Published: 23 September 2011
Effective: 23 September 2011

ATA Chapter: 34


Microair Avionics T2000SFL Transponders


All maintainers and operators of Microair Avionics T2000SFL Transponders.


All maintainers and operators of Microair Avionics T2000SFL Transponders.


This Continuing Airworthiness Notice (CAN) is issued to highlight the potential problems associated with Microair Avionics T2000SFL Transponders embodied with software prior to revision 8.
Transponders prior to revision 7 may generate intermittent replies to interrogations from Mode S Secondary Surveillance Radar (SSR), or stop replying and default to a non-reply mode. Furthermore, Microair Avionics have advised that the QNH compensation in software prior to revision 8 work backwards. In 2010 Microair Avionics released new firmware at revision 8 which corrected the QNH compensation.


The CAA is aware of incidents with certain T2000SFL Transponders where intermittent or complete loss of detection has been experienced in New Zealand by Mode S SSR interrogators. The CAA has received reports that the QNH compensation in some T2000SFL Transponders work backwards. A safe navigation environment in transponder mandatory airspace relies on accurate and reliable surveillance information transmitted by Mode S transponders. Incorrect of missing transponder data can result in increased controller and/or flight crew work load which may develop into a hazardous situation.
With the Australia Airservices plan to roll out Mode S SSR interrogators in Australia, CASA issued Airworthiness Bulletin (AWB) 34-010 issue 1, dated 17 September 2007.


For the reasons described above the CAA strongly recommends maintainers and operators upgrade Microair Avionics T2000SFL Transponders to revision 8 or later to correct the potential problems identified in this CAN. For further advice on T2000SFL Transponders upgrade options Microair Avionics can be contacted at

The following documents provide further information about the contents of this CAN:

Furthermore, if you become aware, or are notified of a transponder deficiency affecting your aircraft, the CAA recommends that you initiate an unscheduled maintenance action to correct any deficiencies.