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Roger Mazengarb

Fly! II data table format ........????

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G'day all,On looking at the *.wng file I see a table for " Drag Verses Angle of attack".I can only assume that the drag in question is TOTAL wing drag. I can't find any reference for Profile drag?I understand that the table data is in Format 1 which is A B notation and I understand that Fly! II interpolates in a linear fashion between one set of data to the next.My problem is the second line from the bottom where there are 4 entries on the line instead of the expected two. Is anyone able to tell me what the 4 entries on the second line from the bottom represent??? I've noticed that this in all "Drag verses angle of attack" tables but not in "lift verses angle of attack" tables.I see that the previous entry for that line has been stored for future reference in a rem at the start of the table. -- Drag vs AOA Data -- -- begin table object -- - data in format 1 0.35 0.03 0.0 4.046 -1.58 7.0 -1.0 2.5 -0.7 0.5 -0.35 0.2 0.35 0.035 0.0 4.046 WHY ARE THERE 4 ENTRIES HERE?? 1.58 0.06 - end formatCheers,Roger

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Roger,My bet is that it's using a curve from .35 to 1.58, the curve is defined by the equation y = 0.035 x

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G'day Alex,Thanks for replying. I'm sorry but I just can't see what you are getting at. I'll keep studying it and maybe the penny will drop. :-) Where did you get the equation from??Could you reword your reply please Alex. Maybe that might help me if you say the same thing differently..If you take the first pair of values in the table-1.58 and 7.0how do they fit into the equation?If I know what they represent then I'll know what I'm changing if I alter one of those values.I thought that this being a Drag V Angle of attack table that one of the values should be for angle of attack and one for a drag coefficient.?? What equation they are using is beyond me. I know the total drag curve sits in between the profile drag curve and the Induced drag curve.Thanks for your patienceCheers,Roger edit: My spelling is no better than my maths! :-lol

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Roger,Let me try again... ;-)The Table 1 format is made up of the following:- The first entry (in each line) is the value of x, in this case the Angle of Attack- The second entry, and beyond are the coefficients of a polynomial equation such as y = a + bx + cx

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G'day Alex,Aha thank you mate Your previous post is so good that it really should be uploaded to Fly!wikki for future referrence by anyone needing help with data tables in Fly! It's an extremely well written explanation of Data table format 1.Just a small question. The angle of attack values are obviously not in degrees so I assume they are in radians..35 radians = 20 degrees (approx)1.58 radians = 90 degrees (approx)But if that's the case then this table is describing the angle of attack/drag relationship OUTSIDE the flight envelope of the aircraft.?The example table is for the tailplane (stabilizer).What's going on Between +0.35 and -0.35 (aircraft flight envelope)Or is angle of attack expressed in some other units??BTW Does Fly! II use a right or left hand co-ordinate system?Which of the above two values is a normal positive angle of attack.? Cheers,Roger

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Roger,Do you have the Fly!2K Notes? Even though it was written for Fly!2K, it is still useful and in many cases applicable to Fly!2.In the Wings.doc document, under "The AeroCenter Manager Entry" section, title "The Airfoil Object", subtitle "", entry "", it specifies the kind of variable expected and it is as follows:" (AeroCf, rad, nd)[ul]The Drag Coefficient Entry is an AeroCf Object where the independent variable is the Angle of Attack (AOA) of the airfoil. The dependent variable is the Drag Coefficient of the airfoil."[/ul] This answers your question about whether it is degrees or radians.As far as the AeroCf, the document says this:"The AeroCf ObjectThe AeroCf Object can store a value as a Gain, a Polynomial or a Table. Since the AeroCf represents only one single variable equation, only the last storage method specified of the three is actually used.Note: Fly! SVH files contain AeroCf Objects with multiple methods specified but only the last method is actually used. (float)[ul]The First Coefficient is used to set the gain or a value multiplied by the input to calculate the output.[/ul] (Polynomial)[ul]The First Polynomial is used to specify the storage of the data as a polynomial.[/ul] (Table)[ul]The First Table is used to specify the storage of the data as a Table."[/ul]More on tables..."TableThe Table Object provides the ability to create piecewise continuous single variable equations that may be defined as a set of points or a set of polynomials. The mechanics of the Table requires an Input Value that is used to Lookup the two Data Pairs that are closest to the Input Value. The first element of the Data Pair is used for the "best match" and is known as the Break Point (BP). Once the two adjacent Data Pairs are found, an interpolation routine determines the returned value based on the parametric distance of the Input Value to the two break points.If the Input Value is less than the First BP, then the Dependent data is evaluated for the first BP. If the Input Value is greater than the Last BP, then the Dependent Data is evaluated for the Last BP.The Tags[ul]The End of Format Tag must terminate a set of data.[/ul][ul]The Format 1 Tag is used so you may specify the data as a set of (X,Y) pairs. Where X is the Break Point and Y is the Dependent Variable. A Pair is specified per line and the set must be terminated with the End of Format Tag.[/ul][ul]The Format 3 Tag is used so you may specify the data as a set of (X,P) Pairs. Where X is the Break Point and P is the Dependent Polynomial.[/ul]Example Table -- Tag Specific to Use --[ul] 1 1 2 2 3 3 [/ul]"Please note that my previous explanation is about the type.Lastly, regarding the coordinate system, here's what the "Basic Object Types.doc" document (also part of the Fly!2K Notes) says:"Parsed ObjectsThe complex objects of the Fly! Code Base are created from relatively simple objects. The Parser has the ability to read these objects without the need for using the Object Tags. These objects have no optional data elements and must be completely defined in order to be used properly.Integer 12Float 12.3Text Ralph MouthString skyhawkVector 45.2,53.3,765.6The Text and String use the same object but in some cases the required value can only consist of alphanumerics.The Vector is a collection of 3 Floats that represent the components of a parameter in 3 dimensions. The 3 components are labeled relative to the Axis they represent in 3D. The X,Y,Z components. Fly! uses Vectors for Linear and Angular (or Translational and Rotational) concepts, but the Axis system remains consistent.Fly! uses a Left-Handed Axis system, where the X axis is a lateral axis pointing to the right, the Y axis is the vertical axis pointing up, and the Z axis is the longitudinal axis point forward. If it where aligned with the Earth, it would be labeled East-Up-North.Since it

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Roger,As far as your question:"What's going on Between +0.35 and -0.35 (aircraft flight envelope)"The table is telling Fly! what to do: -- Drag vs AOA Data -- -- begin table object --[ul] - data in format 1 0.35 0.03 0.0 4.046[ul]-1.58 7.0-1.0 2.5-0.7 0.5-0.35 0.20.35 0.035 0.0 4.046 WHY ARE THERE 4 ENTRIES HERE??1.58 0.06 - end format[/ul][/ul]Starting at AOA -0.35 Drag will be 0.2, at 0.35 it will be 0.530635 (per the equation); Fly! will interpolate between -0.35 and 0.35. From 0.35 to 1.58 Fly! will follow the equation and interpolate it with the value at 1.58 (0.06).Regards,http://www.avsim.com/hangar/fly/dfdg/banneraa.jpg

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G'day Alex,Thanks for being so understanding and for all your help. The Fly! 2k notes are exactly what I need. I was unaware that they existed as I really didn't start "fiddling" until Fly! II was on the scene.They explain all about the structure and composition of the data tables - even to a dummy like me. :-)More stuff for the wikki if it's not already there.Now I've got some serious reading ahead of me :-)Cheers, and many thanks,Roger

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