Howto:Understand console output

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This document lists FlightGear errors, how to get rid of them and other console output. If FlightGear quits but does not give you any error, try increasing the Log Level.

Errors can appear in various locations, but the most common one is the console (a black window), which pops up when you run fgfs.exe.

Errors with known solutions

Aircraft uses deprecated node egt_degf. Please upgrade to egt-degf

The aircraft should be updated to make use of the renamed egt-degf property but it will still work as expected. You could contact the aircraft's author but he/she is probably already aware of this.

Airports/.... ... Done

This is not an error. The message lets us know that TerraSync is updating the $FG SCENERY/Airports directory.

bad/missing argument to <function()>:

This error indicates that an argument the function is either the wrong type or does not exist. It is accompanied by a line showing the location. For instance, executing the below snippet in the Nasal Console will throw the error blow the snippet.

var hash = {
 element: "value"
append(hash, "string", 12, 5.67); # you can only append() to a vector
bad/missing argument to append():
 at <nasal-console/#1>, line 4

Bad operation output detected in configuration file

JSBSim reports that a <output> tag is incorrectly placed in the aircraft's FDM. When used in a <fcs_function>, it should be outside the innter <function> tags, so like:

	<fcs_function name="Flap Cmd Deg">

Base package check failed ... Found version ... at: ...
Please upgrade to version:

When using Git, the data must match the binary or compilation. You cannot use data from a different date than the binary's release date.

Base package check failed ... Found version [none] at: ...
Please upgrade to version:

FlightGear was unable to find the $FG ROOT directory. Set it using the --fg-root= commandline option.

Cannot find specified aircraft

Shows up when you use an incorrect aircraft name in the --aircraft=... command. Check the correct name by running --show-aircraft, or by looking at the aircraft's -set.xml file (eg. --aircraft=737-300 for 737-300-set.xml).

condition: comparison without property[1] or value

A condition (like <less-than> or <equals>) exists, without either:

  • a property to check
  • a value to check the property against

Could not find at least one of the following objects for animation:

This means that FlightGear is unable to find an object in a .ac file. Check the .xml file (where the animation is stored) to see if the object-names match those in the .ac file. Also in the .xml file make sure that there are not spaces at the beginning or end of the object name. If you are not the aircraft's author you can safely ignore such warnings.

creating 3D noise texture... DONE

Tells you that a new noise texture is created. It is not an error and can be ignored.

Error: [Screen #0] GraphicsWindowWin32::setPixelFormat() - No matching pixel format found based on traits specified=

Try changing the BPP value of your FlightGear setup. If that does not work, your graphics card is probably not able to run FlightGear 1.9 and higher. Another graphics card, or an older FlightGear version will likely "fix" the problem.

Error: bind() failed in make_server_socket()

When using multiplayer or socket input, this usually means you specified an invalid ip address or the port is in use. Note: for multiplayer, you don't need to use the --multiplay=in,... option at all, FlightGear (since version 1.0) figures out the proper setting automatically. Only use when you know what you are doing.

Error Building Technique: findAttr: could not find attribute bool

Make sure that your data and source (or binary) match. They must be from the same date, to provide the best performance.

Error: connect() failed in make_client_socket()
SG_IO_OUT socket creation failed

Your computer is not connected with the internet, while a certain enabled feature (eg. multiplayer) does require an internet connection.

Error: RenderTexture requires the following unsupported OpenGL extensions...

Your graphics card doesn't support some graphics feature that FG requires. Update your drivers, change the BPP value and/or try disabling some of the visual goodies like 3D Clouds.

Failed to find .... in apt.dat.gz

You need to edit ATC/default.tower and ATC/default.atis. You can open these files with any text editor. Either remove or fix the entries containing your airports ICAO code (like KSFO).

Failed to locate aircraft carrier = ...

FlightGear is unable to find a carrier under the set name. Check your commandline (--carrier=...) or the airport page of the launcher. Note that you might need to enable a scenario in combination with a --carrier= command.

Hint Make sure your park position and carrier name is correct. See the wiki's carrier page for details.

Failed to open file ...

Check if the file exists on your system. If the missing file is a scenery object; be sure you have the latest Shared Models from the FlightGear Scenery Database.

Fatal error: illegal character after . or ..

Some .xml file contains a fault. Possible solutions:

  • To refer to a top-level property in the tree, ../ should be used instead of .../

Fatal error: mismatched tag ...

In some .xml file, an opening tag (like <sim>) does not match its closing tag (like </sim>). This error is hard to track down, best method is to comment (place code between <!-- and -->) most of the aircraft. Then uncomment code one by one, until the error appears again.

Hint for Developers: Pre-test all your .xml files in Windows by opening them with Internet Explorer (usually by double clicking). IE can tell you if a tag is mis-matched and which tag is mis-matched. You'll probably know there's a problem if IE displays an error message.

Fatal error: name must begin with alpha or '_'

This error comes up when a property should be formed of which the name does not start with a letter of the alphabet or _. If this error only happens with certain planes, contact their authors.

Failed to tie property fcs/ to object methods

This JSBSim error comes up when there are unnamed components (eg. switches) in the FDM of an aircraft. Components must have unique names, from which properties will be created. As long as you are not overwriting an existing property, the name="..." can be used to output the components result to a property.

Fatal error: unclosed token

A token (<!-- -->) has been started, but not closes. Add --> at the correct line.

Hint for Developers: Pre-test all your .xml files in Windows by opening them with Internet Explorer (usually by double clicking). IE can tell you if a comment/token is not closed.

FGMultiplayerMgr::Open - Failed to bind receive socket

This means FlightGear was unable to open the listening network socket required by the --multiplay=in option. Frequently this option can be omitted and FlightGear will figure out the necessary parameters automatically. Common reasons are:

  • Address given in the option does not resolve to one of the IP addresses of the local machine. This parameter should only be required if you want to fine-tune the network behavior. Omitting it directs FlightGear to listen on all local interfaces automatically. Example:

Notice that you still need the comma.

  • The UDP port given in the option (or the default port 5000 if no option given) is already in use. Verify nothing is using the port.

FGMultiplayMgr::MP_ProcessData: No such file or directory

This is telling you that there's someone online on the multiplayerserver, using a plane that you do not have installed on your own system. In order to remove the error (and see the other plane) you have to install the plane that the other pilot is using.

FGMultiplayMgr - No receiver port, Multiplayermode disabled

FlightGear multiplayer has not been set.

FGPropertyManager::GetNode() No node found for ...
In component: ... unknown property ... referenced. Aborting

FlightGear found a reference in the FDM to a non-existing property.

FGPropertyManager::GetNode() No node found for ...
The property ... is undefined.

FlightGear found a reference in the FDM to a non-existing property. Keep in mind that JSBSim reads the FDM from top to bottom. Properties should always be created before they are needed somewhere.

Fgtzfile_read(): : Invalid argument
Fatal error: Timezone reading failed

This one is caused by wrong line ending in a timezone file. Solution might be to download the Timezone/ file manually from flightgear/fgdata/next/Timezone/ (Right mouseclick > Save target as) and overwrite the file in $FG ROOT/Timezone/ with it.

Found unexpected subsystem: system exiting. JSBSim failed to load aircraft and/or engine model

You are probably trying to run an aircraft on a out-of-date version of FlightGear. The planes on the official download page are intended to be used with the latest version of FlightGear. Usage on any older systems may not work.

freeglut (fgfs): Unable to create direct context rendering for window 'FlightGear'
This may hurt performance

This reports that you do not have proper hardware accelerated 3D (direct rendering) configured.

Gate ... doesn't seem to have routes associated with it

A startup location in the groundnetwork is not (properly) connected to a taxi route. Contact the airport author, or import the network to TaxiDraw and run the Verify network command to find the corrupted gate.

glLinkProgram "" Failed

Update your drivers; they have to support atleast OpenGL 2.0 for FlightGear 2.0 and later.

loading scenario '...'

This is not an error. It shows that an AI scenario is loaded.

Model not found: ...

This one tells you that FlightGear was unable to find a certain file. The nice thing is that it also tells you excactly what file.

  1. Check if the file really does not exist at your computer.
  2. Try to locate the file in which the missing file is referenced. This is likely to be -set.xml in the root directory of the loaded aircraft. Between the <model> tags, the base model file is referenced. This file references to all other models that are displayed with the aircraft.
  3. Contact the aircraft author with a detailed bug-report, in which you state the excact location of the missing file and (if you found it) the file in which it is referenced.

Multiplayer packet truncated

2016.1.2: messages that start with "Multiplayer packet truncated" need to be fixed by the model developer, usually by reducing the sie of transmitted strings. Remember that strings take 4bytes per character and therefore should be used sparingly to reduce packet size.[1]

Nasal runtime error: nil used in numeric context

This error is Nasal triggered by a Nasal file (the console should show what file (and line) and from where it was referenced). The Nasal script tried to do something with a property with an empty value. A solution is to fill the property before the Nasal is loaded. This can be done by setting the property in an aircraft's -set.xml file or by adding a listener to the script.

Contact the developers if this error is shown for a $FG ROOT/Nasal/ script.

NavCache: init failed:Sqlite error:Sqlite API abuse (attempt 0)

If you are using non-English characters, your $FG_HOME path may need to be temporally changed:

  1. Create a new empty folder such as C:\temp. Don't include non-English strings in the path.
  2. At the last page of the Flightgear launcher (FGRun), click the [Advanced...] button, select Environment, click [New] button, enter FG_HOME=c:\temp in the field and click [OK].

Near camera not rendering

Near camera off.png

If you screen looks like the image above; make sure you have at least OSG version 2.7.6.

No render bin name specified in render bin section

Update SimGear (or binary) and your data directory.

No render bin number specified in render bin section

Update SimGear (or binary) and your data directory.

... not a valid win32 application

This Windows error could have various reasons to pop up. Usually, the file that is causing troubles is mentioned. Re-installing this file might solve the problem.

OBJECT_SIGN: unexpected } in sign contents

One of the OBJECT_SIGN lines in the .stg file (of the tile that was loaded when this error showed up) contains a fault. Note that } must be preceded by a { character.

OBJECT_SIGN: unsupported glyph `.'

Check the OBJECT_SIGN lines in the .stg file of the tile that was loaded when this error showed up.

OpenAL error <AL_INVALID_VALUE>: bind source <alGenSources>
Failed to generate audio source.

This error is probably displayed because of some misdirected audio settings in the aircrafts setup. Check the -sound.xml file of the aircraft and see if all files refered to really exist. If not, try to contact the author of the plane, so he can fix the problem in the Git version or solve the problem yourself and let someone commit the patch.

OpenAL error (AL_INVALID_VALUE): constructor (alBufferData)
Fatal error: Failed to buffer data.

Disabling sound is a temporarily solution for this problem.

osgDB ac3d reader: could not find texture...

See Failed to open file ...

osgDB ac3d reader: detected surface with less than 3 vertices!

In one of the loaded models a non-existing surface is found. This can be a single line (sometimes used to simulate thin wires) or a fault in the model.

Program's vertex attrib binding ..., usrAttr...

Tells you that an effect binded certain attributes to a shader.


(Q)NAN stands for (Quiet) Not A Number, produced by 0/0 or other floating point break downs. There can be various causes for this:

  • Using a "flap start" value of 0 in the YASim FDM. Use some small value like 0.001 instead.

Scaling image...

This means a texture, whether in the scenery on your aircraft or anyone elses (when multiplayer is enabled), is not sized to powers of two. All textures in FlightGear have to be sized to power of two (eg. 16*16, 32*64, 32*1024). As of version 1.9 textures are resized automaticly, but it does slow your computer down, so it's better to resize the noted textures.

ssgInit called without a valid OpenGL context

In short, your GL libraries are broken. So far only Red Hat 7.x users have experienced this (see The only solutions are possibly complicated ones: you can either change distributions (most of us prefer Debian) or upgrade/downgrade your Mesa libs.

The system cannot find the file specified

  • If you are running Windows Vista; start by looking in C:\Users\Owner\AppData\Local\VirtualStore and seeing if you have a folder called FlightGear in there. If you do, cut-and-paste (merge) that one with C:\Program Files\Flightgear and try to launch FlightGear again.

    Hint: you may need to go under Tools and Folder Options to specify "Show Hidden/System Files and Folders" in order for AppData to be visible.
  • Make sure you did set the right executable (fgfs.exe) on the first page of the FlightGear Launch Control.

Time zone reading failed

This is probably caused by a line-ending problem in the timezone files. Win32 users can resolve the problem by downloading a DOS to UNIX conversion utility available at Run as `d2u *.tab` from within the timezone directory to fix your timezone files

Traffic manager could not find airport

There is either an airport missing from apt.dat, or there is a wrong ICAO code in a traffic file. An airport missing from apt.dat could be due to a recent opening.

Unable to choose requested pixel format

Error should be solved as of version 1.9. If not, try changing your BPP and/or resolution.

Unable to find airport details for .... in FGTower::Init()

This error can be surpressed by disabling AI Traffic, via the AI/ATC menu.

The error appears when an airport in $FG ROOT/Airports/apt.dat.gz cannot be found in $FG ROOT/ATC/default.tower and $FG ROOT/ATC/default.atis. Renaming the airports in the apt.dat.gz file ór in both default ATC files will fix the problem.

Unable to open aircraft directory

The aircraft that you are trying to run most likely relies on another aircraft, which you did not install (yet). The error shows what aircraft, so go download that one!

Unexpected tag '...' found in YASim aircraft description

FlightGear found a non-existing tag in the FDM of the aircraft you are trying to launch. If you have not changed the original aircraft, contact the aircraft author. Else, check the FDM througly for mistakes.

Also, make sure you didn't force a FDM to be loaded.

  • Commandline: --fdm=... should be left out.
  • FGRun: Advanced > Flight Model should be set to jsb (which will leave the whole command out of the commandline, so you can use this setting with any FDM).

Unknown ... aircraft: ... defaulting to C172

FlightGear is unable to load the forced FDM (set through --fdm=... or via Advanced > Flight Model in FGRun) for this aircraft. FlightGear automatically picks the right FDM for each aircraft, so there is no need to set it manually, unless you know what you are doing. In the Flight Model dialog of FGRun, set the FDM to jsb; that is the "auto setting".

Unknown exception to the main loop. Aborting...
Possible cause: No such file or directory

This error could have a variety of sources, among them missing files but also other things. Increasing the log level to debug and repeating excactly what you did when the error came up, might provide some more information on what FlightGear was doing when the error occurred.

  • Setting your BPP to a lower value might work.
  • Changing the resolution to a smaller one might work as well.

Unknown exception in main loop. Aborting...
Possible cause: Not enough space

  • When running 64 bits Windows, make sure to uncheck the "force 32-bits" option on installation.
  • Most notebooks that run Windows 7 have the so called Optimus Technology (NVidia) or Hybrid Graphics technology (ATI) onboard. This is meant to increase battery life, by automatically switching of the powerfull graphics card when it's not needed. However, FlightGear needs it all the time, even if Optimus says it doesn't! See here for instructions on how to disable this behaviour.

When the above mentioned points do not apply or did not work, you are likely to be unable to run FlightGear at the current graphics settings. See Troubleshooting performance issues for instructions on how to switch off demanding eye candy.

Apart from the above mentioned stuff, it may be useful to install the latest drivers for your graphics card:

WARNING: Couldn't convert texture...

You are trying to run an aircraft not compatible with your FlightGear version. Most of the time, this error appears when you fly an aircraft, textured with .png files on versions older than 1.9. Convert the textures manually to .rgb or upgrade your FlightGear version.

Warning: Could not find plugin to read objects from file ...

A library is missing from your computer. Therefore, certain fileformats cannot be read. Try to reinstall/update OSG, as the libraries used by FlightGear should be part of the standard package.

Warning: Picked up TriangleIntersect

Reduce your Log Level to alert. Or send the fgfs output to /dev/null (unix systems) or 2>nul (Windows). The errors might still be shown, but do not affect the sim anymore.

Warning: TangentSpaceGenerator: unknown primitive mode 9

This is an OSG error, showing up when an effect needs tangent vectors, but polygons are not support. The error itself can be ignored, altough some shaders may look wrong. Shader developers should try to minimise the use of polygons and use triangles and quads instead.

YASim SOLUTION FAILURE: Solution failed to converge after 10000 iterations

Some control in the YASim FDM is too weak, according to YASim, to control the aircraft. An effectiveness tag will be required in the FDM to solve this error.

Zero length fuselage

There is a problem in the FDM. A fuselage section with similar ax and ay was created. Change the ax and/or ay values to match the aircraft.


Make sure the JSBSim FDM of the aircraft has a <fdm_config version="2.0" tag.

Errors without known solutions

Please take a look at the upcoming errors and see if you know a solution to get rid of them. Your additions are greatly appreciated!

Aircraft propulsion element has problems in file ...

AL Error (fx): Invalid Value at pitch and gain

The sound effect's pitch (high or low) and gain (volume multiplication factor) values are not valid.

AL Error (sound manager): Invalid Operation at update

AL Error (sound manager): Invalid Value at buffer add data
No such buffer!

Failed to execute command nasal

Has something to do with the Nasal scripting language used by FlightGear.

Failed to tie (or untie while closing) property ... to object methods

A JSBSim error.

FGMultiplayMgr::MP_ProcessData - message from ... has invalid length!

FGMultiplayMgr::MP_ProcessData: Result too large

GPS: malformed route, index=1

Mesa 7.3 implementation error: bad texture level in r300UploadSubImage

Nasal runtime error: stack overflow

No image file for texture, using white

A shader error, possibly you (or the developer) have/has not specified a texture for a surface while modeling the aircraft model in AC3D, Blender, Wings...

No path in /sim/sound/path

You (or the developer) have/has not specified a proper sound file in the aircraft's -set.xml file.

OpenAL error (AL_ILLEGAL_COMMAND): set_source_pos

Has something to do with OpenAL not understanding where the sound comes from.

OpenAL error (AL_ILLEGAL_COMMAND): set_volume

Has something to do with OpenAL not understanding the sound volume.

PT_vs_hpt: ran out of layers

This is issued from the atmosphere implementation in FlightGear's environment system. A comment in the code says: "should never get here". Please provide input when this happens: excessive altitudes? Negative altitudes?

Tried to initialize a non-existent engine!

The developer of the aircraft did not code the engine properly.

Developers: Check that the engine.xml file, FDM.xml, and -set.xml is coded properly.

Unknown Chunk: ***UNKNOWN*** (0xA08A)

I use Autodesk 3ds Max (.3ds) occurs when the 3D data model.

Solution converts the file format AC3D.

Warning: detected OpenGL error 'invalid value' after RenderBin::draw(,)

This warning is generated from OSG. Set your environment variable


Warning: GraphicsWindowWin32::grabFocus() - Failed grabbing the focus

It seems that this happens when you have another window open and you are "focusing" (the window is active) on it. FlightGear will try to grab itself infront of the other window.

WARNING: PUI: Too many live puInterfaces open at once!

Appears when printing large outputs (very) frequently on the screen.

Warning: State::drawQuads(0, 154400) too large handle in remapping to ushort glDrawElements