Real Cessna 172

  • C172 has the following drawback: the device variometer shows the change in vertical speed almost immediately after the change in static pressure. The actual variometer in the Cessna cab shows this speed with a very noticeable delay in time.

    Aerofly has a static pressure channel and a vertical velocity channel, which receives changes from the first channel. How do you slow this down in a tmd file by analogy with the speed difference between OilTemperatureInput and EngineOilTemperature, where Speed = 0.5? The Speed command can only be used for the "needle" type, but not for the vertical speed.

  • The vertical speed indicator "speed" depends on the configuration of the system, there are faster and slower VSIs in the real world.

    Our vertical speed indicator is one of the faster ones but it still not that fast compared to other instruments I have seen IRL


    To delay the signal a bit more you can use this object:

    Code
    1. <[first_order_low_pass][TimeDelayed][]
    2. <[string8][Input][Value.Output]>
    3. <[float64][TimeConstant][1.0]>
    4. <[string8][Value][0.0]>
    5. >

    Adjust the time constant as needed.

  • I have a StaticPressure object. But -

    Code
    1. 16.68-tmmodelmanager: ERROR: object 'StaticPressure' not found
    2. tmfile_properties: WARNING: property 'StaticPressure' is not a member of type 'first_order_low_pass' hash=2961382885451930720.
    3. 16.68-tmmodelmanager: ERROR: object 'StaticPressure' not found
    4. 16.68-tmmodelmanager: ERROR: property 'StaticPressure.Output' not found
    5. 16.68-tmfile_properties: property |StaticPressure| not found in this context |first_order_low_pass|

    That's the initial code:

    Code
    1. // vertical speed
    2. <[vertical_speed_indicator][VerticalSpeedIndicator][]
    3. <[string8][StaticPressure][PitotTube.StaticPressure]>
    4. >
    5. <[output][VerticalSpeed][]
    6. <[string8][Input][VerticalSpeedIndicator.VerticalSpeed]>
    7. >

    That's the modified code:

    As an object for first_order_low_pass, I tried both PitotTube.StaticPressure and VerticalSpeedIndicator.VerticalSpeed - the result is the same.

    Question: What should be in first_order_low_pass as a Value?

  • Hi, Steeve.

    I was glad that I removed the error from the log by finding the right place to insert the first_order_low_pass object. This is the right place in the Cessna file:

    But there was nothing to be happy about anymore. I set TimeConstant values from 0.0001 to 1000.0, - and - I didn't get any reaction from the variometer needle. The speed of its movement was the same in all experiments. So I did not understand how this first_order_low_pass works. Now everything is reliable on Jan...

  • Hi


    I believe you "cured" your problem as you inserted into the graphics section, where I think it was ignored. Every time I use a first_order_low_pass it is in the dynamics section.


    Here is the original code for my Lynx NH gauge output ( engine core speed)


    Code
    1. <[linear][LeftEngineNH][]
    2. <[string8][Input][LeftHighPressureSpool.OutputRotationSpeed]>
    3. <[float64][Scaling][0.000257]>
    4. >
    5. <[output_free][LeftEngineNHOutput][]
    6. <[string8][Input][LeftEngineNH.Output]>
    7. >

    and here is the modified code to slow down the needle



    Note the change of names to keep the final output to the gauge the same.


    I have tried to alter the cessna but I get the same error as you, it doesn't like the static pressure value. I have to admit it was only a quick look ( gorgeous blonde waiting, just don't tell the other half ;)) so perhaps I missed something


    Guess it's over to Master Obi Jan


    Steve

  • Well you haven't actually hooked up the output to anything, that's why nothing changed.

    You need to grab the input either from the vsi or from the pitot pressure and then connect the output to that new logic chain.


    The correct code would be like this:

    or like this:



    Keep in mind, we also have an aerofly wiki where we describe a lot of tmd related things: https://www.aerofly.com/dokuwiki/doku.php/aircraft:tmd

    We haven't covered everything in there so if there are questions remaining just ask.

  • Hi Jan


    That was exactly what I tried prior to my post, both of your examples, and got the same error


    WARNING: property 'StaticPressure' is not a member of type 'first_order_low_pass


    It would appear the simulator doesn't want to play :(


    Steve

  • Wait, that error message doesn't make much sense... unless your missing a ] or > somewhere

    Are you sure you wrote .Output and not .StaticPressure?

  • Thank you, Jan, thank you, Steve.

    I wouldn't have any questions if all the dynamic objects were described in the Wiki in the same way as it was done, for example, in C++ libraries. The function call, the list of its parameters and the range of their values should be shown. I just now understood what the second parameter in the line "first_order_low_pass" means. And what does the "Value" parameter mean in the last line of this object. Now I'll try to write the code again, but I won't poke my nose like a blind little kitten.

  • I got what I wanted. My altimeter needle runs noticeably faster than the variometer needle. That's the code I did it with:

    Note that the string with zeroing of the Value parameter is commented on. I needed the static pressure not to slow down in any way, the altimeter had to work fast.

    And that was my last fix on the C172mod.tmd file. I made a few more editions in it, after which my Cessna in Aerofly began to fly almost the same way as the real one, which I had to pilot. She began to feel the full load of 3 passengers and fuel under the maximum permitted gross weight.

    Thank you for your help.

  • I just saw my mistake and did a good face-palm :D


    that line with the "StaticPressure" wasn't supposed to be there