Graupner's IFS-3—Flawless?

These lines serve as a supplement and response to Beat Huber’s article in *modell flugsport* 4/2009, pages 22–23. The topic is the reliability of the Graupner IFS-3 2.4-GHz radio control system. Above all, however, it concerns the safety of our hobby. A failure of the remote control system while a model—weighing, for example, 20 kg and fueled with kerosene—is in flight can have fatal consequences, even for our hobby. Therefore, unsafe remote control systems should never be used.

In an environment where the 2.4-GHz frequency band is heavily congested, my IFS-3 experienced brief transmission outages (lasting about 1/10 of a second), which were evident in jerky movements of the control surfaces. This was observed in May 2009 in Italy (at the airfield near Ivrea in the Aosta Valley) following a flight that was nearly uncontrollable. The control surfaces moved jerkily or returned to the preselected position with a delay. This was also confirmed in a report to Graupner by the world-renowned model pilots Reto Senn and Urs Mayländer, who were eyewitnesses to the incident. My receiver was not equipped with a satellite receiver, which was supposed to improve reception. These were withdrawn from the market by Graupner shortly after delivery and have not been available since.

Another instance of abnormal behavior with the IFS-3 was total failures lasting several minutes while on the ground (possibly in “hold” mode?). I was able to document this on video, and it can be found on YouTube by searching for “IFS-3.” Such a failure during flight would have meant the loss of the model. 2.4-GHz systems from other manufacturers, which were in use there at the same time, had no problems whatsoever.

Among my friends, there have been instances of complete failures of IFS systems—and consequently crashes of large gliders—in the Bergamo area. These were most likely due to the heavily congested 2.4-GHz frequencies.

I sent my IFS-3 system to Graupner for repair at the end of May 2009. As of today (Sept. 1, 2009), Graupner has not yet responded to this matter. Here’s another fact that gives pause for thought: At the World Championship for jet models in Israel in June 2009, not a single team used the IFS-3. No pilot on the German team had equipped himself with it.

As the 2.4-GHz band becomes increasingly crowded with other users, even in our part of the world, interference and malfunctions with Graupner IFS-3 remote controls could soon occur north of the Alps as well. This is something that should definitely be taken into account.

*Hans Bühr,
MFG Dübendorf and Zumikon
hansbuehr@hotmail.com*