What isyour generally understood definition of wing loading?
Is it the aircraft weight related to the lifting surface available?
That is my understanding.
If so --does the wingloading change with shifts in CG? (not effective wingloading -actual wingloading)
Not a trick question -
this is all relative to a powered craft in a steady speed ,constant altitude condition
The definition I read stated that "wingloading increases if cg shifts forward "
I see the drag from the increased tailplane trim, increasing the POWER requirement to hold original speed /altitude and the possible need for an increase in AOA to reestablish the SAME steady speed and altitude .this would be an increase in lift equal to the increased trim drag load
Am I just straining at semantics?

I've never encountered any definition of wingloading that accomodates a c.g. shift.
Area divided by weight.
In FAI competitions, the area of the wing -and- the horizontal count for their wingloading spec.
Mostly, the rest of us just measure the wing area in plan view. No allowances for alpha, or c.g.

Dick, you know better than most how wing loading is measured in the commonly referred to sense.

When the airplane is in level, unaccelerated flight however, the "actual" load on the wing is the weight of the aircraft, plus any downward acting aerodynamic forces such as those created by the horizontal stabilizer.


As an interesting aside...there was a while back, a modification for the Cessna 182 (full size) which involved a small canard wing mounted near the cowling. This small, forward mounted wing structure allowed the horizontal stabilizer of the aircraft to be "unloaded" as it were. Despite whatever weight/drag effects brought about by the canard, the airplane gained 15-20kts due to nothing other than the airplane being tricked into thinking it was lighter. Less downward acting forces on the plane...lower AOA in level flight....less induced drag....more airspeed. Just like that.

OK that's two for two --in agreement with what I understand
IF the tailplane download (trim) is lessened - the total drag of the plane - (efficiency) changes -so - less power required to keep flying at same speed and same altitude.
any more?
I guess I better attach the "fact" sheet I was referring to.
http://Avstop.com/AC/FlightTraingHan...tribution.html
I am referring specifically to point 2. at lower section of explanation
also the bit about "higher stall speed" seems odd to me

Paul's got it in a nutshell. But I can't help but wonder if this source is thinking along the lines that Racecity is relating. Not that the wing loading definition changes but that as the CG shifts and the lift load provided by the stabilizer changes it places a bigger or lesser burden on the wing. If so then yeah, it does but it is a load change that is not normally taken into account under the classic definition.

A down-lifting tail is not as inefficient as it may look at first glance. The tail is in the wing's downwash and instead of generating downlift by accelerating air upwards, it is decelerating the downwash somewhat and thus is recovering some of the kinetic energy in the downwash. You might say that the tail is "surfing" on the main wing's downwash.

Nevertheless it's operating at a negative lift coefficient and that lift force is communicated into the model and hence to the wing which then has to lift harder and put more energy into the downwash so that the tail can surf on it if that effect is indeed taking place. Either way you can't get something for nothing.

PS: I see that your source site agrees with Race's thoughts. At least the guy shows it as an add on load and in a much smaller size as is befitting of it's effect.

I added a link to previous post -
This all started when thru a discussion about "snapping" on a model - One writer noted that forward CG INCREASED snap tendency -and also -- too much rearward CG increased snap tendency - it then went into the theory that a forward CG increased wing loading -which I would not buy -
this linked page held the explanation -which I saw and still see as only an analogy -in that the real change is simply efficiency due to changes in trim drag required to hold AOA.

Dick, I think to summarize the whole thing as a difference in "trim drag" might be over-simplifying things a bit.

While carrying any amount of trim (ie: displaced control surface to correct an unwanted tendency of the aircraft) would contribute to total drag, the real loss of efficiency in my mind is directly related to the increased AOA of the main wing which is the result of increased AERODYNAMIC loads on the plane. You can add gobs of weight, or...simply move the CG far enough forward and the behavior of the airplane is much the same.

I fly large aircraft as a career, and can attest to the greatly added muscle power it takes to flare that old beast with a forward (but still in the envelope!) CG. It takes a lot of extra hoo-hah on that tail to balance things out so you don't drive the nose 8 feet into the pavement.

Rant concluded.

OK- I buy the idea of increased aerodynamic loading-
I just did not accept it being called "increased wing loading"
I see these as two distinct , different thingies.
Maybe call em dynamic or static wingloadings.
surely, somone does that already

I'd go along with that.

Well,this is really interesting, wing loading,litghweight material technology,structural engineering ,fluids dynamics,physics,time,chemistry,thermodynamics,mat h,electronics,and us our hobby is really a dynamic system to be in ,thank you

When we think of the wing loading as simply a descriptive parameter then it is hard to see why it would change. We should note however that the wing always generates lift normal to its chordwise datum line. A little geometry shows what could be regarded as an increase in effective wing loading.

As the AOA increases the wing's lift vector tilts forward away from "up and down" but only the component of this vector along the "up and down" line actually contributes to "lift" defined as the force holding the weight of the plane up in the air. This component is smaller the greater the AOA. That is, less of the work done by the wing is holding the plane up, so we can regard this in a sense as increasing the loading of the wing - the plane has to fly faster to generate the lift needed to remain at a constant altitude.

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Another way of thinking of this is that the cross-sectional area of the wing as viewed along the "up and down" axis decreases as the AOA moves away from 0 degrees. Since the mass of the plane is constant (neglecting fuel consumption etc) the wing loading at that moment is effectively greater because the wing is generating "lift" as if it had a smaller chord.

of course --
The work the wing has to do increases-so a greater "loading".
The reason the load increased tho -is due to the efficiency of the load distribution.
The actual static weight has not changed.
I looked at the original statement about "wing loading increases with forward shift of CG" as simply a description of forces changing --because the efficiency of the airframe has changed ( it decreased in efficiency).
I have no problem figuring out best C/G trade offs in getting performance I am after using this approach.
IF--Less download is needed on tailplane, the drag of the craft is reduced
If there is less drag - LIFT required is reduced
If less lift is required there is pressure difference required on wing AND /OR less speed required

If we are going to talk vectors and take the time to draw diagrams, the I must speak up here. Lift acts perpendicular to the free-stream velocity, or flightpath, NOT the chord line. The above text and diagram is therefore highly misleading. The force perpendicular to the chord line is called the normal force, and is a resultant vector of the lift and induced drag vectors. The reference to an increase in effective wing loading appears to be a result of the misidentification of vectors. Not considering tail lift, a wing generating 1 g of lift at 1 degree AOA is still generating 1 g of lift at 10 degrees AOA at a lower speed. The "effective wing loading" hasn't changed at all. The lift vector is operating perpendicular to the flightpath in both cases (straight up if flying straight and level). The normal force vector is one that varies with AOA. Again, this discussion neglects tail lift that could increase or decrease wing loading.

OK-
It is a logic question.
If the plane still weighs the same -the total lift must --remain the same - so wing loading is --the same
If shoving the cg forward -eventually slows the plane from level constant flight - then something else is at play - in this case the forces necessary to hold the wing at best AOA for best speed with least power consumed are increasing.
Those forces are -the tailplane force which stabilizes the AOA and the powerplant thrust (inc direction of thrust)
To me , this is a more simple view of what is at play.
If the stabilizing piece (stabilizer?) operates with less drag - less energy is consumed in holding the plane level
You could call it accumulative lift or whatever -but isn't that is what is happening?
again, the only formulas I am really up on, are baby formulas

"Again, this discussion neglects tail lift that could increase or decrease wing loading"

No it hasn't Mesae.....I've said it several times.

The wing loading increases with a forward shift of the CG because the tail down-force required to balance the more forward CG increases. The wing has to support the normal component of aircraft weight plus the added load due to the tail down-force.

The above is not by any means a complete description of stability or pitch control, but taken by itself, it is true and simple, assuming that the tail-lift was zero or negative before the CG shift. If you wanted to QUANTIFY the amount of tail down-force, or reduce it to zero for a certain flight condition, MATH would be required. Sometimes reality is more complex than we want it to be, and meaningful aircraft design, not just copying other stuff that works, with minor personalization, and using the TLAR principle, requires MATH. You don't see me quoting a lot of formulas here, but I grow weary of your continual campaign of implied disdain against "formulas". I respectfully and politely ask you to drop it. This is a forum on AERODYNAMICS, which is most meaningfully and economically modeled using a whole lot of math. So why the implied discouragement against those who would seek a more detailed understanding?

By the way, if we started out with a positive lifting tail, and moved the CG forward, the overall efficiency would usually INCREASE very slightly, especially at low speeds (induced drag decreases), even though the wing loading is increasing slightly, primarily because horizontal tails almost always have a lower aspect ratio than the wing, and are therefore less efficient at lift generation than wings, and create more induced drag carrying their share of the weight, than if the load on the tail was zero and the wing were carrying the whole load. This paragraph neglects stability requirements.

There is another forum on basic aerodynamics for newbies. Perhaps that would be a more appropriate forum for a campaign against complexity. If something is simplified to the point that it becomes grossly inaccurate, what use is it?

<edit> spelling

I was referring to MY discussion. Or maybe I should have used the word, "post", or "paragraph".

Mesae- you may not like my explanation but is it untrue?
or is it grossly innacurate ?
read your first paragraph and see if anything is actually contradictory.

Some of it was vague, but that wasn't my point. My post wasn't to point out errors in your post. I intended to expand on it and to point out that you appear to have an agenda against "formulas", despite the fact that relatively few formulas are posted in this forum. It almost seems as though you try to discredit anyone for using math. I suppose it doesn't matter. Anyone with the drive to learn quantitative aerodynamics isn't going to be deterred. Perhaps even this controversy might encourage further investigation. I know I have learned some things since I started contributing here.

This one still goin strong! WOW.

OK, I'm gonna duct tape a 1'x1' digital bathroom scale to the bottom of a 172 and jump around the cabin while flying. LOL!

Dick, buddy, pal, why are you so hung up on this subject? I thought you like to think 'outside the box'?

But hey, I promise I dont think any less of you cuz you dont like formulas! (except similac - yuck!)


smell you later,

Ted

Are we trying to combine "Static wing load--ing" and "Dynamic wing load--ing, ( + 9 G's at pull out of a dive) " .

The wing knows there are at least 2 real types of wing loads.

Rich

I have no agenda for or against any explanation technique
My comments are simply looking at a problem from other vantage points
If one can discuss a question from other points of view , what is the problem?
Formulas -can be used to explain things - -if that is your bag -go for it
.

"(+9 G's at pull out of dive)" - not really

more along the lines of wing loading change due to cg shift.