The Fugue

The Reviewer

I am a flight sim nut. I've been "flying" on-again off-again since the early 90s. It was Microsoft Flight Simulator back then, with the keyboard. As far as flying goes, it was a pretty sorry situation. But what I really enjoyed doing was navigating with VORs and the like, and it was a lot of fun.

I'm a linux and OS X user/nut. I'm a free/libre software advocate. I'm a cheapskate. I'm not afraid of editing a preferences file. These things will influence my review, but I'll try to point out any bias.

I want to be a pilot, but I haven't actually taken the yoke of a real plane yet.

The Equipment

I'm not a fps nut. I will discuss fps, but don't for a minute think I spent hours upon hours tweaking software or spent dollars upon dollars on hardware to get 3000+ fps. I run both x-plane and flightgear on two machines: my desktop and my laptop.

Desktop is an AMD Athlon(tm) 64 Processor 2800+ running Ubuntu Linux in 32-bit. Its video card is an nVidia NV18GL [Quadro4 NVS AGP 8x]. It has one gigabyte of RAM and SATA disks.

The laptop is a MacBook (not Pro) with 2 GHz Intel Core Duo CPU, 1 GB RAM, SATA (laptop) drive, and an Intel GMA 950 graphics card. I run OS X on it almost all the time.

I have a CH Products Yoke and Rudder Pedals, but I will also mention some experiences with a Logitech Extreme 3D Pro joystick.

The Criteria

I'm going to talk about memory usage, joystick issues, the cockpit, the view out the window, the UI polish, the aircraft that you can fly, freedom and Freedom, scenery, community, and various other things. It's not a rigorous comparison, but more like a prose discussion in which I try to point out strengths and weaknesses in a fair and unbiased way.

How can I be fair and unbiased? I just said I was a free/libre software advocate so wouldn't I be biased toward FlightGear? How did a cheapskate like me get a copy of X-Plane anyway? The answer to all of these questions is that I got X-Plane with world scenery (an $80 value) for Christmas from my family, so the same obligation that makes Ralph wear his pink bunny pajamas when his aunt comes over makes me spend at least equal time in X-Plane. A hefty amount of curiousity helps too.

Executive Summary

To be filled out by an executive.

The Review

Ok, enough blathering. Let's get started.

First, let's discuss memory. Because it's first on my ad-hoc list, that's why. I fired up FlightGear at KSFO (its 'demo' airport) and it used 250 megabytes of resident memory. I fired up X-Plane at its demo airport (San Bernardino) and it used 530 megabytes of resident memory. Both use more memory in OS X for some reason, but X-Plane uses disproportionately more memory. I have never had any trouble with swapping when running X-Plane on linux, but on OS X just about everything swaps to disk except X-Plane. X-Plane has over a gig of virtual memory allocated in OS X. FlightGear uses less virtual memory than Firefox on OS X. I think we can conclude that if you're low on RAM you want to be using FlightGear.

Now, when you sit down with your fancy new joystick or yoke and rudder pedals (or maybe handcrafted rudder bar), how easily can you be up and running? The answer for both simulators is a resounding it depends. If you have a well-known and worthwhile joystick FlightGear will Just Work™. In contrast, no matter what joystick you have you will have to calibrate it with X-Plane. This is rather frustrating in the demo version of X-Plane because by the time you've calibrated your joystick your 6 minutes is almost up. (Hint, don't close X-Plane with the window manager close window button) On the other hand, if you have a joystick not yet supported out of the box by FlightGear, or you have different preferences and wish to change what some of the buttons or axes do, you have to edit an XML configuration file. On the other hand, Even when you figure out that you have to quit from the menu in X-Plane in order to save your preferences, X-Plane does not match your preferences to the joystick by name or ID or any of myriad ways it could recognize the same joystick, but instead by the order in which they were plugged into the system. So, if you plug in the yoke before the pedals this time, and the pedals before the yoke next time, you have to either reconfigure everything or restart X-Plane. FlightGear, on the other hand, matches up joysticks by name and always gets things right.

Speaking of restarting X-Plane, FlightGear starts up much more quickly.

So the joystick verdict is, if you have a good joystick FlightGear wins. If you don't, X-Plane wins. FlightGear's joystick database will continue to grow. X-Plane may or may not wise up and recognize the joystick by name or ID in a future version.

Now that you're sitting in the cockpit and your joystick works, how do they handle? Remember I'm not a real pilot, so I can't really comment on how realistic things are, but based on what I know about aerodynamics and based on comments from my dad who is a pilot, the flight models are pretty good. Some will say FlightGear has a better flight model. Some will say X-Plane does. I really don't know. What I do know is FlightGear has a distinct academic and research flavor, and X-Plane is by a real pilot with a passion for realism. That suggests to me that both are going to be more realistic than the other, in various ways. It also bears mentioning that my interest is in general aviation not jets and heavy metal, while the reverse is apparently true for Austin (the X-Plane author). I do find X-Plane is very jumpy unless you turn on the dampening. I thought it was a joystick issue until I got my CH yoke and pedals for Christmas. Now I think it's just Austin's idea of "realism." It may be more realistic, but unless you have a very sophisticated force-feedback system it must be more like real flying to have things dampened (since your hands can't do the dampening without the aid of your eyes after a very long human reaction time).

When X-Plane starts up the first time you'll be in the cockpit of an airliner. When FlightGear starts up you'll be in the cockpit of a Cessna. The latter is a much better place to start if you have no experience with flying. With FlightGear you have to choose the airplane on the command line (or with a launcher), and can't change it mid-session. With X-Plane you can change planes any time. This is a plus for X-Plane.

Both simulators have a wide array of aircraft available. FlightGear comes with more interesting aircraft, from my perspective. X-Plane has more novel ones that will hold your friends' interest though, like the space shuttle and stealth bomber, etc. Many add-on aircraft are available from their respective communities as well.

X-Plane looks slick. It looks very slick. The textures and runway lights, signs, and windsock give a much more realistic-seeming impression of being there than FlightGear's more idealised textures. The ground textures are pretty nice too. However once you get past the wow factor, both are just textures on a terrain and you will soon find the X-Plane textures as unrealistic as the FlightGear ones. This is a problem I don't see going away for any sim in the near future. X-Plane reportedly has real-world building placement for large metroplises, but I haven't verified this. I'm not sure if FlightGear has something similar. Both simulators use the same terrain and navaid databases, so things like towers and roads and mountains will be the same.

X-Plane looks slick, but it's not without its warts. Both X-Plane and FlightGear support either 2D or 3D cockpits, i.e. either a 2D instrument panel or one that is 3D and allows you to turn your "head" and still see the cockpit. Personal computer flight simulation has three major problems: field of view, lack of feedback, and world detail. In my opinion, in the current state of affairs a 2D cockpit is simply unacceptable because it unnecessarily limits field of view beyond the already restrictive limit. That is to say, I can't stand flying if I can't move my "head" around with the hat switch and still see my instruments. X-Plane has some really nice looking cockpits, but the overwhelming majority of its aircraft are either 2D only, or the 3D version is severely lacking. This is even more the case with general aviation aircraft. However, there are a few aftermarket planes (especially if you're willing to pay, which you might be if you bought X-Plane in the first place) with very nice 3D cockpits. The aircraft included with FlightGear include some with 3D, some with 2D and some with no cockpits (mostly research planes where the creators are worried about the flight model not the flight experience, in which case they just use the HUD). The majority of aircraft for general use have 3D cockpits.

In fact, the development version of FlightGear has a novel new feature where your POV moves around in relation to physical forces, much like your head would tend to move around in real life. It's called dynamic cockpit and it is a bit unsettling at first but turns out to be a very ingenious way of making up some lost ground in the feedback department. It helps in coordinating turns, understanding power and angle of attack, etc.

In short, FlightGear leads X-Plane in the field of view department, but a subset of X-Plane aircraft are neck and neck with the average FlightGear cockpit.

One problem both simulators have is that you can almost never read the altimiter setting on the gauge itself, at least not at the resolution I run (1024x768). FlightGear lets you check if you need to in its properties browser. The closest X-Plane gets to that is it will let you put the display on your windshield, but that really cuts into the realism, you know? In a similar vein, you can set FlightGear to display fps down in the corner, in a nice unobtrusive way, but X-Plane requires you to display eight bits of information or more in the corner of your windshield just to see the fps. On the other hand, X-Plane will dynamically change the visibility setting (essentially adding haze) if your fps gets too low so that you can continue to fly with a smoothly-updating screen. FlightGear does something similar with scenery objects, but it's less useful when you're flying out in the country. However even I get 50fps on average here at KLRU, so any modern computer would be ok too.

I said earlier that while X-Plane looks really realistic, it isn't actually any more realistic. A good example of this is that no matter where in the world I fly it looks like I'm in California. The sky is depressingly grey and hazy even if in reality I can see forever and the sky is a deep blue. FlightGear has a less Californian sky, but has a similar problem with visibility. I'm not sure I can blame them though, because METAR reports generally report 10 mile visibility as a maximum, which isn't anywhere close to how far you can really see here in New Mexico. In FlightGear you can change the visibility with a few keystrokes, which helps if you have too much visibility for your hardware (which X-Plane does automatically), or if you have too little. Even in the desert it's a tradeoff though - if I up the visibility too high I can see the edge of the loaded scenery. I'd have to also up the level of detail which would no doubt impact my bottom line fps. In practice, it's a moot point for the same reason that METAR maxes out at 10 miles. 10 miles is enough. It's annoying to know that you'd still be able to see that airport in real life, but not a problem at all.

It's much more of a problem that you can't tell one mountain from another, except by shape. Or one valley or lake from another except by outline. I once flew from Flaming Gorge to someplace in Wyoming in FlightGear, or so I thought. I ended up some 50 miles from where I thought I was. This was a case of bad planning and pilotage, but it didn't help that everything looks the same. On the other hand, I hear it's surprisingly easy to get lost up there in real life too, so maybe the difference isn't as great as I imagine it. I just know that I could tell the Organ mountains apart from just about any other range in an instant in real life, but it would be much harder in a flight simulator (that didn't have a photorealistic scan of the Organ mountains, but who'd go to that trouble?).

Lack of detail has its advantages. It trains you to look for the lowest common denominator in navigation aids, and you don't get overly used to local landmarks. It's great for excercising the "what if" situation of getting lost. :-)

And now for the discussion you've all been waiting for. You knew it was coming. it's the proprietary vs. free discussion. X-Plane is proprietary. Its 6-minute demo isn't even enough to call crippleware. It costs a lot, but not as much as I've paid for Microsoft Flight Simulator in the past and certainly the price is very nice for what you get. FlightGear is open source software through and through. As such, FlightGear is free and libre both. Since I got X-Plane as a gift, X-Plane was free but not libre. In fact, it is decidedly anti-libre. I had to crack the stupid thing just to get it to run on my primary desktop because it requires you to have the DVD in the drive. They do this so that they can provide a fully functional (if short-lived) demo download with minimal overhead, but I was not going to put up with software terrorism. I emailed X-Plane support and asked if there was anything else I could do, and they said "um, you can buy a DVD drive for about $35." Thanks, punks. My family spent eighty hard-earned dollars which is a significant amount for us genetically-enhanced cheapskates, and you tell me I can't use the software without buying a DVD drive. So I cracked their copy protection. I won't tell you how because that wouldn't be right, but I will tell you that if you have a little determination and debugging skills (and the DVD you bought) you should be able to figure it out.

FlightGear, on the other hand, is refreshingly open. It is rough around the edges as OSS usually is, but it has the most important features and does them well. It is improving at an amazing pace, and it should be considered one of open source's finest posterboys.

Documentation is very good for FlightGear, although sometimes out of date. X-Plane has little documentation. It has a more pointy-clicky interface but I still haven't figured out what everything does, as it seems to have no immediate effect when I try it out. I may be weird, but I do read the documentation. So I do know what FlightGear is doing, and its limitations, but with X-Plane I just have to guess. I haven't bought into the "OSS == bad documentation" for awhile now, and this is just another data point. In my experience proprietary software is more likely to have bad documentation that open source software, plus it doesn't have the advantage that you can just go read the source if the documentation is incomplete or wrong.

Freedom and libre has the biggest practical impact in the area of scenery. As I mentioned earlier, FlightGear and X-Plane use the same terrain and navaid databases (which are generated by open source software). X-Plane has nicer textures, and supposedly better building placement, but they're basically the same underneath. But with X-Plane you either buy one scenery area (e.g. the USA) or spend more and buy the entire world. You have to also have 60 GB or so free hard disk space to install all the scenery. (You can install piecemeal but it's a pain) With FlightGear, you just run TerraSync and it magically downloads only what's necessary to fly around the world. Which, unlike the scenery you pay for in X-Plane's world scenery, includes the biggest state in the nation (Alaska) and everything else up above 60° north.

If you're interested primarily in large cities (below 60° north) or pretty textures, and money and hard disk space aren't obstacles, X-Plane is a better choice for scenery. Otherwise you want FlightGear.

Finally, a few miscellaneous beefs with one or the other (or both).

X-Plane's HID driver seems to be a big buggy hack. Only recently were several bugs with Logitech and other joysticks fixed on OS X, and in Linux the CH (and probably other) joystick hats don't work. That means I can't quickly look to the side with my hands on the yoke. This is a real serious drawback in the field of view on Linux (which is where I fly most).

FlightGear doesn't let you change aircraft without a restart. That's just silly (though I'm sure there's a technical reason for it that can be traced to an early design decision). Hopefully it will be fixed in the future.

X-Plane and FlightGear both let you sync the clock to real time and the weather to real weather. FlightGear automatically sets the clock and weather at startup (unless told not to), but X-Plane remembers the previous setting. This is almost always the wrong thing. If I want a daytime flight at night with FlightGear I just start it up and go to the menu to choose daytime. No hassle, and next time it's back to real time. With X-Plane, I either fly perpetually at 1400 hours or I am synced religiously to the clock. Even when paused. So I can pause and go eat dinner and come back to find that nothing has changed except that now it's dark. Right. If I want daytime hours when it's dark out, I have to deselect the realtime sync, so that next time when I *do* want real time I have to go back and reselect it. The same thing is true with real weather.

Getting FlightGear on OS X is kind of a mess. It's leaps and bounds better than it was a short while ago, but it's still not up to snuff.

X-Plane doesn't do ATIS/AWOS over the radio. It lets you choose from a rather unrealistic set of local ATIS/AWOS in the ATC menu, but you don't have to tune your radio and you don't get continuous broadcasts. X-Plane doesn't have speech synthesis on Linux. Neither has very good ATC, though I hear rumors that it's in the works at FlightGear.

X-Plane's seaplane is pretty cool until you try to land in the 3-foot waves (by default). The water in SoCal may have 3-foot waves but I promise it ain't so at Utah Lake.

FlightGear doesn't have a cool GPS unit like X-Plane does. At least not that I've seen. But I prefer to practice the old fashioned way with pilotage, dead reckoning, and radio instruments. In real life, though, I'm sure I'll love to have a GPS handy.

FlightGear has less fake ATC than X-Plane. X-Plane is a few keystrokes away from useful if unrealistic ATC functions like asking for a wind check or altimiter setting or vectors to the field of your choice. (All without the hassle of setting your radio! Would that the real world were so convenient.)

X-Plane has a nifty map integrated. FlightGear has a companion program that is external. Both have their advantages and disadvantages, and I don't really use either one. (I like good old fashioned sectional charts and looking out the window)

FlightGear has an IRC channel and mailing lists. X-Plane has a community-driven PHP forum.

X-Plane has better sound, especially engine sounds at different RPMs. It even has nifty background radio chatter. Unfortunately it doesn't take long to recognize that it's just looping and get sick of hearing the same radio conversations over and over.

X-Plane has a nifty feature displaying the force normals as green arrows, and a 3D path. It also has a more featured and easier-to-control replay feature.

FlightGear not only does the sensible thing with time and weather sync, it lets you rewind and fastforward in time very easily (t/T keys) to get just the right sunrise/sunset feeling.

I like FlightGear's Cessna better, for many reasons but mostly because of the 3D cockpit. I like the aftermarket Mooney 20K 252 TSE for X-Plane for cross-country flights. I like the Piper Cherokee Warrior II in FlightGear, and it's fun to fly the J3 Cub too.

My Summary

I like both programs. They both have strenghts and weaknesses. I find myself choosing which one based on two factors: whether FlightGear CVS is working right at the moment or not (I track development), and which plane I want to fly. As I mentioned I like the Mooney in X-Plane and the simple aircraft in FlightGear. Also, if I want to fly outside the lower 48, it's easier to do FlightGear+TerraSync than fish out the X-Plane DVDs and extract the piecemeal scenery I need over the network.

If exotic things like the space shuttle and lots of extreme jets and experimental aircaft are your thing, you want X-Plane. If you like general aviation FlightGear is a good choice but you can make do with X-Plane with a little fishing on x-plane.org.

If you're an eyecandy (romantic) person, X-Plane will appeal more to you. If you're the kind of person who cares primarily about form and function (classical) you'll find FlightGear just as satisfying, peraps more so.

If you like to take shortcuts, X-Plane is full of them (GPS, magical "ATC", quick setup for VFR/IFR landing). If you like to take the hard route and learn more FlightGear will be more your style.

If you want to impress friends by landing the space shuttle or flying on Mars, X-Plane is for you.

If you believe in open source software and avoid proprietary software on principle, you'll be glad to know that FlightGear is an amazing piece of free software.

Both X-Plane and FlightGear are worth much more than what you pay for them. FlightGear is less than $80 behind X-Plane, so technically it's the better deal. You'll get a lot more out of your money for a yoke and pedals than X-Plane, if it comes down to that choice.

The Last Word

Whichever you choose, flight simulation is a fun and enjoyable hobby, and a lot cheaper than the real thing. (alas) It's come a long way since the early 90s, and I think we're at the beginning of what will later be remembered as the flight simulation heyday. Enjoy the ride!