Spitfire Mk.XIV vs P-51D Mustang

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Yes a coefficient is a dimensionless figure Bill (Any nr alone is), that is until you add a dimension to it, which is what I did when I used meters as a reference point. The Cl is just a coefficient, meant to either multiply or divide other known dimensional figures with.

And since we know the true Clmax of the Fw-190's P-51's wing, established in fullscale windtunnel tests, we can also tell the difference between the two in terms of which a/c provides the most lift pr. unit of its own weight.
 
I will be honest. I am a merely a technician, but I too have never heard of Lift Loading in aerodymics. I have read it on data plates on our John Deer Tractors that we used to tow the aircraft with.

I just googled it too, to see if I am stupid and I found nothing either.
 
Type "Lift-loading Wing-loading" like so on google and look.

Then try "lift-loading stalling".
 
Wing loading I have heard of, but not lift loading.

I think you are talking about wing loading. Everytime I did a search (even with your search criteria) the only things that came up were "wing loading".

But then again I am merely a technician...
 
Soren said:
Type "Lift-loading Wing-loading" like so on google and look.

Then try "lift-loading stalling".
Click to expand...

Soren - that article, and its reference to 'lif loading' is the influence of flow properties induced by the jet to improve Lift Distribution..or simpler, to reduce tip losses.

It has zero to do with Wing Loading divided by Lift Coefficent.

Back to your thesis, how does arriving at a value for q have anything to do with efficiency, when you divide WL by CL? "efficiency" should be expressed as a non-dimensional number and when you dive a pressure load by a non dimensional number, you get a pressure load which is curiously equal to q for a specific velocity

You would have to solve to determine at which value of V is WL/CL for that CL.. remember you only posed the CL values for a Max CL at some max AoA which you haven't specified but we assume close to stall.
 
I read all the threads KK. Fat Cat and Aerial Target know what they are talking about

This is from Aerial Target

"There are four equal factors in flight; they are lift, weight, thrust, and drag. Wingloading and powerloading only deals with two of those, completely ignoring drag. And although wingloading does involve wing area, it does not account for all of the lift because wing area cannot tell you how much lift the wing is capable of generating. It's just a foundation.

The more weight and drag, the worse an airplane will turn. The more thrust and lift, the better it will turn. Figuring a plane's turning ability, climbing ability, or even stall speed with only thrust and weight is nuts, and throwing in the wing area isn't much better. So no, it's not exactly half of the equation because of there is wing area, but it's far from reliable or accurate. I would agree with it being roughly 70% of the complete picture. And a 30% or even 20% error is a great one. That is something like the difference between a P-38's turning ability and a Zeke's.

Crusty wrote:
gibbs quote thing...
..."I strongly disagree with that since wing loadings says NOTHING about the configuration of the wing itself, and nothing about the amount of LIFT that wing is producing. Wing loading ONLY factors in a standard wing and a standard aerofoil. "


I think the only thing we disagree on is is your second use of the word "NOTHING". in that statement..I would replace it with "RATHER A LOT"


I'm afraid that would be wrong. Wingloading is the weight of an airplane divided by the area of its wings. It does not account for the shape of the wings in any of the three dimensions. I would say that wingloading says "very little" about how much lift the wing is generating.

Picture a wing, 16 feet by 2 feet, with an aspect ratio of 8:1. Picture another with the same dimensions but with an aspect ratio of 1:8. Going by wingloading, the two are exactly the same. Yet they obviously produce drastically different amounts of lift. Or take two wings with the same area and aspect ratio, one being four inches thick and the other twelve inches thick. Again, the two airplanes will not even be close to each other. And that's not getting into things such as swept wings, laminar flow wings, taper ratio, propeller wash, and flap design, size, and location.

The logical conclusion is that anyone who says, "This airplane should do better in this area than that airplane because of wingloading," is a moron. Rather say, "This airplane might be better in this area than that airplane because of wingloading. I'll check out the other factors and see." The same applies, to a slightly lesser extent, to those who use only wingloading and powerloading.

I've been trying to explain this truth to an unwilling simulator community for quite a few years now. For some reason, most simulator users seem to find comfort in simplifying things too complicated for them and assigning to them false meanings, or taking the simulator's portrayal as truth, rather than finding out how things really work. Thus, you have the crowd which insists that this airplane must out-whatever this one, because the god Wingloading says so. Madness! Fortunately, everyone in this discussion is above that, but I do believe that some of you place too much value on wingloading.
 
drgondog said:
Soren - that article, and its reference to 'lif loading' is the influence of flow properties induced by the jet to improve Lift Distribution..or simpler, to reduce tip losses.

It has zero to do with Wing Loading divided by Lift Coefficent.

Back to your thesis, how does arriving at a value for q have anything to do with efficiency, when you divide WL by CL? "efficiency" should be expressed as a non-dimensional number and when you dive a pressure load by a non dimensional number, you get a pressure load which is curiously equal to q for a specific velocity

You would have to solve to determine at which value of V is WL/CL for that CL.. remember you only posed the CL values for a Max CL at some max AoA which you haven't specified but we assume close to stall.
Click to expand...

Bill obviously the reason I'm using the Clmax figure (Which occurs close to the critical AoA) as reference is because that is the area where the a/c are going to be at in a max performance turn, which is what we're discussing here.

It isn't the wing loading which matters, it's the actual lift vs the weight of the a/c i.e. the lift loading. By dividing the Wing loading with the Cl we can directly compare a/c at specific AoA's, in this case close to the critical AoA where Clmax occurs.

What Aerial Target says is exactly the same as what I'm saying.
 
Soren said:
Bill obviously the reason I'm using the Clmax figure (Which occurs close to the critical AoA) as reference is because that is the area where the a/c are going to be at in a max performance turn, which is what we're discussing here.

It isn't the wing loading which matters, it's the actual lift vs the weight of the a/c i.e. the lift loading. By dividing the Wing loading with the Cl we can directly compare a/c at specific AoA's, in this case close to the critical AoA where Clmax occurs.

What Aerial Target says is exactly the same as what I'm saying.
Click to expand...

Soren - what Gene said to separate lift loading from wing loading is correct. What aerialtarget explained regarding the fallacy of depending on wing loading as an absolute determinant is correct.

What you say about dividing lift loading by Cl is not correct.

Lift 'loading' is the distribution of lift spanwise (and chord wise for 3-d) over a wing for a particular condition of flight. If you were to look at a model like lednicers, the 'footprint' of the load distribution is shown as the pressure distribution (you remember, 'suction'?).

This 'loading' is a distribution of pressure (usually greater at the root) which tapers from root to tip - usually in an 'elliptical like' curve if the path of the curve represents the magnitude of the distribution spanwise. The 'pressure' distribution when representing 'Lift' is simply the value of pressure of the accelerating stream and is less than the freestream stagnation pressure until separation occurs -

So, lift distribution is important for aeros to figure out what they wish to do with twist for example, and for structures guys in order to make bending and torsion calculations for the wing structure..

Dividing by Cl has no meaning.

How about proving your thesis mathmatically and start with the AoA at which CL=0?
 
So the valid techincal use for the term "lift loading" would be synonymous with "lift distribution," correct?


I think Soren's point for his deviding weight by Clmax and Wing area is to provide a comparison between aircraft in terms of the maximum lift the wing can produce compared to their weight. (which doesn't really give you data that can be used in equations but makes a side by side comparison of the aircraft's characteristics)

But "lift loading" would not be correct to use here. (I don't think there is an actual term for these figures)
 
kool kitty89 said:
So the valid techincal use for the term "lift loading" would be synonymous with "lift distribution," correct?

Yes, and no. For level flight - 1g the lift loading of the lift distribution would be 1/3 of a 3g flight condition. The aircraft in flight has loads that pertain to the lift on the lifting surfaces.

A wing loading would be equivalent in math terms to 1g flight conditions - namely the weight=lift..


I think Soren's point for his deviding weight by Clmax and Wing area is to provide a comparison between aircraft in terms of the maximum lift the wing can produce compared to their weight. (which doesn't really give you data that can be used in equations but makes a side by side comparison of the aircraft's characteristics)

That might be his thesis but begs the question - if WL/Clmax = q at that flight speed, why would we compare 'q' (a dynamic pressure in #/sqft) and further how do we relate it to efficiency?

But "lift loading" would not be correct to use here. (I don't think there is an actual term for these figures)

QUOTE]

You are correct[/
Click to expand...
 
The purpose of dividing WL with Clmax is to arrive at the 'real' wing-loading for comparative purposes, simply referred to as the lift-loading of the a/c as you now have factored in how effective the wing is at producing lift.

To make it really simple:

If wing A features a Clmax which is 30% higher than that of wing B, the wing area of the two being the same, then Wing A will produce 30% more lift than Wing B.

There's no denying these facts. So the only problem I see here is that you (Bill) haven't ever encountered the term 'lift-loading' before and you're making a pretty big deal out of that IMO. A single term shouldn't matter in a discussion, it is the facts which it stands for which should.

But I am willing to concede that 'lift-loading' might not be a verified term within aerodynamic lectures, but it certainly is very common in discussions on the subject, which is where I encountered it first many years back.

So how about we now move past this terminology nonesense and concentrate on the truth behind the terms ? :)
 
Soren said:
The purpose of dividing WL with Clmax is to arrive at the 'real' wing-loading for comparative purposes, simply referred to as the lift-loading of the a/c as you now have factored in how effective the wing is at producing lift.

To make it really simple:

If wing A features a Clmax which is 30% higher than that of wing B, the wing area of the two being the same, then Wing A will produce 30% more lift than Wing B.

This is true if the velocities are the same for which the CLmax is measured.

There's no denying these facts. So the only problem I see here is that you (Bill) haven't ever encountered the term 'lift-loading' before and you're making a pretty big deal out of that IMO. A single term shouldn't matter in a discussion, it is the facts which it stands for which should.

I am VERY familiar with Lift Loading in the context for which it is defined for aerdynamic loads on a wing. The point of this discussion is that you have extracted 'something' from 'somewhere' and applied it to 'effciciency' and you are citing the 'well known' published background for your claims.

But I am willing to concede that 'lift-loading' might not be a verified term within aerodynamic lectures, but it certainly is very common in discussions on the subject, which is where I encountered it first many years back.

It IS - but not in your context. It doesn't seem to be very 'common in discussions on the subject' of either wing or manuevering efficiency - because you don't seem to be able to produce such documented references???

So how about we now move past this terminology nonesense and concentrate on the truth behind the terms ? :)
Click to expand...

It is simply dimensional nonsense.

It is easy to deny the 'facts' and the 'truth' - do the math

Cl= L/(q*A) where q is the dynamic pressure for the velocity at which CL is correct for the Lift vector at that AoA and velocity

L=CL*q*A

WL = W/A where weight of the aircraft is to be divided by the area
W/A = L/A for that same flight condition in which Lift = weight (or loaded higher g 'weight')

W/A = WL = L/A = CL*q*A/A = CL*q = WL
Divide both sides by CL -----> WL/CL = CL*q/CL = q (dynamic pressure)

L/A divided by CL = q ; Lift Loading divided by CL = q.

So What?

The only useful thing this could tell you (if you knew the altitude and density) is that for a Given CL, and a Given Lift Vector, you could solve for the correct Velocity for that CL

But what does q or solving for V tell You about efficiency?

Which 'aerodynamic expert circles" find this interesting? I really want to know because it sure doesn't mean anything to me and I really find it interesting that it means something to 'experts' in the field.

What is your source Soren?
 
Bill,

First of all:

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

NASA:
One way to deal with complex dependencies is to characterize the dependence by a single variable. For lift, this variable is called the lift coefficient, designated "Cl." This allows us to collect all the effects, simple and complex, into a single equation. 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.

So like I said:

If wing A features a Clmax which is 30% higher than that of wing B, the wing area of the two being the same, then Wing A will produce 30% more lift than Wing B.

And so if you divide the wing loading with the Clmax you get the true difference between the two a/c percentage wise, which is good for comparative reasons, esp. for the amateur reader out there.

If I wanted to find the actual lift vs the weight of the a/c then I'd use an entirely different approach as I then need the actual speed of the a/c and the air density of the inviroment it flies in:

Aircraft weight: 4,000 kg
Aircraft wing area: 20 m^2
Speed: 120 m/s
Alt: Sea level
Clmax: 1.50

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

1.5 * 20 * .5 * 1.225 * 120^2 = 264,600 Newtons

264,600 N = 26,981.690 Kgf

26,981.690 Kgf / 4,000 Kg
________________________
= 6.74 G


Secondly please stop dwelling on a single term, it is the truth behind it which is interesting. Why is it you insist upon discussing the term instead of the facts, is that really interesting to you ???

When I say I heard the term in discussions regarding aerodynamics then it is because I did so.. Or are you calling me liar ? If so what would I get out of lying about such a thing ? Seriously ? I have never researched the authenticity of the term itself, just used it in discussions regarding the usability of wing loading as a measuring stick for turn performance, cause if you want to find the true difference between two a/c you need to take into account the Clmax, and that is the truth.
 
Soren said:
Bill,

First of all:

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

NASA:
One way to deal with complex dependencies is to characterize the dependence by a single variable. For lift, this variable is called the lift coefficient, designated "Cl." This allows us to collect all the effects, simple and complex, into a single equation. 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.

So, Soren what do you think "q" is? Hint: It is 1/2 x rho x Velocity squared. It appears you didn't understand what dynamic pressure is.

So like I said:

If wing A features a Clmax which is 30% higher than that of wing B, the wing area of the two being the same, then Wing A will produce 30% more lift than Wing B.

So, like I said - this is true for each wing at a specific AoA and Velocity.

And so if you divide the wing loading with the Clmax you get the true difference between the two a/c percentage wise, which is good for comparative reasons, esp. for the amateur reader out there.

it makes good reading for an amateur - whether making the claim or reading the claim - but your thesis is nonsense

Secondly please stop dwelling on a single term, it is the truth behind it which is interesting. Why is it you insist upon discussing the term instead of the facts, is that really interesting to you ???

Soren - neither your term nor your f'acts/truths' are correct

When I say I heard the term in discussions regarding aerodynamics then it is because I did so.. Or are you calling me liar ? If so what would I get out of lying about such a thing ? Seriously ? I have never researched the authenticity of the term itself, just used it in discussions regarding the usability of wing loading as a measuring stick for turn performance, cause if you want to find the true difference between two a/c you need to take into account the Clmax, and that is the truth.
Click to expand...

Sources Soren. Truth always has a foundation in physics and math. References Soren. Applied math to a physical model, measured against test data and refined to a 'truth'

I don't claim you are a liar - just uninformed.
 
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