Free flight software for linux

The FlightGear flight simulator project is an open-source, multi-platform, cooperative flight simulator development project. Source code for the entire project is available and licensed under the GNU General Public License.

The goal of the FlightGear project is to create a sophisticated flight simulator framework for use in research or academic environments, for the development and pursuit of other interesting flight simulation ideas, and as an end-user application. We are developing a sophisticated, open simulation framework that can be expanded and improved upon by anyone interested in contributing.

There are many exciting possibilities for an open, free flight sim. We hope that this project will be interesting and useful to many people in many areas.

FlightGear is a free flight simulator project. It is being developed through the gracious contributions of source code and spare time by many talented people from around the globe. Among the many goals of this project are the quest to minimize short cuts and "do things right", the quest to learn and advance knowledge, and the quest to have better toys to play with.

The idea for Flight Gear was born out of a dissatisfaction with current commercial PC flight simulators. A big problem with these simulators is their proprietariness and lack of extensibility. There are so many people across the world with great ideas for enhancing the currently available simulators who have the ability to write code, and who have a desire to learn and contribute. Many people involved in education and research could use a spiffy flight simulator frame work on which to build their own projects; however, commercial simulators do not lend themselves to modification and enhancement. The Flight Gear project is striving to fill these gaps.

There are a wide range of people interested and participating in this project. This is truly a global effort with contributors from just about every continent. Interests range from building a realistic home simulator out old airplane parts, to university research and instructional use, to simply having a viable alternative to commercial PC simulators.

Flight Dynamics Models

With FlightGear it is possible to choose between three primary Flight Dynamics Models. It is possible to add new dynamics models or even interface to external "proprietary" flight dynamics models:

1. JSBSim: JSBSim is a generic, 6DoF flight dynamics model for simulating the motion of flight vehicles. It is written in C++. JSBSim can be run in a standalone mode for batch runs, or it can be the driver for a larger simulation program that includes a visuals subsystem (such as FlightGear.) In both cases, aircraft are modeled in an XML configuration file, where the mass properties, aerodynamic and flight control properties are all defined.

2. YASim: This FDM is an integrated part of FlightGear and uses a different approach than JSBSim by simulating the effect of the airflow on the different parts of an aircraft. The advantage of this approach is that it is possible to perform the simulation based on geometry and mass information combined with more commonly available performance numbers for an aircraft. This allows for quickly constructing a plausibly behaving aircraft that matches published performance numbers without requiring all the traditional aerodynamic test data.

3. UIUC: This FDM is based on LaRCsim originally written by the NASA. UIUC extends the code by allowing aircraft configuration files instead and by adding code for simulation of aircraft under icing conditions.

UIUC (like JSBSim) uses lookup tables to retrieve the component aerodynamic force and moment coefficients for an aircraft... and then uses these coefficients to calculate the sum of the forces and moments acting on the aircraft.

Extensive and Accurate World Scenery Data Base

Over 20,000 real world airports included in the full scenery set.
Correct runway markings and placement, correct runway and approach lighting.
Taxiways available for many larger airports (even including the green center line lights when appropriate.)
Sloping runways (runways change elevation like they usually do in real life.)
Directional airport lighting that smoothly changes intensity as your relative view direction changes.
World scenery fits on 3 DVDs. (Im not sure thats a feature or a problem!) But it means we have pretty detailed coverage of the entire world.
Accurate terrain worldwide, based on the most recently released SRTM terrain data.) 3 arc second resolution (about 90m post spacing) for North and South America, Europe, Asia, Africa, and Australia.
Scenery includes all vmap0 lakes, rivers, roads, railroads, cities, towns, land cover, etc.
Nice scenery night lighting with ground lighting concentrated in urban areas (based on real maps) and headlights visible on major highways. This allows for realistic night VFR flying with the ability to spot towns and cities and follow roads.
Scenery tiles are paged (loaded/unloaded) in a separate thread to minimize the frame rate hit when you need to load new areas.

Accurate and Detailed Sky Model

FlightGear implements extremely accurate time of day modeling with correctly placed sun, moon, stars, and planets for the specified time and date. FlightGear can track the current computer clock time in order to correctly place the sun, moon, stars, etc. in their current and proper place relative to the earth. If its dawn in Sydney right now, its dawn in the sim right now when you locate yourself in virtual Sidney. The sun, moon, stars, and planets all follow their correct courses through the sky. This modeling also correctly takes into account seasonal effects so you have 24 hour days north of the arctic circle in the summer, etc. We also illuminate the correctly placed moon with the correctly placed sun to get the correct phase of the moon for the current time/date, just like in real life.

Flexible and Open Aircraft Modeling System

FlightGear has the ability to model a wide variety of aircraft. Currently you can fly the 1903 Wright Flyer, strange flapping wing "ornithopters", a 747 and A320, various military jets, and several light singles. FlightGear has the ability to model those aircraft and just about everything in between.

FlightGear has extremely smooth and fluid instrument animation that updates at the same rate as your out-the-window view updates (i.e. as fast as your computer can crank, and not artificially limited and chunky like in some sims.)

FlightGear has the infrastructure to allow aircraft designers to build fully animated, fully operational, fully interactive 3d cockpits (which even update and display correctly from external chase plane views.)

FlightGear realistically models real world instrument behavior. Instruments that lag in real life, lag correctly in FlightGear, gyro drift is modeled correctly, the magnetic compass is subject to aircraft body forces -- all those things that make real world flying a challenge.

FlightGear also accurately models many instrument and system failures. If the vacuum system fails, the HSI gyros spin down slowly with a corresponding degradation in response as well as a slowly increasing bias/error.

Moderate Hardware Requirements

The intention of FlightGear is to look nice, but not at the expense of other aspects of a realistic simulator. Our focus is not on competing in the "game" market and not on the ultra-flashy graphic tricks.

The result is a simulator with moderate hardware requirements to run at smooth frame rates. You can be reasonably happy on a $500-1000 (USD) machine (possibly even less if you are careful) and dont necessarily need $3000 (USD) worth of new hardware like you do with the many of the newest games.

That said, the more hardware you throw at FlightGear, the better it looks and runs, so dont feel like you have to chuck your expensive new hardware if you just purchased it. :-)

Internal Properties EXPOSED!

FlightGear allows users and aircraft designers access to a very large number of internal state variables via numerous internal and external access mechanisms. These state variables are organized into a convenient hierarchal "property" tree.

Using the properties tree it is possible to monitor just about any internal state variable in FlightGear. Its possible to remotely control FlightGear from an external script. You can create model animations, sound effects, instrument animations and network protocols for about any situation imaginable just by editing a small number of human readable configuration files. This is a powerful system that makes FlightGear immensely flexible, configurable, and adaptable.

Networking options

A number of networking options allow FlightGear to communicate with other instances of FlightGear, GPS receivers, external flight dynamics modules, external autopilot or control modules, as well as other software such as the Open Glass Cockpit project and the Atlas mapping utility.

A generic input/output option allows for a user defined output protocol to a file, serial port or network client.

A multi player protocol is available for using FlightGear on a local network in a multi aircraft environment, for example to practice formation flight or for tower simulation purposes.

The powerful network options make it possible to synchronize several instances of FlightGear allowing for a multi-display, or even a cave environment. If all instances are running at the same frame rate consistently, it is possible to get extremely good and tight synchronization between displays.

Flight Gear and its source code have intentionally been kept open, available, and free. In doing so, we are able to take advantage of the efforts of tremendously talented people from around the world. Contrast this with the traditional approach of commercial software vendors, who are limited by the collective ability of the people they can hire and pay. Our approach brings its own unique challenges and difficulties, but we are confident (and other similarly structured projects have demonstrated) that in the long run we can outclass the commercial "competition."

Contributing to Flight Gear can be educational and a lot of fun. A long time developer, Curtis Olson, had this to say about working on Flight Gear:

Personally, Flight Gear has been a great learning experience for me. I have been exposed to many new ideas and have learned a tremendous amount of "good stuff" in the process of discussing and implementing various Flight Gear subsystems. If for no other reason, this alone makes it all worth while.

JSBSim Flight Dynamics Model is an open source flight dynamics model (FDM) that compiles and runs under many operating systems, including Linux, Apple Macintosh, Microsoft Windows, Linux, IRIX, Cygwin (Unix on Windows), etc.
The FDM is essentially the physics/math model that defines the movement of an aircraft under the forces and moments applied to it using the various control mechanisms and from the forces of nature.
JSBSim has no native graphics. It can be run by itself as a standalone program, taking input from a script file and various aircraft configuration files; or, it can be run as an integrated part of a larger flight simulator implementation that includes a visual system.
The most notable example of the use of JSBSim is currently seen in the open source FlightGear simulator. JSBSim models the aerodynamic forces and moments by the classic coefficient buildup method.
JSBSim has seen the growth of a fairly large user base, with some of the more notable projects (of which I am aware) described on the Users page.
Main features:
- Fully configurable flight control system, aerodynamics, propulsion, landing gear arrangement, etc. through XML-based text file format.
- Rotational earth effects on the equations of motion (coriolis and centrifugal acceleration modeled).
- Configurable data output formats to screen, file, socket, or any combination of those.
Enhancements:
- This release includes new options for the standalone JSBSim executable, including improved real-time capability.
- This release also includes experimental (but tested) logic to reduce ground reactions jitter while on the ground.

GPLIGC is a software package for glider* pilots. IGC flight data files can be analysed and visualised.
The package contains two components:
*and all others who want to view GPS track logs (para-glider pilots, hang-glider pilots and even pilots of radio-controlled (sail)planes.
- GPLIGC, analysation
- openGLIGCexplorer, 3d visualisation (can be used as a viewer for digital elevation data too)
GPLIGC can be used on Linux, Unix, Windows and Mac OS X.
GPLIGC application can be used under the terms of the GNU General Public License (GPL).
Enhancements:
- This release fixes a few bugs.
- Some options were added that allow you to specify a destination folder and filenames for screenshots.
- The background colors (including gradients) can be changed.

Thunder&Lightning is an Open Source Action Flight Simulator Game.

Thunder&Lightning is the new name of a rather old project of me, Jonas Eschenburg. What started in 1999 as a technology demonstration has become quite an advanced flight simulator.

This has always been my pet project but now Im going to release it to the public, under the GPL, an Open Source license. This means that development can continue including other people than just myself. While it is already playable, Thunder&Lightning is by no means a finished game. If you like it, think about contributing!

In the long run, I plan to incorporate features from the 80s classics Carrier Command and Midwinter. There will be multiple Islands to conquer, each with its own defense strategy. Thunder&Lightning will not be mission oriented, but there will be scripted events for each island.

nionet is a complete client/server VPN solution for raw ethernet tunnels. Clients are available for Linux and Windows; the server is Linux only.
Due to its object oriented architecture, it is possible to easily plug in new transports. So far it features UDP and DNS tunneling. Being an ethernet layer 2 bridge, several network segments can be connected transparently.
When used in an ISP environment, nionet allows per-user traffic-shaping and precise reporting of used bandwidth. On the fly load balancing is possible. nionet uses sqLite or MySQL for account storage; changes to accounts are immediately active.
Main features:
- Compatible with all protocols that work over 802.3 Ethernet
- Uses mySQL or sqlite as backend for user accounts and session log
- Includes traffic accounting and billing for usage in an ISP environment
- Built-in traffic-shaper allows individual bandwidth-limits
- Values in the database can be changed in flight - e.g. new shaper-values will be activated during a running session. This allows dynamic load balancing.
- Built-In fragmentation - full Ethernet MTU of 1514 is tunnelled
- Transport via UDP or DNS
- Uses a virtual Ethernet adapter to be compatible with all existing software (Linux tap-driver, Windows NDIS driver)

ACFTools project is an utility for manipulating X-Plane ACF and WPN files.

ACFTools is a utility for manipulating X-Plane flight simulator aircraft and weapon models without using its Plane Maker. It can decode both Apple and Intel ACF/WPN formats into plain text files with a syntax similar to C, which can be edited and then re-converted into binary data.

It is able to extract almost complete 3D models of aircraft (fuselage, floats, tanks, wings, stabs, propellers, engines) and write it in AC3D modeler format. Edited 3D parts can then be merged into plain text and consequently converted into binary ACF files.

Allows you to:
- export X-Plane (www.x-plane.com) aircraft data files to human-editable plaintext format and 3D mesh editable in AC3D modeler (www.ac3d.org).

- import plaintext/3D mesh back to ACF file.

RedShift is an OpenGL/SDL flight simulator. RedShift aims to eventually support civilian flight, combat, and multiplayer capabilities with a realistic flight model.

Intellidiscs is a Remake of Tron: Deadly Discs for the classic Intellivision console. Its also one of the few, if not the first, Tron freeware games that has nothing to do with light-cycles.

Basically, you run around in an arena fighting off bad guys with your disc. There are four different varieties of bad guy, and one of them has three different varieties of disc. More difficult enemies appear as your score increases, with the most difficult showing up if you can reach 1,000,000 points.

Bad guys enter through doors on the sides of the arena. You can jam these doors open by either hitting them with your disc, or by running into them. If you jam open doors that are opposite each other, you can run in one side and come out the other. This is very important to your survival.

If you jam enough doors, eventually a recognizer will be dispatched to fix them. If you can hit the recognizer when its eye is open, it will stop fixing the doors and leave the arena. Plus, you get lots of points for this.

You can take three hits before you die, and every hit makes you slower! You will eventually recover from damage, regaining your speed as well. Touching the recognizer kills you instantly, so dont do it.

Default controls are the familiar WASD to move, and the outer keys of numpad (1, 2, 3, 4, 6, 7, 8, 9, non-Mac users turn Num Lock on!) throw your disc in any of eight directions. If you press one of the throw keys while your disc is in flight, it will return to you. Discs are harmless when returning. If you move away from your disc as it is flying back, it will never catch up to you, you must stop and catch it. All of the controls can be changed from the main menu.