Spitfire Mk.XIV vs P-51D Mustang

[drgondog]

Originally Posted by huskerapache

If they both took off from England and fought over Berlin I'll take the Mustang.

Or from Iwo Jima and fight over Tokyo..

[Soren]

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

For a specific AoA yes (In this case near the critical AoA at Clmax), but not just for specific velocities, no for all velocities Bill.

The below is the undeniable truth:
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 at Clmax

Originally Posted by drgondog

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'

Then tell me with numbers where I got the term lift-loading from - that makes about as much sense as what you just said

Bill, I've had heated discussions about wing loading and its importance many times before and it always ends up with all parties using the term lift-loading when relating to turn performance of an a/c, wether it be the right term for the subject or not. I took it to me as I found it an easy and logical way to explain the importance of knowing the Clmax while at the same time showing the true difference between both a/c percentage wise.

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

Aren't we all ?

[drgondog]

[quote=Soren;407667]
Then tell me with numbers where I got the term lift-loading from - that makes about as much sense as what you just said

I would not presume to tell you where you got either your notion of lift loading as an 'efficiency' or WL/CLmax as an efficiency or anything else you have said.

Only you can reach for the sources or references

Bill, I've had heated discussions about wing loading and its importance many times before and it always ends up with all parties using the term lift-loading when relating to turn performance of an a/c, wether it be the right term for the subject or not.

Lift loading in the context of manuevering is a perfect way of contrasting Wing Loading to actual aerodynamic loads. Wing loading and Lift Loading are only the 'same' at one G.


I took it to me as I found it an easy and logical way to explain the importance of knowing the Clmax while at the same time showing the true difference between both a/c percentage wise.

QUOTE]

You are free to take anything anyway you want - doesn't mean we (or I agree). You are still avoiding sources and references to show why your brand of 'stuff' regarding dividing WL (or Aerodynamic lift Loading) by CLmax means anything at all.

The one and primary 'efficiency' indicator for a wing is L/D - and you note it is non-dimensional.

[Soren]

Again where did I say that lift-loading was an efficiency factor ?

Cl is an efficiency factor, that is what I said.

[drgondog]

Originally Posted by Soren

Again where did I say that lift-loading was an efficiency factor ?

Cl is an efficiency factor, that is what I said.

Your post 146 - which started all this

"Wing loading is simply weight divided by wing area, while lift-loading is weight divided by wing area and then divided by the lift coefficient in order to get the true difference. (That is the point of establishing the coefficients, they are efficiency indicators)"

This is nonsense Soren.



Lift loading is the actual lift applied to the wing divided by area as opposed to Weight of airframe divided by the area. If that airplane is in a 3g turn in horizontal plane the Lift Loading is far higher than the airframe weight on the ground - and more than 3x as the total lift and normal forces on the wing are greater than the lift force vector equal and opposite the accelerated mass vector

Further dividing Lift Loading by CL (or CLmax) simply gives you "q" as I have shown you several times. (1/2 rho V^2)[/b]

You go on to speak of 'amateurs' in next paragraph on 146

"Wing-loading, while the prefered way for the amateur to compare a/c, is very misleading for comparative purposes as obviously different wing & airfoil designs will perform differently in terms of lift & drag production. Dividing the wing-loading with the lift coefficient eliminates the inherent inaccuracy of wing-loading as a comparative method and gives us the lift-loading which is completely accurate as it is based on a proportional efficiency factor established by extensive windtunnel lab test results on the particular wing."

Babble. Lift Loading has zero to do with 'proportional efficiency' or 'proportional efficiency factors'.

"

[Soren]

Bill,

I was talking about the lift coefficient, that is an efficiency indicator/factor. I never said lift-loading was an efficiency factor, you're twisting my words.

Here's what I said in post #146 from the very beginning of our discussion:

"Wing loading is simply weight divided by wing area, while lift-loading is weight divided by wing area and then divided by the lift coefficient in order to get the true difference. (That is the point of establishing the coefficients, they are efficiency indicators)"

I don't see how one can translate that into me claiming lift loading is an efficiency factor from this at all. What I am saying however is, like I explained afterwards, that establishing the lift loading is a great of accurately comparing a/c percentage wise.

If that airplane is in a 3g turn in horizontal plane the Lift Loading is far higher than the airframe weight on the ground - and more than 3x as the total lift and normal forces on the wing are greater than the lift force vector equal and opposite the accelerated mass vector."

That is true, and as you can see from my posts I said that as-well;

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

I never claimed that lift loading was an efficiency indicator or factor, just a way of easily and accurately comparing a/c percentage wise. It is the lift coefficient I say is an efficiency indicator/factor, and it is.

[drgondog]

Originally Posted by Soren

Bill,

I was talking about the lift coefficient, that is an efficiency indicator/factor. I never said lift-loading was an efficiency factor, you're twisting my words.

Bill how does my analysis not prove it ???

To do an accurate comparison you HAVE to know the Clmax and you HAVE to divide the wing-loading with it. Why ? Because it's a coefficient, it's meant to tell you how efficient the wing is at providing lift pr. surface area.

So if the wing of aircraft A has a lift coefficient which is 30% higher than that of aircraft B, then aircraft B's wing provides 30% more lift for every square cm, m, foot etc etc than the wing of aircraft A. The very purpose of Cl as an efficiency indicator.


So - you say
"You have to know ClMax (TRUE) and you HAVE to divide the wing loading with it (FALSE)". BTW -I'll assume you meant wing loading in the context of the aerodynamic loads..

"The very purpose of Cl as an efficiency indicator" (FALSE- L/D and Cl/CD are 'efficiency indicators'. Cl is merely a plot point for a 2-d airfoil section as a function of AoA. Cl may also be derived in test or wind tunnel conditions for level flight without knowing the AoA - at 1g level flight - when the gross weight, wing area and true airspeed is known.

CL absent context of CD is NOT an efficiency factor

Here's what I said in post #146 from the very beginning of our discussion:

"Wing loading is simply weight divided by wing area, while lift-loading is weight divided by wing area and then divided by the lift coefficient in order to get the true difference. (That is the point of establishing the coefficients, they are efficiency indicators)"

You said this and you are wrong. You are wrong that Lift Loading is Wing loading divided by Cl, and wrong about the usefulness or relevance of dividing lift loading by lift coeeficient. When you do that you get "q" or dynamic pressure - which gets you 'q', not a true difference, not an efficiency

I don't see how one can translate that into me claiming lift loading is an efficiency factor from this at all. What I am saying however is, like I explained afterwards, that establishing the lift loading is a great of accurately comparing a/c percentage wise.

Back to nonsense.


That is true, and as you can see from my posts I said that as-well;

Saying it is true time after time doesn't make your case Soren.

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:

In level flight for one g - the Lift IS the weight... the lift loading IS the wing loading. This is a little simpler than

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

at 1 g you go no further ----> Lift = weight = 4000kg

Lift loading = wing loading at 1g = 4000/20 = 20Kg/m^2 but this a/c must flying at a very high AoA for CLmax=1.5 - did you want this illustration?

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

????

After all the math Lift should be equal to Weight (4000kg) at 1g. For a higher value of lift than weight the little beastie will climb, for a lower value of lift than weight - it will sink!

I never claimed that lift loading was an efficiency indicator or factor, just a way of easily and accurately comparing a/c percentage wise. It is the lift coefficient I say is an efficiency indicator/factor, and it is.

Lift Coeeficient/Drag Coefficient is an efficiency indicator of the wing.

Lift Coefficient is a point on a plot for a specific AoA for a 2-d airfoil section, or a calculated value if Weight, velocity and density, and wing area are known for 1 g steady flight

[Soren]

I give up, you only wish to twist and misunderstand what I say, even when I cut it out in cardboard for you.

Don't you even understand that my calculation was for an a/c in a turn ?? Hence the use of Clmax!

What I established in the above calculation was the G-forces a 4,000 kg aircraft with a 20m^2 wing with a Clmax of 1.5 will pull at 120 m/s when doing a max performance turn, which is 6.74 G. A similar a/c with a lower Clmax will only be able to pull less G's, hence why dividing wimg-loading with Clmax is good for comparative reasons as you can then directly compare the turn performance of a/c percentage wise.

That's it for me, I don't wish to continue this anymore as you really don't wish to understand, just preach.

[kool kitty89]

Soren, I think the problem is that you still using "Lift loading" in your personal context, while Bill is using the true aerodynamic concept that that term applies to.
(your's is somthing more like lift-corected wing loading, or CLmax corrected wing loading)

I agree though about your original post (about the "efficiency" issue), while I don't think Bill was trying to twist your words, I see how it could be confused. (thought that you were implying "lift loading" was an efficiency figure, though you'd meant the coeficients were efficiency figures)


Also, I think this is the "performance thread" Bill was referring to: http://www.ww2aircraft.net/forum/avi...1-a-13369.html (Bf-109 vs Spitfire vs Fw-190 vs P-51)

Given the consistent use of the term "lift loading," I'm surprised this issue hasn't come up before.

[drgondog]

Originally Posted by Soren

I give up, you only wish to twist and misunderstand what I say, even when I cut it out in cardboard for you.

Mis understand and disagree are two different concepts Soren. I understand what you want and I disagree your physics.

While I was poking fun at you - there were no boundary conditions to prove that that particular ship had the Thrust available to maintain that velocity to sustain 6.74 G's

Don't you even understand that my calculation was for an a/c in a turn ?? Hence the use of Clmax!

Yes Soren

What I established in the above calculation was the G-forces a 4,000 kg aircraft with a 20m^2 wing with a Clmax of 1.5 will pull at 120 m/s when doing a max performance turn, which is 6.74 G.

See above. What you say is true if the one takes into evidence that the ship illustration you used in fact can do that turn at that bank angle and maintain level flight.

A similar a/c with a lower Clmax will only be able to pull less G's,

THE SAME a/c with the same wing but a lower CLmax (say - no slats) will be able to pull less G's. To get to the different a/c with different a/c the available Thrust in excess of drag, the total drag in the profile are also important variables. CLmax is Important but not determinant.

hence why dividing wimg-loading with Clmax is good for comparative reasons as you can then directly compare the turn performance of a/c percentage wise.

nonsense from a rigorous mathmatically sound repeatable basis as a unit of direct comparison -

see if works when you compare a B-36 to say a Mustang. IIRC the 63-420 airfoils have a ClMax at 1.6+ and WL of 34 empty and 55 loaded and fly it with your values against a maxed out Mustang at 11,800 pounds and WL of 60.

That's it for me, I don't wish to continue this anymore as you really don't wish to understand, just preach.

I didn't 'wish to continue' a long time ago. bye.