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Organize your {Airplane Geometry} section

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[/p] FS2002 Application Note [/p] [/p]Organize your {Airplane Geometry} section [/p] [/p]The following is an example of a typical Airplane Geometry section that comes with a downloaded Sim model. This data was likely generated from running the Sim with an Aircraft.CFG file containing only a preamble such that it could be selected in the FS menus. The Aircraft.CFG file is then generated by FS2002 and the values are populated into each section based on the AIR and perhaps the MDL file. [/p] [/p] [/p]Sample {airplane_geometry} section:{airplane_geometry}wing_area=6470.000000wing_span=231.833333wing_root_chord=29.000000wing_dihedral=6.998291wing_incidence=0.000000wing_twist=-3.999023oswald_efficiency_factor=1.570486wing_winglets_flag=1wing_sweep=0.000000wing_pos_apex_lon=0.000000wing_pos_apex_vert=0.000000htail_area=1820.000000htail_span=73.166667htail_pos_lon=-102.500000htail_pos_vert=0.000000htail_incidence=0.000000htail_sweep=0.000000vtail_area=1350.000000vtail_span=41.892720vtail_sweep=0.000000vtail_pos_lon=-116.666667vtail_pos_vert=5.833333elevator_area=455.000000aileron_area=268.720000rudder_area=229.500000elevator_up_limit=32.501974elevator_down_limit=26.626481aileron_up_limit=19.480565aileron_down_limit=14.896903rudder_limit=23.491270elevator_trim_limit=19.480565spoiler_limit=59.988681spoilerons_available=1aileron_to_spoileron_gain=0.000000min_ailerons_for_spoilerons=0.000000min_flaps_for_spoilerons=0.000000 [/p] [/p] [/p]Reorganized {airplane_geometry} section{airplane_geometry}// data in ft. or sqft.wing_area = 6470.00wing_span = 231.83wing_root_chord = 29.00wing_pos_apex_lon = 0.00wing_pos_apex_vert = 0.00// data in deg.wing_sweep = 0.00wing_dihedral = 6.998wing_incidence = 0.00wing_twist = -3.999// wingoswald_efficiency_factor = 1.570486wing_winglets_flag = 1htail_area = 1820.0htail_span = 73.17htail_pos_lon = -102.5htail_pos_vert = 0.0htail_incidence = 0.0htail_sweep = 0.0vtail_area = 1350.00vtail_span = 41.89vtail_sweep = 0.0vtail_pos_lon = -116.67vtail_pos_vert = 5.83 [/p] [/p] [/p]SummarySome important observations clearly come out of this: * The wing efficiency cannot exceed 1.00 * The excessive wing_twist has been used to tune for pitch * The wing sweep is greater than 0.00 for jets [/p] [/p] [/p]What to doThe following is a standard procedure for configuring your model: * Define the correct empty and station load weights * Set wing efficiency in the range or 0.71 - 0.83 * Set wing incidence to 0.997 and wing twist to -1.050 * Enter the correct wing sweep angle (swept back from right angle) * Adjust cruise pitch (lift vector) fore-aft by changing apex_lon * Adjust (lift vector) magnitude by changing cruise_pitch_scalar * Run a number of test flights and tweak * Enjoy flying your Sim model [/p] [/p] [/p]Gregory Abbey - Edwinnengineering

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G'day EdwinnInteresting post - I have saved it and will consider it in detail later today. I have a "problem" aircraft -- the Junkers 52 . (see my recent posting in the Panel and Aircraft Design forum) It has excessive "roll back" - that is , It banks in either direction Ok , but when you want to go back to straight and level flight , it wants to go past the straight and level point and banks in the opposite direction!!Here is the relevant section in the Aircraft CFG file [airplane_geometry]wing_area=1189.4 wing_span=95.9 wing_root_chord=12.0 wing_dihedral=6.25 wing_incidence=0 wing_twist=5 oswald_efficiency_factor=0.7 wing_winglets_flag=0 wing_sweep=2.5 wing_pos_apex_lon=-2.2 wing_pos_apex_vert=1.0 htail_area=169.0 htail_span=32.8 htail_pos_lon=-35.9 htail_pos_vert=6.5 htail_incidence=0.0 htail_sweep=0.0 vtail_area=69.9 vtail_span=8.5 vtail_sweep=5.0 vtail_pos_lon=-39.4 vtail_pos_vert=8.5 elevator_area=57.85 aileron_area=25.25 rudder_area=43.0 elevator_up_limit=17.0 elevator_down_limit=15.5 aileron_up_limit=18.0 aileron_down_limit=18.0 rudder_limit=30.0 elevator_trim_limit=15.0 spoiler_limit=60spoilerons_available=0 aileron_to_spoileron_gain=0 min_ailerons_for_spoilerons=0 min_flaps_for_spoilerons=0 The first thing I notice are large numbers for the Dihedral and Wing twist.You said in your post >Some important observations clearly come out of this: >> * The wing efficiency cannot exceed 1.00 Do you mean by this that the Oswald Efficiency fact "should not" or "must not" exceed 1.00 . Not wishing to sound too pedantic , "cannot " is a much misused word ! :) In the case of the Junkers , it obviously "can" because it "has".regards Barry

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>>G'day Edwinn >>Interesting post - I have saved it and will consider it in >detail later today. I have a "problem" aircraft -- the >Junkers 52 . (see my recent posting in the Panel and >Aircraft Design forum) It has excessive "roll back" - that >is , It banks in either direction Ok , but when you want to >go back to straight and level flight , it wants to go past >the straight and level point and banks in the opposite >direction!! >>Here is the relevant section in the Aircraft CFG file >[airplane_geometry] >wing_area=1189.4 >wing_span=95.9 >wing_root_chord=12.0 >wing_dihedral=6.25 >wing_incidence=0 >wing_twist=5 >oswald_efficiency_factor=0.7 >wing_winglets_flag=0 >wing_sweep=2.5 >wing_pos_apex_lon=-2.2 >wing_pos_apex_vert=1.0 >>The first thing I notice are large numbers for the Dihedral >and Wing twist. >>You said in your post >>Some important observations clearly come out of this: >>>> * The wing efficiency cannot exceed 1.00 >> Do you mean by this that the Oswald Efficiency fact "should >not" or "must not" exceed 1.00 . Not wishing to sound too >pedantic , "cannot " is a much misused word ! :) In the case >of the Junkers , it obviously "can" because it "has". >>regards >>Barry Hi Barry..The OEF (wing efficiency) valid range is 0.0 - 1.0 and it looks like yours is 0.7 which is about right for that type of aircraft. The wing dihedral of 6.25 means the wings are in a V shape when looking from the front-view and level (12:00) and that also seems ok.. maybe a bit high!! The dihedral is so that when you `let go' of the stick.. the plane tends to come back to level flight.The Wing Twist has a PROBLEM however. It's saying at the wing root.. the angle is 0 (wing incidence) but the tips are twisted +5 deg!! YIKES!! This may be your problem. Set the Wing incidence to 0.997 and the twist to -1.000 which will give you a slight UP angle at the root with a twist just below `neutral' at the tip. If you have better geometry data.. use that instead. For this vintage plane.. you could set both incidence and twist to 0.00 like a `straight wing'.. but not with tips-up 5 deg.. { smile }Now the cruise pitch will be off because the mean lift vector used-to twist `back' (because of +5 twist). Compensate for this by increasing cruise_lift_scalar from 1.000 to 1.219 or similar.. experiment with it.Please reply and let us know if it FIXED the problem.Gregory Abbey - Edwinnengineering

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