Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.
Issue link: http://experimenter.epubxp.com/i/90184
News From HQ Don't Forget Your Transponder's ICAO Address The FAA reports that a number of homebuilders are not correctly setting up their Mode S transponders during installation. If a transponder is not configured correctly during installation, it can cause confusion in the air traffic control system and may also confuse airborne traffic warning systems, with which all larger airplanes are equipped. Mode S transponders—the S stands for "selectable"— broadcast two different identifi cation codes. One code is the familiar four digits we set as assigned by controllers. But there is another permanent Mode S address that is assigned to your aircraft at registration. This is the 24-bit ICAO address that is an international identifi cation for your specifi c airplane. When an N-number is assigned, an algorithm generates an eight-digit (24-bit in computer speak) code that is part of your registration. You can fi nd that code by looking at your N-number registration data. When a Mode S transponder is installed, specifi c programming steps must be followed to enter the ICAO code during setup. Not all builders are following the correct steps to enter the ICAO code when they install a transponder. The result is airplanes fl ying around and broadcasting incorrect addresses. The ICAO address must also be programmed into any universal access transceiver (UAT) when that system is 6 NO. 3/NOVEMBER 2012 installed to participate in automatic dependent surveil- lance-broadcast (ADS-B). The immediate problem for wrong ICAO addresses mostly involves airborne collision avoidance systems in larger airplanes. Traffic collision avoidance systems (TCAS) required in all larger airplanes use the ICAO address to keep track of nearby Mode S transponder- equipped airplanes. A wrong ICAO address could possibly threaten the proper functioning of the traffic warning system. A more widespread problem with wrong addresses will develop as the FAA moves to its NextGen (next gen- eration) air traffic control system that relies on ADS-B signals to locate and track aircraft. Mode S signals are a fundamental component of ADS-B, so the proper ad- dress is essential. The solution is for builders to carefully read all setup instructions and follow them closely when they install a Mode S transponder or UAT system in their aircraft. Avionics shop technicians are well trained on this step, so the problem of incorrect ICAO addresses is almost entirely with homebuilts. It's also vital that an airplane owner or second owner change the Mode S ICAO ad- dress in his Mode S transponder if the aircraft N-num- ber changes. Photography courtesy Garmin