Use of Transponder

Use of Transponder

Best Practice - Use of Transponder

  • Use a transponder. It will help ATC to see you on radar and may help to prevent an infringement or provide a quick resolution if an infringement occurs.
  • Use the ALT function. It will show your height on radar and is particularly useful to controllers when you are flying below controlled airspace.
  • Use of a transponder enables TCAS installed in commercial aircraft to be aware of your presence, providing a significant safety net.

Cost – None if equipped


The increased use of transponders has shown to be beneficial in reducing the risk associated with airspace infringements. The controllers ability to more easily see a secondary radar return, particularly with the altitude information has enabled controllers to react much more quickly when infringements have occurred. In the UK and in the Netherlands, the most serious risk associated with infringements was from aircraft without a transponder flying above the base of controlled airspace. Controllers were unaware that these aircraft were at the wrong altitude until they were reported by commercial aircraft in close proximity. Most Dutch airspace now requires the mandatory carriage of Mode S transponders, it is mandatory to use a transponder above 7000 feet in Switzerland and the UK and Germany have Transponder Mandatory Zones in some infringement hotspot areas.

Sample Material

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