REFLEX XTR² Simulator by Stefan Kunde

REFLEX XTR² has been known as high-end simulator for the hot helicopter models at a time, but this role has been since taken on by kind of a successor, neXt by Eiperle CGM. Today, REFLEX makes its mark with modern, full-featured multicopter models and is the simulation environment for several of the EPP models made by Multiplex (also in a special version named MULTIflight). Even if there are no new models, REFLEX is still a high-end simulator – in my case particularly for my own simulator models (see below) – and very well suited to learning to fly – airplanes and helicopters alike.

Off-the-shelf, game-controller compatible USB adapters are used to connect a regular R/C transmitter. There are adapters with a cable but also some convenient wireless adapters, effectively 2.4GHz receivers in or on an USB stick (see REFLEX FAQ). REFLEX is now distributed as a mere software download in a Web shop, without the former, special USB adapter (dongle), which still perfectly works though. REFLEX is a dedicated MS Windows application (Windows 7 or newer) and runs only in true virtual machines under MacOS or Linux. See the menu at the top right of the REFLEX web pages with DOWNLOAD of the full version (free 14-day trial possible), SHOP for the license, and FAQ for technical issues.

REFLEX is my favorite simulator because it's very realistic but not 'cluttered' with features. I'm a genuine airplane guy, only a late starter to helicopters, and not exactly multicopter savvy. So I'll primarily mention the simulator's airplane capabilities, which are perhaps less noticed but top-notch as well. Its good helicopter capabilities should be taken for granted.

The physics of a model are well rendered and it's easy to experiment with the parameters. I cope well with the kind of parameters, obviously unlike others. However, I have some tools to calculate the 'true' parameter values (see the pages on Brummi). With the REFLEX model construction program RMK we are able to render the appearance of a model very authentically (photo-realistic). Besides, there are photo-realistic sceneries, made with the REFLEX scenery construction program RSK, in addition to the former standard scenery, which is generated by the simulator. It has still some advantages and is shown first here:

This simple-looking REFLEX scenery is yet adjustable by parameter: Shape of terrain, covering by trees, clouds, weather, and "camera" are obviously set to reasonable defaults, as shown in the picture. The wind sock is working realistically. Maybe the most notable feature is the changeable pilot's position including the modes 'following the model' (good it's only in the simulator) and 'onboard' (FPV). That's not (technically) possible in the photo-realistic sceneries because they are based upon a panorama picture shot from a fixed position:

This is St. Johann im Rosental in Austria, the field of the MFG Klagenfurt. The famous Hanno Prettner once practised here flying his aerobatic models. The scenery has been made by Horst Lenkeit, an independent author who unfortunately died too young. He also made the MFC Coesfeld scenery of a rural field with grass runways, well suited to thermalling (amongst other things):

The Mill Hill near Shoreham in England is a REFLEX stock scenery, one of those that are perfectly made to show a famous place to fly as well as the great features of REFLEX. As in reality, all aspects of slope soaring may be experienced, including downwash behind bushes, dynamic soaring in different wind speeds, and forced landings far below the pilot's position:

The same holds for the Hörnle (Teck) scenery, made by another independent author (Markus Vogt). It very well renders the location of the famous Teck slope-soaring competitions in Germany, even though it's technically not quite as perfect as the stock sceneries:

It has been even managed to create a water look-alike in REFLEX. So it's possible to experience float and boat planes, as well as such helicopters, in their natural surroundings. The behavior on the 'water' is not quite realistic yet shows the essence of water flying, for instance on a gravel pit lake in northern Germany:

This scenery has been made by Harald Bendschneider, another independent author, who is expert in making sceneries for all of the 'big' simulators. He has a workshop and even offers help at his website www.Szenerien.de (well worth a visit). The same holds for Paul Duerr, his sceneries being offered at sceneries.paulduerr.info. Some of them are special and actually more suited to helicopter flying, though challenging for airplane flying like the yard of Emmendingen Castle:

There are more famous places in other sceneries, both by REFLEX and independent authors, for instance the summit of mount Gerlitzen in Austria, 6250 ft above sea level, the field of the TOC competitions near Las Vegas, or the AMA Flying Site #3 in Muncie, Indiana:

This is the pits area in Muncie, with a model taxying in the forbidden zone. Most stock sceneries and even some sceneries made by independent authors have such forbidden zones. As shown in the picture, they are marked by red and white stripes if and when they are violated. If the model is below 20 feet altitude the simulation even stops. These zones can be switched off because some people dreadfully complained about them. Don't be mislead, these zones are no problem at all because you won't even notice them once you mastered keeping orientation in the simulator and in the respective scenery. After all, you would not fly over the pits or other no-go zones in reality, either. Unfortunately, there was some campaigning against REFLEX using these zones as a pretense.

In my description of the C-130 Hercules model is a whole section (the last one) with short reviews of several nice REFLEX sceneries by various authors (Hercules.pdf, 2.0M). In the descriptions of the MDM-1 Fox (Fox.pdf, 2.4M) and the Scheibe Bergfalke II/55 (Bergfalke.pdf, 0.7M) are short descriptions of slope-soaring and thermalling sceneries. Directions for downloading the sceneries are in all of these descriptions. In most of the model installers, several sceneries can be even downloaded and installed as well. And there's a "super-installer" that can download and install more than 40 sceneries (here).

The scenery pictures above also show examples of how realistic the models look in REFLEX. That holds not only for REFLEX stock models but also for those made by independent authors (like me, but others as well). Importance is attached not only to photo-realistic appearance but of course to realistic flight behaviour as well. Especially some models are so well behaved that they are suitable for beginners, so these might learn to fly in the simulator.

Some models are even delivered with their genuine sound. Often we're in the dark about the authors of the sound files since there is still no 'market' especially for model sounds. Besides, the current REFLEX version has really improved sound including wind noise in the sceneries and the whistling noise of vortices on models. There are only standard sounds for different model classes so far, but there is still no program for creating more of the high quality sounds.

Stefan Kunde, author of REFLEX, once wrote for the FAQ of RC-Sim: »Flight behaviour is essentially determined by the .par file. It contains all model and physical parameters. The .mod file actually determines only the appearance. Experience shows that, despite an objectively identical flight behaviour, on account of a different model appearance a subjectively different flight behaviour will be perceived. Besides, only the positions of rotors, propellers and landing gears (at ground contact) influence flight behaviour.« (translated literally) I could only emphasize this statement.

That's just why I'm aiming not only at a correct rendering of my models' flight behaviour. Little by little I also copied their appearance as detailed and realistic as possible, as far as that is practicable in RMK and noticeable in REFLEX. I'm still amazed again and again at how far even the drive sound influences the perception of a model's flight behaviour. So for building a REFLEX model are needed 1) measurement and calculation of parameters, 2) reproducing the appearance of the model in RMK and 3) recording the drive's sound. Finally it's again stunning how realistic the flight experience is in REFLEX.

Move the mouse pointer over a picture to see the model's name.

My first two models, Pedro by Graupner and Brummi by Multiplex, are described at some length on special pages (in German) (Pedro, Brummi, see also the menu on the left side, topic 'Model Aircraft...'). The threedee400 has a special page (in German) as well (threedee400). That was my first model for REFLEX with ribs-and-spars structure and textures. Quite a lot of work and time is needed till rendering is really good. Super Miss (like Miss 2) is simply derived from Brummi so there is only a description of the REFLEX model (see also the menu on the left margin, topic 'Simulators...'). Like my other real models, also Thermik-Star is described on a special page in German (Thermik-Star). Its flight behaviour is very pleasant and very well rendered in REFLEX.

You may notice that I'm offering parkflyers und gliders in the first place, all having an electric drive. They are well suited to learn flying, from the beginning (Slow Stick, Miss 2, Brummi, Pedro) to aileron usage (Super Miss, Thermik-Star) and to aerobatics (threedee400, Jitterbug) and thermalling (Pedro, Thermik-Star). The individual descriptions (see also the menu on the left margin, topic 'Simulators...', subtopic 'REFLEX') and the demo flights should be an inspiration. Explicit questions on that topic I would answer by e-mail (please click on "e-mail »" at the upper left side). Please read the text file belonging to each model (ModelName.txt)!

Of course, my REFLEX models render 'only' special real models in a special configuration (trim, drive). Rendering is very realistic, though, and they are each very 'typical' of a certain class of models. Eventually they are very well suited to learn model flying exclusively in the simulator. It's not absolutely necessary to use certain other, own models for that purpose. You even should learn using several different models. Once you are really able to fly at all, you may get yourself your favorite model. You will then be able to control it also in reality, without previously practising with exactly this model in the simulator. Only a 'professional' would possibly need exactly 'his' model in REFLEX e.g. to practise difficult patterns. But even then one would mostly do with a 'standard' model.

On this subject, "Learn model flying with a simulator and especially with REFLEX XTR²", I have compiled frequently asked questions and my answers on them in a quite long text. If you are interested look here to read or download it. The models and sceneries mentioned in the text can be conveniently downloaded and installed as a "package (here).

Move the mouse pointer over a picture to see the model's name.

Additionally, in REFLEX I recreated a very simple model which I used to learn flying in the 1960s. Nowadays and in the simulator you would of course use the aileron version to begin with. You might be surprised how calm the model will stay even in wind and gusts and how unhurried but directly it responds to control inputs. The versions without ailerons or even with only rudder and throttle not only show how it was in the old days but also how a model will respond to subtle trim changes. An interesting learning example! You may download the installer for this model, named VEBF, here. A comprehensive description will be found in the menu 'Program Files-REFLEX-models'. Demo flights (hit F9 in REFLEX) will show typical flight behavior of the three versions.

Move the mouse pointer over a picture to see the model's name.

Several models followed that I don't have in reality. They have been built using only information from the Internet and sometimes plans and articles kindly sent to me by fellow modelers. I built the Jitterbug just because I like her so much and because she's flying so well. There was a request for the GWS Slow Stick by a fellow modeler, and the model is fascinating due to its simplistic and effective design. V-173 was a project in the RC Groups Simulator forum (here). We tried out how realistic the rendering of such an unusual configuration could be in REFLEX (result: quite good). Das Ugly Stik is a great classic brought out 1966. I wanted to see how flying was in those old days (nearly as today, classics are just ageless). The same holds for Kwik-Fli Mark III, 1967 pattern world-champion model, and the alternate model Bar-Fli as well as the 'shrunk' version Flea Fli. Brushfire has been designed in 1978 and is simply a very good classic 'ballistic' pattern model. Eventually, a hardly known design of the all the more well-known Ed Kazmirski was reconstructed: Simla (for an RC Universe thread, here).

Move the mouse pointer over a picture to see the model's name.

Senior Telemaster is just another classic, brought out 1968 and well-known world-wide. Giant Telemaster is a modern - well, giant version having interesting flight characteristics. And Senior Telemaster Plus is an even more modern version (2011) with equally interesting flight characteristics, big flaps, and wide fuselage. I even own this model (see own page in English), so it's rendered very realistically.

Move the mouse pointer over a picture to see the model's name.

By now I'm interested also in scale models if the originals are interesting designs. That's true for the Bölkow Junior and the Bergfalke, both vintage airplanes today, but also for the Fox as a modern aerobatic glider.

Move the mouse pointer over a picture to see the model's name.

Finally I badly wanted to have the Junior on floats, what even worked. After that, both Telemasters and the Middle Stick have been put on floats as well, followed by even more models. The Junior has even been put on skis for winter sceneries.

The definition files of my REFLEX models are each packaged in their own installer programs. Most of them are quite big, but after downloading one of them you can simply run it and select models to install. My download page (see menu on the left side) presents all these files and some more, including RMK objects, sounds, and parameter calculations.

The greatest number of models, both airplanes and helicopters, had been available at the RC-Sim.de website, which has been closed down in late 2021 though. The following pictures give an overview of interesting models for REFLEX for which I adjusted the flight behavior to suit me better and which are hence still available here (at the Downloads page). And there's a "super-installer" that can download and install more than 60 models (here).

Move the mouse pointer over a picture to see the model's name and author.

By the way, REFLEX is able to do 3D, not only flying, but also display rendering. It calculates not only two coordinates for a flat screen picture, but produces the third, the 'Z coordinate' for spatial impression as well. If the PC has a modern graphics adapter with at least 512 MB dedicated (not mapped) video RAM, REFLEX is 3D capable. Using appropriate 3D glasses can give a real spatial impression when flying in REFLEX. The glasses may be annoying and the eyes are stressed, but it may be useful, especially when flying close by, for instance flying 3D with a helicopter or airplane, or when slope soaring.

The generated scenery, shown on top of this page, has always been 3D suited, but the photo-realistic sceneries are 3D suited as well. Most of the stock sceneries and some of those by independent authors have even been improved especially for 3D. That means you can see a bit "behind" close-by obstacles like bushes or trees, and they appear three-dimensional without annoying effects. That way you can really reckon the model's distance to these obstacles.

This is a screenshot of REFLEX in 3D mode. If you view it with red-cyan glasses it will be like looking through a window into the scenery.

An appropriate graphics driver, together with simple red-cyan glasses, allows 3D display using even any type of monitor (that means also the usual TFT flat screens). Colors are not too bad and the display looks really three-dimensional, but it's rather dark and all colors become dull. (Try the picture above with red-cyan glasses.) Besides, your eyes will be stressed, so for instance nVidia always recommended it for trying only, of course just to spark interest in 'the real thing' (which is more expensive).

Indeed, 3D display might be more useful with an expensive fast flat (TFT) monitor. The graphics adapter should be twice as fast as normal for the 3D shutter glasses, which are connected via USB or Bluetooth. They alternately shut the glass for the left and right eye. Using a usual TFT monitor or a notebook PC, 3D with shutter glasses is still impossible because they are too 'slow'. The PC's graphics performance should be really high since the amount of 3D effect also depends on screen resolution. And the monitor has to achieve at least 120 Hz refresh rate at the desired resolution (60 Hz for each eye), or the picture will flicker too much. And it's still a bit darker.

Considering the expensive display and the still annoying shutter glasses, an autostereo display (no glasses needed) seems to be a better alternative (see Stereo3D). These devices are getting comparable in price to the expensive fast monitors. Even though red-cyan (anaglyph) glasses are much cheaper, I was always in doubt if 3D in REFLEX is actually worth the effort. Personally, I find 3D 'cool' but too stressful for my old eyes. I'm flying airplanes but no 3D and hence prefer the bright and brilliant 'flat' display to the darker and dull 3D one. And 3D has been just a periodical 'hype' for quite a while now. But to each his own! (Meaning everybody has to decide for oneself.)

My decision was influenced by the experience I once had in a computer graphics laboratory. REFLEX was looking like "real" 3D there, in high-resolution rear projection (the projector beaming at the back of a ceiling-high transparent screen), seen through wireless shutter glasses, and powered by a high-performance computer. (Wireless transmitter connections did not exist yet.) One could stand quite close to the screen, corresponding to the simulator's camera, which is usually set to wide-angle to see enough scenery for orientation. Only this way you feel like being there, but you wouldn't or couldn't be that close to a monitor. I even suspect that's the reason why a lot of simulator users feel the flight behavior of simulator models is unnatural or unrealistic – kind of an optical illusion.

The shutter glasses had even sensors to track head movements, and REFLEX supported or used them to pan the field of view in the scenery. That is not reasonable, though, neither in the simulator nor in other applications, because you have to turn your head to pan the camera, but the screen or a monitor is fixed. So you have to peer askew to the screen, what is even less natural than focussing your eyes on a spot in a plane for 3D. There is no solution for the latter, but there is one for realistic spatial impression and for panning the field of view.

REFLEX supports this solution already, namely the new virtual-reality glasses (VR glasses or headsets). These are like two small screens, one for each eye, so no shutter is needed and color and brightness are unaffected. The screens are close to the eyes, making for a relatively wide field-of-view (more than 110 degrees) and hence a very realistic spatial impression (3D).

That's how the two head-mounted display screens look like.

(Picture borrowed from the REFLEX online help.)

And that's what the optics make from the left picture for the left eye.

(Picture borrowed from the REFLEX online help.)

By appropriate sensors, panning is possible in all six degrees of freedom (6DOF) – and the screens are swayed with your head so it's natural. You don't unnaturally stare at the spot in the middle of the screen where the model is fixed, but realistically follow the moving model with eye and head movements. The best of all: You can stand in front of your computer and turn around on your feet like on the flying field. I wouldn't have thought that this contributes so much to the realistic experience! A gimmick: If you look down you see the REFLEX transmitter in front of your belly. Small speakers close to the ears include audio in the 3D experience. All in all you have a nearly perfectly intuitive simulated flying experience. (By the way, there is wind noise in REFLEX but you'd need a fan to feel any wind. Just kidding…)

So let's forget red-cyan glasses and even shutter glasses! VR headsets provide a realistic impression in the simulator for the first time ever – and perhaps even regarding flight behavior.