How To... Build A Digital Radio Altimeter For FS2004

By Ulrich Klein (13 March 2006)

"To the best of my knowledge there is nothing in development on the FS scene, and like you I have heard nothing either. As a developer, I would normally know if there was." That's what a well-known developer and designer wrote me lately when I kept on wondering why there is such an ominous silence about everything concerning the next version of MS Flight Simulator. Now, surprisingly, Microsoft has just opened the Wizard's curtain for an early sneak peek at what's in store for us with FSX, which is said to be many months away. So the wait will be painful.

In the meantime, while we are waiting for the next iteration of our granddaddy flightsim of all time, I found there was ample time to carry out a final project that I have had in my mind for several months now. What I mean is building a digital radio altimeter for FS9 that would be very easy to use and could be implemented into various panels in an unobtrusive way. Analog radio altimeters like the one shown in the screenshot need quite a lot of space within a cockpit panel window, so the basic idea was to develop an instrument that would cover only a very small area. The only way to achieve this goal was to build a digital version of the radio altimeter. At the same time this tiny gauge should have backwards compatibility right down to FS2002. Vague ideas of how to do this had formed in my mind about half a year ago but things develop differently from time to time, and so there was never time enough to go ahead with it. However, it's done by now and in the following lines I'd like to give you some closer insight into how this job was performed.

FIVE VERSIONS OF DRA (Digital Radio Altimeter)

To begin with, let me give you a brief survey of the different versions of the new digital radio altimeter by placing them at various positions within the Lear panel window. Note that this is no longer the default panel window as I have made a lot of minor modifications so far. However, this is of no importance as to the current topic of implementing the new digital radio altimeter. Of course, you are not expected to have the digital radio altimeter (DRA) installed five times on your panel. You may choose the one that suits you best and then deactivate all the others in the panel.cfg file of the Aircraft\Lear45\panel\ folder by putting a semicolon at the beginning of the respective command line.

On the right you can see the modifications and new entries which must be made in the panel config file of the default Lear45. The DigRadAlt5 gauge is a version of the DRA which is only made for the Lear45 because it represents an optimized and enhanced Lear radio stack, completely built from scratch in xml code. There is also a command line for the avionics toggle switch which I have added to the panel and which fully influences all new digital AV readouts (screen shot down on the left). Many of the default digital displays only disappear when main battery power and the engines are shut off (screen shot down on the right).

A word to those simmers who no longer have the panel config file in its default status because they have modified it in the past either by themselves or by what I have suggested in my former article here on FlightSim.Com about implementing new enunciator warning lights for the default Learjet and Boeing 737-400. So you may find it a good idea not to overwrite your panel config file by the one which is comprised in the package today. Just open your old one and add the necessary new command lines as listed in the above screen shot. But beware that you must deactivate the original line with gauge14 (highlighted in blue) by a semicolon at the beginning of this line. And there is something else you should know: the new gauges, all written in xml code, do not make any modifications to the default Lear_45.gau in the GAUGES\ folder of FS9.

THE HANDLING OF DRA

The handling of the DRA is almost self-explanatory if you take a look at the following shots which display the plus- and minus-hands of the cursor. The only thing you should know is that both for the decrease (minus) and increase (plus) of the Decision Height digits there is a slow and a fast scan that you can use. The quick scan is a little bit more on the far left or on the far right side, whereas the slow scan is on the inward side to the center of the DH readout. Just check it out. Also, with the tiniest and smallest version which only shows the RA readout at first sight, there is a blank white hand by which you can toggle between RA and DH digits if you click into the middle of the area, as shown in the shot (second from left). That's all there is to it.

By the way, the color of the RA digits turns orange when going below DH which is set to 328 ft by default but can be changed manually, of course. The design of all the versions is slightly different so I guess you will find one that suits your needs best.

Version 1 of the DRA can also be implemented in the top right corner of the Lear EICAS. In the above shot the DH is manually set to its max value of 600 ft. The warning indicators for the left and right reversers are not contained in this package but can be downloaded from the file library at FlighjtSim.Com (FS9EWL.ZIP). For those of you who are fairly acquainted with xml coding I'd like to add that you may feel free to modify the colors of the digits by using PaintShopPro8 or higher version. You will find the HTML-color code down at the bottom of the color dialogue window (highlighted in red). This is the code you must use for xml-coded gauges in the .xml file of the gauge.

The following shot displays the typical text of xml-coded gauges, revealing the internal structure of this programming language that has existed since 2001 and was first used for Flight Simulator in FS2002. Files containing such code have an .xml extension and can easily be edited by a simple text editor such as Notepad or Editor, which is part of the Windows OS.

The above extract is only part of the code used for the LearRadioStack2.xml file which is included in the package. It is easy to see where to modify colors or the size and type of the font that should be displayed in the gauge. The behaviour of images can be influenced by commands such as BRIGHT="YES" or LUMINOUS="YES". If nothing is specified, the bitmap will adjust to the overall night characteristics of the cockpit panel illumination.

All the xml gauges for the digital radio altimeter are finally combined into a single cabinet file (DigRA.CAB) by means of the MS Cabdir utility (cabdir.exe), which is part of the FS2004 SDK. It comes along with a document (cabdir.doc) that explains how to create cab files.

There is indeed no reason why you should not have a DRA in the B737-400 panel, too. Version 2w has been integrated on top of the primary airspeed indicator and in the clock at the middle post. As many simmers won't have this middle post with the clock, I have only given the entry for the position of the DRA in the HIS.

SOME FINAL REMARKS

XML programming provides a far more open platform for gauge design, far more open than the old gau-format gauges do. So, nowadays many simmers try to modify such gauges in a rash attempt, but you may be warned to be very cautious in doing so. That said, there's nothing to stop you doing it the way you prefer.

WARNING: Replacing PART OF the CODES IN THE XML GAUGES WITHOUT SUFFICIENT KNOWLEDGE WILL MOST LIKELY result in the crash of FLIGHT SIMULATOR, to say the least.

Note: It shouldn't hurt your computer but if you imagine it has, we accept no liability. This goes for all modifications and for the gauges included in the downloadable archive.

To download the package which contains detailed information on how to install the gauges you may have to log in to FlightSim.Com first. You can follow this member login hyperlink and register as a user, which is free of any charge, by the way, and you won't get deluged with junk emails. I haven’t received a single one in all these years. If I can say it, it’s got to be true, so go and get registered, and, first of all, enjoy the new gauges. Off we go!

Happy flying and, first of all, safe landings.

Ulrich Klein
huki.klein@t-online.de

Download FS9DigRA.zip for FS2004

[ Back | Home | Main Menu | Logout | Help ]