adjusting drag
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Thread: adjusting drag

  1. #1
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    adjusting drag

    IS there a way to adjust the drag on an aircraft? The Challenger model tends to accelerate faster than real life in both takeoff as well as descents. I have been looking at the aircraft config and Im not really sure what Im looking at. Any help would be great. Is there a website that explains the variables?

    Thanks,
    Sean

  2. #2
    You have to make the changes in the airfile.

    You will need a program called Aircraft Airfile Manager V1.0 for FS9 and 2.2 for FSX

    Table 1101

    Section (INT 16_2)
    Cdo Drag Coefficient - Zero Lift
    Cd_df Drag Coefficient - Landing Gear
    Cdg Drag Coefficient - Spoiler

  3. #3
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    Thanks, Ill look for it.

    Sean

  4. #4
    A word of caution on editing airfiles

    Adjusting this normal affects this and that so that you have to adjust that to get the other this right.

    It's a rabbit hole sometimes.

    Ultimately all flight models are a compromise on reality. You have to choose which performance inaccuracies you can live with.

    Getting it 100% correct is not going to happen.

    If you start trying to perfect flight models it can take 100s of hours to get it where you want it.

  5. #5
    I found it. You can still get it here

    https://www.aero.sors.fr/fsairfile.html

  6. #6
    You can adjust the scalars in the .cfg file,
    Normally they are set at 1.0 , but you can increase or decrease the values .... however changing 1.0 to 2.0
    will change things by a factor of ten, so use 0.1 increments.

    Take a look at the fs9 'software developers kit' files , more commonly addressed as 'sdk' for the aircraft container manager.

    However, as Dave says it can be a rabbit hole; you adjust something, then something else is put out by that adjustment... so you adjust that... which takes you back to square one

    Ttfn

    Pete

  7. #7
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    If it is accelerating too much that indicates to me that there is too much horsepower, the program in the Herve Sors website 'AFSD' is good & is in effect a live parameter readout. If the propeller is too efficient at low speed it can also give too much acceleration, but that needs .air file adjustment. What I have yet to experiment with is drag of the propeller, i.e. there does not appear to be the ability to windmill the engine with sufficient friction to decelerate the aircraft with throttle fully closed. As noted by motormouse one can up the drag in the .cfg file, there is also one factor in the [propeller] heading that can affect take off power, & that is 'low_speed_theory_limit', the value normally entered is 80 feet per second, so try changing that & see if you get any appreciable effect.
    Good luck & happy experimenting
    Keith

  8. #8
    LOL and so starts the Rabbit hole.

    Keith is 100% right. It might not be a drag problem if you are looking for reality. It might be an engine that is Too Hot(piston or jet) or a propeller that is too efficient.

    I am not going to try to discourage you from trying to improve it. Before you do any poking at the airfile or aircraft config get the manuals for the plane and start doing some research. Find out all you can about its performance.

    Start with testing the engines in the model. Too hot try to tune it down. Too weak, tune it up. Note that some FDE developers choose to modify the drag on an aircraft rather than change engine power. Typically that would happen with a Piston engine not a jet.

    Tuning a propeller takes more talent and knowledge than I have. I have always used the default propeller tables and modified the airfile from there.

    Myself I leave all of the scalers set to 1 and do all of the work in the airfile.

    It is a lot of work but personally very rewarding to know you got it as right as you can.

  9. #9
    rabbit hole indeed, this kind of thing is what led me way down the development hole back in the days of FS98... it's frustrating sometimes but a lot of fun, especially the research part

    - dcc
    - -

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