Keep bumping against this one:

[Cees Donker]

Thanks for the tip about the program Milton. I found out what caused my last problem with the turning off of the engine. I didn't select a plane in the list of installed planes that functions as a 'dummy' during the exporting, i.e. the airfile and cfg are 'loaned' from that plane.

Cees

 

[sparks]

THE most important part at this point; is to get all of the 3-dimensional locations accurate.. CoG, wing_apex, wing area, control-surface location, size, and deflections.. pilot/passenger/baggage locations, fuel-tank size and location.. and of course contact points... doing this with AirWrench is redundant at best, as the cfg file has the last word.

For the most part I agree, but I'm not sure you understand what AirWrench does.

AirWrench is not really an air file editor, it's a flight dynamics compiler that considers the aircraft.cfg file and the AIR file a matched set. It was designed on the premise that aircraft.cfg files from FS2002 forward contain nearly every parameter necessary to compile a complete air file from scratch.

AirWrench reads every aircraft.cfg parameter you listed above (and more), displays them in a well organized set of tabs for editing, and writes everything back to the aircraft.cfg file along with a new AIR file calculated completely from scratch.

The feature list has grown over the years and sometimes the built-in sanity checks can be frustrating. But with experience, the results can be commercial quality.

 

[Cees Donker]

That's correct!
:salute:
Been doing the flight models of three planes, and I'm pleased with the results.



Cees

 

[Brett_Henderson]

For the most part I agree, but I'm not sure you understand what AirWrench does.

AirWrench is not really an air file editor, it's a flight dynamics compiler that considers the aircraft.cfg file and the AIR file a matched set. It was designed on the premise that aircraft.cfg files from FS2002 forward contain nearly every parameter necessary to compile a complete air file from scratch.

AirWrench reads every aircraft.cfg parameter you listed above (and more), displays them in a well organized set of tabs for editing, and writes everything back to the aircraft.cfg file along with a new AIR file calculated completely from scratch.

The feature list has grown over the years and sometimes the built-in sanity checks can be frustrating. But with experience, the results can be commercial quality.

Interesting.. I kinda wondered what it did, other than allow access to AIR file parameters that do not have CFG file entries. And CFG file editing can be a bit cumbersome by text-editor.. a good GUI (like even the old FSEdit that came with FS2002), helps, when building a new one from scratch (I still just use a text editor, though).

Now, as far as the tables and ratios in the AIR file go (like LIFT vs AoA, etc), does AirWrench literally fill the subtle differences between generic type ? (FSEdit would create a nice CFG file per all the parameters you choose, but the intricate stuff in the AIR file was decided by a short list of airframe types.. 2-engine GA, 4-engine Jet, 1-engine Prop, 2-engine Turboprop, etc). If so, does it REALLY take ALL cfg entries into account and generate completely unique tables and coefficients in the AIR file ? I'm a bit sceptical.. but will look into it.

And even if it does.. we're still working with the base, MSFS flight-model,, so for decently realistic performance across the entire envelope, you still have to fudge and compromise... ie.. an airplane that will use up a realistic amount of runway to get airborne across its entire load spectrum, will likely not have realistic performance per altitude and power settings,, especially level-flight cruise (virtually all models, even 'commercial' add-ons, fall horribly short of realistic in this arena). The only way to get there, is labor-intensive testing, using three load profiles (min/mid/max).. and then tinkering with a combo of; thrust, wing-efficiency, parasitic-drag, induced-drag settings... testing for climb-rates at the published Vy/Vx, and cruise-speeds per published altitude/power-settings.. and of course matching fuel-consumption at every point... all the while tweaking for realistic flap effects, too. What you end up with, are AIR and CFG files that hardly resemble what something like AirEd, or AirWrench would generate by raw, data-entry... especially when you add in the; load-station, empty CoG, control-surface apexes area and deflections tweaking needed for realistic pitch/roll/yaw.. ie.. coordinated turning, and lifting off the runway as opposed to launching.. and beeing able to realistically rollout and flare at landing, instead of having to choose between flying it to the pavement, or floating half-way down the runway (another area where even commercial add-ons often fail).

IOW.. to avoid ending up with a model that would leave a real pilot sayng, "there's no way a loaded Cessna 310 could get airborne that quickly", or, "there's no way it could maintain that climb-rate at this altitude", or, "this attitude, airspeed, and rate-of-decent isn't even close, for full-flaps"... etc, etc, etc... You're best off starting with an existing AIR file, most like the model you're working on .. AirWrench might warn you when you ask it to compile an set of files that don't even make sense, but getting anywhere near that point might leave you trying to tune a flight-model with a flawed enough foundation, that you'll NEVER get there..

You gotta get your hands dirty, and THEN go into the tables and such for fine-tuning. Ninety percent of what I do in the AIR file, involves things like drag for deployed gear, or gauge response (CHT, EGT, Oil temp/pressure), or minor table adjustments.

For the tedious, numerous edits of just a few parameters while building a good flight-model foundation.. in and out, in and out... it's easier to just open the CFG file with NotePad.

 

[bstolle]

That's interesting. For me it's exactly the opposite. I use as much RW values in the cfg file to start with and then I work only with the air file for the rest of the development.
Different behaviour e.g. at low and high angle of attack can't be changed in the cfg file.
In fact there's not a single important aerodynamic item that can be changed in the cfg, especially interactions e.g. between roll and yaw can't be controlled via the cfg file or the attitude and rotation rate during a spin.
I never use airwrench or any other fancy program which 'automatically' writes changes into the airfile as I need to know exactly what needs to be changed and where.
The cfg file just tones down or amplifies values set in the air file.

 

[Brett_Henderson]

I think your confusing one file for the other... and/or what each does.

In fact there's not a single important aerodynamic item that can be changed in the cfg, especially interactions e.g. between roll and yaw can't be controlled via the cfg file or the attitude and rotation rate during a spin.

Most every important factor IS in the CFG file... weight, CoG, thrust, control surface effect and location, Moments of inertia, wing area, etc etc etc..

And AoA effect (alpha) for pitch/roll/yaw can be manipulated in the CFG file too..

[flight_tuning]
cruise_lift_scalar = 1.0
parasite_drag_scalar = 1.2
induced_drag_scalar = 1.0
elevator_effectiveness = 0.56
aileron_effectiveness = 1.22
rudder_effectiveness = 1.0
pitch_stability = 2.0
roll_stability = 1.6
yaw_stability = 1.0
elevator_trim_effectiveness = 1.1
aileron_trim_effectiveness = 1.0
rudder_trim_effectiveness = 1.0
torque_on_roll =0.6
p_factor_on_yaw =0.5
hi_alpha_on_roll =3.0
hi_alpha_on_yaw =3.5
hi_alpha_on_pitch =4.0

And entries in the CFG matching AIR data don't tone/amplify the AIR file, they over-ride them completely.

I never use airwrench or any other fancy program which 'automatically' writes changes into the airfile as I need to know exactly what needs to be changed and where.

I don't think it's possible to edit an AIR file without a special editor.. if you open it with a text editor, it's cryptic jibberish.

 

[bstolle]

>Most every important factor IS in the CFG file... weight, CoG, thrust, control surface effect and location, Moments of inertia, wing area, etc etc etc..

Well that's not the 'aerodynamic' part I'm talking about.
As I mentioned before, that's where the easy non aerodynamic stuff like weight, dimensions etc...belongs to.
'Thrust' is a good example because the airfile actually determines the engine performance.
You can put the correct thrust value into cfg file and still the actual thrust can be 10 times too low or too high if set incorrect in the air file.
E.g. 'flight control effect' needs to be defined in the air file before you can make changes in the cfg.
If these are wrong in the airfile you can't use RW values in the cfg file.

>And AoA effect (alpha) for pitch/roll/yaw can be manipulated in the CFG file too..

Of course but it's the same as above. If you don't define the behaviour in the air file first or have put no effect at all into the airfile you can put high_alpha_on_yaw=1000 into the cfg file and nothing will change.
The value in the cfg file is only a multiplier!

>And entries in the CFG matching AIR data don't tone/amplify the AIR file, they over-ride them completely

If you don't screw up when programing the air file there's no need to change e.g. the elevator effectiveness from 1.0 to anything else.

>I don't think it's possible to edit an AIR file without a special editor.. if you open it with a text editor, it's cryptic jibberish

I said 'automatically' writes changes. Aired etc. just saves the changes you make.
Airwrench etc.. changes a lot of values you don't even know about that they have been changed automatically.
With that 'automatic way' it's almost impossible to make changes to just very specific areas of the flight dynamics

 

[Brett_Henderson]

Of course there's alway more than one way to skin a cat.. but you're still confused a bit, on the relationship between the files.

As I mentioned before, that's where the easy non aerodynamic stuff like weight, dimensions etc...belongs to.

All of the aerodynamic data is in the CFG file (and the AIR file too), not just weights and dimensions. Using the OP's airplane (single engine light tail-dragger), an un-touched AIR file from a Cub is just fine. You can set every, major paramter needed for a sound flight-model foundation in the CFG file. ..

'Thrust' is a good example because the airfile actually determines the engine performance. You can put the correct thrust value into cfg file and still the actual thrust can be 10 times too low or too high if set incorrect in the air file.

Not true.. If you're talking about about a thrust modifier for a piston airplane, it's part of the propeller data. Now, as for the engine performance, the thrust-point (engine location); number of cylinders and their displacement; Max RPM; Horse-power; prop size; prop MOI; prop pitch (pitch range if constant-speed), and a generic 'power' index (usually left set at 1.0) .. are all in the CFG file. Again, so long as the AIR file is of the proper type, the subtle tables and so-forth, in the AIR file, are just fine. All of the performance characteristics can be tuned in the CFG file, and if they're corresponding to entries in the AIR file, the AIR file entry will be ignored.

Now, since we used a single-engine piston AIR file, the table/curve data for things like, RPM vs Torque vs HP vs will be pretty darn close.. trying to get it exact at his point is fruitless, until you get a 'generic' engine (defined by cylinders/displacement/RPM/HP in the CFG file) functioning reasonably realistically (Manifold-pressure/thrust, per different power setting at different altitudes), you'll just be setting/moving the engine characteristic foundation, without a goal in mind.

Onto the airframe:

E.g. 'flight control effect' needs to be defined in the air file before you can make changes in the cfg.
If these are wrong in the airfile you can't use RW values in the cfg file.

Mostly untrue.. you have to have SOMEthing in the AIR file, but whatever it is that you put into the CFG file (per the next paragraph) does not modify the AIR file data, it over-rides it. Example: If you set wing efficiency in the AIR file, the CFG entry will not "build" from that, it will replace it.

The CFG file defines where the wings are centered, what the span is, what the area is, what the root-chord is, what the overall efficiency is (Oswald-factor), and what the dihedral is.... The CFG file determines where the empty CoG is... The CFG file sets the pitch/roll/yaw moments of inertia... The CFG file sets where the horizontal and vertical stabilizers are, what the area and deflections are for; ailerons/rudder/elevator... and of course all of the weight-station locations for occupants, baggage and fuel, so that the airplane's handling and performance correspond not only to the total load, but how it's loaded... and lastly, all of the contact points.

If you don't screw up when programing the air file there's no need to change e.g. the elevator effectiveness from 1.0 to anything else.

That's true, but redundant. The same can be said about the 'Airplane_Geometry' paragraph in the CFG file. If you set control surface; locations, areas, and deflections accurately; you can also leave their corresponding 'effectiveness' modifiers at 1.0


Let me sum this up, because this could become a book (and is well explained in the FSX SDK)... The MSFS flight-model looks first to the CFG file. If there's nothing there, it then looks to the AIR file, and if there's nothing there, it uses a generic default value. While testing and editing, all data in the CFG file, does not rely on an AIR file setting. Even if there is one, it's ignored.

Now.. if you have a bad parameter in the AIR file, and there's no available CFG entry, you CAN end up with some nonsensical results.. that's why you start with a comparible AIR file.. You can be certain that all that subtle stuff that would be near impossible to represent (and near impossible to start editing without opening a can-o-worms) in the CFG, file is already in place. There's no point in going into the AIR file, until you've gotten everthing darn close by CFG file editing. And even at that point, it can become counter-productive, because the MSFS flight-model aint that sophisticated, in the first place.

 

[bstolle]

the MSFS flight-model aint that sophisticated, in the first place.

That's the wrong assumption!

I don't know why you mentioned 'thrust' before, something normally associated with jet engines and now you suddenly mention a piston engine.

Point is that if you use the Cub airfile and change data in the cfg, the basic behaviour will be still similar to a Cub, just with a different top speed, or roll rate etc....

There's no way you can get a Cub to e.g. perform dutch roll by just modifying the cfg file.
Or make a plane spin that didn't spin before etc....

The MSFS flight model is acutally very sophisticated!
In the airfile you can control everything, from the way the plane enters a spin to it's rotation speed an spin attitude.(something an x-plane designer can only dream of)

Here's e.g. a quote from the SDK according r.g. the wing incidence in the cfg file:
"Note: this parameter is not used in the real-time aerodynamic calculations "

 

[Cees Donker]

Gentlemen!

I have this great idea! I've got three planes WIP that I want to behave as realistic as possible. No doubt about it that here are two people with a vast knowledge of this matter. What would you say: I'll pack up what I have until now and send it the two of you and we'll make this a joined effort? Off course you'll get mentioned in the readme! PM me your e-mail addy if you're interested. It is for FS9, btw.

:salute:

Cees

(I never used so many different smilies before.....)

 

[fliger747]

I haven't used Airwrench in a while and need to update my versio, which might be several years old.

However it does do a lot of .Air file calculations. There are the basic cfg type dimensional entries, and otheres that are performance goals. The calaculations try to bend these two together. The myriad of sliders do adjust the .Air file, for instance stabilities, flap and gear pitch values, stall behavior etc. The graphs showing derived performance curves are a good cross check and provide a lot of information.

If I have one beef with it, it would be a desireability to isolate individual parameters and not have the program go back and recalculate everything.

Cheers: T

 

[Brett_Henderson]

That's the wrong assumption!

I don't know why you mentioned 'thrust' before, something normally associated with jet engines and now you suddenly mention a piston engine.

Point is that if you use the Cub airfile and change data in the cfg, the basic behaviour will be still similar to a Cub, just with a different top speed, or roll rate etc....

There's no way you can get a Cub to e.g. perform dutch roll by just modifying the cfg file.
Or make a plane spin that didn't spin before etc....

The MSFS flight model is acutally very sophisticated!
In the airfile you can control everything, from the way the plane enters a spin to it's rotation speed an spin attitude.(something an x-plane designer can only dream of)

Here's e.g. a quote from the SDK according r.g. the wing incidence in the cfg file:
"Note: this parameter is not used in the real-time aerodynamic calculations "

Yes.. there are few entries in the CFG file that appear to be for "show".. I imagine that they were for paramaters that MSFS would eventually use, as the flight-modeled improved.. but that's just a guess. The incidence you mention WAS used in in FS2002, but mostly for visual effect.. ie.. changing the visual model's pitch ,, especially in level flight.. a TRUE incidence would have to account for the different drag coeficient for a fusealage at different attitudes.. this is some of under-sophistication I'm talking about.

Point is that if you use the Cub airfile and change data in the cfg, the basic behaviour will be still similar to a Cub, just with a different top speed, or roll rate etc....

Two, small, single-engine, piston powered tail-draggers are SUPPOSED to behave similarly. Different thrust (as in one of the four basic flight forces, regardless of engine-type).. different pitch/roll/yaw, different MOIs, different ratios twixt control surface impact, different arms (the physics type of arm) for those control surfaces, ARE what seperate them... and that is accomplished FIRST in the CFG file.. 'cause the same parameters are ignored int the AIR file.

Now of course, once you've got it to where a real pilot of that airplane could sim with it, and not point out blatant performance flaws, you can dive into the AIR file and start pin-pointing the intricate stuff, that cannot be accessed in the CFG file... Like tweaking points in a control surface effect table..or.. a Horse-power/RPM table. If you, "cart before the horse" data in the AIR file .. you're just moving your test bed, before even knowing what you're trying to accomplish. And even then, you're starting a tail-chase... fixing one subtle thing in an AIR file table for a specific, envelope scenario.. will likely through some other envelope scenario out of whack.. again referencing the lack of sophistication in the base, flight-model.

 

[sparks]

Gentlemen!

I have this great idea! I've got three planes WIP that I want to behave as realistic as possible. No doubt about it that here are two people with a vast knowledge of this matter. What would you say: I'll pack up what I have until now and send it the two of you and we'll make this a joined effort? Off course you'll get mentioned in the readme! PM me your e-mail addy if you're interested. It is for FS9, btw.

:salute:

Cees

(I never used so many different smilies before.....)

Be happy to run them thru AirWrench for you and post settings/results/observations. More likely than not, it will take longer to write up than to do the actual development work.

 

[Brett_Henderson]

Gentlemen!

I have this great idea! I've got three planes WIP that I want to behave as realistic as possible. No doubt about it that here are two people with a vast knowledge of this matter. What would you say: I'll pack up what I have until now and send it the two of you and we'll make this a joined effort? Off course you'll get mentioned in the readme! PM me your e-mail addy if you're interested. It is for FS9, btw.

:salute:

Cees

(I never used so many different smilies before.....)

That sounds like fun.. however, alas, I don't use FS9.. **there is much about it I miss**

If you're ever tuning an FSX model.. I'd be happy to take a stab at the flight-dynamics.. The list of freeware designers I've built flight models for, is long. And my own models (C177RG, C310, Bonanza P35) netted countless emails from real pilots of those airplanes, saying that I nailed it. I have many, real hours logged in all of those airplanes.. so that helped.

A problem that even commercial developers have, is that all too often, they substitute 'easier to fly', for 'realistic to fly'. I'm guilty of it to a point... If I distributed my models with the AIR/CFG that I use for myself... the average sim-only pilot would dump the model into the their recycle-bin, after one, virtual flight.. especially if the aren't using a Yoke-n-pedals.. you just can't fly a realistic sim model using a joystick's "fly by wire" feel, and no rudder pedals.. it's impossible to execute the subtle feathering of rudder/aileron/elevator with one hand.. all the while modulating the throttle, during a gusty, X-wind landing.

BTW.. here's an 8 page discussion on this forum.. about my Bonanza.. lotsa flight-dynamic discussion, and screen-shots too :mixedsmi:

http://www.sim-outhouse.com/sohforums/showthread.php?29325-New-Bonanza

 

[sparks]

I haven't used Airwrench in a while and need to update my versio, which might be several years old.

However it does do a lot of .Air file calculations. There are the basic cfg type dimensional entries, and otheres that are performance goals. The calaculations try to bend these two together. The myriad of sliders do adjust the .Air file, for instance stabilities, flap and gear pitch values, stall behavior etc. The graphs showing derived performance curves are a good cross check and provide a lot of information.

If I have one beef with it, it would be a desireability to isolate individual parameters and not have the program go back and recalculate everything.

Cheers: T

AirWrench updates have always been free. :mixedsmi:

The graphs showing derived performance curves are calculated using the same equations used to calculate the AIR file coefficients. The equations are just rearranged to solve for different variables. For the performance curves, the program solves for air speed, roll rate, climb rate, etc given known aircraft parameters and coefficients. The same equations are turned around to solve for AIR file coefficients given known physical parameters and specified performance characteristics.

There are too many interdependencies in the software design to turn the automatic calculations off to isolate individual parameters. Your talking about an entirely different back-burner project - AirWizEd

 

[bstolle]

fixing one subtle thing in an AIR file table for a specific, envelope scenario.. will likely through some other envelope scenario out of whack.. again referencing the lack of sophistication in the base, flight-model.

Of course it's a lot of work but if you know exactly what you are doing nothing will be out of whack.
Problem is that FSX doesn't always use RW values correctly and that is where the fun in flight dynamics design starts. There's for sure no 'lack of sophistication' in the flight model. Sometimes it just takes a rather long time to find out how somethings needs to be programmed to get realistic results in FS9 or FSX.
E.g. I can't remember anymore how long it took until we had the first planes capable of spinning in FS9.

@Cees
sorry, but no fs9 here either

 

[fliger747]

Jerry:

It is a great tool and I haven't gotten around to updating mostly as a "roundtuit" issue. Most of the air stuff I do these days is for other people....

Thanks for all of the help you have provided to many of us over the years, both in the matters of understanding and tools.

Regards: Tom