Hi,Excuse my ignorance, but can someone explain to me what the difference is between these two drag parameters in the Aircraft.cfg file?parasite_drag_scalar = 1.0induced_drag_scalar = 1.0What do they control?http://www.scandicair.com/images/Banner_ariane_4.jpg

These explain the difference between the two better than I:http://en.wikipedia.org/wiki/Induced_draghttp://en.wikipedia.org/wiki/Parasitic_dragThe scalars allow you to increase or decrease drag vs. having to do the same in the .air file. -John

Thanks John. :-)So, if I understand correct,...Parasite drag is a plain "body" friction drag. While the induced drag has more to do with the winglift vs speed drag...?http://www.scandicair.com/images/Banner_ariane_4.jpg

As I understand it, AOA comes into play as well for induced drag. But I'm no expert, it's been thirty years since I studied this stuff and in order to preserve space in my gray matter, I simpify things to no wings=no flying today :) and have blissfully forgotten the finer technical details.-John

Its rather easy:Parasite drag is at full speed, and at altitude.Induced drag pronounces itself at takeoff and in the first part of the climb.So to lower a bit the highaltitude speed, and increase the fuelburn then increase the parasite drag a tad.If you want to lower the takeoff speed, try the induced drag.Johan[A HREF=http://jdserver.no-ip.com]Personal Server[/A]A LITTLE LESS CONVERSATION, AND A LITTLE MORE ACTION PLEASE!HELP:http://support.microsoft.com/?kbid=238882

Hi,Thanks for that information. So,..if I for example would like to get some more drag at descent, inorder to not need to deploy the speedbrakes that much. Then I should increase the induced drag slightly?http://www.scandicair.com/images/Banner_ariane_4.jpg

"So,..if I for example would like to get some more drag at descent, inorder to not need to deploy the speedbrakes that much. Then I should increase the induced drag slightly?"No--you would want to increase the parasitic drag. In descent you are still at a fairly high speed and the AOA is either close to neutral or slightly negative. However, add to this that some engines, when at "idle" thrust, are still producing some thrust and adding to the speed during descent. This varies from .air file to .air file and there's some tables in the .air file which control this. The problem with increasing parasitic drag is it takes more thrust--and thus a higher fuel burn--to maintain speed. You can end up throwing the whole flight model out of whack and end up using the scalars to "fudge" things to an approximation of what they should be.-John

In addition to this, parasite drag increases with airspeed, while induced drag decreases with airspeed. If you plotted this on a chart these two lines would meet, and where they would meet is called L/Dmax. This can help determine several things, not the least of which cruising speed. Also, induced drag is the main factor that creates ground effect. Because induced drag is caused by wingtip vortices, as the airplane nears the ground the runway will cut those vortices, decreasing induced drag and creating more lift, hence the float that is prevelent especially in low wing airplanes.

Hello Steffan,have a read ofhttp://perso.wanadoo.fr/hsors/FS_Soft/dragtheory.pdfIn MSFS they use the simple model for drag which is parasite + lift induced drag.Or CD = CDo + K * CL^2CDo is the parasite drag coef in the .air file and is multiplied by the parasite_drag_scalarK is the induced drag factor in the .air file and is multiplied by the induced_drag_scalar.CL is the lift coefficient.Also there are mach Nr. factors plus drag from LG, flaps etc etc.Ian

>In addition to this, parasite drag increases with airspeed,>while induced drag decreases with airspeed. If you plotted>this on a chart these two lines would meet, and where they>would meet is called L/Dmax. This can help determine several>things, not the least of which cruising speed. >>Also, induced drag is the main factor that creates ground>effect. Because induced drag is caused by wingtip vortices, as>the airplane nears the ground the runway will cut those>vortices, decreasing induced drag and creating more lift,>hence the float that is prevelent especially in low wing>airplanes.Hi,So, this really means that I should go for an increased induced drag, since the drag I want should be between 230 - 260 IAS, just before approach, and not at high altitude/speed. :-)http://www.scandicair.com/images/Banner_ariane_4.jpg

Thanks Ian. :-)http://www.scandicair.com/images/Banner_ariane_4.jpg

No--you still want to increase parasitic drag. 230-260 IAS is high airspeed--many bizjets cruise in this range at altitude. Although their indicated airspeed may be 250 Kts at FL350, their groundspeed is around 420 kts. or faster.-John

>No--you still want to increase parasitic drag. 230-260 IAS>is high airspeed--many bizjets cruise in this range at>altitude. Although their indicated airspeed may be 250 Kts at>FL350, their groundspeed is around 420 kts. or faster.>>-JohnThanks John,So what speed do we talk about when it comes to the induced drag,..around 100 IAS or..?http://www.scandicair.com/images/Banner_ariane_4.jpg

I would imagine the speed is determined by a number of factors and depends on the performance envelope of the aircraft involved. Both types of drag are always there--one increases as speed decreases (induced drag) and one increases as speed increases (parasitic drag). I've played with the induced_drag scalar and find its effect is much more subtle than parasitic drag. As I noted earlier though, the engine is generating some thrust even at idle, and some .air files have it a bit exaggerated. If you are having trouble keeping the speed down during descent, just for test purposes simulate a total engine failure. See how much an impact idle thrust is having on speed.-John

A further expansion is that the constant K can be regarded as equivalent to K1/A where A is the aspect ratio of the wing. Aspect ratio can be calculated as l*l/S where l is the wingspan and S is the wing area. The higher the aspect ratio the lower the induced drag, which is why sailplanes have high aspect ratio wings.