Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Karnak on October 22, 2001, 05:10:00 AM
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Here is a sampling of the wing loading figures that I am using. If you see anything that is wrong please tell me.
Mosquito FB.VI Series 2
Wing Area: 454 sq ft
Empty: 31.5 lbs per sq ft
Typical: 42.95 lbs per sq ft
Maximum: 49.12 lbs per sq ft
Bf109G-6
Wing Area: 173.3 sq ft
Empty: 34 lbs per sq ft
Typical: 40.05 lbs per sq ft
Maximum: 43.25 lbs per sq ft
Bf110C-4
Wing Area: 413.3 sq ft
Empty: 27.71 lbs per sq ft
Maximum: 36.01 lbs per sq ft
Fw190A-8
Wing Area: 197 sq ft
Empty: 35.53 lbs per sq ft
Maximum: 54.83 lbs per sq ft
Ju88C-6c
Wing Area: 586.65 sq ft
Empty: 34.05 lbs per sq ft
Typical: 46.41 lbs per sq ft
Me410A-1/U2
Wing Area: 389.69 sq ft
Empty: 45.16 lbs per sq ft
Typical: 63.57 lbs per sq ft
A-26B-15 Invader
Wing Area: 540 sq ft
Empty: 41.43 lbs per sq ft
Maximum: 64.81 lbs per sq ft
F6F-5 Hellcat
Wing Area: 334 sq ft
Empty: 27.66 lbs per sq ft
Maximum: 46.15 lbs per sq ft
P-38L Lightning
Wing Area: 328 sq ft
Empty: 39.02 lbs per sq ft
Typical: 63.11 lbs per sq ft
Maximum: 65.85 lbs per sq ft
P-47D-25 Thunderbolt
Wing Area: 300 sq ft
Empty: 33.17 lbs per sq ft
Maximium: 58.34 lbs per sq ft
P-51D Mustang
Wing Area: 235 sq ft
Empty: 32.49 lbs per sq ft
Typical: 51.49 lbs per sq ft
A6M5c Reisen
Wing Area: 229.27 sq ft
Empty: 18.04 lbs per sq ft
Maximium: 26.28 lbs per sq ft
N1K2-J Shiden-Kai
Wing Area: 253 sq ft
Empty: 23.15 lbs per sq ft
Typical: 34.85 lbs per sq ft
Maximium: 43.25 lbs per sq ft
C.202 Folgore
Wing Area: 180.83 sq ft
Empty: 30.66 lbs per sq ft
Typical: 35.72 lbs per sq ft
Maximium: 37.43 lbs per sq ft
La-5FN
Wing Area: 189.34 sq ft
Empty: 32.6 lbs per sq ft
Typical: 39.12 lbs per sq ft
Hurricane MkIIc
Wing Area: 258 sq ft
Empty: 21.93 lbs per sq ft
Maximium: 31.18 lbs per sq ft
Spitfire MkXIVe
Wing Area: 244 sq ft
Empty: 27.05 lbs per sq ft
Typical: 34.25 lbs per sq ft
Maximum: 40.05 lbs per sq ft
Typhoon MkIb
Wing Area: 279 sq ft
Empty: 31.54 lbs per sq ft
Maximum: 47.49 lbs per sq ft
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Karnak,
Interesting.
What are you using them for?
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I only use it to get an idea of how well an aircraft might turn.
Verm and I were talking about it at the Con. He was saying that he doubted the Mossie's turn rate was correct and that the real indicating factor was wing loading while empty.
Thus this post.
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What makes p38 to turn so good with this high wingloading?
Old fashioned wing profile maybe?
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Karnak,
Yes wingloading is a good indicator of turn ability. Careful with empty wingloading though. Depending on what source you read empty may be without oil, water, coolant or the pilot. I prefer to use the combat loadout. However you need to adjust for range. For instance a P-47 certainly handles better without max fuel and still has more endurance than most WW2 fighters. So a P-47 with 50% fuel is about the same as some others with 100%.
The P-38 turns resonably well because of it's high aspect ratio wing(Widewing span vrs short wing cord ratio). It creates high lift with low induced drag. This compensates for horrible wing loading although I will never understand the claims of incredible turn performance with the bird. The trade off for high aspect ratio is poor aileron response and roll performance. IE. a F-15 vrs a U-2.
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F4UDOA,
Yes, I was only using the typical and maximum take off figures. Verm was telling me that the real indicator was the empty number. That's why I included it here, I've never even calculated it before compiling this list.
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Interesting,
I'm curious as to why he uses the empty wing loading?
Verm,
You out there?
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Originally posted by F4UDOA:
The P-38 turns resonably well because of it's high aspect ratio wing(Widewing span vrs short wing cord ratio). It creates high lift with low induced drag. This compensates for horrible wing loading although I will never understand the claims of incredible turn performance with the bird. The trade off for high aspect ratio is poor aileron response and roll performance. IE. a F-15 vrs a U-2.
It's the same in Ki-61, Ki-100 and Ta-152 too.
Mitsu
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Hi Karnak,
>I only use it to get an idea of how well an aircraft might turn.
Turning ability depends on many factors.
In high-speed turns (above corner speed), the limiting factor is the structural strength of the airframe. A higher wing-loaded aircraft can turn better than a lower wing-loaded one at the same high speed if it is able to withstand higher forces.
In low-speed sustained turns (below corner speed), the limiting factor is power versus drag. A plane with higher wing loading can turn better than a plane with lower wing loading if it has less overall drag, or more power. (The difference of power and drag in relation to the aircraft's mass is called "specific excess power" or short "Ps".)
In low-speed instantaneous turns (at and below corner speed), it's the relation between maximum available lift and aircraft mass that determines which aircraft is going to turn better. This is where wing loading comes into play - but it's a coarse simplification as at the same wing loading, different profiles will yield different maximum lift forces.
Since subvariants of one aircraft type usually feature the same wing profile, you can use wing loading to compare their instantaneous turning ability, but comparing different aircraft types, the results are much less accurate. Even with subvariants of a single aircraft type, the later, heavier and more powerful variant could end up with a poorer instantaneous, but a better sustained turn. Why? The increase in wing loading might be compensated for by a decrease in power loading.
In short, the actual wing loading figure is not as helpful in determining turn performance as one might think at first.
Regards,
Henning (HoHun)
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Hohun's examples are true. But all other things being equal, a plane with lower wingloading can turn in tighter and faster circles than a plane with higher wingloading.
Wingloading plays a big part in determing stall speed and thus minimum turning radius.
It's also a big player in the equations for induced drag. Higher wingloading requires higher lift coefficient to execute a given maneuver. Induced drag increases with the square of lift coefficient. Differences in induced drag are largely responsible for what flight simmers call "E-retention".
W is weight, S is wing area. W/S is wingloading. Basically all of the equations for things that you want to be small for good turning performance have powers of W in the numerator and powers of S in the denominator.
[ 10-23-2001: Message edited by: funkedup ]
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I agree with both HoHun and Funked.
My point in my talks with Karnak is that wingloading is a general indicator of sustained turning ability, but I agree its not an absolute.
What we were trying to do, is without a large cache of flight test data and spending a large amount of time doing calculations, how could we do a "quick and dirty" test on the Mosquito to see if its turning ability falls into the general range we would expect it too. (Remember we were at the CON, and I was drunk and didn't figure on spending hours doing flight testing :p Plus none of us had our aviation libraries)
My idea was to look at wingloading for several aircraft and the Mosquito, do some quick and dirty 360 degree turn time tests (maybe 5 times averaged) for each and then see if the results were generally believeable.
We weren't trying to absolutely validate the FM :)
My reasoning that "empty weight" is more appropriate than "fully loaded weight" is that fully loaded weight (ie 100% fuel) artifically penalizes the aircraft designed for long range flight.
You can take two planes that are the same general size, weight, and ability empty, but your tests will artifically show the long range aircraft inferior.
If you want to take this "theory" of comparison to AH, I think it would be best to calculate the %25 fuel load weight and go from there.
True this is not without its own problems, but since fuel loads are so variable in the arena, this would be the most representative for the kind of tests we were discussing.
Karnak, I haven't had time to look at your numbers yet, I've been really busy since I got home from Dallas.
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Hi Funked,
>Hohun's examples are true. But all other things being equal, a plane with lower wingloading can turn in tighter and faster circles than a plane with higher wingloading.
Assuming the aircraft in Karnak's list to be equal in all other things would be just the "coarse simplification" I mentioned :-)
>Wingloading plays a big part in determing stall speed and thus minimum turning radius.
It would be more logical to use stall speed iself as key parameter instead of wing loading which neglects airfoil properties.
Wing loading can be useful for rule-of-thumb comparisons, but if you don't keep their limitations in mind, you'll arrive at wrong conclusions. (Applying it indifferently to sustained turns is the most popular error.)
Regards,
Henning (HoHun)
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Hi Vermillion,
>My point in my talks with Karnak is that wingloading is a general indicator of sustained turning ability, but I agree its not an absolute.
It's actually a general indicator for instantaneous turns.
For sustained turns, you could try to combine climb rate with stall speed :-)
Seriously, climb rate is the Ps figure for 1 G flight, and the quotient of climb rate and square root of 1 G power-off stall speed might actually be a better indicator of sustained turning ability than wing loading.
(The square root calculation serves to coarsely take into account that sustained turns usually are flown at perhaps 2 G.)
That's no proven procedure, but I'd be interested how the aircraft listed by Karnak rank by this criterium, anyhow :-)
Regards,
Henning (HoHun)
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HoHun is right. :)
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Yeah, HoHun is mostly right but it should be noted that structural strenght is not allways limiting factor at high speed turns because compressebility constrains maneuverability specially at high altitudes. Forexample the P-38 could not do more than a bit over 3g turns at 30k at any speed while the Vampire could turn at 5g at 30k. This is because new high speed profiles sustained compressebility better. I don't know if this is modeled in the AH.
gripen
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Structual strength is almost never the issue in sustainable turns with WWII fighters.
Every WWII fighter that I am aware of will stall way before suffering a structural failure in a sustainable turn.
Instantaneous turns/snap turns are a whole different story.
In general the higher the wingloading, the fewer Gs it takes for the aircraft to depart controled flight. There are several other factors, but an easily obtained, very rough estimate can be reached with wingloading data.
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Originally posted by Karnak:
In general the higher the wingloading, the fewer Gs it takes for the aircraft to depart controled flight.
Iīd say departing controlled flight has more to do with wingdesign. You leave controlled flight wenn the outer wing (aileron) stalls. Thatīs why leading edge slats werenīt build over the whole wingspan for the 109 f.e. It would have allowed even higher AoA, but this advantage could not have been used due to harsh stall characteristics. The ailerons would have stalled first now, before the wingroot section stalls. Slats covering only the wingarea for the aileron allow aileron control while the wingroot section is already stalling.
This way you kept controlled flight and increased lift. The Spit went the opposite way, with thin wings (and a lot of washout?)it reduced the total lift to keep good aileron control near the stall.
This is at least my interpretation :)
niklas
niklas
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Well Karnak,
I'm not sure what you wanted to argue? Pretty much all WWII fighters could reach their structural limits (max sustained limit which normally were around 6-9g when breaking load factor were around 10-14g and safety coefficient 1,5-2) in the high speed turns or pulls or what ever maneuvers at low altitude. It is true that max sustained turns were around 2-4g but no one has argued otherwise here.
And high wingloading does not mean poor ability to sustain g specially at high altitude and high speed.
gripen
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Hi Gripen,
>Yeah, HoHun is mostly right but it should be noted that structural strenght is not allways limiting factor at high speed turns because compressebility constrains maneuverability specially at high altitudes.
Good point! It fits well with what I wrote, however, if you consider that corner speed increases with altitude until the aircraft will have difficulties actually reaching corner speed.
For example, an aircraft with a 110 mph stall speed at 1 G and a 9 G structural limit has a corner speed of Mach 0.43 at sea level. At about 23000 ft, it's corner speed will be Mach 0.68 - which is the P-38's critical Mach number. If our fictitous aircraft is similarly Mach limited, at higher altitudes, corner speed simply is beyond its capabilities.
By my definition, it can only make "low-speed turns (below corner speed)" above that altitude, though I admit that this term might be somewhat misleading as actually, the aircraft is going very fast :-)
Regards,
Henning (HoHun)
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HoHun,
Actually you are missing my point. Very few WWII fighters could reach their structural limits in normal maneuvers (say turning or looping maneuvers) at high altitude. The critical mach number decreases when g load increases, forexample the P-38 had critical IAS about 290mph at 30k and 0-2g but with a bit over 3g load buffeting started around 200-250mph IAS and higher g loads caused buffeting or dive tendency at all speeds. See the AHT or manual. You can find similar phenomena from the manual of the F4U too.
gripen
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Hi Karnak,
>Every WWII fighter that I am aware of will stall way before suffering a structural failure in a sustainable turn.
Since you weren't specificially mentioning sustainable turns, I just decided to cover them all :-)
>In general the higher the wingloading, the fewer Gs it takes for the aircraft to depart controled flight.
Actually, it's not wing loading that counts but maximum available lift in relation to aircraft weight.
Regards,
Henning (HoHun)
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Hi Gripen,
>Actually you are missing my point.
You're right, I missed it! :-) Thanks for the info, that was new to me!
Regards,
Henning (HoHun)