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Ranges of Values of FG Properties?

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Ranges of Values of FG Properties?

Postby ScottBouch » Wed Jul 05, 2017 9:25 pm

Hi all,

I've had success with passing data to flightgear, and found that the aileron and elevator expect a value between -1 and 1, and the throttle between 0 and 1. I have found this more by experimenting by trial and error, rather than actually finding out the required ranges documented anywhere....

The Docs/README.properties file lists some great properties to interact with, and gives the data type, but frustratingly, not the ranges.

Is there any way of examining the actual property tree to see the ranges of the properties values within Flightgear?

I'm now trying to read data via serial by an Arduino to operate some real cockpit indicators. First one I'm starting with is a Desynn type flap position indicator from a Hawker Hunter. I've written the code to successfully operate it by the Arduino, and documented how it works here: http://www.scottbouch.com/aircraft-cock ... ation.html

So far with the Hunter flap position indicator I can manually send it numbers from the serial monitor of Arduino IDE to move the pointer, and it works nicely.

Once I've learnt the ranges of the data coming from flightgear, I'll then try to sort out some sort of method in the Arduino of making sense of it and driving the indicator.

Cheers, Scott.
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Re: Ranges of Values of FG Properties?

Postby ScottBouch » Wed Jul 05, 2017 9:33 pm

is my best place to look the http: view of the proprties of the aircraft being flown?

for example from http://localhost:5500/engines/engine:
Code: Select all
oil-pressure-psi (22.76004474)
oil-temperature-degf (65.43373385)
rpm (601.6347858)
running (true)
starter (false)
thrust_lb (24.79041829)


These are real world engineering values. Are these the values I'd expect out of the serial port using the xml <output> properties?... or is there a factor and offset involved to generate these real-world values from whatever is in the property tree?

I can't think of an easy way to view the serial data from the serial port, as I could get the Arduino to read it, and print it back to the port and read with the Arduino serial monitor, but I don't think you can have two pieces of software using the serial port at the same time? or can you??

Cheers, Scott.
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Re: Ranges of Values of FG Properties?

Postby ScottBouch » Wed Jul 05, 2017 11:09 pm

Managed to figure it out a bit... seems that the Debug menu allows you to view internal propitiates, and it seems as though what can reasonably be put in real world engineering units are (such as RPM), but some are not, such as surface positions.

However, by viewing this box, you get to see how the figures change form min to max by using the game.

So I think I've found a workaround for my own question, so it's kind of answered, unless someone can show me where the Min and Max values are kept?

Cheers, Scott.
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Re: Ranges of Values of FG Properties?

Postby Thorsten » Thu Jul 06, 2017 5:58 am

So I think I've found a workaround for my own question, so it's kind of answered, unless someone can show me where the Min and Max values are kept?


Inside the tags that generate them in the aerodynamics/systems definition files, and it's really up to the aircraft developer to decide what values and ranges are meaningful.

Sorry, for your purposes that's probably not useful, but that's how it is - there's no guarantee that a throttle property is the value that's actually used later by the plane.
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Re: Ranges of Values of FG Properties?

Postby ScottBouch » Thu Jul 06, 2017 7:02 am

Ah, right... thank you... You've actually answered a broader question I had too.. whether you can build generic "one size fits all" hardware, or if it has to be configured on an aircraft-by-aircraft basis.. clearly the latter.
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