Author Topic: Draining E in turns (Read 10181 times)

humble · « **Reply #15 on:** August 24, 2004, 12:35:14 PM »

Removing all the "techno-babble" a plane with higher wingloading has to "work harder" than a plane with lower wing loading to achieve the same result under the conditions you describe. So the more efficient wing will get a bigger return for each unit measure of energy expended. Basically the "gas milage" of the wings is significantly different. Your confusing size and design. Each wing was designed to maximize results under different variables...(at least thats what I come to boiling all this stuff into english)

GODO · « **Reply #16 on:** August 24, 2004, 01:03:13 PM »

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Originally posted by hitech
For this discusion just think of AOA as how far you are holding the stick back.

Correct, and is in that "violent" pull of the stick where I find the noticeable initial lose of speed. Then the speed lose rate seems to stabilize. What I mean is that this initial violent pull of the stick seems to affect more to the small winged planes. I understand that this movement may end in an earlier stall for the smallwinged planes while the lose of speed would be more noticeable in the large-winged ones.

Crumpp · « **Reply #17 on:** August 24, 2004, 01:38:17 PM »

Just the act of turning in ANY A/C under G's bleeds tremendous amounts of Energy over the Potential Energy the plane had flying straight and level.

Crumpp

dtango · « **Reply #18 on:** August 24, 2004, 02:31:14 PM »

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I understand that this movement may end in an earlier stall for the smallwinged planes while the lose of speed would be more noticeable in the large-winged ones.

Mandoble: Think about the statement you just made- "...earlier stall for a small-winged planes...".

What does the "earlier stall" mean? It means high aoa = very high induced drag + some rise in pressure drag due to increased boundary layer separation (as pictured). All this means significant bleed in speed for the "small-winged plane".

This means that aerodynamics is in contradiction with the rest of your statement "...while the lose of speed would be more noticeable in large-winged ones.".

Tango, XO
412th FS Braunco Mustangs

GODO · « **Reply #19 on:** August 24, 2004, 03:03:03 PM »

dtango, lets use a contemporary example, Su27 and Cobra manouvre. It suddenly gains great AOA just pulling the stick violently and chopping throttle, the wings and body of the plane act like a big airbrake and the plane almost stops in the air pointing up. Being the Flanker smaller (smaller wings and body), the "brake" effect would be less noticeable. Now, at a much minor scale, that should be present also with WW2 planes.

Sable · « **Reply #20 on:** August 24, 2004, 03:17:22 PM »

Here's a simplified way to look at it.

Plane A weighs 9000 lbs and has a wing loading of 40 lbs/ sq. ft.

Plane B weighs 9000 lbs and has a wing loading of 30 lbs/ sq. ft.

Assume they have a similar wing design, just a different area.

Both are traveling the same speed and make a sharp turn, pulling the same G force. They weigh the same, and so they have to produce the same amount of lift to turn at the same G. Plane A's wing has to work harder - pull higher AoA - to produce the necessary lift to turn at the same G.

Now parasite drag is basically unaffected - the aircrafts shape hasn't changed (assuming no flaps are in use etc.).

What does increase is induced drag. Think of induced drag as the rearward component of lift - the higher AoA you use the more you will create. In normal flight at 0 Aoa the lift vector of the wing is exactly perpendicular to the direction of travel of the airframe, and so all the lift of the wing goes towards lifting the plane. But as you increase the angle of attack to increase lift, the wing is tilted back from the direction of travel. Now part of the lifting force created by the wing is acting against your forward motion! This is induced drag.

In our example with plane A and B, Plane A is producing more induced drag turning at the same G force as plane B because it is having to pull a higher AoA.

In the real world it gets more complicated because different wing designs produce differing levels of lift at different angles of attack. So wing loading doesn't tell the whole story. And if a plane has a big power advantage it can partially overcome the drag it is creating. But generally the worse turning plane will bleed more E pulling the same G from the same speed as a better turning plane.

dtango · « **Reply #21 on:** August 24, 2004, 03:27:49 PM »

Mandoble:

The cobra maneuver is a specialized case but it is not an example of dumping E not because of the size of the wing but because of improvements in aerodynamics to achieve greater AOA without departing flight - in the neighborhood Cl of 2.5. The canards and thrust vectoring of the Su27 has a lot to do with this - not the size of it's wings acting like airbrakes.

Tango, XO
412th FS Braunco Mustangs

GODO · « **Reply #22 on:** August 24, 2004, 04:09:36 PM »

Sable, Isnt that drag a function of AOA and also of the wing area? can we assume that in your example both planes can suffer from similar inducted drag, one because higher AOA and the other because higher wing area while lower AOA?

dtango, basic Su27 performing Cobra doesnt has neither canards nor thrust vectoring.

Crumpp · « **Reply #23 on:** August 24, 2004, 04:30:39 PM »

Actually,

The Lower wingloaded plane DOES produce more drag. For induced drag it depends on the Aspect ratio and the wip tip efficiency factor.

Lift-to-Drag = Low Wingloading = MORE REFERENCE AREA = more drag.

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The drag coefficient Cd is equal to the drag D divided by the quantity: density r times half the velocity V squared times the reference area A.

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

http://www.av8n.com/how/htm/aoa.html#sec-weight-drag-speed

Induced drag greatly depends on the ASPECT RATIO and WING TIP "e" factor. More so on the AR (bigger number) than the "e" factor (usually 1 or less).

Low Wingloading = More lift = More induced drag

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

http://www.av8n.com/how/htm/airfoils.html#sec-induced-drag

Instantaneous turn is NOT sustained turn. A low wingloaded plane usually has a great sustained turn rate but that has nothing to with cornering speed and instantaneous turn. In fact most (not all) low-wingloaded planes have low instantaneous turn speeds and are crappy high speed turners. Just look at the Zeke.

Doubling the Velocity Quadruples the Force = ALL the Force = DRAG and LIFT.

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

Crumpp

Crumpp · « **Reply #24 on:** August 24, 2004, 04:59:50 PM »

This is another factor that having a low aspect ratio hurts.

Downwash

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

Crumpp

bozon · « **Reply #25 on:** August 24, 2004, 05:19:55 PM »

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Low Wingloading = More lift = More induced drag

err... no.

A plane will produce the same needed lift in order to fly level reguardless of wingloading.

Lowering the wingload (say increase size) will result in less induced drag when flying level.

Bozon

Sable · « **Reply #26 on:** August 24, 2004, 05:31:27 PM »

GODO, as far as induced drag, the lower wingloaded plane is going to make less for the same G (assuming all else is identical).

As far as parasite drag (the form drag that all airplanes experience), yes having more surface area hurts you - however this parasite drag is only varying based on speed or configuration changes (lower landing gear etc). Turning in and off itself doesn't change parasite drag.

g00b · « **Reply #27 on:** August 24, 2004, 05:38:50 PM »

There is a lot of confusion here. Just listen to HT, he knows of which he speaks. Got me thinking about one my my favorite hobbies though.

Check out http://www.reeseproductions.com/mpegs.html

Look at the dynamic soaring videos. Now THAT is draining energy in turns.

g00b

Crumpp · « **Reply #28 on:** August 24, 2004, 05:47:41 PM »

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err... no.

errr -yes.

Induced drag is a function of Aspect ratio and wing tip efficiency.
Lower wingloading produces a higher Cl too.

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Lowering the wingload (say increase size) will result in less induced drag when flying level.

Lower wingloading will make up for it in increased Drag. Not induced drag which is totally seperate. Drag is a function of AREA. To be a low wingloading plane usually means more surface AREA. Induced drag is reduced with speed. HOWEVER, Drag quadruples with velocity.

Crumpp

Crumpp · « **Reply #29 on:** August 24, 2004, 06:14:27 PM »

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As far as parasite drag (the form drag that all airplanes experience), yes having more surface area hurts you - however this parasite drag is only varying based on speed or configuration changes (lower landing gear etc). Turning in and off itself doesn't change parasite drag.

Yes, IF you make a 1 G turn. Pull any G's and your drag increases in proportion to the Force/Area and that force is quadrupled with velocity. Hence you put the brakes on in a turn.

Crumpp