1D, F4U-1C) match exactly two specific NAVAIR docs which I have full copies of. In those Docs it specifies the blade type used on the F4U-1 as 6443(non-paddle). On the F4U-1D/C doc it specifies blade type 6501A-0(paddle blade). The 6501A-0 is mentioned specifically in several sources as incresing the performance of the F4U. These are
1. The F4U-1D vrs FW190 test
2. The F4U-1A vrs P-51B
3. The F4U pilots manual which it says to use the latter blade type as it increases performance.
Second on the issue of weather the F4U-1D is modeled with external stores pylons is simple. Just look at your performance charts for the -1D and look at this note on the F4U-1D NAVAIR doc. It states an increase in performance from 358MPH at sea level to 366MPH at sea level. Also at 20k from 409MPH to 417MPH.
The Full report can be found here.
Notice it matches your FM speed, weight, climb etc. Also prop blade type is listed second to the last page.
F4U-1D charts (http://www.geocities.com/slakergmb/id71.htm)
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Here is the second part of that document. I had to clip out the section because the doc is way to big.
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HT,
Did I loose your attention??
What do you think of this data?
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hehehehehehehee Whose right on what :)
Ok one more ? for me to ask.
The P-47s and The f4s had paddle props installed and flew combat missions.. Right??
If the props improved performance why not have them in AH???
I have read some threads on the 47 drivers wanting paddle props on there 47s.. If these props were modeled it would even up the Jugs and Hogs more to fight the endless spits and niks.
DOA you have posted some big climb rate numbers for the F4s
Which are bigger the the P-38L climb rate numbers. So did the Hogs out climb the Fork Tails??
Cw
=Twin Engined Devils=
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F4U-1 and D & C is blue with strange wings and then can't climb well. But everybody knows climb better all japanese planes except niki, climbs better F6F, climbs near P51 or better him.
No comments about F4U4 climb rate and speed (it's blue with strange wings too) who runs & climbs more p51 at real life. Of course climbs near or better a p38L.
WB, AW F4U climbs very close a p51 since 12k a lot better since 17k. But AH is AH (or maybe La7landia,nikilandia and spitlandia)
Data from Navy or USAF only good when employed vs LW
Well Hog is a hog and Jug is a Jug
=S= ALL
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Want to see the next column f4udoa, btw a 10mph speed differenct at top end do to added drag will only effect climb rate very slightly. as in 50 fpm range. But it apears to me we hit the 3370 climb rate. See our f4u1d climb rate chart.
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"AW F4U climbs very close a p51 since 12k a lot better since 17k. But AH is AH (or maybe La7landia,nikilandia and spitlandia) "
The AW F4U-1D could also climb at 2900 FPM at 30,000 feet. It was more than a "little" over-modeled.
J_A_B
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Originally posted by F4UDOA
If only I had 20 more points on my IQ instead of having enormous genitals;)
LOL! Hehehe, thanks for the laugh.
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BigCrate,
No I abosolutely do not think the F4U-1 series should outclimb the P-38 at any alt. However if a P-38F is modeled then yes the F4U-1D would outclimb it. The F4U-3, F4U-4 and F2G would also outclimb the production P-38's at most alts.
Hitech,
You are correct about your FM matching the charts. I do not question that at all(although I do not know how to confirm initial climb rate). I am only questioning the addition drag of the external stores pylons when other A/C such as the P-51, P-47 and F6F used the same typr of pylon. The F4U-1D is the only one modeled with a drag penalty regardless of loadout.
Here is the second column.
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Once again f4udoa, your confusing me, why do you think AH has drag from the external pylons?
If they are showing on the plane , it does not meen that the drag for them is there.
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Erhh,
Because the top speed of the F4U-1D in AH is 358MPH at sea level and 409MPH at approx 20K with combat power. This matches the charts exactly in combat condition. IE. with external pylons attatched. Without external pylons the top speed is measured in the "Clean Condition". 366MPH at Sea Level and 417MPH at Combat power. Military power would also increase to some degree as would climb rate marginally. This would put the F4U-1 and -1D top speeds almost identical with the -1D being slightly faster on the deck.
F4U-1D In AH currently modeled FM
Combat Power/ Combat condition(with Pylons)
Top speed
sea level= 358MPH
19,000FT= 409MPH
F4U-1D Not modeled in AH FM
Combat power/ Clean Condition(no pylons)
Top Speed
Sea Level= 366MPH
19,000FT = 417MPH
Here is the data for the "clean" condition.
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Wait Wait!!
If there was a P-38J-5 modeled it would have a climb rate of about 3400fpm(no WEP)at SL now thats coming in about 16500lbs.. So if a 38J-5 was modeled the F4u-4 would out climb it??? I'm not saying the F4u-4 couldn't do it just saying I always read the 38 was the best US climber during the war. Am I wrong in this??
Cw
=Twin Engined Devils=
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BigCrate,
The F4U-4 could out climb it. But not the -1 series. However the P-38 had a turbo supercharger giving it a very linear climb rate all the way up. So at some alts the P-38 may have the upperhand. Especially over 20K were the air gets thin.
The F4U-3 also had a turbo supercharger and had an outstanding climb rate and was the fastest of all the F4U's with a top speed of about 490MPH!! at 27,000FT. However only about 30 were built and they never saw combat. They did however stay in the Naval inventory until the late 40's doing high alt research.
HITECH,
You still out there??
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Kind of curious about the pylon issue and wondering what the answer is....
Hooligan
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Heya Hooligan
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Me too. I hope he understood my point. Did you or did I not make my point?
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F4UDOA:
Engine BHP/Weight ratio is a wholly inaccurate predictor of rate of climb. This method assumes incorrect variables for evaluation and entirely leaves other important aerodynamic variables out.
As Wells pointed out:
ROC = (T - D) * V / W
[list=1]
- Engine BHP does not equal Thrust. BHP is only the ideal maximum power available from the engine that can be used for the production of thrust.
- You correctly pointed out prop efficiency in adjusting BHP ("ideal power available") to thrust horsepower (THP - "real power available"). Prop efficiency is a correction factor/ratio to help us determine THP available from BHP. However THP does not equal thrust either. THP is just a the power available for the production of thrust, not thrust itself. One equation for Thrust using prop efficiency is:
Thrust = BHP * prop eff. / Velocity
So thrust is a function of THP and velocity. The point is neither Engine BHP or THP = Thrust.
In actuality determining thrust is even more complex than the above equation. E.g. using momentum theory, prop diameter, actual prop revolutions, air density and velocity are all variables that determine thrust.
- BHP, prop efficiency, thrust all vary based on various conditions and are not constant. BHP varies with changing air density and the engines ability to perform combustion. This is where differences between differing engines turbo-supercharging shows up. Prop Efficiency varies with the aerodynamics of the prop blades, pitch, speed, and revolutions of the prop.
- In your analysis through this thread you also left out certain key variables. Considering the ROC equation above T-D is broken down to:
T-Di-Dp
You talked about the induced drag differences between the P-38 and F-4U. You left out entirely the parasite drag part of the equation. This is a substantial part of the drag calculations that directly impacts the excess thrust available for climbing.
[/list]
Tango, XO
412th FS Braunco Mustangs
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But but... can this dog hunt...
With ordance loaded AH F4u performs as charted.
With out ordance loaded AH F4u should be faster.
Agree/Disagree?
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The peformance data regarding the pylon vs. non-pylon F-4U performance is interesting.
However a single report regarding aircraft performance is hard to gauge as THE definitive source detaling its performance.
[list=1]
- Pilot "error" / accuracy plays a part in the performance numbers. Wells shared with me an interesting bit from a book that showed the deviation between performance characteristics of the same aircraft for the same flight conditions. It was interesting to see.
- Atmospheric conditions also vary in real life. I believe Pyro told me that AH uses a uniform atmospheric density where air density is uniform for a given altitude around the whole AH arena. In real life this is not true. Wind conditions also are different in real life. All this to say that environmental variables affect the outcome of flight tests.
The point is it is hard to gauge an aircraft's performance on a single flight test report because there are numerous variables in real life that affect its outcome. Which flight test report is right? The answer is probably they all are given the specific flight conditions they were performed in! The question is how does HTC make judgements about this? I'm glad I'm not Pyro or HiTech who have to sort through all this complexity and translate this to a flight model that is as accurate as possible :D.
Let me close by saying that I think analyzing flight models is a good exercise. Just keep in mind the complexity and nuances involved (physics, flight test data, etc. etc.).
Tango, XO
412th FS Braunco Mustangs
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Hi Dtango,
>All this to say that environmental variables affect the outcome of flight tests.
Environmental variables in flight tests affect the measured figures. However, by taking the environmental variables into account, it's possible to arrive at standardized performance values even from a test under non-standard conditions.
The aircraft standard characteristics were prepared with slide rules as much as with stick and throttle, and they were meant to give the most accurate picture of the aircraft they are describing.
If the actual aircraft (or the actual atmospheric conditions) deviated from the standard aircraft (or the standard day) in any way, that would make it deviate from the standard aircraft performance values as well.
Still, the standard aircraft characteristics make it possible to compare the performance of different aircraft types and predict their performance under different conditions or in different configuations - such pylons for air-to-ground ordnance installed or removed.
Regards,
Henning (HoHun)
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Punt for so pyro can find this.
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You can look at it as being too slow or you can look at it as being too fast if you look at the footnote about rocket rails. In the game, I try to go with what is typically inherent to the plane when that much information is available. For example, a -1D with it's pylons removed would be pretty atypical and even in the docs you cite, it's only mentioned as a footnote. There's other things that affect top end speed such as whether the gun ports are taped over or not that we don't go into either. Tops speeds are not absolutes and small differences add up quickly when you consider that parasitic drag is a squared term(a plane at 400 mph has 16 times the parasitic drag that it did at 100 mph).
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Okay I just want to make sure I understand this.
The F4U-1D in AH is modeled with pylons on (i.e. combat condition not clean condition). The weight of evidence indicates that clean condition was atypical: It's only mentioned in a footnote in the navy docs and most pictures I have seen of F4Us have had drop-tanks, rockets or something hanging off of them. Sounds fair enough to me.
This is a bit of a segue but an interesting use for perk points (IMO) is to make atypical configurations available for a small perk cost (i.e. clean F4U-1Ds, assuming that somebody comes up with proof that they were used as day fighters: F6Fs with the mixed battery, LW rides with the rare mods, spits with the 9 billion octane gas, F4Us with cannon armament :) etc...)
And as long as we are talking about F4U's, an early FG-1 with no WEP and lacking carrier gear and folding wings would be a cool addition. Please keep it in mind for one of the next 50 planes or so.
Hooligan
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Pyro,
I hope you read this because I really hate not knowing if you guy's read or don't read post. It takes to much energy to do the research to not even get an acknowledgment that it got read. Anyway I hope you read this.
I had no intention of trying to get the F4U-1D speed uprated. If it was your choice to model it with Pylons and rocket rails so be it. I was simply pointing out one possible reason in the desparity between F4U flight test against the A6M2/5, F6F-3/5 and FW190A5. In all of these test with no exception the F4U outclimbed it's opposition at the F4U's best climb speed of 155MPH. This is not the case in AH. The drag penalty of the pylons and rails was one possible explanation in my mind.
HOWEVER (there is always "one more thing" like Columbo say's).
If the F4U-1D in it's typical configuration is to be modeled with Pylons and Rocket rails should not all AH fighters with extensive ground attack capability be modeled with there Pylons and rocket rails ala the P-47, F6F, P-51 and FW-190? Remember late in the war there were not that many enemy A/C to shoot down. Most action sorties were ground attack. The F4U is a paradox in this regard because it fighter capabilties were enhanced with a prop change, Up rated HP, canopy, etc. but it is limited in AH by additional drag. The P-37D-30 was also used in this manor but is not penalized in AH. Should A/C that did not ordinarly carry ordinace such as the NIK2 or Spit not be allowed to carry any because it was not the "typical configuration?
IMHO all AH A/C should be modeled on an even playing field regardless of the special circumstances of the war. What many people do not realize is how much the F4U was considered superior as a fighter bomber compared to the F6F. It dropped nearly three times as many bombs and rockets, and yet had far less losses both operationally and in action despite flying almost exactly the same amount of missions.
Here is the record.
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Hooligan:
Hey- that is a really neat idea regarding perk points for special modifications / atypical aircraft configurations. :cool: I like it.
F4UDOA:
I'm only guessing but I wager for Pyro to come up with the flight models one of the methods he uses to determine performance to base the flight model off of when he has more than a few sources of performance data is to model the performance that can be considered more or less statistically in the realm of 1 or 2 sigma (65%-95%) region of the normal distribution of all the data he has- hence typical vs. atypical configurations.
You can debate if this is "fair" or not and the side of the debate you choose depends on your definition of what is "fair". However, If Pyro is approaching his flight modelling somewhat like what I described above then I think your definition of an even playing field would #1 make it more complicated for Pyro to model aircraft (e.g. have to find performance data for the specific configuration you are looking for) and #2 introduce inaccuracy to the flight model (e.g. have to base FM on a single report that has noticable variances from other reports).
Just my opinion :)
Tango, XO
412th FS Braunco Mustangs
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Dtango,
Actually when Pyro does a flight model his specs match the performance specs of the charts 100% on all A/C in which the information is available with 0% variance. I say this because I have tested all of the F4U's flight characteristics down to cruise speeds and fuel consumption at different manifold pressures. And I can tell you that they match exactly.
All I am saying is that if the P-47 used the exact same external stores pylons then why is the F4U-1D the only A/C in AH that is modeled with them regardless of loadout? Is it a typical load out? Yes, but it would have been on many other A/C during the later years of the war due to simple lack of anything airborne to shoot at.
In the end it would make it easier to model A/C and say that unless you are carrying ordinance you are not penalized for external drag. I would say that there is more detailed information available on the F4U than just about every other A/C in AH allied or axis. Based on that I would say that getting detailed drag information on the LA-7 or NIK2 is almost impossible, but the F4U-1D should not be unique because of this.
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F4UDOA:
Just wanted to clarify that I didn't mean HTC would pool all the data together from different flight performance reports, but that it would make sense to base it off of a report that fell within close performance proximity to the collection of the majority of the reports since you have a higher statistical confidence in the accuracy of the report you are basing your FM from and that you aren't using some anomolous performance data. In our specific case it sounds like that there are quite a few performance reports on the F4U-1D and that the no pylon drag information only shows up on just one of the reports and that as a footnote. In my opinion I would go with the data that seems to match with the majority of data that I have.
This doesn't detract from your point however and your point is well taken. Obviously I can't say that I agree with you regarding the "fairness" of doing what you suggested. Personally I think Pyro's decision to go with the approach of "typical" modelling is just as fair. You've made a good point though.
Tango, XO
412th FS Braunco Mustangs
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And as long as we are talking about F4U's, an early FG-1 with no WEP and lacking carrier gear and folding wings would be a cool addition.
Nice idea Hooli.... but you mistyped it ! ;) It should be an early F2G Corsair :D
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Gents,
Just as an aside. Another A/C in AH that has the pylons visible in AH in all conditions but suffers no drag penalty is the F4U-4.
Just a little irony I thought.