FlightGear

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FlightGear

Boeing 787 with Continental Airlines livery in version 1.0.0
Developed by FlightGear Developers & Contributors
Initial release July 17, 1997
Latest release 1.0.0 / 17 December 2007
Written in C++ [1]
OS 32-bit Windows, Linux, Mac OS X, FreeBSD, Solaris or IRIX
Platform Cross-platform
Development status Active (1996-)
Genre Flight simulator
License GNU General Public License
Website http://www.flightgear.org/

FlightGear is a collaborative project that aims to create a sophisticated free, completely open-source flight simulator framework.[2]

The project was started in 1996, with the first release in 1997. The latest public release is 1.0.0 in December 2007, with specific builds for a variety of operating systems including Microsoft Windows (Win 32), Mac OS X, Linux, IRIX, and Solaris, although hardware requirements, especially OpenGL hardware graphics acceleration constrict systems capable of running Version 1.0.

FlightGear code is released under the terms of the GNU General Public License, and it is free software.

Contents

[edit] History

[edit] Beginnings (1996, 1997-2001)

Development formally started in the late-1990s with an online proposal and code being written in 1996, but using custom 3D graphics code. Development of an OpenGL based version was spearheaded by Curtis Olsen starting in 1997, after the initial start in 1996. A large community response lead to many contributing to the project from its start in late '90s up to the present. [3] [4]

Rather than start entirely from scratch, FlightGear developers made use of the LaRCsim flight model from NASA, with OpenGL for 3D graphic code, and freely available elevation data. First working binaries came out in 1997, with an intense updating of newer versions for several years resulting in progressively more stable and advanced programs.

3D Cockpit panel for A-10 in version 1.0.0 in 2008
3D Cockpit panel for A-10 in version 1.0.0 in 2008

By 2001, the team was releasing new beta versions regularly (0.7.x, 0.8.x over 2001-2003). Later in the decade, the rate of final public releases slowed, but had larger amounts of content (0.9.8, 0.9.10, etc.). The maturity of software by 2005 lead to more widespread reviews, and increased popularity. The use of version numbers slowed dramatically after the late 2002 release of version 0.9.0. Versions 0.9.9 (2005) and 0.9.10 (2006) had about 8 all-new or redone aircraft adding to a total of 70-90 aircraft, while 0.9.11 has about 33 new or redone designs.

[edit] Version 0.9.0-1.0 (2002-2007)

KLM Boeing 737-300 in version 1.0.0 in 2008
KLM Boeing 737-300 in version 1.0.0 in 2008

FlightGear graphics are outdated in many respects compared to flight simulators such as X-Plane of the same period, but can compare well to older versions and to open source contemporaries such as ACM Flight Simulator or Vertigo. Also, the whole world is well represented using the freely available SRTM elevation data, and a number of special features are available, such as sloped runways. Over 20,000 runways, 3d clouds, multi-platform support, multiple open flight data model (FDM) choices, roughly 100 aircraft choices by version 0.9.10 provide a well-rounded feature set.

FlightGear is requires OpenGL and 3D hardware acceleration, with NVIDIA hardware and binary drivers having better support. Early versions had support for 3dfx cards, though this was dropped as hardware requirements increased.

FlightGear has been used in a range of projects in academia and industry.[5]

[edit] Software

The simulation engine in FlightGear is called SimGear. It is used both as an end-user application and in academic and research environments, for the development and pursuit of flight simulation ideas.

This customizability of FlightGear is illustrated by the wide range of aircraft models that are available in FlightGear, from gliders to helicopters, and from airliners to fighter jets. These aircraft models have been contributed by many different people.

The FlightGear aircraft use one of three main data models JSBSim, YAsim, or UIUC as of version 0.9.10. Currently only one terrain engine is used, TerraGear. Weather effects include 3D clouds, lighting effects, and time of day.

Another huge advantage of FlightGear is that it is completely open source — it has a rich set of existing external interfaces, and most of the major configuration can be done with standard XML-based text files. We make no attempts to obfuscate or hide our internals. This is big win for people using FlightGear as an academic or research platform, or for those that want to interface it to their own home-built cockpits.[6]

Curtis L. Olson , O'Reilly Network, 2003

[edit] Flight Dynamics Models

Flight Dynamics Models (FDM) are how the flight for an aircraft is simulated in the program. FlightGear uses a variety of internally written and imported flight model projects. Any aircraft must be programmed to use one of these models. Currently FlightGear is the only graphical flight simulator for which all the FDM are used, and UIUC and YASim were developed specifically for FlightGear.

Early version used an FDM based on LaRCsim by NASA, which was replaced with more flexible FDM.

  • JSBSim - the default flight dynamics model software since 2000. Started by Jon Berndt. [7]
  • YASim - another FDM using different calculation method. Introduced starting in 0.7.9 in 2002. Developed by Andy Ross [8]
  • UIUC - another included FDM, developed by the UIUC Applied Aerodynamics Group at University of Illinois at Urbana-Champaign, also made use of LaRCsim.[9]
  • Flight Gear can also be setup to render using inputs from an external FDM source, such as from Matlab.
  • Other custom FDM for a specific aircraft type have been written, such as for lighter than air aircraft.

[edit] FlightGear dependencies

Unlike commercial software titles, the main output of the project is simply the release of a collection of code. To turn it into a usable program it must be compiled for a given platform. The software libraries used to create FlightGear have varied over time. The main one is SimGear, which is the underlying sim engine for FlightGear. TerraGear is not a dependency, but simply a name for the default terrain data program in FlightGear. OpenAL is used for sound/audio software, including support for SDL (since 0.9.5).[10] PLIB is used for hardware support routines, formerly used for sound support also which was taken over by OpenAL. OpenGL is used for its integrated 3D graphics routines, and other hardware acceleration (namely DirectX) is not supported. OpenSceneGraph is also integrated into FlightGear. Finally, Simple DirectMedia Layer is a software library which is used for compiling. Some of the dependencies vary depending on which platform the code is being compiled for. FlightGear users must either compile the code themselves, or find a third party to release a binary, if it is not among the ones available from the project.

[edit] Networking and multi-display

Several networking options allow FlightGear to communicate with other instances of FlightGear. A multiplayer protocol is available for using FlightGear on a local network in a multi aircraft environment. This could be used for formation flight or control tower simulation. Multiplayer was soon expanded to allow playing over the internet. Other features include a Google maps based moving map that allows users to observe where other players are.[11]

Several instances of FlightGear can be synchronized to allow for a multi-monitor environment. If all instances are running at the same frame rate consistently, it is possible to get good and tight synchronization between displays.

[edit] Additional software

A comparison between a FlightGear 1.0 screenshot in 2008 and a photo of San Fransico Airport
A comparison between a FlightGear 1.0 screenshot in 2008 and a photo of San Fransico Airport

There are programs that are either integrated into FlightGear (dependencies) or perform a function with it. Some of these are included in the release of FlightGear for a specific platform but made by the project, while others are independently distributed but are hosted by the FlightGear project.

One major additional software is the actual interface for launching an executable of FlightGear. For most of its early life FlightGear was only run through command line interfaces. However, the FlightGear Launch Control has been included with the FG launcher front-end since 0.9.3 in 2003. KFreeFlight is a launcher/front-end for KDE. FGTools is an alternative windows launcher front-end. FGKicker is a GTK+ based front-end.

Other significant programs include editors and projects for Terrain Data. Atlas is a chart/map support for FlightGear; Kelpie Flight Planner is a Java based flight planner for FlightGear. FlightGear Scenery Designer is a FlightGear scenery editor for working with terrain data. The World Custom Scenery Project is a project coordinating custom scenery efforts. Finally, Taxidraw is an editor for airport runways and taxiways.

[edit] FlightGear code vs. binaries

Unlike most commercial software, the project release dates only apply to a release of code, not an executable program. To create a runnable program the code must be compiled, which requires several specific libraries (see section of #FlightGear dependencies), including some general ones and, in some cases some platform specific ones. However, since this too difficult for most mainstream users, other contributors will work to make binaries available for a specific platform and operating system. These packages vary in their stability, performance, dependencies, and how up to date they are with the code base. For example, some older binaries work on Mac OS 9 but newer releases require specific Mac OS X versions.

For example, by late 2007 the latest code release was 0.9.11-pre1 (pre-release) and 0.9.10 (final). However, the actual binaries available vary significantly. Examples of actual binaries available a year after the release of the 0.9.10 code release:

  • Win-32 has ~138 Mb package (v0.9.10) (For Windows 98, 2000, ME, 32-bit XP)
  • Linux- pre-built packages for specific Linux distributions
  • Solaris packages either for it running on either SPARC or x86 processors.
    • SPARC (v0.9.8), x86 (v0.9.9)
  • Silicon Graphics IRIX;at the time had SGI binaries for (v0.9.9)
  • Mac OS X has a version for Mac OS 10.4 (v0.9.10) and for Mac OS 10.3 (v0.9.9)
  • FreeBSD has a package for(v0.9.10)

By early 2008, many versions for 1.0.0 became available although older releases remained for several aforementioned platforms. Increased hardware requirements for 1.0.0 reduced performance on older systems.

  • Win-32 has a ~172 Mb package (v1.0.00) (For Windows 98, 2000, ME, XP, Vista)
  • Linux- pre-built packages for specific Linux distributions included (v1.0.00) for Slackware and Debian
  • Macintosh OS 10.4 (v1.0.00)

[edit] Critical reaction

Wright Flyer in 0.9.9, which uses the UIUC FDM
Wright Flyer in 0.9.9, which uses the UIUC FDM

Although not developed as a game in the traditional sense, FlightGear has nevertheless undergone reviews in a number of online and offline publications. FlightGear 0.9.10 received many reviews, being highlighted as an accurate simulation but requiring patience and some pre-game work.[12] PC Magazine noted how it is designed to be easy to add new aircraft and scenery.[13]

In contrast, an older review some years early, a June 2002 review by FlightXPress, had been more critical, noting a lack of functions and the scenery (this would be for version 0.7.10 of FlightGear).[14]

[edit] Release timeline

Final build code release dates by year. [15] Prototype code using LaRCsim, OpenGL, USGS DEM data, and VRML were tested by July 3, 1997 by C. Olson. [16]

Date Version
July 17, 1997 First Release
1st working win-32
September 23, 1997 0.12
December 9, 1997 0.15
December 17, 1997 0.18
December 30, 1997 0.19 (first binaries)
January 6, 1998 0.22
Mar 11 98 0.37
April 8, 1998 0.41
April 14, 1998 0.42
April 23, 1998 0.43
Apr 28, 1998 0.44
May 7, 1998 0.45
May 11, 1998 0.46
May 18, 1998 0.47
June 9, 1998 0.48
June 27, 1998 0.49
July 13, 1998 0.50
July 21, 1998 0.51
August 15, 1998 0.52
September 2, 1998 0.53
September 25, 1998 0.54
October 23, 1998 0.55
November 23, 1998 0.56
January 21, 1999 0.57
February 10, 1999 0.58
March 31, 1999 0.59
May 26, 1999 0.6.0
June 21, 1999 0.6.1 (Stable)
September 11, 1999 0.7.0 (Development)
0.6.2 (Stable)
October 22, 1999 0.7.1 (Development)
February 17, 2000 0.7.2 (Development)
May 18, 2000 0.7.3 (Development)
July 20, 2000 0.7.4
September 18, 2000 0.7.5
December 19, 2000 0.7.6
June 20, 2001 0.7.7
July 13, 2001 0.7.8
February 16, 2002 0.7.9
April 20, 2002 0.7.10
September 7, 2002 0.8.0
December 3, 2002 0.9.0
December 5, 2002 0.9.1
June 4, 2003 0.9.2
October 24, 2003 0.9.3
March 26, 2004 0.9.4
July 29, 2004 0.9.5
October 12, 2004 0.9.6
January 18, 2005 0.9.8 [17]
November 17, 2005 0.9.9
April 5, 2006 0.9.10
May 2007 0.9.11-pre1
December 17, 2007

[edit] Models & aircraft

FlightGear started out with an aircraft included in NASA's LaRCsim, a Navion, which was replaced by a Cessna 172 by 2000. UIUC as well as JSBsim development brought several more aircraft with them, as did the development of YASim which have since become the main FDM used in FG. [18]

[edit] 1.0.0 and earlier aircraft

Hawker Sea Hawk in 0.9.9
Hawker Sea Hawk in 0.9.9

The basic installer is limited to about 15 aircraft, with several dozen more official aircraft at varying states of development for download. The CD/DVD version includes all official aircraft and terrain data, though all the same material can also be downloaded for free. Non official aircraft from third-party sources also exist, but are not included here. Also included are a number of custom buildings, especially around San Francisco; a Nimitz class aircraft carrier is included as well (which aircraft can land on). In addition, several of the developmental UIUC aircraft developed in the late 1990s were still included but were not all maintained.

All Official aircraft for 0.9.10, with flight data model type and cockpit type listed for some such as found on the 0.9.10 CD release of FlightGear. Some aircraft are FDM only. Third party aircraft are excluded from the list (such as in additional add-ons). Aircraft in 0.9.10 installer are noted with a *, and ** for the 1.0 installer. New or heavily re-worked aircraft up to 1.0 public release, including some that came out with the 0.9.11-pre1 FlightGear (pre-release version) as well as 9.10 aircraft. Many aircraft that have not been updated no longer work, such as ones before .7.x/.8.x/.9.x as well as a number in the later releases that were not maintained to the current version depending on the model and its dependencies. Includes from about 0.7.0 to 0.9.10 and 1.0.0.

List of FlightGear Aircraft
Model FDM 3D Cockpit M. Update Debut
1903 Wright Flyer* UIUC - 0.9.9 0.8.0
Aerostar Super 700 YASim 3d cockpit 1.0.0 0.9.10
Boeing 707 JSBsim v2 - 0.9.10
Boeing 737-300* 0.9.4 1.0.0 0.9.2
Boeing 747-100 JSBSim,YASim 1.0.0, 0.9.10 0.8.0
Boeing 777-200 YASim 3d cockpit
Boeing 787-8 JSBsim 3d cockpit 1.0.0
Boeing 314-A JSBsim 1.0.0 0.9.9
Boeing F-18 Hornet 1.0.0
Boeing E-3B Sentry 1.0.0
Boeing KC-135E (FDM only)
Douglas A4F Skyhawk YASim, UIUC 1.0.0, 0.9.10 0.8.0
Northrop Grumman A-6E Intruder YASim 1.0 1.0.0
Fairchild A-10 Thunderbolt II* YASim 3d cockpit 1.0.0 0.9.2
Airbus A300 1.0.0
Airbus A320-200
Airbus A320-100 1.0.0
Antonov An-2 1.0.0
Antonov An-225 YASim 0.9.10 0.9.3
Arsenal VG-33 1.0.0
Beechcraft 99 YASim, UIUC 1.0.0** 0.9.5
Beechcraft B1900D YASim 3d 1.0.0 1.0.0, 0.9.10 0.9.8
Beechcraft Starship I YASim 1.0.0
Rockwell B-1B Lancer 3d cockpit 1.0.0
Northrop B-2 Spirit 1.0.0
B-29 Superfortress JSBsim, YASim 0.9.10 0.9.9
B-52F Stratofortress 1.0.0, 0.9.10 0.9.2
BAC TSR2 YASim 0.9.2
Bailey Dragonfly (Moyes/LiteFlite) (Ultralight)
Blackburn Buccaneer YASim 1.0.0
Bleriot XI YASim 1.0.0
Blohm & Voss BV 141 YASim
Bristol Beaufighter 1.0.0
Bugatti 100P YASim 1.0.0**
Cessna 150L 1.0.0 1.0.0
Cessna 172P Skyhawk* (1981 model) JSBSim 0.9.2 0.9.10
Cessna 172LE Skyhawk JSBSim
Cessna 172R Skyhawk JSBSim
Cessna 182 1.0.0 0.7.9
Cessna 182RG (c. 1978) 1.0.0
Cessna 310R (1979 model) 3D cockpit 0.9.10 0.7.9
Cessna U-3A YASim 3D cockpit 0.9.10; 0.8.0 0.7.9
Cessna 550 Citation II YASim 3d cockpit 0.9.8
Cessna Citation Bravo* YASim 3d cockpit 1.0.0, 0.9.10 0.9.9
Cessna Citation X 1.0.0
Comper Swift YASim 0.9.4
Concorde (v2.4) 3D cockpit 1.0.0, 0.9.10 0.9.5
Cri-Cri(Colomban MC-15 Cri-Cri) YASim 1.0.0**
Douglas DC-3 0.8.0
Douglas X-3 Stiletto YASim 1.0.0**
Dornier Do-335 1.0.0
Dornier Do X YASim 1.0.0**
Dorner-Dassault Alpha Jet YASim 1.0.0**
de Havilland Canada DHC-2 Beaver YASim 3D cockpit 1.0.0, 0.9.10 0.9.8
de Havilland Canada DHC-6 Twin Otter (Floats & Wheels) 1.0.0**
de Havilland Mosquito 1.0.0
de Havilland DH.89 Dragon Rapide YASim 1.0.0
de Havilland D.H.110 Sea Vixen FAW 2 YASim 1.0.0
English Electric Canberra B(I)8 YASim 0.9.10
English Electric Lightning F.1A 1.0.0 1.0.0 0.9.10
McDonnell Douglas F-15 Eagle (fdm only) 0.9.2
McDonnell Douglas F-15C Eagle 3D Cockpit 1.0.0
General Dynamics F-16* 3D cockpit 0.9.10 0.9.2
Northrop YF-23 YASim 0.9.10 0.9.2
Lockheed F-80C Shooting Star 0.9.10
North American F-86F Sabre 1.0.0
Lockheed F-104 Starfighter 0.9.2
Chance Vought F4U Corsair 1.0.0
Farman IV YASim 1.0.0
Fieseler Fi-156 Storch 1.0.0
Focke-Wulf Fw-190 A8 1.0.0
FK 9 Mark 2 YASim 1.0.0
Fokker 50 0.9.8
Fokker 70 JSBSim
Fokker 100 JSBSim 0.9.8
Fokker Dr.1 UIUC
Grob G 115 YASim 1.0.0**
Grumman Albatross 1.0.0
Harrier YASim 1.0.0
Hawker Hurricane IIb 0.9.10 0.9.9
Hawker Hunter GA11* YASim 1.0.0, 0.9.10 0.9.4
Hawker Sea Hawk 0.9.10
Hughes H4 Hercules YASim, JSBSim 1.0.0
Issoire APM 20 Lionceau YASim
Soko J-22 Orao / IAR-93 0.9.3
Junkers Ju 52 1.0.0
Kawasaki T-4 "Blue Impulse" JSBSim, YASim 1.0.0 **
Kyushu J7W 1.0.0
Let L410 FDM only JSBSim 3D cockpit
Lockheed C-130 Hercules JSBSim 1.0.0
Lockheed 1049(Lockheed Constellation) 1.0.0 0.9.10
Lockheed P-38 Lightning & F-5B 1.0.0
Lockheed SR-71 Blackbird (2 FG versions) YASim 3d cockpit 1.0.0
McDonnell Douglas MD11 0.9.5
Macchi Castoldi M.C. 72 YASim 1.0.0
Martin-Marietta X-24B JSBsim
Mainair Flash 2 Alpha 1.0.0
Messerschmitt BF-109 G14* 1.0.0 0.9.10
Messerschmitt Me 262 YASim) 1.0.0
Dassault Mirage 2000 1.0.0
MiG-15bis YASim 1.0.0, 0.9.10 0.9.9
Nakajima Ki-84 Hayate (疾風, "Gale")('Frank') 1.0.0
Nakajima A6M2('Rufe') 1.0.0
Nord Noratlas 1.0.0
North American OV-10A Bronco 1.0.0 0.9.10
North American P-51D Mustang* YASim 0.9.2 0.9.2
North American X-15
Payen Pa 100 YASim 1.0.0
Consolidated Aircraft PBY-6 Catalina 1.0.0
Piaggio P180 Avanti II(FDM only) YASim 1.0.0
Pilatus PC-7 1.0.0, 0.9.10
Piper J3 Cub (J3C-65, 1946 model) 091 0.8.0
Piper Comanche 250 (1962 model) 1.0.0 0.9.10
Piper Cherokee Warrior II* (1979 model)
Piper PA34-200T Seneca II JSBsim,YASim 1.0.0
Pitts S1C
Saab J35Ö Draken (J35oe) 1.0.0
Siai Marchetti S.211(FDM only) UIUC
Space Shuttle (fdm only) JSBsim
Sopwith Camel 1F.1 UIUC, YASim 1.0.0
Supermarine Seafire MkIIIc 0.9.10
Supermarine Spitfire IIa 0.9.10 0.9.5
Supermarine Spitfire Mk IX 1.0.0
Sukhoi Su-26M
Sukhoi Flanker-F YASim 1.0.0
Cirrus SR-20 0.9.10 0.9.9
Cessna T-37 0.9.10 0.9.4
Northrop T-38* 0.9.2
Tupolev Tu-114 YASim 0.9.9
Tupolev Tu-154 YASim 0.9.5
A24 Viking(Aeroprakt) YASim 1.0.0
Bell/Boeing V-22 Osprey YASim 1.0.0
Vickers Vimy YASim 3d 1.0.0**
Avro Vulcan B.2 1.0.0
Zlin Z-50LX YASim 1.0.0**
Helicopters
Bo 105* 1.0.0, 0.9.10
Boeing CH-47 Chinook YASim 1.0.0
Bell 206 JetRanger 1.0.0 0.9.3
Bell/Boeing V-22 Osprey 1.0.0
Piasecki HUP Retriever (H-25) 1.0.0
Piasecki H-21C Shawnee 1.0.0**
Robinson R22 1.0.0
Sikorsky S-51(R-5) 1.0.0
Sikorsky S-58(H-34) YASim 1.0.0
Sikorsky S76C++ 1.0.0
Sikorsky S-70 (UH-60) 1.0.0
Sikorsky CH-53E Super Stallion (S-80) 1.0.0
Aérospatiale Alouette II YASim 1.0.0
Aérospatiale Alouette III 1.0.0
Aérospatiale SA 321 Super Frelon Yasim 1.0.0**
Eurocopter EC 135 1.0.0
Ecureuil AS 350 (FDM only) 1.0.0 0.9.3
Westland Lynx WG13 1.0.0
Gliders & Miscellaneous
Schweizer 2-33 (TG-4) (Glider) 1.0.0
Schleicher ASW 20 (Single Glider) UIUC 0.9.3
Schleicher ASK 21 (Glider) 1.0.0
Bielsko SZD-9 Bocian (Glider) 1.0.0
Colditz Escape Glider
Airwave Xtreme 150 hang glider UIUC
Paraglider JSBsim 0.9.3
Hornet Autogyro
Ornithopter UIUC 0.9.2
Rascal 110 (R/C)* YASim, JSBSim
Malolo1 (R/C) -
Manta (R/C) (FDM only) -
Ogel JSBSim 0.9.10
Santa Claus Sleigh 3d cockpit
UFO (Video Assistant), YardStik
Snowplow (Truck)(+AI) 1.0.0
Willys Jeep YASim 1.0.0

[edit] See also

[edit] References

  1. ^ SourceForge.net: FlightGear - Flight Simulator
  2. ^ Barr, Joe (4 December 2006). FlightGear takes off. Retrieved on 2007-06-25.
  3. ^ The Flight Gear Manual Version .9, April 2006
  4. ^ "Flight Gear Flight Simulator" Proposal http://www.flightgear.org/proposal-3.0.1 checked June 26, 2007
  5. ^ Applications for the Simulator. Retrieved on 2007-09-03.
  6. ^ Wen, Howard (11 December 2003). Flying the Open Skies with FlightGear. O'Reilly Network. Retrieved on 2008-03-04.
  7. ^ Wen, Howard (11 December 2003). Flying the Open Skies with FlightGear. O'Reilly Network. Retrieved on 2008-03-04.
  8. ^ LinuxDevCenter.com - Flying the Open Skies with FlightGear
  9. ^ Aircraft Dynamics Models for Use with FlightGear. UIUC Applied Aerodynamics Group at University of Illinois at Urbana-Champaign. Retrieved on 2007-06-26.
  10. ^ FlightGear v0.95 Released. LockerGnome. Retrieved on 2007-06-24.
  11. ^ Flying high with FlightGear
  12. ^ Flying high with FlightGear. Free Software Magazine (2006).
  13. ^ Smith, Tim (1 September 2006). FlightGear 0.9.10. PC Magazine (UK). Retrieved on 2007-06-29.
  14. ^ FlightGear, Marc Stoering, Issue June 2002 FlightXPress magazine.
  15. ^ http://www.flightgear.org/index.shtml (checked June 24 , 2007)
  16. ^ http://web.archive.org/web/19990209201526/www.flightgear.org/News/ (checked March 4, 2008)
  17. ^ http://www.pcmech.com/article/flightgear-flight-simulator/ (checked June 24 , 2007)
  18. ^ The Flight Gear Manual Version .9, April 2006

[edit] External links

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