Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Urchin on November 28, 2007, 04:14:33 PM
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I was playing around with the "Fighter comparison" website earlier, and I plugged in the Spit 14 vs the Spit 9. Now, I have flown the Spit 14 a fair amount, and I actually like the plane, but it doesn't turn anywhere near as well as a Spit 9 does (in my subjective opinion).
In real life, according to a test report I've seen linked several times here, the Spit 14s turning circle was reported to be "identical" to the Spit 9s. This is in spite of the fact that it was 1,000 lbs heavier. I guess the extra horsepower made up for the weight, in the test.
The website (Fighter Comparison page (http://gonzoville.com/ahcharts/index.php) ) agrees with my subjective assessment. The smallest turning circle with flaps down is 509 feet for the Spit 14, and 433 feet for the Spit 9. With flaps UP, the circles are nearly identical, with the Spit 14 having an edge that may or may not really be there (I'd say that difference is probably well within the margin of error for the data collection).
I don't understand why the turning circles are identical with flaps up (which matches the test report), but drastically different (15%) with flaps down. The wing and flap design didn't change between versions.
A different way to look at it is to compare turning circle size with flaps up to that with flaps down.
The Spit 5 is 503 / 386 (~23% smaller).
The Spit 9 is 632 / 433 (~32% smaller).
The Spit 16 is 567 / 450 (~21% smaller).
The Spit 14 is 629 / 509 (~19% smaller).
Do the flaps on the Spit 9 just work exceptionally well?
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It looks to me like, with the exception of the Spit V, as the HP goes up the flaps up/flaps down differential goes down which would make sense given the same wing/flap configuration (except on the XVI), meaning more power to overcome the flaps.
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Originally posted by Urchin
I was playing around with the "Fighter comparison" website earlier, and I plugged in the Spit 14 vs the Spit 9. Now, I have flown the Spit 14 a fair amount, and I actually like the plane, but it doesn't turn anywhere near as well as a Spit 9 does (in my subjective opinion).
In real life, according to a test report I've seen linked several times here, the Spit 14s turning circle was reported to be "identical" to the Spit 9s. This is in spite of the fact that it was 1,000 lbs heavier. I guess the extra horsepower made up for the weight, in the test.
The website (Fighter Comparison page (http://gonzoville.com/ahcharts/index.php) ) agrees with my subjective assessment. The smallest turning circle with flaps down is 509 feet for the Spit 14, and 433 feet for the Spit 9. With flaps UP, the circles are nearly identical, with the Spit 14 having an edge that may or may not really be there (I'd say that difference is probably well within the margin of error for the data collection).
I don't understand why the turning circles are identical with flaps up (which matches the test report), but drastically different (15%) with flaps down. The wing and flap design didn't change between versions.
A different way to look at it is to compare turning circle size with flaps up to that with flaps down.
The Spit 5 is 503 / 386 (~23% smaller).
The Spit 9 is 632 / 433 (~32% smaller).
The Spit 16 is 567 / 450 (~21% smaller).
The Spit 14 is 629 / 509 (~19% smaller).
Do the flaps on the Spit 9 just work exceptionally well?
You are talking about a big weight difference between the 9 and 14. More internal fuel as well.
The 14 was a different beast. Spit V should out turn the IX for the same reason.
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I'll preface this by saying I don't know much about aerodynamics. And my Spitfire book is at my parents house, so I can't look up the horsepower numbers for all the types.
Looking at these numbers though, I am very puzzled.
All the Spitfires we have in the game share the same wing (except the Spit I, but I don't think the shape of the wing changed between the 8 gun wing and the cannon wing). So the weight and the horsepower change, but the wing / flap stays the same.
Type / Weight / HP / turning circle no flaps / flaps ( % change)
Spit I - 5844 lbs. 1030 hp. 471' / 371'
Spit 5 - 6785 lbs. 1440 hp. 503' / 386' (~6% / ~4%)
Spit 8 - 7875 lbs. (??? hp). 632' / 433' (from Spit 5, same for the rest)
Spit 9 - 7400 lbs. (??? hp). 568' / 448' (~13% / ~16%)
Spit 14 - 8500 lbs. (2050 hp). 629' / 509'
Spit 16 - 8500 lbs. (??? hp). 567' / 450'
So the Spit 5 is 900 lbs heavier than the Spit 1 (~16%) and shows roughly a 6% / 4% increase in turning circle.
The Spit 9 is roughly 600 lbs heavier than the Spit 5 (~9%), and shows roughly a 13% / 16% increase in turning circle.
The Spit 8 is 1100 lbs heavier than the Spit 5 (~16%), and shows roughly a 25% / 12% increase in turning circle.
The Spit 14 is roughly 1700 lbs heavier than the Spit 5 (25%), and shows roughly a 25% / 31% increase in turning circle.
The Spit 16 is also roughly 1700 lbs heavier than the Spit 5 (25%), and shows roughly a 13% / 16% increase in turning circle.
So there are a couple questions I have. The Spit 14 actually has more wing area than the Spit 16. I don't know what kind of horsepower difference there is between the 14 and the 16, but the Spit 14 takes a turning hit twice as bad as the Spit 16.
Another thing I noticed is that the difference in circle size is fairly consistent across the family, except for the Spit 9.
Using (Tf - Tnf) / Tf , where Tf is flaps out, and Tnf is flaps up.
Spit 1 - 27%
Spit 5 - 30%
Spit 9 - 46%
Spit 8 - 27%
Spit 14 - 24%
Spit 16 - 26%
I don't remember there being a massive difference in horsepower between the Spit 14, Spit 8, and Spit 16. But the Spit 8 and Spit 16 have comparable turn performance to the Spit 9 (the Spit 16 has nearly identical performance in spite of losing 2 feet off each wing and gaining a half ton of weight), and the Spit 14 isn't even close. If someone could explain to me why it is like this, I'd appreciate it, more for my own personal edification than anything.
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The Spit XVI weight listed is wrong. I know it is what is listed on the AH site, but the Mk XVI's weight should be very close to the Mk IX's weight.
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Just tossing this out there.
Possibly the MK IX is the best balance of wt/hp/wing area, for the spit fire airframe. That's why it gains the most.
More of a question than a statement btw.
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Spit VIII is the best balance I think, and many RL Spit pilots agreed. For example, Supermarine's chief test pilot, Jeffrey Quill, thought the VIII was the best of the Spits.
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My question would be why there seems to be no turn penalty for the Spit 16's clipped wings. Seems like they would create more induced drag, higher wing loading while boosting the roll rate.
Maybe the higher amount of torque on the 14 may make it tougher to control in a sustained turn when compared to the Spit 9. Perhaps that contributed to the difference?
14 had a longer fuselage and a bigger vertical stabilizer too right?
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Nose is longer and vertical stabilizer is bigger. Fuselage is a bit stronger, but the same length.
The clipped wings should have an effect on the XVI. Everything I've read says it was a noticable reduction in turning capability.
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Originally posted by Karnak
Nose is longer and vertical stabilizer is bigger. Fuselage is a bit stronger, but the same length.
The clipped wings should have an effect on the XVI. Everything I've read says it was a noticable reduction in turning capability.
Depends on the alt. There wasn't much difference at the lower alts that AH is flown at. Take an 8 vs a 16 and get in a turn fight. The 8 will win it 9 out of 10 times. The extra wing will make the difference. Before some of the great Spit sticks start howling, I'm talking about pilots of equal skill.
Folks seem to forget the XVI is nothing more then an LFIX with the American Merlin 266 instead of the Rolls Merlin 66. Same bird otherwise.
They also forget that the XIV was a beast and not a turn fighter like the others. They seriously considered giving it another name as it really wasn't a Spitfire in many ways. It was much more of a B n Z bird then it was a turn fighter.
I still remember having a guy in a 14 bounce me in a 5. I'm sure he thought 14 is bigger then 5 so I should be able to clobber this guy. But instead of using the power and the climb, he thought he could out turn the 5. It was no contest as he didn't use the best atributes of the XIV.
A guy in a 14 using it's strengths can control a fight vs a 9 as he's got the wheels to come and go as he pleases, unless he decides to turn fight. Once it gets slow the IX should eat him up.
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The max horsepower for the Spit8 (Merlin 66) /9 (Merlin 61) /16 (merlin 266) respectively are 1720 hp /1565 hp / 1710 hp.
What I don't get are all the weights.
I've looked up many figures on Spitfire Performance (http://www.spitfireperformance.com) but I couldn't successfully find the right numbers for the Spit XVI and the IX and VIII numbers whack.
After playing Aces High II for quite a while, I've felt that the Spitfire VIII (1943, Merlin 66, Griffon tail, b-type arm; c-type wing) is a much heavier plane than the Spitfire IX (1942, Merlin 61, Merlin tail, b-type arm; c-type wing), and that the Spitfire XVI (1944, Merlin 266, Griffon tail, e-type arm; clipped e-type wing) is too light. I know that the Spitfire VIII has hydraulic fluid for its retractable tailwheel, extra wing fuel tanks (don't know if they self-seal) and wing strengthening but when the IX and VIII are at tare weight, there's only a 182 lb. difference. Exactly how heavy is hydraulic fluid ?
The weights are displayed as such:
Spitfire VIII: full ammo/100% fuel (124 Imp Gal) - 7807 lbs.
full ammo/25% fuel (31 Imp Gal) - 7137 lbs.
light (no ammo/fuel/bombs) - 6679 lbs.
Spitfire IX: full ammo/100% fuel (85 Imp Gal) - 7303 lbs. - should be 7445 lbs.
full ammo/25% fuel (21.25 Imp Gal) - 6843 lbs. - should be 6986 lbs.
light - 6455 lbs. - should be 6590 lbs.
Spitfire XVI: full ammo/100% fuel (85 Imp Gal) - 7241 lbs.
full ammo/25% fuel (21.25 Imp Gal) - 6781 lbs.
light - 6329 lbs.
Are these figures close to accurate?
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Spit IX and XVI weights would be the same as they are the same airframe. All that's different is the engine in the Spit IX is Rolls Royce Merlin 66. XVI is Packard Merlin 266
Empty weight is 5610 lbs, normal weight is 7500 lbs.
Spitfire VIII normal weight was 7767 lbs.
Those are from Bruce Robertson's book on the Spitfire
Spitfire the History lists the VIII normal weight as 7807 lbs
Spit the hist lists the XVI normal weight as 7549 Spit IXe as 7500.
Again they're the same bird, just different engines. Put a 266 in an IX and it effectively becomes an XVI.
So you've got the VIII a couple hundred pounds heavier then the IX or XVI. Extra fuel tanks and retractable tail wheel adding to the weight I imagine.
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Dan's numbers are what I'd expect. I can't see why the XVI would be lighter than the IX when it has two .50s replacing the four .303s as well as more hardpoints. The wing tips don't weigh that much.
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Thought these numbers were interesting from tonite of the AH 2 stage Merlin birds and the Griffon XIV vs each other.
Interesting to me that the Spit IX, with the higher alt Merlin 61 seems to be the bird that holds it's own with the others best. Wonder if it's better sticks in the IX?
Guessing the XIV numbers more reflect guys trying to turn fight the lighter Spits then it it's actual performance being poor.
Spitfire Mk VIII has 368 Kills of Spitfire Mk IX
Spitfire Mk VIII has 44 Kills of Spitfire Mk XIV
Spitfire Mk VIII has 933 Kills of Spitfire Mk XVI
Spitfire Mk IX has 414 Kills of Spitfire Mk VIII
Spitfire Mk IX has 34 Kills of Spitfire Mk XIV
Spitfire Mk IX has 629 Kills of Spitfire Mk XVI
Spitfire Mk XIV has 26 Kills of Spitfire Mk IX
Spitfire Mk XIV has 35 Kills of Spitfire Mk VIII
Spitfire Mk XIV has 72 Kills of Spitfire Mk XVI
Spitfire Mk XVI has 1064 Kills of Spitfire Mk VIII
Spitfire Mk XVI has 664 Kills of Spitfire Mk IX
Spitfire Mk XVI has 75 Kills of Spitfire Mk XIV
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I'd argue thats the "LW factor"... better pilots in the Spit 9.
I know I've fought a Spit 16 in a Spit 9 where the guy didn't completely suck - and he could do everything I could do, plus zoom away from me in the vertical if he felt like he was losing position in a rolling scissors.
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Originally posted by SgtPappy
The max horsepower for the Spit8 (Merlin 66) /9 (Merlin 61) /16 (merlin 266) respectively are 1720 hp /1565 hp / 1710 hp.
Just to add a point the MK IX is the high alt version.
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But why does the Spit 8 seem to have flaps that are so much more effective than the other Spits?
EDIT:
Just noticed that I made a really dumb mistake. The Spit 8 has a turning circle of 632 / 433 , giving it a 46% decrease in turning circle size with flaps out.
The Spit 9 is 568 / 448 , nearly identical to the Spit 16 at 567 / 450.
I'm going to go ahead and change the rest of my posts around to fix it.
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Originally posted by Urchin
All the Spitfires we have in the game share the same wing (except the Spit I, but I don't think the shape of the wing changed between the 8 gun wing and the cannon wing)
i thought they were:
I - A wing
V, VIII, IX - B wing
XIV, XVI - C wing
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AFAIK the wings were all identical in regards to size and shape. The difference was the armament that could be mounted in them.
If I am wrong on that then maybe that explains the differences.
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Originally posted by RTHolmes
i thought they were:
I - A wing
V, VIII, IX - B wing
XIV, XVI - C wing
I - A wing
V - B wing
VIII, IX - C wing
XIV, XVI - E wing
And that refers to guns only. Hardpoints and ailerons are separate.
VIII, IX and XIV have the same hard points. XVI has additional points.
IX and XVI have full length ailerons. VIII and XIV have reduced length ailerons.
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doh I meant:
I - A wing
V, VIII, IX - B wing
XIV, XVI - E wing
... so if we got the C-wing on the VIII and IX where is the 4xHizooka option? :D
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B wing was exclusively on the Mk V. It had the Hispanos Mk Is with 60 rounds per gun.
We don't have the four Hispanos because it was never used on the Mk IX and only two Mk VIIIs that I know of.
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All wings are near identical in wing area... about 242 sq. ft.
The C-wing was mounted on the IX's and VIII's in our game and they have those little cannon blanks just outboard of their 20 mm.
The B-wing is only on Spitfire V's in the game and that wing is a little lighter as it's got less reinforcement. The Vc's in WWII were fun because they did carry 4x20 mm before, but usually only from carrier-to-Malta runs. They had no ammo in those ops.
I imagined the e-wing to be heavier than the c-wing but I guess the removal of 2x0.303" guns made the XVI lighter.
Also, Guppy states some good figures. You can see that the weight differences between the Mk.IX and Mk.VIII Spitfire are different than what we have in the game.
According to the performance page (http://www.spitfireperformance.com) , the Spitfire VIII fully loaded weight (100% fuel, ammo) is 7,800 lbs. Not much different from the one in the game. The spitfire IX is 7445 lbs. Knowing it has 85 Imp Gallons of fuel, we can multiply that by 7.2 lbs/IG and find the weight of the fuel. The 20 mm ammo is 150 lbs/240 rounds and the 303 ammo is 93 lbs/1400 rounds. Do the calculations and youve got a heavier IX than the one in game... some 120 lbs heavier in all configurations. Thus, the Mk.VIII is not supposed to have that much of a weight disadvantage vs. the IX. Drain the extra fuel the VIII has and bingo, you've got almost the same plane but the VIII being superior overall.
Urchin's also got a good question, let's pay attention to him. I also noticed that the VIII sometimes seems to turn better with its flaps down but both the Mk.VIII and IX had exactly the same wing except for the VIII's 8.5" clipped ailerons, which didn't affect the flap length at all.
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Remember the Spit I had fabric ailerons too so it didn't roll as well. When they switched to metal it was a fairly dramatic improvement.
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I'm not sure if I'm worth listening to, but thanks :) .
I actually still have questions that I'm waiting for some aero guys to chime in on. I pinged a couple guys at work about it, one said that it could be a lot more complex then I'm making it, but the other one did agree that it seemed a little odd how well the Spit 8's flaps work compared to the others.
Anyway, this started off being about the Spit 14, and my first question is still why does it take such a hit in turn performance relative to the other Spits (8/9/16 in particular)?
Second question has changed a bit. How can the Spit 16 have a turning circle the same as the Spit 9 when it weighs the same, has roughly the same horsepower, but has less wing area? Wouldn't that make its wingloading higher, and adversely affect turning performance?
Third question is about the Spit 8's flaps. Why are the flaps on that bird so much better than the flaps on all the other Spits? As far as I know, the wing and flap design didn't change from the Spit 5 all the way up through every model we have in the game. I understand that the gun and hardpoint options may have changed a bit, but the wing as an airfoil didn't (I don't think).
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Airfoil and flaps remained constant so far as I know.
I have also never read so much as a hint of a Spit ever using flaps in combat.
I sure don't use them in AH when flying the Spit.
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The Spitfire XIV gained literally, a ton of weight over the 9/8/16. It weighed a whopping 8488 lbs. with full ammo, fuel (112 Imperial Gallons), oil and hydraulic fluid. It has wing tanks like the VIII, but a larger tail fin, wing strengthening, the mighty Griffon 65, a 5 blade prop, larger radiators etc.
It has a lot of thrust, yes, but not enough to counter its vastly increased wingloading.
The Mk.XVI has lost some 11 sq. ft. in wing area but its extra thrust over our IX and lightness over the IX makes it seem as if it turns tighter. I may have to say that the turning performance listed on Gonzo's page is incorrect for the IX.
But let's take a looksee at the XVI.
231 sq. ft., 6781 lbs (25% fuel, full ammo) = wingload of 29.35 lbs/sq.ft
the Mk.IX is 242 sq.ft., 6843 lbs (same config as XVI) = wingload of 28.28 lbs/sq.ft.
Clearly the Mk.IX has a small advantage due to a lower wing loading but the XVI accelerates better. In reality, you may have just been experiencing a XVI that's turning faster rather than tighter. Ever try fighting an Me163 in a Tempest? Temp turns much tighter, but the 163's X-treme speed gives it a faster turn rate. The XVI isn't quite that fast compared to the IX, but you get the idea. Additionally the XVI has better E-retention. Fighting in the vertical only helps it kill the IX.
Karnak's got a good point. Those flaps cause way too much drag in a horizontal turn fight. The only time I use them is when I need to flip over at the top of a loop. In the XIV, I don't even use them unless I'm landing.
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Never met a real Spit driver who used flaps in combat and I've talked to many over the years.
Flaps remained the same from the Spit I through the 19.
Get in a sustained slow turning fight with a 16 in a IX or a VIII and eventually the wing area will make a difference. There was not much difference in turning circle at medium and low alts. It was much more noticable at higher alts.
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XIV gained about half a ton, ~1,000lbs.
Also, don't think about thrust too much in WWII fighters. The F4F-3 has about 1,100lbs of thrust. The overengined Mk XIV has about 1,800lbs of thrust. That is what I remember Widewing saying. As a comparison, the F-15 has 75,000+lbs of thrust. No WWII fighter's thrust is going to make all that much difference in pulling a significantly tigher circle through sheer power.
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Originally posted by Urchin
Anyway, this started off being about the Spit 14, and my first question is still why does it take such a hit in turn performance relative to the other Spits (8/9/16 in particular)?
Could it be that during the tests that produced these stats the pilot turned all of the Spit models in the same direction, but the counter-rotating engine/prop in the XIV actually hurt it's performance? If so, and the turns were reversed in another test we may find the XIV out-turning the rest.
Another factor may be that the higher torque engine in the XIV would add an increased gyroscopic effect that would work to keep the nose pointed in it's current direction. Number and pitch of prop blades may also cause a similar effect.
Anyway, there are a lot of complex factors at work in individual aircraft performance beyond HP, weight and wing-loading. My question is, is the performance of the models in AHII representative of the actual performance of these models in real life? If so, I'm good :)
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Both the RAF and AH players tested the real and AH Spits, respectively, turning in both directions.
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Sustained turn performance is a tricky animal. For what it's worth Urchin, here are my educated guesses.
First some math:
Radius(turn) =
V^2
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g x sqrt [ ((Cl / Cd) x (T / W))^2 - 1]
From other relationships we can replace V^2 with 2x(W/S) where S= wing area. This gives us the following:
Radius(turn) =
2 x (W/S)
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g x sqrt [ ((Cl / Cd) x (T / W))^2 - 1]
So now we have turn radius as a function of the following aircraft variables:
a) weight
b) wing area (S)
c) lift (Cl)
d) drag (Cd)
e) thrust
(1) Spit 14 vs. 8/9/16 sustained turn radius
Others have pointed out already that the Spit 14 is significantly heavier than the other variants. The AH website does list the Spit 16 as the same normal weight as the 14 but as pointed out by others this is probably incorrect and that the 16 is about the same weight at as the 8.
Looking at the equation we can see that turn radius increases with increasing weight. So my guess is that though the 14 has probably a larger wing area and greater thrust, the greater weight more than offsets these other things and is the primary factor for the larger sustained turn radius.
(2) Spit 9 vs. Spit 16 sustaine turn radius
In AH if you look at the current climb charts the Spit16 has a much greater excess power margin compared to the Spit9 meaning the Spit16 having greater excess thrust. In our friendly equation we can see that as thrust increases, turn radius decreases. I surmise the additional thrust is the primary factor that gives the Spit16 a better sustained turn radius compared to the Spit9.
Tangent for sgtpappy - wingloading will give you an indication of instantaneous turn performance. For sustained turn performance you have to evaluate it considering the variables above.
(3) Flaps flaps flaps
Where flaps come into play in is how the Cl/Cd values differ between the variants at the specific airspeeds that these sustained turns were flown at for each plane.
I Don't know anything about the spitfire flaps and don't have the time to spend researching the alphabet soup spit wings :) to try and figure what the lift-to-drag ratios with flaps are for the Spit variants. What the tests suggest IMHO is that the spit 8 with flaps out has a good Cl/Cd ratio.
Cheers!
Tango, XO
412th FS Braunco Mustangs
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dtango,
The Spit XVI will have such a negligibly greater thrust that it will have no meaningful impact on turn radius. See my earlier post vis-a-vis the thrust of the F4F-3 Wildcat, Spitfire Mk XIV and F-15 Eagle.
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Originally posted by dtango
I Don't know anything about the spitfire flaps and don't have the time to spend researching the alphabet soup spit wings :) to try and figure what the lift-to-drag ratios with flaps are for the Spit variants. What the tests suggest IMHO is that the spit 8 with flaps out has a good Cl/Cd ratio.
All Spits used a NACA 2213 root and 2209.5 tip. NACA did not include data for the 2212 or 2214 in its Report 824, but they did include data for the 2400 series. On the 2400 series, simulated split flap deployment @ 60 degrees boosts Clmax by approximately .8. I don't know how to do it, but it could be interesting to plug that relationship into the formula to see what the overall affect on turn radius would be.
Given that the wing area was the same for all but the Spit XVI, and that the flaps were the same, only weight, drag, and thrust remain as the variables, right?
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Karnak:
I saw that. I'm inferring that it does :). But you probably don't believe me so I'll demonstrate.
Let's say we have an airplane with the following parameters:
(a) sustained turn airspeed of 140 mph
(b) L/D = 8.4
(c) W = 7500 lbs
(d) engine BHP = 1720 hp
(e) prop efficiency @ 140 mph = .4
Calculated thrust = 1842 lbs
Turn Radius = 644 ft
Now let's increase the BHP = 2000 hp while holding everything else constant..
Calculated thrust = 2142 lbs
Turn Radius = 552 ft
So you see thrust does make a difference even for the values we would typically find for WW2 aircraft.
One thing to point out: Thrust is a function of BHP and Airspeed. Here's the simple relationship:
Thrust = (prop eff. * BHP) / V
The lower your velocity, the greater your thrust.
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Stoney-
Thanks for the info! We'll need more info than that though. Basically we'll also need the drag polar meaning the corresponding Cd for a given Cl clean and with flaps deployed.
Tango, XO
412th FS Braunco Mustangs
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How are you calculating the effect on radius?
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I posted the equation in my initial response to Urchin above.
Radius(turn) =
V^2
-------------------------------------
g x sqrt [ ((Cl / Cd) x (T / W))^2 - 1]
Tango, XO
412th FS Braunco Mustangs
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Heheh, that's where I learned that thrust was a variable.. thanks Dtango. If there's something that you and Crumpp agreed on, it was that thrust is a factor.
I may also like to add. The Spit VIII and Spit XIV actually technically have more wing area as their ailerons have been cut short, but that's probably negligible.
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Originally posted by SgtPappy
I may also like to add. The Spit VIII and Spit XIV actually technically have more wing area as their ailerons have been cut short, but that's probably negligible.
Ailerons and all but split flaps count as wing area.
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Originally posted by dtango
Thanks for the info! We'll need more info than that though. Basically we'll also need the drag polar meaning the corresponding Cd for a given Cl clean and with flaps deployed.
Fired up XFoil to generate the drag polars. I don't yet know how to make all of its functions work yet, so bear with me, but I did get a simple set of numbers. A couple of questions...
In order to generate Reynolds number, I used an average chord length of 6.5 feet, as this was the result of dividing the wing area by the span. I don't know the root or tip chords, so I had to guess. I used 150 mph as a velocity, as I figured this was approximately flap deployment speed. This gave me a Mach of approx. .2 and Rn of 9X10^6. Do these numbers seem right? I don't know how to make XFoil generate the flapped Cl, so I simply added the .8 to the clean Cl. Unfortunately, NACA didn't generate the Cd flapped for the similar airfoils, so I hit a brick wall there. Finally, which AoA should I use, the AoA at Clmax or any of them. Obviously the relationship Cl/Cd changes based on AoA. I've got the numbers generated after plugging all of the above in. Unfortunately, I couldn't figure out how to make Excel plot them properly, so I can only present them in text form...
First column is AoA, Second is Cl, and Third is Cd
-4/ -0.2525/ 0.00680
-3 -0.1347/ 0.00669
-2 -0.0169/ 0.00663
-1 0.1009/ 0.00663
0 0.2190/ 0.00659
1/ 0.3353/ 0.00619
2/ 0.4528/ 0.00595
3/ 0.5704/ 0.00586
4/ 0.6883/ 0.00577
5/ 0.8056/ 0.00596
6/ 0.9204/ 0.00632
7/ 1.0316/ 0.00691
8/ 1.1373/ 0.00782
9/ 1.2412/ 0.00885
10/ 1.3579/ 0.01003
11/ 1.4566/ 0.01118
12/ 1.5527/ 0.01247
13/ 1.6393/ 0.01390
14/ 1.7081/ 0.01572
15/ 1.7713/ 0.01817
16/ 1.8223/ 0.02180
17/ 1.8578/ 0.02730
18/ 1.8761/ 0.03540
I think I may have entered something wrong, as I was expecting 18 degrees of alpha to carry me through the stall, which obviously didn't happen (perhaps as a result of such a relatively high Rn?).
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RAE used following polars for the Spitfire I in the report called "Notes on the Turning Performance of the Spitfire Affected by Altitude and Flaps".
Basic form of the polar is given as:
Cd = (Cd0 + kCl^2) + Cl^2/(pi*A)
Cd0 flaps up = 0,018
Cd0 flaps 85deg = 0,0491
A = 5,61
k flaps up = 0,02
k flaps 85deg = 0,008
For more normal presentation:
Cd = Cd0 + Cl^2 / (pi * A *e)
these result values of e as 0,74 flaps up and 0,88 for flaps at 85deg.
The full throttle Clmax values at level flight stall in the report are:
Flaps up: 1,89
Flaps 85deg: 2,56
In the minimum radius of level turn at 12k the Cl values are:
Flaps up: 1,46
Flaps 85deg: 1,97
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Originally posted by Urchin
AFAIK the wings were all identical in regards to size and shape. The difference was the armament that could be mounted in them.
If I am wrong on that then maybe that explains the differences.
Another difference -
E wings had a strengthened/stiffer main spar.
Lot of discussioin has gone on over E wings, my own personal take on them -
1) C wings with mod kits to fit .50 cals (avail prior to D-Day)
2) C wings fully modded at source
Both above recognised by still having the .303 panels.
3) Wings built as E wings, noticeable by lack of .303 panels.
I can only imagine that the XVI's stiffer E wing allows it a good turning circle.
The XIV is an anomaly though, what I've read -
Turning with the Griffons torque it 'should' match a IX, against the torque the turning circle is larger.
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The only factor a wing's strength should contribute is max. +G/-G loads.
A slight warp in wing shape during high G maneuvers may have some affect, but not a lot. If the wings are warping, then you're probably screwed.
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"I was expecting 18 degrees of alpha to carry me through the stall"
I would be surprised if it had. My guess would be somewhere around 15 degrees. The effect of wash-out needs to be considered too.
"A slight warp in wing shape during high G maneuvers may have some affect, but not a lot. If the wings are warping, then you're probably screwed."
The warpage would increase the washout momentarily worsening the turn performance some but would also contribute in delaying high speed stall.
-C+
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Originally posted by Karnak
dtango,
The Spit XVI will have such a negligibly greater thrust that it will have no meaningful impact on turn radius. See my earlier post vis-a-vis the thrust of the F4F-3 Wildcat, Spitfire Mk XIV and F-15 Eagle.
I find this argument a bit silly. Take any plane and turn it as tightly as you can. Then reduce power and watch as the circle grows quite larger. Obviously thrust has a major impact on sustained turning.
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An aircraft that has increased wingloading will need some "X" increase in power to keep the SAME turning circle/radius.
AFAIK the Spit XIV had the same turning as the IX, however I do not know the alt/power curves or the alt during the test.
If my memory serves me the 109F could outturn the 109E by a margin while being heavier...Viking?
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In my experience the 109F out-turns or is at least on par with the Emil in sustained turning. I don't know if there were any wartime test done to support this though. The 109F also has a slightly smaller wing area than the Emil.
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It does? Always thought it was a tad larger due to the rounded tips.
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Yeah, I thought so too until recently. They are in fact slightly smaller.
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Did they chop of the chord or the span?
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The original wing for the Bf 109F (as seen on the V24/V25) had rectangular tips and wing area 15,1m2. Later the wing area was increased to 16,05m2 in the production planes by attaching rounded wing tips to the 15,1m2 wing (there is also some other differences).
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109E-4 wing area 16.17 m2
109F-4 wing area 16.10 m2
A very slight decrease in wing area.
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The wing area of the Emil was 16.17 square meters, but the area of the F and all standard later models (not counting odd-balls like the H) was 16.40 square meters.
EDIT: At least, I thought it was. Now I've got to check when I get home.
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Well, there is some variance between the sources. Below is an original Mtt specsheet (source Jet&Prop 5/2001 p.8), the original F type wing (V24 and V25) was very close the production F wing except the the rounded tips (+ some minor dimensional differences, differences in flaps etc.). Click picture to see the higher resolution image.
(http://img146.potato.com/loc1121/th_25197_wings_122_1121lo.jpg) (http://img146.potato.com/img.php?image=25197_wings_122_1121lo.jpg)
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Originally posted by gripen
The original wing for the Bf 109F (as seen on the V24/V25) had rectangular tips and wing area 15,1m2. Later the wing area was increased to 16,05m2 in the production planes by attaching rounded wing tips to the 15,1m2 wing (there is also some other differences).
This is exactly what I thought.
Got to dive into my 109 books ;)
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I don't think that's right. One Internet source (I know! I'm not saying it's right!) says the wingspan of the Emil is 8.76 meters and the wingspan of the 109F is 9.92 meters. That's over a full meter more. From what I thought, they used the same planform of the 109E and simply rounded it OUTSIDE of that planeform (meaning they tacked on more rather than taking off). This might support that idea.
That's what I thought. Could be wrong.
If the wing is essentially the same span, but one had rounded tips, then I can understand smaller area. However, if the rounded wingspan is significantly longer, even with a curved shape it should have more area.
Now the question is finding accurate numbers.
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I don't know more relevant evidence than manufacturers drawings. The original F type wing as in the V24 and V25 had span of 8,89m, area 15,1m2, MAC at 1,78m, AR 5,22 and taper ratio 0,495 (values from Mtt report on V24 wind tunnel tests) so some writers might have confused E type wing with that.
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Originally posted by Krusty
I don't think that's right. One Internet source (I know! I'm not saying it's right!) says the wingspan of the Emil is 8.76 meters and the wingspan of the 109F is 9.92 meters. That's over a full meter more. From what I thought, they used the same planform of the 109E and simply rounded it OUTSIDE of that planeform (meaning they tacked on more rather than taking off). This might support that idea.
8.75m = 26.74ft :huh
9.92m = 32.55ft
9.87m = 32.38ft
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Originally posted by Urchin
I was playing around with the "Fighter comparison" website earlier, and I plugged in the Spit 14 vs the Spit 9. Now, I have flown the Spit 14 a fair amount, and I actually like the plane, but it doesn't turn anywhere near as well as a Spit 9 does (in my subjective opinion).
In real life, according to a test report I've seen linked several times here, the Spit 14s turning circle was reported to be "identical" to the Spit 9s. This is in spite of the fact that it was 1,000 lbs heavier. I guess the extra horsepower made up for the weight, in the test.
The website (Fighter Comparison page (http://gonzoville.com/ahcharts/index.php) ) agrees with my subjective assessment. The smallest turning circle with flaps down is 509 feet for the Spit 14, and 433 feet for the Spit 9. With flaps UP, the circles are nearly identical, with the Spit 14 having an edge that may or may not really be there (I'd say that difference is probably well within the margin of error for the data collection).
I don't understand why the turning circles are identical with flaps up (which matches the test report), but drastically different (15%) with flaps down. The wing and flap design didn't change between versions.
A different way to look at it is to compare turning circle size with flaps up to that with flaps down.
The Spit 5 is 503 / 386 (~23% smaller).
The Spit 9 is 632 / 433 (~32% smaller).
The Spit 16 is 567 / 450 (~21% smaller).
The Spit 14 is 629 / 509 (~19% smaller).
Do the flaps on the Spit 9 just work exceptionally well?
Hi Urchin,
Since I did the testing for the data on the site you referenced I'd like to throw in a couple of comments about the data.
You are correct, the website has the wrong data on the full flaps radius for the Spits. The last testing I did was on 11-18-06 with Ver 2.09.1 . Here's what my spreadsheet says for the Spits:
Spit 1 is 471 / 395
Spit 5 is 502 / 434
Spit 16 is 567 / 460
Spit 8 is 568 / 476
Spit 9 is 632 / 528
Spit 14 is 629 / 538
The data used must be from an older test series or it got screwed up importing it into the web engine. So the answer to your question is with correct data, no, the Spit 9 flaps don't work exceptionally well! Thanks for pointing out the mistake. I'll see if we can get the correct data posted up.
In case you are wondering how fuel load affects turn radius:
Spit 16 25% fuel is 567 / 460
Spit 16 50% fuel is 583 / 482
Spit 16 75% fuel is 590 / 495
Spit 16 99% fuel is 605 / 511
1) I did the best I could to be consistent in the testing, but it is by no stretch what I would call very accurate. The biggest problem was with judging airspeed during the turning circles.
2) These tests show how well I flew the planes, others will be better or worse than me. For instance WideWing can usually turn a smaller circle than I can. However the relative performance to each other we have found to be fairly consistent.
3) The data is a getting old now. The drag modeling has changed, therefore some planes may fly differently now than when I did the testing.
I haven't flown much the last 9 months so I doubt I'll get enthused to spend the time it will take to retest all the planes.
I have been thinking of sponsoring a "Beat MOSQ's Turn Radius" contest. I might post a thread asking folks to try to beat my Radius, if they do I'll update the data with their info and give them credit for it. However they will have to send in FILM to prove it!
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Originally posted by dtango
Radius(turn) =
V^2
-------------------------------------
g x sqrt [ ((Cl / Cd) x (T / W))^2 - 1]
From other relationships we can replace V^2 with 2x(W/S) where S= wing area. This gives us the following:
Radius(turn) =
2 x (W/S)
---------------------------------------
g x sqrt [ ((Cl / Cd) x (T / W))^2 - 1]
I need to make a correction. Earlier in this thread I posted two sustained turn radius equations. The 1st equation is valid.
The 2nd equation with the 2 x (W/S) term in the numerator is incorrect. I made a couple of errors in derivation.
Many thanks to Badboy for noticing something odd and also for helping me check my math on request.
Tango, XO
412th FS Braunco Mustangs
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Question
If 2 different planes are the same speed and at the same angle of bank, will the turn radius be the same.
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You mean spits or any?
If "any" then no. That would totally negate differences in wings.
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Weight will also cause the radius to be different.
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Originally posted by MiloMorai
Question
If 2 different planes are the same speed and at the same angle of bank, will the turn radius be the same.
Technically yes. Here's another form of the turn radius equation:
Radius = V^2 / gravity * tan(b) ---- where (b) is the bank angle
This equation masks how V and bank angle are limited by the dynamics (e.g. cl/cd, thrust, weight, etc. etc.) because maximum V and bank angle in a level turn are all dependent on a bunch of factors.
Tango, XO
412th FS Braunco Mustangs
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Originally posted by MiloMorai
If 2 different planes are the same speed and at the same angle of bank, will the turn radius be the same.
Yes, assuming that the altitude is keeped constant and the turn conducted "ball in the middle. But that is pointless; the plane with better turning performance can maintain higher angle of the bank at this speed and therefore turns better.
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More available power with absolutely same weight and airframe will give the availability to tighten a turn.
Now, what the debate is about is whether the increased weight of the Spit XIV is matched with the increased power.
Since the ROC is up with the power, it means that the total lift is more, however the weight starts sagging in when the wing area "reduces" in a banking situation,- there the increased wingloading kicks in (relatively).
Anyway, the test pilots say that there is nothing to choose from. And that was after all, - a test. So I'd put my pennies on that there was not much difference.
About the 109F, - I really thought it was exactly what Krusty said. Rounded tips outside the boxed form. So?
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My first book on the 109 Gives me a 109F with EXTENDED wings due to the rounded tips. On the 109E-7 I have a span of 9.86 (32-4).
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We should get one of the 109 experts in here (if anyone's left). I got chewed out because I claimed the F had bigger wings, but was forced to concede.
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Originally posted by Viking
We should get one of the 109 experts in here (if anyone's left). I got chewed out because I claimed the F had bigger wings, but was forced to concede.
No expert here, but I see that the 109F had a span of 9.92 meters, vs 9.86 meters for the 109E... Not much, but certainly different.
My thought was that the 109F had a substantially redesigned wing.
My regards,
Widewing
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Hmm let's see. Two 109 experts I know of are gripen and butch2k.
Tango, XO
412th FS Braunco Mustangs
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Hehe, Izzy had some data on the 109 ;)
Anyway, this is data-data. Must be in the books.
BTW, was paging through some and found errors without even looking up (obvious ones). By getting some more books for christmas, I have more data, so I'm still looking though.
One line claimed the 109F had a redisigned and smaller wing.
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Oh, getting back on the topic of the Spit XIV vs the IX, bear in mind that the XIV's power overcomes the weight in terms of ROC.
Now in the case of 109's, this was the case with turn performance however yet getting worse.
The difference between those two however are mostly wing loading and span, where the Spitty is bigger. Now a turn AFAIK relies a bit on those both, - clip a glider's wings and in a given degrees of banks the shorter or the heavier will stall before.
Then there is the enormous power increase.
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"Oh, getting back on the topic of the Spit XIV vs the IX, bear in mind that the XIV's power overcomes the weight in terms of ROC."
Bear in mind? I have a beaver, does it count? :D
I think that even if there is more weight but there is more power it is possible to stay in the turn with a lighter plane, you just need to pull some more on the stick. If the best turn is achieved near the max permissible AoA you might run into problems because of excessive drag starting to negate the extra power you have and impeding stall dictated by wing design. So the point is: do you have enough excess power to overcome the drag caused by more AoA which is caused by the need to turn the more weight as tightly as less weight?
On practical level it may well be that XIV could just fly a bit bigger circle with better rate and wait for the IX to fall in a stall trying to gain lead for a shot flying a smaller circle.
I'd trade turning circle to RoC any day.
"Now in the case of 109's, this was the case with turn performance however yet getting worse."
Could you explain what you mean by this?
-C+
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ROC has some relation with turning circle.
And the AoA is a bit twisted with almost vertical wings. Not sure which come out better there, span or chord. But wingloading definately counts.
Beer that in mind :D