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Adjusting flight in aircraft.cfg?


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13 replies to this topic

#1 Inactive Member_Douglas K_***

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Posted 29 November 2005 - 07:54 AM

Thanks Ron, some more good info for future reference.>>>>Moving the CoL aft is similar to moving the CG forward. Which does tend to stabilize AC in pitch. Further, the real CoL and main LG locations are critical as far as realistic TO rotation goes. <<<

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#2 Inactive Member_Ron Freimuth_***

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Posted 28 November 2005 - 10:34 AM

>>>>>I really appreciate everyone's help and wish you all the>best in the upcoming festive season :)<<<<>No problem. Happy holidays to you too.>RF>>>Some postitive trim will be required for TO and lower>speeds, but that's appropriate.<<<<>>Depends on the plane. Some may require the trim to be neutral>or nearly so in the takeoff range, and be nose down for>cruise. By setting realistic Pitch Trim Range, Cm_dh, Cm_dt in my Jet Transports, I expect them to require TO trim as given in FM tables. Which depends some on GTOW and CG. Five degrees is typical for Jet Transports, in cruise it runs close to zero. > However, in MSFS, the trim is too sensitive, and>feedback is limited compared to a real airplane, so trimming>off the pressure is possible only to a limited degree and>prone to error. I think there are 1024 clicks of Pitch trim. Near half is wasted if it is set for 'Stab Trim', since the real AC Horiz Stab can typically only go 2 deg neg, 12 positive. In fact, some simple gauge code to make it impossible to set unrealistic negative trim is desirable. Generally, one click is enough for final climb or cruise trim. I watch a digital trim display in my Jet Test window so I can see just where it is. Light AC are just about as sensitive. If one reduced Cm_dt to reduce sensitivity, he wouldn't have enough trim for landing with fore/aft CG. Note the slope of TBL 478, Cm_alpha provides most of the opposing pitch moment to time and elevators. So, it has to be appropriate if (near) real values are used for Cm_dh, Cm_de, and Cm_dt. Jet transports generally have a Cm_alpha near 1.0. I think 0.87 for the 747, 1.5 for the 727. >I think that anything you can do to ease the>virtual pilot

#3 Inactive Member_Douglas K_***

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Posted 28 November 2005 - 07:35 AM

>>>>I really appreciate everyone's help and wish you all the best in the upcoming festive season :)<<<>>>Some postitive trim will be required for TO and lower speeds, but that's appropriate.<<<

#4 Inactive Member_Ron Freimuth_***

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Posted 27 November 2005 - 06:16 PM

>> Also, get my info at Herve' Sor's site on Aircraft.cfg,>etc.>> It tells what the different lines really do.>> Ron>Thanx Ron, I already grabbed that before you mentioned it :)>>Well, after reading your detailed instructions Douglas, I now>have a beautifully flying DHC-2 Beaver. I used the Steven>Grant version but had tried a couple others and they all>seemed to go nose down and head for the dirt. I don't know>why... my computer / joystick?? dunno. I modified the .air>file and now it just floats along with almost no trim>required. Getting the wing_apex_long right in aircraft.cfg is important. I always adjust REC 1101, 'Cmo (Trim Offset)' in the AIR file for near zero pitch trim in cruise. Some postitive trim will be required for TO and lower speeds, but that's appropriate.Ron

#5 Alky

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Posted 27 November 2005 - 05:03 PM

> Also, get my info at Herve' Sor's site on Aircraft.cfg, etc.> It tells what the different lines really do.>> Ron>Thanx Ron, I already grabbed that before you mentioned it :)Well, after reading your detailed instructions Douglas, I now have a beautifully flying DHC-2 Beaver. I used the Steven Grant version but had tried a couple others and they all seemed to go nose down and head for the dirt. I don't know why... my computer / joystick?? dunno. I modified the .air file and now it just floats along with almost no trim required.The other plane I had trouble with was the default FS9 C-182, I haven't tackled that one yet, but I'm sure the results will be excellent. I've not heard of anyone else complaing about these two aircraft for FS9 so I'm thinking it's something on my end hardware-wise.What this little excersise has done is made me more curious and wanting to learn more about the editing of the FD... thanx a lot guys!!I really appreciate everyone's help and wish you all the best in the upcoming festive season :)

#6 Inactive Member_Ron Freimuth_***

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Posted 26 November 2005 - 02:31 PM

>>See the link below for a website where this information, and>>utilities for editing are available.>>>>Douglas>>Thanx Douglas and Shad. I won't have time to look into this>till Sunday, but those are excellent links and suggestions :)>I really appreciate the response, thank you. I'll pop back>into this thread and let you know how it went :)> Also, get my info at Herve' Sor's site on Aircraft.cfg, etc. It tells what the different lines really do. Ron

#7 Alky

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Posted 26 November 2005 - 01:08 PM

>>>>> Is there anywhere one can find info on what some of>these things do when changed and how to change them?<<<<>>George,>>See the link below for a website where this information, and>utilities for editing are available.>>Douglas>Thanx Douglas and Shad. I won't have time to look into this till Sunday, but those are excellent links and suggestions :)I really appreciate the response, thank you. I'll pop back into this thread and let you know how it went :)

#8 Inactive Member_Douglas K_***

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Posted 26 November 2005 - 04:25 AM

>>>> Is there anywhere one can find info on what some of these things do when changed and how to change them?<<<>>>They both will go nose down as soon as you turn autopilot off and have trim at zero.<<<http://perso.wanadoo.../fsairfile.htmlMake sure you also download the latest Aired ini file, then place it in the Aired directory, overwriting the original.You can also use AAM, it

#9 Inactive Member_iholrf_***

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Posted 25 November 2005 - 08:21 PM

If you look at the aircraft config for the default aircraft you will see they are all commented with descriptions of what everything is. Its a good place to start.The other thing you will need to do is change the airfile as well as many of the entries within the aircraft.cfg do nothing.CheersShad

#10 Alky

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Posted 25 November 2005 - 04:23 PM

I'm not a modeler but I'd like to be able to adjust the flight characteristics in the aircraft.cfg. Some of the stuff in there is pretty cryptic. Is there anywhere one can find info on what some of these things do when changed and how to change them?I have a couple of planes that I'd like to adjust the flight attitude on. They both will go nose down as soon as you turn autopilot off and have trim at zero. In order to fly level you need to set trim to maximum up, I'm not a pilot but I don't think that's right. I've tried loading up the tail with baggage but that has no effect.I've searched most of the places I know looking for info on editing the flight dynamics in FS9 but am coming blank :(Any help would be appreciated. Thanx!

#11 Inactive Member_Ron Freimuth_***

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Posted 01 December 2005 - 09:40 AM

>I'm attempting to modify the performance of a particular>turbine engine aircraft whose fuel flow at cruise needs to be>120 g/ph and cruise speed at 248 kias. I've played with the>fuel scaler and can get it to fly at around 120 g/ph with some>extra throttle available, but my cruise speed is down around>180. In reading Ron's config info I'm gathering that the>parasite drag comes into play here also... is that correct? >I see these two entries in the aircraft.cfg.>>[flight_tuning]>parasite_drag_scalar =0.504>induced_drag_scalar =0.504>>Are thes the ones I need to adjust to pump up the cruise>speed, or is there somewhere else in the .air file?>- George - Hmm, those values are already set rather low. Maybe the AIR file has a really high REC 1101 'Cdo'. '35' is typical of clean jets, Maybe '45' at the most. If the wing is set correctly in aircraft.cfg and oswald_efficiency is about 0.80, then the induced drag should be pretty close with that induced_drag_scalar set to 1.00. Depending on the turbine, fuel_flow_scalar varies from about 1.15 (high efficiency) to 1.66 (JT8D vintage). Unless something else is drasically wrong with the AIR file, those values should give a reasonably close fuel flow. One 'something else' I can think of is TBL 430, Mach Drag. It has often been set too high. Values of '5' at Mach 0.8 (4 divisions to the right) and '20' at Mach 1.0 (5 right) are typical. One can also check the values of the above with AFSD. It accounts for those drag scalars, it might be good to set them both to 1.0 so AFSD displays the actual AIR file values. Ron

#12 Inactive Member_IanK_***

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Posted 01 December 2005 - 04:56 AM

That will increase the fuel consumption by 1/sqrt(0.504) but the cruise speed will stay the same. To change the cruise speed change the ratio of these two numbers or increase the engine thrust by the square of the needed speed increase ratio.Ian

#13 Alky

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Posted 30 November 2005 - 10:20 PM

You guys are getting pretty deep for this wannabe tinkerer :)I'm attempting to modify the performance of a particular turbine engine aircraft whose fuel flow at cruise needs to be 120 g/ph and cruise speed at 248 kias. I've played with the fuel scaler and can get it to fly at around 120 g/ph with some extra throttle available, but my cruise speed is down around 180. In reading Ron's config info I'm gathering that the parasite drag comes into play here also... is that correct? I see these two entries in the aircraft.cfg.[flight_tuning]parasite_drag_scalar =0.504induced_drag_scalar =0.504Are thes the ones I need to adjust to pump up the cruise speed, or is there somewhere else in the .air file?I've been trying to follow the posts here and do this on my own but not having a whole lot of success. In most any of these aircraft I've come across, it seems that if you can get the thing to fly level and have the right cruise speed and fuel flow, then for a casual virtual flyer like me, that pretty much covers any tweaking that would need to be done. Thanx for any help :)- George -http://members.shaw....y/FSEbanner.jpg

#14 Inactive Member_Ron Freimuth_***

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Posted 29 November 2005 - 02:59 PM

>Thanks Ron, some more good info for future reference. And, things I hope to implment.>>>>>Moving the CoL aft is similar to moving the CG forward.>Which does tend to stabilize AC in pitch. Further, the real>CoL and main LG locations are critical as far as realistic TO>rotation goes. <<<< Though, moving the CG forward can make an AC excessively stable in pitch. Which can also make it harder for a pitch controller to manage rapid pitch/VS changes.>That