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mynameisroland
07-08-2007, 07:19 AM
What is the point in having a fighter with a low wing loading?

I know some of the cons of having a large wing area is increased drag but what are the others.

GH_Klingstroem
07-08-2007, 07:33 AM
Lower stall speed, tighter turns (in general). Usually wings will stall att the same angle of attack however planes with low wingloading will reach this angle of attack at a lower speed.

Think of wingloading as the whole weight of the aircraft dived by the area of the total wing(s).

This tells you that if you have huge wing and a low weight aircraft you will get a very very low stallspeed for example and probably a pretty good turner. BUT, as u mentioned, w big wing will also creat lots of lift.
Lift=drag.
And to that not only will lift create drag, the bigger the wing the more resistanse will have to fly through the air hence the best wing is usually a compromise between size and profile.
I dont want to go too deep into this but an a/c will a small wing will be very fast but poor turners(fw190, p47, p51 etc) and a/c with big wings will usally be slow and good turners(any biplane, spitfire etc etc)
Hope this helps a bit!
cheers

mynameisroland
07-08-2007, 07:49 AM
But here is the complication, aircraft like the Tempest or even P51 have a low wingloading compared to some other late war fighters but they have aerofoils which are laminar flow. Another example is the P38 which has a high wing loading but had high lift devices such as fowler flaps which help increase its turn radius.

VW-IceFire
07-08-2007, 07:57 AM
It all seems to me, having done some reading trying to understand the pros and cons of how all of this works that its a really complicated balance that the aircraft designer had to go for.

With the FW190 it was a balance between achieving a high top speed without an extremely powerful engine. I don't think the Germans had the option of something like the P&W R-2800 nearing full production at such an early stage of the war so they went with the low drag approach and created aircraft with higher loading.

But for all of the high wingloading, low wingloading, and everything in between I often wonder if airfoil is even more important. The profile of the wing seems to be pretty significant...the Spitfire is another contradiction in my mind having very thin wings but the wings being of generally a higher lift configuration.

Its a tricky business trying to be an armchair aeronautical engineer http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

stalkervision
07-08-2007, 08:56 AM
Look up advantages of "Mid-wing fighters" if you really want to confuse yourself.. http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

I believe the Japanese "george" was flown with both configurations.. http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

Viper2005_
07-08-2007, 09:28 AM
Generally speaking the wings of a fighter are sized by either takeoff/landing performance requirements. Bigger and better runways therefore translate directly into higher wing loadings.(Manoeuvre requirements only really started to bite at the design stage when the lessons of Vietnam were learned). The Spitfire and F-104 have more in common than most people think - they were both point defence interceptors which traded above average landing speeds (for their time) for above average performance (for their time). The Spitfire was never intended to be a turn fighter - it was simply intended to be as fast as a late 1930s RAF pilot could handle from a grass airfield.

Of course, the lesson of History is that once the design is frozen the wing area will tend to remain constant whilst the weight continues to increase inexorably with each new modification or mark...

Clever flaps or thick aerofoils can allow you to reach a higher CL and get away with a smaller wing at the expense of considerable extra complication.

1940s laminar flow aerofoil sections tended to have rather poor values of CLmax and therefore fighters designed to exploit them tended to feature lower wing loadings because of the need to meet their takeoff/landing performance targets; the reduced frictional drag meant that the designers expected to realise a nett drag reduction despite the extra wing area.

In general, aircraft with higher wing loadings tend to be faster but less manoeuvrable. Since speed is life, this has historically been a good betting proposition. However, once top speeds become supersonic the trend can break down due to the operational, aerodynamic and thermodynamic issues associated with supersonic flight. As a result of this, current fighters are no faster than 1960s fighters, but generally have lower wing loadings, since if you can't go faster the next best thing is to turn harder (apart from which, low wing loadings are necessary for high supersonic L/D and therefore help towards supercruise). As such, wingloadings are likely to stay roughly constant or possibly even decrease in future designs until such time as the upward trend in speed reasserts itself.

DKoor
07-08-2007, 09:28 AM
Build the 109 put the Spitfire wings on it and get it over with.

Jaws2002
07-08-2007, 09:39 AM
With lower wing loading you should be able to reach better climb for the same engine.

You can also take off easier with higher bombloads.
There were a lot of FW-190 Pilots that complained about scary high takeoff speed of a bombed up 190.
Fighter aircraft design is a very precise busines. They had to find a perfect balance while taking into account the main task for the aircraft and in the sam time take into account future developement on the airframe. Planes tend to get heavier and heavier as the design gets older.
If you start with a high wing loading few years along the way you end up with somenting like the TA-152C, F-104. A scary fast plane with great zoomclimb and dive, but that needs a lot of runway for take off and leaves no room for error for the pilot. Because of high take off, landing and stall speed.

Usually for planes like this ones you need experts only. Like one Starfighter pilot puts it:
"The F-104 was sort of like owning the sharpest knife in the world. It was an honest airplane; you knew what was going on all the time. but like using a sharp knife, you better not make any mistakes. it did not suffer fools at all."

GerritJ9
07-08-2007, 10:21 AM
The "George" was developed from a Kawanishi floatplane fighter design, the "Kyofu" or, to give its Allied codename, "Rex". Initially it was built in mid-wing design as the "Shiden". However, it was redesigned in order to simplify it- the mid-wing version had, among other things, a complicated undercarriage retracting system. The redesigned low-wing version had some 21,000 parts less than the mid-winger.

mynameisroland
07-08-2007, 10:27 AM
Originally posted by DKoor:
Build the 109 put the Spitfire wings on it and get it over with.

How about this one?

http://www.unrealaircraft.com/hybrid/pages/dbspit_1.php

Seems that it had better performance on the same engine than the Bf 109.

DKoor
07-08-2007, 10:36 AM
So after all, it's not so unreal is it.... http://forums.ubi.com/images/smilies/59.gif
Wing l0ad FTW http://forums.ubi.com/groupee_common/emoticons/icon_cool.gif

M_Gunz
07-08-2007, 11:37 AM
Originally posted by mynameisroland:
What is the point in having a fighter with a low wing loading?

I know some of the cons of having a large wing area is increased drag but what are the others.

If you have the power to overcome the increased drag then you can turn harder at faster speed
sustained, or spiral climb steeper, tighter. And you might be called Spitfire or Zero.

It is also true with high wing loading up to a point....

Bremspropeller
07-09-2007, 04:10 AM
Let's keep it simple.

Lift is an equation of AoA.

Lift is not only dependant on speed - it's dependant on AoA at given speed (planes stall at a certain speed, because they have to pull the stalling AoA to keep lift equal with gravity - more weight (ergo a higher wingloading) will increase the speed).

However, wingloading can only be taken as a comparison factor when you're talking of the same profile (each airfoil has different equations for lift and AoA).
Plane A and plane B might have the same wingloadings, but totally different wing-profiles and therefore totally different turning-capabilities and lift-curves.
Other factors, such as wing-sweep are also important, but most WW2 a/c were straight-wing designs anyway.

Laminar flow wings produce few lift and tend to stall at low AoAs (BTW: neither the P-51, nor the Tempest had low wingloadings).
The P-51 could, however, deploy combat flaps, which offset the profile-penalty a bit.

AoA also relates to Gs (at higher speeds, the same AoA produces more (excessive) lift, which is nothing but acceleration/ G-force).

mynameisroland
07-09-2007, 05:22 AM
Originally posted by Bremspropeller:
Let's keep it simple.

Lift is an equation of AoA.

Lift is not dependant on speed - it's only dependant on AoA. (planes stall at a certain speed, because they have to pull the stalling AoA to keep lift equal with gravity - more weight (ergo a higher wingloading) will increase the speed).

However, wingloading can only be taken as a comparison factor when you're talking of the same profile (each airfoil has different equations for lift and AoA).
Plane A and plane B might have the same wingloadings, but totally different wing-profiles and therefore totally different turning-capabilities and lift-curves.
Other factors, such as wing-sweep are also important, but most WW2 a/c were straight-wing designs anyway.

Laminar flow wings produce few lift and tend to stall at low AoAs (BTW: neither the P-51, nor the Tempest had low wingloadings).
The P-51 could, however, deploy combat flaps, which offset the profile-penalty a bit.

AoA also relates to Gs (but we have to add speed to this equation as at higher speeds, the same AoA produces more excessive lift, which is nothing but acceleration/ G-force).

Brem you make some good points here but you make one assertation that I do not agree with. The P51 has a poor wing loading at 100% fuel load but at an assumed combat weight of say 60/50% its wing loading is much lower. The Tempest on the otherhand has a wing loading at 100% fuel which compares very favourably with other late war fighters.

Tempest V

Wing area : 302 ft²
Weight : 11,400 lb
Wing Loading : 37.75lb/ft²

Spitfire XIV

Wing area : 242.1 ft²
Weight : 8488 lb
Wing Loading : 35.06 lb/ sq ft

At a combat weight of 50/60% fuel load the Tempest may even have an equal or lesser wingloading than the Spitfire.

Bremspropeller
07-09-2007, 05:27 AM
Okay, you're right, didn't take that into account.

BTW: I edited my first post, as lift is of course directly related to speed. What I mean is that it's actually not the low speed that causes a 0g-stall, but the high AoA.


http://img.search.com/thumb/b/b1/Lift_Curve.jpg/300px-Lift_Curve.jpg
This graph is more or less what you should have in mind.

Wurkeri
07-09-2007, 05:31 AM
Generally low wing loading gives possibility to carry more stuff; bombs like Jaws noted but also pretty much everything else like fuel, armour, electrical equipment or what ever is needed.

Flying wise low wing loading tend to need less trimming because the needed lift can be generated with small AoA changes.

M_Gunz
07-09-2007, 05:35 AM
http://www.grc.nasa.gov/WWW/K-12/WindTunnel/Activities/lift_formula.html

An aircraft's lift capabilities can be measured from the following formula:
L = (1/2) d v2 s CL

* L = Lift, which must equal the airplane's weight in pounds
* d = density of the air. This will change due to altitude. These values can be found in a I.C.A.O. Standard Atmosphere Table.
* v = velocity of an aircraft expressed in feet per second
* s = the wing area of an aircraft in square feet
* CL = Coefficient of lift , which is determined by the type of airfoil and angle of attack.

The angle of attack and CL are related and can be found using a Velocity Relationship Curve Graph (see Chart B below).


It's no less true for being school material.

Lift is proportional to air density, CL (which is determined by the type of airfoil and
angle of attack.) and by the >>> square <<< of velocity.

Just going faster when not at zero-lift AOA or less will generate more lift, squared.
10% faster gets 21% more lift at the same lift-producing AOA. If you want to fly level
as you increase speed, the only way is to keep nosing down otherwise you rise.

AOA has two limits for flying and that's where it's critical, pun intended.

mynameisroland
07-09-2007, 05:50 AM
So how much is the disadvantage of having a laminar flow wing for turning and generating lift at turn speeds offset by having a low wing loading?

Im trying to rationalise the design decision made by Hawker to have a very clean wing design that was so large, larger imo than it needed to be increasing drag - unless there were benefits which offset this. For example the Tempest could have used a smaller wing and still had a wing loading inline with other late war fighters like the Fw 190 or the P51 ?

Bremspropeller
07-09-2007, 05:57 AM
So how much is the disadvantage of having a laminar flow wing for turning and generating lift at turn speeds offset by having a low wing loading?


Depends on the profile.
Laminar wings in general are fine for speed and range, but not for AoA dancing.


For example the Tempest could have used a smaller wing and still had a wing loading inline with other late war fighters like the Fw 190 or the P51 ?

Wingloading is surface/ mass.
Do the math http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Laminar flow wing-profiles reduce drag by placing the point where laminar flow turns into turbulent flow backwards.
That reduces drag.

Telling "how draggy" the Tempests wing is quite a complicated formula (wetted area increase compared to savings by laminar profile..).

The question is, does the lower drag (and therefore higher speed) pay off the turning-tradeoff?

I'd say yes - I'd always take speed over turning capabilities.

mynameisroland
07-09-2007, 06:05 AM
Brem, not being a mathematician by any means, thats why im asking others. Obviously all things being equal (power, weight, wing area ect )a wing which is not laminar flow but of a high lift variety should out perform the laminar flow wing in a turn at medium to slow speeds.

However if you have a highly loaded wing of a normal WW2 fighter ie the Fw 190/Hellcat(wing section,not insinuating that the Hellcat's wing was heavily loaded) eg and a more lightly loaded laminar profile wing ie the Tempests how big does the disparity in wing loading need to be for the laminar wing to match or exceed the normal wing? Again assuming power/weight is similar.

As your your last point - taking speed over turn - so would I. Thats why I query the design choice of chosing a large laminar flow wing, over a smaller wing which would allow for higher speeds but with no huge reduction in handling.

Bremspropeller
07-09-2007, 06:14 AM
Well, as I said before, wingload alone won't contribute turn by any means.
It'll only shift stallspeeds a few knots and you'll be able to pull slightly more Gs (less mass while you have the same lift, which is linked to AoA).
Remember, G-force is nothing but the difference between gravity and lift. (excessive lift leads to an acceleration, which is measured in "times g")

The shifts in G and stallspeed are (depending on mass difference between 100% and X%) not too much.

As for your question - very hard to tell, but given the complexity of the equation, I'd generally say "NO".

mynameisroland
07-09-2007, 06:18 AM
There has to be a point where a larger wing would out perform the smaller wing > but perhaps you would need to go towards the extreme of a F-104 Starfighter's wing compared to a Su 27 sized wing ?

So a lower wing loading, drops the stall speed allowing more G's to be pulled for a little longer

M_Gunz
07-09-2007, 06:24 AM
The lower your wingloading, the less AOA you have to pull to get the same lift vector.
It is you lift vector that turns the plane as well as allows it to climb and fly.

For turning I would rather have a wing that needs less AOA than one that allows me to use more
but really needs it. The latter will have worse drag.

Of course the wingloading is nothing without powerloading, either should be able to balance off
the other to some degree.

mynameisroland
07-09-2007, 06:35 AM
But a greater ability to increase AOA allows a better instantaneous turn rate to the point where speed drops too low?

Power loading for most of the late war fighters is pretty similar, I was just interested in the contrast between the Spitfires wing and the XIVs wing loading and that of the Tempest Vs wing and wing loading. Power loading for the two should be very close too.

WOLFMondo
07-09-2007, 06:36 AM
Originally posted by DKoor:
Build the 109 put the Spitfire wings on it and get it over with.

So you played 4.09 then? Spitfire MkK4 25lbs.

Bremspropeller
07-09-2007, 06:37 AM
Yeah, it's quite simple.

Just think of the forces involved while flying at the same alt and speed.
Drag and thrust equal out. So do lift and gravity.

Reduced mass leads to a lower gravitational force Fg (=m*g). But at the same AoA, you produce the same lift, which is (at lower weights) exceeding the gravity. Therefore you get an upward acceleration (G >1.0).

That is a reason, why some planes (the F-4 Phantom for example) stick to flying a dedicated AoA on approach - speed is set "automaticly" for any mass by that procedure.

Coming back to the original thought:
IRL an increased lift will also get you increased drag (thus, thrust and drag don't equal out each other anymore) and you'll decelerate.
That again influences your lift, as speed bleeds off, your lift will decrease, holding a constant AoA.

Okay, I've turned this into another E-retention discussion - I'll take the blame. http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif


As to your F-104 Su-27 coparison:
You're right. An Apollo capsule creates lift, when it re-entries the atmosphere. That is a reason why the angle is so important (too flat and the lift will bounce you off, too steep and your decelleration will tare apart the ship).
Any area set into an airflow produces lift - that is not only by "conventional" airflow.

As you can see in the lift-coefficient-curve I posted, lift does not immediately drop off above the stall AoA. That is because the wing set into an airflow will create a downwash when it's hit at the underside of the wing.
So even when the airflow above the wing has collapsed, you produce lift (well, to a certain extent..).

The problem in practical flying is that that amount of AoA has the same effect as throwing an anchor out of your plane.
Spedd will bleed off, the downwash force decreses and there you are...above stalling AoA and at LOW speed. Congrats, you've just put yourself in a FU situation. http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

Okay, back to topic - you see, increased wing-area will contribute to lift and therefore to turning ability (downwash lift above stall), BUT that is only a minor improvement, as your speed will bleed off too quickly to make use of that effect.

Kurfurst__
07-09-2007, 10:33 AM
Originally posted by Bremspropeller:
Well, as I said before, wingload alone won't contribute turn by any means.

Basically wingloading usually defines the aircraft's stall speed (a least in combat, without lift assisting devices such as slats and flaps), and through it, how slow the aircraft can get in turn, and thus the turning circle.

Simply to put, planes with low wingloading are usually having smaller turning circles.

Low wingloading on the other hand is not so pronounced as far as turn rate, or in other words, turn times go. Turn times are basically defined by how high G the aircraft can hold up in a sustained manner. That is basically speaking a race between the thrust of the propeller vs. the drag of the aircraft in turn. Here low wingloading doesn't give much of an advantage, as - all things equal - you will have a larger area wing, and thus higher drag to achieve lower wingloading. You will need more thrust to overcome the greater drag, if you're pulling the same Gs, or rate of turn.

The effect of increasing thrust (ie. engine output, 'boosting') on turn is interesting. Even huge increases in excess thrust (either by increasing engine power or doing a descending turn - tactics, tactics!) have very small effect on turn radii, since the aircraft just can't go below it's given stall speed at a given G-loading. However, increasing excess thrust can have a VERY pronounced effect on turn times.

Simply to put, low wingloading planes don't neccesarily beat high wingloading planes in turn times.

Best examples are the Yakovlevs vs. Spitfires. Spitfires have very low wingloading, and high thrust, high drag; the Yakovlevs have a fairly high wingloading, low thrust (poor engines), and very low drag. Comparing their real life turn radii and time values reveals the Yakovlevs have larger turn radius (by about 50m - about as much as the 109G, differences in turn radii were not as pronounced as some may think), but at the same time they beat the Spits in turn time by about 2 secs for a 360 degree turn.

It's classic example of how drag, thrust and wingloading effects turn time and radii. Turn time is IMHO more important, not to mention the other benefits of high wingloading being still there - lower drag, effecting level speed, zoom climb, dive performance etc.

mynameisroland
07-09-2007, 10:38 AM
One area hasnt been mentioned and that is the effect of low wing loading on altitude performance and turn.

ochi
07-09-2007, 10:46 AM
I read that the P51 mustang had the first laminar flow wing design, and that meant no drag from the wings. Perhaps I'm misinformed.

Kurfurst__
07-09-2007, 10:53 AM
Originally posted by mynameisroland:
One area hasnt been mentioned and that is the effect of low wing loading on altitude performance and turn.

It's more of a question of aspect ratio, actually. (P-38, Ta 152 anyone..?) Of course, lower stall speeds help in thin air, if you can't keep up speed due to insufficent engine power. If you have the engine for it, higher stall speed is won't be a problem. (P-47 anyone...?)

JG14_Josf
07-09-2007, 11:13 AM
I like the title of this thread.

When a myth gets started, rolls along for years, and practically becomes a known fact' there may be little that can be done to bust it, generally speaking, but much can be done on the individual level.

When someone says low wing loading increases maneuverability' the myth is fueled.

The fact is that a plane at twice the weight will be as maneuverable as the plane at half the weight so long as the speed flown is greater than both planes stall speed.

The increase in weight merely shifts the maneuverability' to a higher speed.

Therefore; the myth is busted.

It is true to say that a lower wing loading lowers the stall speed and this can be seen as a true measure of slow speed (stall fighting) maneuverability.

Example:

A Fokker Tri Plane has a lower wing loading and is more maneuverable (slow speed stall fighting) than an F-16.

The F-16 has a much higher turn rate and is therefore more maneuverable than the Fokker Tri Plane.

That last sentence may not be true when one only considers sustained level (maintaining altitude) turn performance.

On the other hand suppose the idea is to look deeper into the measure of maneuverability and imagine a maximum performance turn at the highest possible g load and the lowest possible speed (when altitude loss is not a consideration).

The Fokker Tri-Plane may be good for 3 g, perhaps 4g, (who knows) before the wings come off in a high speed (high for the Fokker is what less than 300 km/h?) diving turn.

What then is the turn rate for a 4 g turn at 300 km/h?

The F-16, on the other hand, may be able to handle (the pilot can handle) 9 g at 500 km/h?

Who knows?

If you don't know, then, the myth will remain a myth.

Maneuverability is not limited to how slow a plane can fly while turning and maintaining altitude. If this were the limit of maneuverability, then, there wouldn't be such a thing called Energy Tactics where a plane is flown vertically up and down.

Stall fighting (anchoring the fight perhaps) is a term used to describe Angles Tactics where on plane maneuvers into the rear hemisphere of the opponent and saddles up' there (in the rear hemisphere of the opponent).

If maneuverability is pigeon holed into meaning only slow speed sustained' turn performance, then, wing loading (a big wing and a low weight) becomes a defining measure of maneuverability. If not, then, not.

The F-16 happens to be more maneuverable than the Fokker Tri-plane when the measure isn't limited to slow speed sustained' turn performance.

A historical reference (http://www.amazon.com/Focke-Wulf-190-Part-Monograph/dp/838620835X) may suffice to aid the topic starter in the effort to bust the myth:

http://ec1.images-amazon.com/images/I/51K71F7DHAL._BO2,204,203,200_PIlitb-dp-500-arrow,TopRight,45,-64_OU01_AA240_SH20_.jpg


The Fw 190V5, W.Nr.0005, powered by BMW 801C-0 engine, was first flown in early spring of 1940. After a series of trials against the V1 it was found that the weight increase affected flying characteristics, which would clearly get worse in the future as the design would inevitably acquire more armament and equipment. Thus, the wing also needed redesign, and increasing the wing area would improve the performance. This was achieved by a slight increase in wing span and moving the leading edge forward. A new wing was thus created, with an area of 18.30 sq. m, span of 10.506 m and an unchanged airfoil. The tailplane was also modified, with a span of 3.650 m. Shortly afterwards the tailplane area was also enlarged by moving the leading edge forward. The new wing was to be tested on another prototype, but it was finally fitted to the V5, when in August of 1940 Hans Sander damaged its wing during a force landing after the engine cowling opened in flight. So modified, the prototype was called V5g (g = gosser larger), while in any reference to the previous standard the name of V5k (k = kleiner smaller) was used. As proved by flight testing, the new wing only reduced the top speed by 10 km/h, while greatly improving the flying characteristics, especially climbing speed.

In other words: The climb speed lowered. The stall speed lowered.

The older, faster top speed, and higher wing loaded standard' Fw190 (small wing) required more speed to generate the lift required to lift the weight and more speed to generate the lift required to accelerate the mass. Once at the higher speed the older, faster top speed, and higher wing loaded Fw190 fighter plane produced enough lift to accelerate the mass.

The flying characteristics' moved to a higher speed (with the older and smaller wing) and once at the higher speed the flying characteristics' were unchanged by the change in wing area alone.

Why did Fw190 also change the area of the tail surfaces?

Any increase in size will increase drag. A small missile makes a very good fighter plane because it generates very little drag. With vectored thrust the missile can maneuver better than any fighter plane. What is the wing-loading on a missile? Where does the pilot sit?

How about an aerodynamic study (http://us.share.geocities.com/hlangebro/J22/EAAjanuary1999.pdf)?

Once at speeds where maximum lift force can be generated the maneuverability' of the Fw190 increases due to wing design that is elliptical in function (not just elliptical looking). The wing suffers elastic deformation under high g load and untwists which causes an increase in CLmax and an abrupt stall if the pilot isn't proficient in piloting the Fighter Plane.

High speed maneuverability isn't a function of increasing mass in order to decrease wing loading on purpose. High speed maneuverability is a function of decreasing drag by making the size of the aircraft as small as possible. If the size of the main wing is too small, then, slow speed maneuverability suffers as stall speeds increase.

If the control surface size is too small, then, agility suffers and high speed control suffers.

If, on the other hand, the control surface size is too large, then, drag increases and the possibility of over loading the main wing structure increases at high speed where the pilot can literally tear the wings off the plane by pulling too hard on the stick.

There are reasons for increasing the forces required by the pilot to turn the plane at high speeds.

Example:

http://www.onpoi.net/ah/pics/users/503_1157821750_bobweightsresults.jpg http://www.onpoi.net/ah/pics/users/503_1153401717_mkvdiveaccident.jpg
http://www.onpoi.net/ah/pics/users/503_1153402735_elevatorlimits.jpg
http://www.onpoi.net/ah/pics/users/503_1153401667_bobweightopinion.jpg

Above is extracted from here (http://forums.ubi.com/eve/forums/a/tpc/f/23110283/m/8511049574?r=3651094084#3651094084)

hop2002
07-09-2007, 12:14 PM
Low wingloading on the other hand is not so pronounced as far as turn rate, or in other words, turn times go. Turn times are basically defined by how high G the aircraft can hold up in a sustained manner. That is basically speaking a race between the thrust of the propeller vs. the drag of the aircraft in turn. Here low wingloading doesn't give much of an advantage, as - all things equal - you will have a larger area wing, and thus higher drag to achieve lower wingloading.

The lower the wingloading, the lower the angle of attack you have to pull to carry out the same manoeuvre (other things being equal)

If you look at the lift and drag equations, you can see why that's so important.

Lift (N) = CL * area (sq m) * .5 * pressure (kg/cubic m) * velocity (m/s) squared

Coefficient induced drag (CDi) = (CL^2) / (pi * aspect ratio * Oswald efficiency)

Drag = coefficient * area * density *.5 * velocity squared

If you look at the equations, induced drag increases with the square of CL, and proportionately with the increase in wing area. So double wing area = a quarter the CL = half the induced drag.

To plug some figures in, an example aircraft with weight 3000 kg and wing area of 10 m^2, then the same aircraft with 20 m^2 wings. (this assumes weight doesn't increase with the larger wings, of course)

Assuming lift = 4 times weight, sea level density, speed = 400 km/h

117,600 = CL * 10 * .5 * 1.225 * 111^2
CL = 1.56

CDi = (1.56^)/(pi*6*.8) = 0.16

Induced drag = 0.16 * 10 * 1.225 * .5 * 111^2

Induced drag = 12,074 N

Now the same thing but with double the wing area

117,600 = CL * 20 * .5 * 1.225 * 111^2
CL = 0.78

CDi = (0.78^)/(pi*6*.8) = 0.04 (note how doubling the wing area results in a quarter of the CDi, because CL is squared)

Induced drag = 0.04 * 20 * 1.225 * .5 * 111^2

Induced drag = 6,037 N

Of course, parasitic drag increases with a larger wing area, but basically lower wingloading = an increasing advantage the tighter the turn, and the lower the IAS you fly (and IAS of course is lower at high altitudes)

Kurfurst__
07-09-2007, 12:30 PM
It's half the induced drag in your example, which assumes a plane that weights the same despite fitted with a twice as big wing, and that has only induced drag.

Simply to put, such plane doesn't exist.

With twice the wing area, you won't have half the wingloading, because of the weight will increase, the wing will weight much more. With twice the wing area, you'll have massively increased parasitic drag, which your example simply ignores.

You basically found out that increasing wing area will decrease induced drag.
That's true, but it doesn't tell much.

JG14_Josf
07-09-2007, 12:41 PM
Induced drag = 6,037 N

N is Newtons (http://en.wikipedia.org/wiki/Newton)?



A newton is the amount of force required to accelerate a body with a mass of one kilogram at a rate of one meter per second squared.



The higher mass plane starts out with more Newtons to spare. More force (http://www.onlineconversion.com/force.htm) to move air mass and therefore generate more lift.

This is why aircraft performance science turned from aerodynamic calculation into EM theory.

Why go back into the stone age?

The earth is not flat.

M_Gunz
07-09-2007, 02:00 PM
Originally posted by mynameisroland:
But a greater ability to increase AOA allows a better instantaneous turn rate to the point where speed drops too low?

The wings make lift with speed and aoa and G's turning force possible is by lift / weight. How
much AOA does it take to circle at 3 G's and how much induced drag... larger area wings suffer
while higher AOA suffers more, yes by square of Cl and square of speed, only once by wing area.

For sure each way has advantages and disadvantages.


Power loading for most of the late war fighters is pretty similar, I was just interested in the contrast between the Spitfires wing and the XIVs wing loading and that of the Tempest Vs wing and wing loading. Power loading for the two should be very close too.

P-47D-27 @ so many tons with 2000HP compared to late model 109 for power loading.
P-51D-5 should run somewhere between?

Power was getting more in the same range but some of those planes were Heavy, some Real Heavy
compared to the lighter ones. Those low-alt wonder planes don't have to carry weight of more
supercharger or have modified charger (Spit LF's) and get better powerloading by less weight.
What else is most Yaks?

M_Gunz
07-09-2007, 02:18 PM
Originally posted by Kurfurst__:
Low wingloading on the other hand is not so pronounced as far as turn rate, or in other words, turn times go. Turn times are basically defined by how high G the aircraft can hold up in a sustained manner. That is basically speaking a race between the thrust of the propeller vs. the drag of the aircraft in turn. Here low wingloading doesn't give much of an advantage, as - all things equal - you will have a larger area wing, and thus higher drag to achieve lower wingloading. You will need more thrust to overcome the greater drag, if you're pulling the same Gs, or rate of turn.

If you have less wing area then you need more AOA or speed to regain the lost lift.

Induced drag formula, wing area is straight factor while speed and Cl both get squared.

It's a tradeoff. How fast is sustained corner of a real Spit IXc? Not slow I bet!

I'd rather have the bigger circles at higher speed, I have more vertical capability then.
Doesn't matter what plane I am in either, pulling the smallest circle possible is really weak.

M_Gunz
07-09-2007, 02:21 PM
Originally posted by ochi:
I read that the P51 mustang had the first laminar flow wing design, and that meant no drag from the wings. Perhaps I'm misinformed.

badly
they tried and got less drag is all

mynameisroland
07-09-2007, 02:25 PM
Dont want to nit pick but a P47 at lowish fuel loading with 2,800 Hp probaby isnt a million miles away from a Late war Bf 109, nor is a Tempest V at 2,400 HP or a P51 at around 1900 HP. What I was angling at was that the power/weight ratio generally is pretty close in most of these match ups unless you go for extremes.

Low alt wonder planes on the allied or German side often have very good performance over all altitudes. Even a Merlin 66 Spitfire has good altitude performance while a D9 and even the Tempest to a lesser extent can perform reasonably as well at 20/25,000ft. If you compare either to a P47 with all its TurboSupercharger gear then ofcourse their engines look light weight but thats more a reflection of supercharger vs turbocharger technology.

hop2002
07-09-2007, 02:27 PM
The higher mass plane starts out with more Newtons to spare. More force to move air mass and therefore generate more lift.

And it needs more, too.

To do the equations again, 20 m^2 wings, mass of the first aircraft is 3000 kg, for the decond it's 6,000 kg:

117,600 = CL * 20 * .5 * 1.225 * 111^2
CL = 0.78

CDi = (0.78^)/(pi*6*.8) = 0.04 (note how doubling the wing area results in a quarter of the CDi, because CL is squared)

Induced drag = 0.04 * 20 * 1.225 * .5 * 111^2

Induced drag = 6,037 N

Second aircraft, 6,000 KG:

235200 = CL * 20 * .5 * 1.225 * 111^2
CL = 1.56

CDi = (1.56^)/(pi*6*.8) = 0.16

Induced drag = 0.16 * 20 * 1.225 * .5 * 111^2

Induced drag = 24,149 N

Note that doubling the wieght, if all else remains equal, quadruples the induced drag in a turn.

The energy in each aircraft:

First, the 3000 kg one:

e = .5 * 3000 * 111^2
Energy = 18,481,500 joules

The 6000 kg aircraft:

e = .5 * 3000 * 111^2
Energy = 36,963,000 joules

As you can see, the heavier aircraft has twice the energy, but requires twice the force to turn, and generates 4 times the drag doing so.


You basically found out that increasing wing area will decrease induced drag.
That's true, but it doesn't tell much.

It tells us that lower wingloading tends to equal lower drag in turns.

If we are talking about aircraft whose primary characteristics are known, for example speed, then it tells us that the lower wingloaded aircraft will have an increasing advantage the tighter the aircraft turn.

The original question was of course about the effects of wingloading.


With twice the wing area, you won't have half the wingloading, because of the weight will increase, the wing will weight much more. With twice the wing area, you'll have massively increased parasitic drag, which your example simply ignores.

Well, for a start parasitic drags tends to be dwarfed by induced drag in even moderate turns. For example, the Spitfire IX at 4G 201 mph at sea level:

132,745 = CL * 22.48 * .5 * 1.225 * 90^2
CL = 1.19

CDi = (1.19^2) / (3.14 * 5.61 * .8) = 0.1

Cdi for the Spitfire at 200 mph at 4G at sea level is approx 0.1. CD0 is, according to the RAE, 0.0229

In other words, parasitic drag makes up about 20% of total drag under these conditions. Halving the wing area isn't going to make that much difference to parasitic drag (The RAE says 36.4% of the Spitfire IX profile drag was caused by the wing)

So if you halve the wing, and halve the drag from it, you remove say 18% of the total profile drag of the aircraft, which in a 4g turn at 200 mph at sea level accounts for about 20% of total drag.

Examples:

132,745 = CL * 22.48 * .5 * 1.225 * 90^2
CL = 1.19

CDi = (1.19^2) / (3.14 * 5.61 * .8) = 0.1

Drag = (0.1 + 0.0229) * 22.48 * 1.225 * .5 * 90^2

Drag = 13,707 N

Now the same thing but with a wing of half the area:

132,745 = CL * 11.24 * .5 * 1.225 * 90^2
CL = 2.38

CDi = (2.38^2) / (3.14 * 5.61 * .8) = 0.4

Drag = (0.4 + 0.0188) * 11.24 * 1.225 * .5 * 90^2

Drag = 23,354 N

Halving the wing area results in a lot more drag the tighter you turn.

M_Gunz
07-09-2007, 02:33 PM
If you want to see the effect of power and wingloading then go look at AEROBATICS PLANES.
Find out how many are built extra heavy to improve the maneuvering. Be sure to ask!

Kurfurst__
07-09-2007, 03:38 PM
Originally posted by hop2002:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">You basically found out that increasing wing area will decrease induced drag.
That's true, but it doesn't tell much.

It tells us that lower wingloading tends to equal lower drag in turns. </div></BLOCKQUOTE>

You're merely repeating yourself, fact is still you speak of a physical impossibility, a plane that has only parasitic drag, and a plane that doesn't gets hundreds of kilograms heavier if the wing area is doubled.

If lower wingloading would equal lower drag in turns, the Spit would turn faster than the Yak 9 or Yak 3.
Fact is it doesn't, despite having no less than 400 horsepower more.

Two things :

Weight
Parasitic drag

None of which is factored into your calculations.

Your theory just doesn't work in practical conditions, because it's flawed for the reasons pointed out above.
Real aircraft have parasitic drag and weight effecting their manouveribility, Hop.


If we are talking about aircraft whose primary characteristics are known, for example speed, then it tells us that the lower wingloaded aircraft will have an increasing advantage the tighter the aircraft turn.

You're repeating yourself again.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">With twice the wing area, you won't have half the wingloading, because of the weight will increase, the wing will weight much more. With twice the wing area, you'll have massively increased parasitic drag, which your example simply ignores.

Well, for a start parasitic drags tends to be dwarfed by induced drag in even moderate turns. For example, the Spitfire IX at 4G 201 mph at sea level: </div></BLOCKQUOTE>

... and since when a 4 G turn is a 'moderate' turn? It's actually about double the Spitfire (or any other WW2 piston engined fighter) may hope to pull in a sustained fashion.

You're simply trying to set conditions in which favours the lower wingloading plane, turns at lower speed.

Yup, that's why low wingloading comes with smaller turning radii.

Of course the solution is fairly simple, higher wingloading aircraft (say higher wingloading aircraft than the Spitfire) will not turn at their best rate at 200 mph but at say 250 mph.


Cdi for the Spitfire at 200 mph at 4G at sea level is approx 0.1. CD0 is, according to the RAE, 0.0229


.. at which point the Spitfire turning at 4 G will rapidly loose airspeed because it just can't even out and eventually getting outturned by even a poorer turning opponent pulling a sustain 2.5 Gs....

Again you only managed to tell drag increases rapidly with AoA. That's nothing new.


[QUOTE]In other words, parasitic drag makes up about 20% of total drag under these conditions. Halving the wing area isn't going to make that much difference to parasitic drag (The RAE says 36.4% of the Spitfire IX profile drag was caused by the wing)

So if you halve the wing, and halve the drag from it, you remove say 18% of the total profile drag of the aircraft, which in a 4g turn at 200 mph at sea level accounts for about 20% of total drag.

.... again assuming an aircraft in your calculations which has been ballasted by an equivalent amount of dead weight to compensate for weight decrease after half the wing was removed... since in your examples the aircraft has to pull twice the Cl, ie. it's at the same speed and weight. http://forums.ubi.com/groupee_common/emoticons/icon_eek.gif

Of course, that's dumb physics and dumb flying. A real aircraft after halving the wing area will be lighter, and if the pilot is any good he will simply turn at a higher airspeed - this way he doesn't actually need to increase his AoA so much since he has more air flowing under the wings, and he can avoid greatly increasing induced drag at a higher angle of attack, at a slightly increased parasitic drag (but his parasitic drag at half the wing area is already MUCH less to start with). The result can be that his overall drag will be lower, at a higher airspeed.

That's how the Yak 9 makes a 360 degree turn in about 16 seconds at 410 km/h, outturning the Spitfire doing a 360 degree turn in 18 seconds, but turning around 300 km/h. (The Yak 9 has higher wingloading, and much less power)

In real life, that is.

JG14_Josf
07-09-2007, 04:18 PM
As you can see, the heavier aircraft has twice the energy, but requires twice the force to turn, and generates 4 times the drag doing so.

Hop,

I can't see the heavier aircraft generating 4 times the drag. Perhaps you can explain how that works in a way that makes it easy to see.

If the same aircraft at half the weight is turning at the same speed and at the same g, then, your calculation proves that the heavier aircraft is generating 4 times the total drag force measurable as energy (joules)?

That suggests that the heavier aircraft will be in a much steeper dive angle at the same speed and at the same g force in a diving spiral with the engine off because the energy loss rate is 4 times as fast for the heavier aircraft when all else except mass is equal.

In other words: if two exactly the same aircraft are diving in a 6 g spiral with the engines off and both aircraft are exactly the same (everything including mass is exactly the same on paper) and both aircraft are diving a spiral exactly at the same angle and exactly the same speed, say 400 km/h and one plane dumps half the internal mass (as fuel being dumped for example), then, the lighter plane must drastically decrease the dive angle in order to maintain the same speed (400 km/h) and the same g force (6 g) because dumping the weight lowers the energy loss rate by a factor of 4 for the lighter aircraft and the weight doubled for the heavy aircraft quadruples the energy loss rate therefore requiring a much steeper dive angle to make up the difference in energy loss rate.

Is that what your calculation shows for everyone to see clearly?

ElAurens
07-09-2007, 04:56 PM
An interesting operational consideration:

During the air campaign over New Guinea, The Imperial Japanese Army Flying Corps had far fewer non-combat operational losses than did the Allies fighting them. In other words, the Japanese experienced far fewer crashes not related to combat. Why? Their lower wing loaded aircraft were easier to operate off of the crude airfields that characterized operations in that theater.

Most basic trainers are lightly wing loaded for this reason. More benign handling at low speeds.

hop2002
07-09-2007, 05:08 PM
You're merely repeating yourself, fact is still you speak of a physical impossibility, a plane that has only parasitic drag,

Huh?


and a plane that doesn't gets hundreds of kilograms heavier if the wing area is doubled.


The point is to try to simplify the situation so the principle becomes clear, because you obviously didn't understand the principle.

Of course weight will increase if the wing area increases, but the principle is still valid, because wingloading will still go down. Doubling the wing area would not of course double the weight, because the armament, pilot, engine, fuel, fuselage, radios etc would all still weigh the same.


Two things :

Weight
Parasitic drag

None of which is factored into your calculations.


Huh? Did you actually look at them? Weight is of course included in all of them, parasitic drag in the second lot where I pointed out that parasitic drag is a small proportion of overall drag in tighter turns.


Your theory just doesn't work in practical conditions, because it's flawed for the reasons pointed out above.

"My theory"? You think I invented the lift and drag equations? You give me far too much credit.


Real aircraft have parasitic drag and weight effecting their manouveribility, Hop.


Which is why the equations have weight included, and why I illustrated one with parasitic drag as well.


You're repeating yourself again.

I tend to be a traditional English speaker. If someone can't understand what I'm saying, I repeat it more slowly. I might have to start using lots of capital letters soon http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif


and since when a 4 G turn is a 'moderate' turn? It's actually about double the Spitfire (or any other WW2 piston engined fighter) may hope to pull in a sustained fashion.

No, a standard Spitfire IX should be capable of about 3 G sustained at sea level. The 25 lb version should be able to approach 4G sustained at sea level. Even the Spitfire I could sustain 3G at 12,000 ft.

If you look at the equation for prop thrust, it's thrust (lbs) = hp * 375 * efficiency / speed. That works out to about 3000 lbs thrust for the Spitfire at 25 lbs boost at sea level at 200 mph at 80% efficiency. That's pretty close, considering the margin of error we're dealing with.


You're simply trying to set conditions in which favours the lower wingloading plane, turns at lower speed.


Of course I am. I gave an example of what happens in a turn. I could have chosen to give figures for a 1.1 G turn at 400 mph, but then that would hardly illustrate the principle, would it?

You made the erroneous claim that wingloading had little effect on manoeuvrability, Josf then made an even more far out claim, I posted some figures to show where you were going wrong.


You're simply trying to set conditions in which favours the lower wingloading plane, turns at lower speed.

Yup, that's why low wingloading comes with smaller turning radii.

Again you seem to be missing the point. Lower wingloading helps tuns because it results in less induced drag. The effect becomes more pronounced the tighter you turn, and the lower the indicated air speed.


Of course the solution is fairly simple, higher wingloading aircraft (say higher wingloading aircraft than the Spitfire) will not turn at their best rate at 200 mph but at say 250 mph.

You still don't seem to understand.

Lower wingloading means less induced drag. The more you turn, and the slower you fly, the greater the proportion of induced drag to total drag.


at which point the Spitfire turning at 4 G will rapidly loose airspeed because it just can't even out and eventually getting outturned by even a poorer turning opponent pulling a sustain 2.5 Gs

Or the Spitfire can drop down to 2.5G, and use some of the excess energy to climb.

There are certainly parts of the envelope where both the high and low wingloaded planes can pull the same manoeuvres.


again assuming an aircraft in your calculations which has been ballasted by an equivalent amount of dead weight to compensate for weight decrease after half the wing was removed... since in your examples the aircraft has to pull twice the Cl, ie. it's at the same speed and weight.

Yes. That's the point. I illustrated the point with examples. It's much easier to illustrate the principle if you keep all the other variables the same.

The original question is what is the point of low wingloading, bearing in mind that lower wingloading tends to mean higher parasitic drag. I gave an example to show the point.


Of course, that's dumb physics and dumb flying. A real aircraft after halving the wing area will be lighter, and if the pilot is any good he will simply turn at a higher airspeed

Which will of course mean the other aircraft is turning inside him.


Hop,

I can't see the heavier aircraft generating 4 times the drag. Perhaps you can explain how that works in a way that makes it easy to see.

Despite Kurfurt's habit of attributing information he doesn't like to me, so he can dismiss it, I didn't invent the lift and drag equations. You can find them in various books, and on websites. Here's the lift one courtesy of Nasa:


The lift equation states that lift L is equal to the lift coefficient Cl times the density r times half of the velocity V squared times the wing area A.

L = Cl * A * .5 * r * V^2

http://www.grc.nasa.gov/WWW/K-12/airplane/lifteq.html


Here's the coefficient of induced drag:


The induced drag coefficient Cdi is equal to the square of the lift coefficient Cl divided by the quantity: pi(3.14159) times the aspect ratio AR times an efficiency factor e.

Cdi = (Cl^2) / (pi * AR * e)
http://www.grc.nasa.gov/WWW/K-12/airplane/induced.html

And the drag equation:

The drag equation states that drag D is equal to the drag coefficient Cd times the density r times half of the velocity V squared times the reference area A.

D = Cd * A * .5 * r * V^2
http://www.grc.nasa.gov/WWW/K-12/airplane/drageq.html

Go ahead and plug in some figures. Just to repeat the ones I did earlier:


To do the equations again, 20 m^2 wings, mass of the first aircraft is 3000 kg, for the decond it's 6,000 kg:

117,600 = CL * 20 * .5 * 1.225 * 111^2
CL = 0.78

CDi = (0.78^)/(pi*6*.8) = 0.04 (note how doubling the wing area results in a quarter of the CDi, because CL is squared)

Induced drag = 0.04 * 20 * 1.225 * .5 * 111^2

Induced drag = 6,037 N

Second aircraft, 6,000 KG:

235200 = CL * 20 * .5 * 1.225 * 111^2
CL = 1.56

CDi = (1.56^)/(pi*6*.8) = 0.16

Induced drag = 0.16 * 20 * 1.225 * .5 * 111^2

Induced drag = 24,149 N

The only figures I don't think I've explained are density, which is 1.225 in SI units for standard atmosphere at sea level (although it doesn't matter what you use, as long as it's consistent for both aircraft) and the lift required, which I've given in Newtons (weight in KG x 9.8)

Kettenhunde
07-09-2007, 06:52 PM
We can sum things up in a few basic principles.

1. Weight is bad. It shrinks our aircrafts entire flight envelope as long as the vector of lift is above the horizon. Absolutely nothing good can be said about weight from a performance perspective. Unfortunately in an aircraft it is usually a necessity if we build these aircraft to do things, not just fly circles.

2. Airfoil selection and wing design determines a large portion of the flight characteristics of our aircraft. Remember in some portions of the flight envelope, our performance is aerodynamically limited.

3. Power is very good. It forms the fundamental relationship which determines all aircraft performance, Power available to Power required. For much of the envelope our aircraft's performance becomes power limited.

4. Aircraft are not one characteristic, they are a system. Examining one characteristic will not lead to a correct conclusion about the value or performance of a design. The fundamentals of this system are found in our L/D relationship.

Good design can go a long way towards mitigating or eliminating what might at first appear to be a "poor" design choice to a layman.

Some comments on the Laminar flow wings. Laminar flow exhibits some special characteristics. Laminar flow wings gain their distinct performance characteristics in what is termed "the drag bucket". If you look at a true laminar flow polar, you will see a distinct "bucket" that exits in a specific coefficient of lift range. In this bucket our coefficient of drag decreases while our coefficient of lift remains the same. Remember that L/D relationship as this is both unique and very good for our laminar flow aircraft. Outside of this range the polar is similar other airfoils. This bucket does not exist at high AoA such as slow flight or maneuvering flight.

Most experts agree that although laminar flow was considered desirable, it is highly unlikely an WWII design achieved it outside of a laboratory or specially prepared aircraft. The airfoils are very sensitive to surface finish and quality of build. The mass manufacturing techniques of the day combined with in-service conditions just did not lend themselves well to a laminar flow design.

All the best,

Crumpp

JG14_Josf
07-09-2007, 09:17 PM
Josf then made an even more far out claim, I posted some figures to show where you were going wrong.

Hop,

Why start with the false propaganda insults?

If you make a false and stupid accusation you can, at least, back it up with a quote no?

Your claim about 4 times the energy loss rate remains unclear.

Can you express that in terms of dive angle as two exactly the same aircraft diving in a 6 g turn at 400 km/h without engine power where one plane is half the mass (all else being equal).

If you can do that, then, your claim will be clearly a matter of dive angle.

Example:

Plane A and B are the same exact plane with the only difference being Plane A is half the weight of Plane B.
Both planes are flying in a diving spiral at 400 km/h and 6 g with no engine power.

----------------------Dive Angle
Plane A --------------Blank
Plane B ---4 times the rate of energy loss expressed as a steeper dive angle

So...do you simply continue making your baseless false claims without reference and continue to post vague and misleading applications of math calculations that are as clear as you pretend them to be?

Having two dive angle numbers for one plane with half and double internal mass can show how much energy loss is caused by the increase in energy required (drag production) to accelerate the heavier mass at 6 g.

If, as you claim, the energy loss rate is 4 times more for double the weight (all else being equal = all else being exactly equal), then, the dive angle difference should illuminate this fact clearly.

Example:

----------------------Dive Angle
Plane A --------------20 degrees
Plane B --------------60 degrees

Plane B, therefore, would have a usable combat advantage in dive acceleration where the lighter plane cannot maintain as steep a dive angle at 400 km/h and 6 g.

Speeding up; the light plane will suffer a larger turn radius at the higher speed (g limit to pilot endurance) in the effort to increase dive angle. Slowing down; the light plane will decrease dive angle. Pulling more g will black out the pilot. The heavy aircraft motors on down in the defensive (higher acceleration) spiral dive.

Please do two things or please stop misrepresenting me in public.

A. Quote my words that you claim to be in error.
B. Fill in the blanks rather than ignore the question asked.

You can, of course, continue to misrepresent what I write and continue to make your vague and misleading statements that you claim to be clear.

JG14_Josf
07-09-2007, 09:23 PM
1. Weight is bad. It shrinks our aircrafts entire flight envelope as long as the vector of lift is above the horizon. Absolutely nothing good can be said about weight from a performance perspective. Unfortunately in an aircraft it is usually a necessity if we build these aircraft to do things, not just fly circles.

Falsehood,

Increased mass increases the force required to slow down that mass (air resistance) therefore increasing unloaded acceleration against air resistance in a dive and decreasing unloaded decleration in a climb.

Why continue to publish false statement that are proven wrong?

Is it stupidity, ignorance, or both?

Kettenhunde
07-10-2007, 03:41 AM
http://img183.imagevenue.com/loc453/th_60354_aircraft_wieght_122_453lo.jpg (http://img183.imagevenue.com/img.php?image=60354_aircraft_wieght_122_453lo.jpg)

Kurfurst__
07-10-2007, 03:57 AM
Originally posted by hop2002:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">You're merely repeating yourself, fact is still you speak of a physical impossibility, a plane that has only parasitic drag,

Huh? </div></BLOCKQUOTE>

My reaction exactly, when I saw your first post which simply ommitted parasitic drag from the formula..


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">and a plane that doesn't gets hundreds of kilograms heavier if the wing area is doubled.


The point is to try to simplify the situation so the principle becomes clear, because you obviously didn't understand the principle.

Of course weight will increase if the wing area increases, but the principle is still valid, because wingloading will still go down. Doubling the wing area would not of course double the weight, because the armament, pilot, engine, fuel, fuselage, radios etc would all still weigh the same. </div></BLOCKQUOTE>

Of course it won't double weight. It will increase the weight still, and it will have a much more pronounced effect since the connection between the increase of weight and the increase of parasitic drag is far linear.

And it's no small weight. Let's take the Spitfire I. The two wings, without installations and weapons such as radiators, weighted 400 kg. Simplifying things a bit, halving wing area will remove about 200 kg, doubling wing area would add 400 kg - that's a considerable weight.

That 200/400 kg decreas/increase in weight is simply missing from your calculations.



<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Two things :

Weight
Parasitic drag

None of which is factored into your calculations.


Huh? Did you actually look at them? Weight is of course included in all of them, parasitic drag in the second lot where I pointed out that parasitic drag is a small proportion of overall drag in tighter turns. </div></BLOCKQUOTE>

I am sorry you still don't understand.

Your calculations do not contain the realistic increase of weight from a major increase of no less than doubling the wing area.

The funny thing about it, you argue Josf that weight is a very bad thing about turn at the same time, yet you don't include weight increase from doubling the wing area in the calculations you show to me.


Your theory just doesn't work in practical conditions, because it's flawed for the reasons pointed out above.

"My theory"? You think I invented the lift and drag equations? You give me far too much credit.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Real aircraft have parasitic drag and weight effecting their manouveribility, Hop.


Which is why the equations have weight included, and why I illustrated one with parasitic drag as well. </div></BLOCKQUOTE>

They don't have the increased weight included.

If you want to investigate the effects of lowering wingloading by increasing the size of the wing, you need to add the increased of weight and drag from the larger wing into your calculations, otherwise they're just nonsense about zero-weight and zero-drag extra wing area.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">You're repeating yourself again.

I tend to be a traditional English speaker. If someone can't understand what I'm saying, I repeat it more slowly. I might have to start using lots of capital letters soon http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif </div></BLOCKQUOTE>

I have someting better in mind. Just answer how it is possible for the higher wingloading Yaks to outturn Spits and having far less drag in turn. You're ignoring that part in all your posts.

Thanks in advance.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">and since when a 4 G turn is a 'moderate' turn? It's actually about double the Spitfire (or any other WW2 piston engined fighter) may hope to pull in a sustained fashion.

No, a standard Spitfire IX should be capable of about 3 G sustained at sea level. The 25 lb version should be able to approach 4G sustained at sea level. Even the Spitfire I could sustain 3G at 12,000 ft. </div></BLOCKQUOTE>

Well, let's see the numbers for parasitic and induced drag at 250 mph, 3 Gs then... then see the same for 300mph. See if it's still 4 times the induced drag as at 200mph/4G.


If you look at the equation for prop thrust, it's thrust (lbs) = hp * 375 * efficiency / speed. That works out to about 3000 lbs thrust for the Spitfire at 25 lbs boost at sea level at 200 mph at 80% efficiency. That's pretty close, considering the margin of error we're dealing with.

Actually, you're proving my point with that. The Spit at +25lbs, via using more excess power, can turn faster and tighter than the Spit with +18 lbs boost.

Wasn't that my original post was all about, that low wingloading does not equal turning, and that power is a major factor which which greatly reduced sustained turn times can be achieved...?

Good thing is, I don't have to figure it out all myself, since some engineer at Mtt did that work for me 60 years ago in a report from 1940, showing the effects of increased power on turning radii and time. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

It's very ambitious of you to prove those guys wrong.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">You're simply trying to set conditions in which favours the lower wingloading plane, turns at lower speed.


Of course I am. I gave an example of what happens in a turn. I could have chosen to give figures for a 1.1 G turn at 400 mph, but then that would hardly illustrate the principle, would it? </div></BLOCKQUOTE>

Actually, it would nicely illustrate the point about low wingloading planes finding it increasingly difficult to turn with higher wingloading planes at speed, all things being equal. A Spitfire IX, for example may find it difficult to turn at all at 400mph. A Mustang won't - and it's all down to parasitic drag.


You made the erroneous claim that wingloading had little effect on manoeuvrability,

I am sorry if you did not understand, so I repeat it for you what I actually said :

'Simply to put, low wingloading planes don't neccesarily beat high wingloading planes in turn times.'

When we check against RL figures, it holds true, the Yak 9 has higher wingloading than the Spit IXLF, and yet the Yak has lower turning time.



<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">You're simply trying to set conditions in which favours the lower wingloading plane, turns at lower speed.

Yup, that's why low wingloading comes with smaller turning radii.

Again you seem to be missing the point. Lower wingloading helps tuns because it results in less induced drag. The effect becomes more pronounced the tighter you turn, and the lower the indicated air speed. </div></BLOCKQUOTE>

That's only one side of the coin, the positive side. The negative side is of course lower top speed, and the fact that at higher speed higher parasitic drag turns against you in turns.

After all, that's why everybody went with high wingloading monoplanes, even the RAF.


Of course the solution is fairly simple, higher wingloading aircraft (say higher wingloading aircraft than the Spitfire) will not turn at their best rate at 200 mph but at say 250 mph.

You still don't seem to understand.[/QUOTE]

Oh yes, I perfectly understand what you're doing. You're coming up with a physical nonsense, an example where increasing wing area to double have none of it's disadvantages : increased drag and increased weight (which means increased lift needed).

Queen Elisabeth II's powerplant in a Mini Morris, that's what your example is, basically.


Lower wingloading means less induced drag. The more you turn, and the slower you fly, the greater the proportion of induced drag to total drag.

... and in reverse, the faster you fly, the less the proportion of induced drag to total drag, meaning the higher the airspeed, the better for the high wingloading plane vs. low wingloading plane.

Point is, the high wingloading plane can match or even best the low wingloading plane in turn, only that it happens at a higher airspeed.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">[QUOTE]at which point the Spitfire turning at 4 G will rapidly loose airspeed because it just can't even out and eventually getting outturned by even a poorer turning opponent pulling a sustain 2.5 Gs

Or the Spitfire can drop down to 2.5G, and use some of the excess energy to climb. </div></BLOCKQUOTE>

Again, it depends on the airspeed. At 200 mph it might do that, at 400 mph it just doesn't have any excess power above 1G, but the other plane can still turn.


There are certainly parts of the envelope where both the high and low wingloaded planes can pull the same manoeuvres.

OH PRAISED BE THE LORD JESUS YOU'VE FINALLY REALIZED THAT WAS BEING THE POINT ALL THE TIME...!


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">again assuming an aircraft in your calculations which has been ballasted by an equivalent amount of dead weight to compensate for weight decrease after half the wing was removed... since in your examples the aircraft has to pull twice the Cl, ie. it's at the same speed and weight.

Yes. That's the point. I illustrated the point with examples. It's much easier to illustrate the principle if you keep all the other variables the same. </div></BLOCKQUOTE>

Your example is like if someone would argue that power to weight ratio is important in a car's acceleration, and this can be achived with a bigger engine the best. So, the example goes, if we put the Queen Elisabeth II's entire powerplant into a Mini Moris, it will accelerate much faster.

All the other variables the same, of course. The Mini still about 1.40 m wide and tall, and still weights about 700 kg, with the QEII's engine compartment in it.

Of course, it's nonsense. If you change one design variable, ie. size of the wing, other variables will change as well, ie. weight and size (=drag) of the aircaft.


The original question is what is the point of low wingloading, bearing in mind that lower wingloading tends to mean higher parasitic drag. I gave an example to show the point.

Yup, you've shown that lower wingloading tends to result in better turn at low airspeeds. Question is, what's the point going with low wingloading if you can achieve the same turn, at higher airspeeds with high wingloading...?


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Of course, that's dumb physics and dumb flying. A real aircraft after halving the wing area will be lighter, and if the pilot is any good he will simply turn at a higher airspeed

Which will of course mean the other aircraft is turning inside him. </div></BLOCKQUOTE>

Nope, it will simply mean the other aircraft will have a smaller turning radius while the aircraft turning at higher speed will gradually outturn him with a higher turn rate.

Take a real life example with . Spitfire IXLF with 1700 HP vs. the Yakovlev 9 with 1250 HP. The Yak has considerably higher wingloading than the Spit.

The Spit will do the turn with a radii of 235 m and will finish it in 18 seconds.
The Yak9 will do the turn with a radii of 280 m and will finish it in 16 seconds.

That's an example I put in front of you in, and you somehow never notice it.

Basically you're only telling half the story, speaking only of high-G turns at low speeds.
There's more than that in the realm of turning.

mynameisroland
07-10-2007, 04:10 AM
Kufurst I have a couple of questions.

If the Yak 9 could complete a 360 turn in 16 seconds why is it not modelled with this performance in IL2?

If a higher wingloading can lead to better turn performance at higher speed then why does the Bf 109 have to slow down enough for its slats to come in to play for its turn to be competitive ? Surely the same laws of physics should apply to the Bf 109 as the Yak ? or is the Yak's airframe and wing just cleaner and more efficient?

The Spitfire could be out turned at high speed by the P51, the Tempest, the Fw 190 - seemingly the Yak 9 ect why does the Bf 109 not appear on this list as it has smaller wing and higher wing loading too ?

Bremspropeller
07-10-2007, 05:22 AM
If a higher wingloading can lead to better turn performance at higher speed then why does the Bf 109 have to slow down enough for its slats to come in to play for its turn to be competitive ?


Higher loads (mass) gives you a higher inertia working against drag and energy bleed-off.

The 109 had both, high stick loads and mechanical operated slats. The slats were some kind of "blowback" design. Thus, they came in "automaticly" as soon as the force/ pressure on it's leading edge would exceed a certain value and vice-versa.

Kettenhunde, it's not only about finish-quality.
A single fly or mosquito splashed onto the leading edge of those early laminar-flow profiles will set-off it's benefits. Disturbtions (turbulent flow) extend in a 45? angle behind the "obstacle".

That is not just a theoretical effect.
Take a high-performance glider of today. Most of them have laminar-flow profiles (and a very good surface-quality). LE-contamination with flies or other insecs harms their gliding-ratio at about two or even three points. Even flying through rain will seriously harm you performance.

mynameisroland
07-10-2007, 05:37 AM
While no airforce fielded an airplane with true laminar flow wing design in WW2. It is undeniable that designs which attempted it had less drag effect than more conventional aerofoils.

Ps Thanks for the contributions Bremspoller, and others

Kurfurst__
07-10-2007, 05:38 AM
Originally posted by mynameisroland:
Kufurst I have a couple of questions.

If the Yak 9 could complete a 360 turn in 16 seconds why is it not modelled with this performance in IL2?

Because Oleg models Soviet planes only to lower specs due to manufacturing quality etc., after much b*ing from the community.. Khazanov, the NII VVS trials show the aircraft having a 16 sec turn time, yet Oleg is giving us a 'frontline' Yak with imperfect finish and higher drag. None of the Western planes suffer from this effect of real life, they all work to 'factory specs'.


If a higher wingloading can lead to better turn performance at higher speed then why does the Bf 109 have to slow down enough for its slats to come in to play for its turn to be competitive ?

You mean in the sim ? In the sim it works such because we have pilots who have one of their arms amputated and they simply can't pull higher Gs at high speeds on some high stick force planes.

Besides, we've been talking about similiar airframes so far, which only differ in wing area.
The 109 and the Spit differ in a lot more than just wing area (engine, aiframe drag, high-lift devices etc.).

Slats only help the 109 to get to insane Cl level without stalling, and a cost of greatly increased drag. The 109 turns well with slats because it's small airframe with a big engine can actually overcome this greatly increased drag.


Surely the same laws of physics should apply to the Bf 109 as the Yak ? or is the Yak's airframe and wing just cleaner and more efficient?

The Yak is probably just cleaner and more efficient, at least from the drag point of view. It's turn time is better than the 109's, too, altough the turn radius is about the same. Just look at engine powers and the speeds achived. It's an amazing airframe. Have you ever seen a Yak up close? I've seen a Yak 3... nothing comes close to it's surface finish actually, it's so smooth. It's easy to do, it has no rivets at all in the wings for example, being made of composite wood!


The Spitfire could be out turned at high speed by the P51, the Tempest, the Fw 190 - seemingly the Yak 9 ect why does the Bf 109 not appear on this list as it has smaller wing and higher wing loading too ?

Look at the planes you mentioned. All have light elevator forces, which can bring you to maximum acceleration with the one-hand stick force limit we have in the sim.

Actually, the 109K for example quite easily outturns the Spit IX even in the sim above 450 km/h in sustained turns, the only reason it's difficult to do only is because we can't apply the Gs on the stick due to the artificial limitation on the stickforce in the sim (one hander only). Yak 3, too. Check Il-2 compare.

Engine power plays a huge role, too. It's quite simple. The Spitfire has much more parasitic drag from those big wings. And at high speed, parasitic drag dominates.

All the 3 planes you've mentioned have high wingloading BTW..

M_Gunz
07-10-2007, 05:55 AM
Anyone not a pilot but who knows one can ask ahow much better their plane turns loaded full
including cargo to the safe limit, as opposed to near empty, just pilot and fuel for 30 mins.

Turning is accomplished by tilting the lift vector to the side. That makes a sideways force
to the flight path. Forget about just how and how much, assuming reasonableness in both.
The sideways force pulls the mass of the plane out of straight flight and through the turn.

Point being that same force inwards will accelerate (turn is acceleration, ALL change in
movement/momentum including direction is acceleration) less mass faster than more mass.
It's easy to wing a gravel stone faster than a half-brick.

The lighter weight under the same force moves faster, also decelerates faster but in a turn
it is just less weight to have to change the movement of. Heavy weight only helps in drag
where the thrust is unable to keep up speed. If the turn is started at sustained turn speed
then the plane will not slow down and extra forward momentum of mass does not contribute at
all ***and STILL has to be forced along the curve with full weight penalty***.

Ask veteran bomber pilots if the bomber turns better when loaded as opposed to no bombs and
less than half fuel (like on the way home from a drop) and you will get some horrid looks.

mynameisroland
07-10-2007, 06:33 AM
Because Oleg models Soviet planes only to lower specs due to manufacturing quality etc., after much b*ing from the community.. Khazanov, the NII VVS trials show the aircraft having a 16 sec turn time, yet Oleg is giving us a 'frontline' Yak with imperfect finish and higher drag. None of the Western planes suffer from this effect of real life, they all work to 'factory specs'.

But not in all cases Kufurst. If you look at the La5FN or La7 these perform the same or better than test production examples. While the Yak9U ,Yak3Vk-107 and I-185 dont suffer from being artificially hamstrung by Oleg. I disagree with you here Kufurst.


You mean in the sim ? In the sim it works such because we have pilots who have one of their arms amputated and they simply can't pull higher Gs at high speeds on some high stick force planes.

Besides, we've been talking about similiar airframes so far, which only differ in wing area.
The 109 and the Spit differ in a lot more than just wing area (engine, aiframe drag, high-lift devices etc.).

Slats only help the 109 to get to insane Cl level without stalling, and a cost of greatly increased drag. The 109 turns well with slats because it's small airframe with a big engine can actually overcome this greatly increased drag.

To my original point, I said that the Bf 109 is a more heavily loaded fighter - like the Yak 9 compared to the Spitfire. The conditions which make the Yak turn faster should also apply to the Bf 109? That the Bf 109 turns well at low speeds is due to its slats and power to weight ratio, but is was not reputed to out turn the Spitfire at high speeds one hand on the controls or two. Is this soley a control force issue?


The Yak is probably just cleaner and more efficient, at least from the drag point of view. It's turn time is better than the 109's, too, altough the turn radius is about the same. Just look at engine powers and the speeds achived. It's an amazing airframe. Have you ever seen a Yak up close? I've seen a Yak 3... nothing comes close to it's surface finish actually, it's so smooth. It's easy to do, it has no rivets at all in the wings for example, being made of composite wood!


The Yak is a very good design. Its weight reduced as its design progressed because of the desire to make the most out of limited engine power. As such the designers concentrated carefully on certain factors. Small wings were a cause of the necessity to have light weight for example, as was the limited armament. For a direct contrast I like to compare it to the Bf 109 F4. Similar engine power and similar weight.

As for it being a clean aircraft, undoubtedly so. Having seen Yaks and La's upclose I cant say whether they strike me as being cleaner in finish than a P51 or a Tempest but that is only my observation.


Look at the planes you mentioned. All have light elevator forces, which can bring you to maximum acceleration with the one-hand stick force limit we have in the sim.

Actually, the 109K for example quite easily outturns the Spit IX even in the sim above 450 km/h in sustained turns, the only reason it's difficult to do only is because we can't apply the Gs on the stick due to the artificial limitation on the stickforce in the sim (one hander only). Yak 3, too. Check Il-2 compare.

Engine power plays a huge role, too. It's quite simple. The Spitfire has much more parasitic drag from those big wings. And at high speed, parasitic drag dominates.

All the 3 planes you've mentioned have high wingloading BTW..

I know they all have higher wing loadings that is why I chose them as examples.

While the K4 out turns the IX in the sim at high speeds if you compare a G6 to an IX the SPitfire turns better at high speeds. When you compare an IX 25lb to a K4 the IX again comes out on top.

Im not sure how big a problem the Spitfires wing and radiators were for turning given that its engine power increased relative to that of its opponents during WW2.

M_Gunz
07-10-2007, 07:40 AM
High wing loading is good for speed and dive. Comparing planes on basis of wingloading alone
only leads to wrong ideas about wingloading and then threads based on those but called 'facts'.

Easy to show that the same plane with added weight will turn wider at given turning force
than without added weight.

Using the acceleration portion of the Rectilinear Motion Equations as posted by Crumpp with
some changes from the zoom example. We have our 9000lb plane and turning force of 3000lb
by component of lift tilted into the turn and then we add 1000lb and do the same.

Sum the forces, Plane at 9000lbs
3000lbs sideways is our force. It is sideways to the flight so the rest don't matter.
a = F/m
m = 9000lbs/32.2 = 279.5 lb-s^2/ft
a= 3000lb/279.5lb-s^2/ft
a = 10.733 ft/s^2

Plane at 10000lbs, same sideways force
m = 10000lbs/32.2 = 310.559
a = 3000lb/310.559lb-s^2/ft
a = 9.66 ft/s^2

The same plane with more weight is accelerated slower into the turn, radius is wider.
In order for the plane with added weight to make the same turning force while flying level
it must either fly faster or with more AOA or both which requires more drag to create the
same turning force.

How many maneuvers use turning or lateral movement? Less wingloading benefits all of those.
Same plane, lighter is better. Try playing DF with 100% full tanks only and say how much
faster you can turn... oh but that would only 'prove' IL2 is wrong, LOL! Just like all science!

JG14_Josf
07-10-2007, 09:58 AM
The weight change on an airplane has even more far-reaching effects on performance than a change in parasite drag. All performance items suffer by an increase in weight.

Crumpp,

Does your quote above prove something or are you merely parroting something you read in a book?

You and any of the misinformed have been challenged to prove how weight change affects a specific performance variable in a very basic manner without any complication whatsoever and you ignore the challenge why?

Why continue to parrot the same old unspecified general statements of nothingness?

Your example is prime:


The weight change on an airplane has even more far-reaching effects on performance than a change in parasite drag. All performance items suffer by an increase in weight.

The first sentence is meaningless without scale.

Example:

Two exactly the same planes side by side where one doubles internal mass.
The other doubles parasite drag.

What are the scales and the proportions of doubling parasite drag? Does the plane grow a barn door bolted to the tail section? Does the fuselage grow to twice its size? Do the designers simply scale up the plane size including wing area?


The weight change on an airplane has even more far-reaching effects on performance than a change in parasite drag. All performance items suffer by an increase in weight.

The second sentence is simply false. The rate of deceleration caused by contact with air resistance is a performance item' and increase in internal mass decreases the rate of deceleration caused by contact with air resistance. That is a proven fact. In unloaded vertical dives and zooms the rate of deceleration caused by contact with air resistance is lowered with increases in mass and that rate of deceleration caused by contact with air resistance is increased with increases in parasite drag; therefore the first sentence is proven to be false on two counts.

The twice internal mass plane with half the parasite drag will decelerate at a much slower rate in unloaded dives and zooms compared to the half internal mass with twice the parasite drag plane.


The weight change on an airplane has even more far-reaching effects on performance than a change in parasite drag. All performance items suffer by an increase in weight.

Your quote is misinformation.

You have been misinformed.

You are parroting falsehood.

Why don't you answer the simple question?

Which aircraft has the steeper dive angle in a power off spiral dive at 400 km/h and 6 g the same exact plane at twice the weight or the same exact plane at half the weight?

If Hop's claim, where the heavy plane produces 4 times the energy in drag force, is true, then, this question should be very easy.

If the accurate answer is that the heavier plane must dive at a steeper angle to maintain 400 km/h and 6 g, then, that is a performance advantage as a means to escape especially when the factor of difference is 4 times the energy loss rate.

Even if Hop's claim is more falsehood the challenge remains.

Which plane must dive at a higher angle to maintain 6 g and 400 km/h where both planes are exactly the same (all else is exactly equal) except internal mass (no engine power because that introduces an unequal proportion)?

Plane A and Plane B are the same exact plane except Plane B is twice the internal mass of Plane A.

How about using an Fw190A-8 as Plane B?

Power is off; there is no engine thrust to complicate the calculation with either a change in total thrust or a change in thrust to weight (can't be both at the same time).

Both planes are diving down from 10,000 meters and they are racing to see which plane can reach the ground first when both planes maintain 400 km/h and 6 g.

Both planes will not scribe the same exact turn when one plane is a WWII Fw190A-8 Fighter Plane plucked from the front lines during combat and the other one is an exact copy with the only exception of being half the internal mass.

If both planes can maintain 400 km/h and 6 g (even if the pilot's can't the calculation can) from 10,000 meters both planes can't be dumping altitude at the same rate and maintaining 400 km/h and 6 g. One plane will dump more altitude than the other plane and that will show up as dive angle. That will measure Energy Bleed.

One plane will dump more altitude because more energy is required to maintain 400 km/h and 6 g.

The higher mass plane at 400 km/h is at a higher energy state.

The higher mass plane at 400 km/h and 6 g may not be at a higher energy state due to the production of induced drag force; however that plane will still be more mass going just as fast and therefore it will be measuring up with more momentum.

Which plane must dive a steeper angle to maintain the speed and maintain the acceleration of 6 times the rate of gravitational acceleration?

No answer?

Still - no answer?

How about anther cut and paste job of some meaningless quote?

Kettenhunde
07-10-2007, 06:12 PM
I have someting better in mind. Just answer how it is possible for the higher wingloading Yaks to outturn Spits and having far less drag in turn. You're ignoring that part in all your posts.

Hi Kurfurst,

This is probably a good example of how good design can mitigate the effects of weight.

I say probably because I have not done an analysis as I don't know the details.

Wing loading is function of the basic relationship of Power available to Power required. Power available to Power required is the relationship which actually determines our aircrafts turn performance. Examining wing loading alone may not show the true picture of Pa to Pr. Aircraft are a system, not one characteristic.

Lowering drag is another technique to increase power available. If we turned at the Yak's minimum power required which is also called the minimum drag point it probably has more power available than the Spitfire as it is at a different point on the L/D curve.

If the Yaks lead in power available is large enough, it will outperform the Spitfire in a turn despite the lower wing loading of the Spitfire.

Of course examining the L/D curve may reveal portions where the Yak is not able to do this too.

Remember if we are talking instantaneous performance, all aircraft at the same angle of bank and velocity will make exactly the same turn.

Once you understand the power of this fact, in 98% of the envelope, there is not any difference between a lighter design and a heavier one.

All the best,

Crumpp

M_Gunz
07-10-2007, 10:42 PM
Originally posted by Kettenhunde:
Once you understand the power of this fact, in 98% of the envelope, there is not any difference between a lighter design and a heavier one.

As long as it's not a specially chosen or theoretical pretty much unreal situation.

M_Gunz
07-10-2007, 11:01 PM
I'm looking at how energy retention test is proposed and then I look for how it is done for real.
I don't see it here:
NASA Dryden Flight Tests (http://www.dfrc.nasa.gov/Education/OnlineEd/Intro2Flight/index.html)

There are specific other tests that could be considered to show something ABOUT energy retention
but nothing that says what those results are worth compared to other results. That's good news
for the smoke and mirrors players but no good for actually determining anything like final numbers.

I get the feeling strongly that any scale set will be either biased by the "tests" or all the
planes lumped together and then at the low end is declared losers and the winners at the top
and still the magic secret of "which plane will be the winner" won't work and the 109 guys and
the Spit guys won't have their big "proof that the other plane is overmodeled" or any of that.