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What I'm doing:

While I participate very marginally in flightgear-devel, I'm ramping up my C++11 skills, learning more about git, getting to know a few editors, IDEs, Build and Debugging tools.  I hope to eventually be able 24-7 to build and effectively debug flightgear on any operating system, and to be able to support anyone else wishing to do so.

At the same time, I'm trying to form a coherent view of Flightgear's structure as an application.  Not as a user, but as a developer.  This involves gaining knowledge of the various subsystems that make up flightgear, the underlying technologies each subsystem uses and the flow of control and data  between these subsystems.

The techniques are the same as any other developer faced with a new 'job' with unfamiliar tools, a new programming language, and a new social environment. Select some tools from among those used by others on the project. Learn the ins and outs of those tools. Get a look at every menu item, configuration item, dialog or other interface and get a good sense of how that fits with the tasks of a developer. Find a small problem to examine and perhaps solve, get some advice, try different approaches, ask about the approaches used by others. Learn or deepen your knowledge of the prevailing coding language or languages. Study the way people on the project behave. Find out what's important, Find out what's not. Try to understand where the group is headed and how they think they'll get there.

Technically, dig in to the code to learn how it is built, debugged and run. Know about all the configuration items. Find all the big pieces in its hierarchy of objects. Some of them are important to know well. Others it is important to know of their existence. Some you can just be marginally aware of. Any that deal with subsystems, creating visual elements, communication between subsystems or keeping things running correctly from cycle to cycle are important. Fine details can wait till later.

Git Workflow

Callahanp - Flightgear From Scratch

Callahanp - Flightgear Technical Manual

Flightgear and Simgear Code

Callahanp - Flightgear Working Groups

C172P Team on Github


PID Autopilot PID Controller Tuning Resources

Development Operations

I am making an effort to define and give detailed examples of development file and repository operations for various parts of Flightgear Code and Data including all SourceForge Git repositories, Scenery, Aircraft, Aircraft Hangars, Airport Data. Add-Ons and anything else that can be used with Flightgear. This will include items that fall under the FlightGear SourceForge project, and other projects that do not.

This Page will be organized not around specific kinds of development, but around the development operations common to all of them. Operations include obtaining source materials, preparatory steps, ongoing operational readiness tasks, building, modifying, debugging, testing, and submitting changes. I'll explain further and give examples of the individual operations needed to accomplish these tasks for all types of FlightGear material, whether source code or data, regardless of the type of file or where it's upstream repository resides.

When finished, this guide is intended to be comprehensive up to a point. If you participate in the development of anything used with or within flightgear, with few exceptions, you'll be able to find information on specific commands and procedures needed to complete the listed operational tasks. We'll leave to other pages, specifics of the internals of working on files of different types, and the kinds of edits and additions that should be made within a file. and focus on the environments that support the actual work to be done and on the resulting files, giving their types, and generally describing contents, without going into details.

The page is currently under rapid development, with attention focused currently on correctly obtaining source materials for C & C++ programming of the main application. Where expansion is needed to cover other types of materials, we'll add a note soliciting your input on what should be said.

Here are a few examples of the Operations of each type:

Operation Category Examples
Preparatory Steps
  • installing pre-requisite software libraries needed for building flightgear, simgear and possibly plib or OpenSceneGraph
  • Collecting information about the exact current location for upstream source code and data
  • Establishing a SourceForge Account
  • Creating an SSH Key and readying it for use with Sourceforge
  • Understand where and to what extent each pre-requisite library is used withing flightgear and simgear
  • Understand all the basic steps needed to build a working flightgear installation using distribution versions of Plib and OpenSceneGraph
  • Understand the additional steps needed to build a working flightgear installation using locally built versions of Plib and OpenSceneGraph
  • Installing and Configuring IDE or Editing Software and extensions for use with CMake and for debugging
  • Establishing a build script that can be used with multiple branches or commits and which can build Release, RelWithDebInfo and Debug versions of executables
  • Ensuring that Ongoing Operational Readiness Tasks are well documented, understood and used as appropriate
  • Obtaining Source Materials
  • Cloning Flightgear Git Repositories Locally
  • Creating Personal Forks of Flightgear Repositories and cloning them locally
  • Ongoing Operational Readiness Tasks
  • Ensuring that when switching branches, that changes on the previously current branch are not lost
  • Ensuring that local clones used in a build are on the correct branch for the desired build
  • Establishing working branches for specific enhancements
  • Ensuring that sufficient testing has been performed before pushing changes upstream
  • Building Executing a script containing a series of CMake commands to build specific parts of flightgear
  • Executing a script or program that processes data in raw form to produce a different form of data directly usable by FlightGear (OSM data for example)
  • Modifying
  • Using an Editor or IDE to modify or add C++ Code
  • Using Blender, GIMP, or other graphical editing tool to do something for an aircraft
  • Adding a building to scenery
  • Debugging
  • Using the GDB debugger in command line mode
  • Using the GDB debugger in an IDE
  • Observing position and details of an aircraft, building or other object from multiple points of view in the Flightgear Application
  • Automated Testing
  • Writing, Executing or Debugging CPPUnit tests
  • Submitting changes
  • Doing a git push to a personal fork for a branch created for a specific set of changes
  • Creating a merge request for changes present on a personal fork.
  • Development Operation Targets

    Each of the operation categories listed above applies to a number of separate parts of the Flightgear Puzzle. A few of these parts together make up the basic application and are treated together. Others can be treated as if they were optional add-ons to the development process, even if the item itself is vital to the operation of the basic application.

    Target Executable Description Source Materials
    FlightGear This executable is the simulator. It can be built in several ways, Release, RelWithDebInfo and Debug possibly including optional features such as Compositor and OpenRTI. Three Sourceforge FlightGear Git Repositories:
    FlightGear CPPUnit Tests This executable is build separately and can be executed to run all of the CPPUnit based tests at once Two Sourceforge FlightGear Git Repositories. They're the same as are used for the main executable above.
    Resource Compiler
    Utilities There are several utility programs that are part of the flightgear build process
    • flightgear/FDM/JSBSim JSBsim_bin
    • flightgear/FDM/YASim yasim
    • flightgear/FDM/YASim yasim-proptest
    • flightgear/Input fgjs
    • flightgear/Input js_demo
    • flightgear/main metar
    • flightgear/utils/fgcom fgcom
    • flightgear/utils/fgelev fgelev
    • flightgear/utils/fgpanel fgpanel
    • flightgear/utils/fgtraffic fgtraffic
    • flightgear/utils/fgviewer fgviewer
    • flightgear/utils/GPSSmooth GPSSmooth MIDGsmooth & UGsmooth
    Build Systems There are several ways to build executable programs including but not limited building within an IDE, fg_from_scratch,, Jenkins servers and custom build scripts
    OpenRadar Example
    Flight Gear's Flight Manual It's called Get Start * getstart
    Scenery Example
    Multiplayer Map Example
    Navigation Data Example Example
    Airport Data Example Example
    Mac Launcher Example
    Open Street Maps (OSM) Example Example
    Open Scene Graph (OSG) Example Example
    Open Scene Graph - Earth (OSG-Earth) Example Example
    C172P Skyhawk The C172P-Team produces the C172P used in Flightgear as the default Aircraft. A copy of the Aircraft's files is included by the Flightgear project in the SourceForge FlightGear FGData repository See C172P-team Github Repository
    Add-On 1 Example Example
    Add-On 2 Example Example
    Add-On 3 Example Example
    Plib Example Example

    Obtaining Source Materials

    FlightGear related Source Materials may be hosted in a number of different services. Depending on the exact material, you may be working with files from the FlightGear Project on SourceForge, other SourceForge projects, projects from GitHub, GitLab or other SCM repository service. You may be dealing with data that originates in other Simulation Projects, or with code from supporting libraries such as Open Scene Graph.

    Quite a lot of the source materials for the flightgear application are maintained as repositories on SourceForge. Complete FlightGear SourceForge Repository List. Two of these Repositories are no longer used: FGCom and FGRun. These repositories are obsolete because their functional parts have been included within FlightGear.

    The rest are documented in the section above.

    Part 1 - Creating a Sourceforge Fork

    Part 1A - Create a Sourceforge Account, SSH Key and Verify that it works
      • Requires one personal sourceforge account
      • Requires an ssh login be setup
        • Create an SSH Key for use with Sourceforge
        • Update Sourceforge SSH Keys
        • Login to the shell with your key to make sure things are working right.
        • Logout from the shell - You won't be working there.
        • Login to Sourceforge on the web. You will be working with the web interface to sourceforge to create Forks.
    Part 1B - Create Sourceforge Forks for each Flightgear git repository you need to work in

    If you are not going to make changes to a particular repository, but only wish to do builds tracking next, you only need a clone of the official Flightgear on your local machine. You don't need to bother with creating a SourceForge Fork. You can have a mixture of local gits, some with multiple remote connections origin, upstream and possibly others, others only connected once to flightgear as origin.

    In order not to strain SourceForge resources, it's a good Idea to get rid of any forks that are not used for a while, certainly any that are not used at all for changes and experimental branches. This is especially true of resources that are large.

    Note that if you later decide to contribute to a new area, or to resume contributing, you will be able to create a fork and attach it to the local clone you previously created using the steps below.

    • Open
    • Log in to your sourceforge account by clicking the login button if you're logged out.
    • Hover over Me and select Profile with a right click and select open link in new window.

    If you don't see Git under personal tools in your profile page, it's because you've not set up any SourceForge Forks yet.

    Creating a Sourceforge fork is easy, Just go to the FlightGear Repo you wish to fork and click the fork button on the Left. It takes a few minutes and is pretty easy to figure out. You'll get to see the clone statement for the repo after refreshing the page after the fork is created.

    Part 2 - Create a local clone for each Sourceforge Fork

    If you already have clones of Flightgear git repos from Sourceforge, there's no need to re-do them as clones of your SourceForge Forks, they can easily be converted using the same steps you would use on a fresh clone of a personal fork.

      • create origin remote
      • create upstream remote
      • set upstream fetch to main flightgear repositories
      • create a branch for working on changes
      • checkout next
      • checkout a change branch
      • stash changes on a branch
      • push a change branch to your SourceForge fork
      • pull changes from next
      • got fetch


    Tools for a Flightgear Developer (see also Tools of the Trade)

    From Command Line to Holding Short

    From Command Line to Holding Short. A look at what gets called when you start Flightgear from the command line until you are on the runway. This is a work in progress, somewhat stalled after Eduard Auvergne's initial work on subsystems. It needs a re-vamp to make it current and publishable.

    • FlightGear Manual
    • fgdata/doc/img Look at each image in, noting the name of the image and what the image is trying to say
    • fgdata/doc/keyboard/map.pdf Note that key bindings can be specific to an aircraft. Note that the pdf was produced from a .tex file.
    • fgdata/Docs/model-combined.eff/README.model-combined.eff Read and not What's "rembrandt" - Key terms can be pulled from this document
    • fgdata/Serial/nmeafaq.txt Garmin - Key terms can be pulled from this document. This document describes a data protocol
    • AI_doc.html
    • FGShortRef.html
    • fgdata/Docs/fschool_0.0.3.pdf
    • fgdata/Docs/index.html
    • fgdata/Docs/model-howto.html
    • and lots of others - point is you have to read them all

    Once they're read, is there a way to organize them so the result is an overview?

    Sure there is. Just write a book:


    Working on Configurations for Visual Studio, Visual Studio Code, Atom, Eclipse and QTCreator IDEs and other tools for working with FlightGear Data.

    The day to day work of a FlightGear Developer will include the use of a variety of software to work on various kinds of FlightGear material. The material includes Source Code written in C and C++, Scripts written in Nasal, Build procedures using CMake and in scripting languages of 3 operating Systems, Data Files representing Airports, Runways, Taxiways, Airport Markings, Navigation Beacons, Instrument Landing System Transmitters, Taxiway and Runway Lighting, Buildings, Roadways,

    The workflow for all of these has a few basic steps.

    • Get copies of the original source material
    • Establish a fork repository for your changes to the materials
    • Make a local copy of the materials
    • Change the materials
    • Check the Validity of Changes
    • Deliver changed materials to your fork
    • Request that the changes be accepted and merged with the original source materials.

    The workflows differ based on the true owners of the originating material and the materials format.

    These are the basic tasks that a developer will need to complete

    • Setting up forks of FlightGear Git Archives
    • Identifying non-git Open Source Resources for use with Flightgear and establishing forks for them
    • Downloading appropriate tools for working on the kind of files that make up the FlightGear application and it's data
    • Configuring these tools and FlightGear itself to operate in one or more modes
    • Learning the steps to use inside and outside the tools

    Figuring out how to contribute to FlightGear

    Getting things done in Flightgear

    As part of my Cockpit Building efforts, I'm also working on


     Email Callahanp through the wiki

    I show up occasionally on discord, #flightgear on and am a member of several public forums related to cockpit building.

    Callahanp (talk) 09:45, 11 November 2017 (EST)

    The Howtos

    -- Oh yeah... those...

    I'm working on these along side building my cockpit. Some of the early attempts were not that useful. My current approach is to build and document actual hardware. I hope this will be more helpful.

    Current Projects: